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SCIENCE

AND THE

SEA

1966

U.S. NAVAL OCEANOGRAPHIC OFFICE
WASHINGTON, D. C.

—

FOREWORD

Oceanography, the application of the sciences to the study of the oceans, has been the
subject of considerable worldwide attention during the past few years. The reason behind its
popularity is, of course, the almost universal acceptance of the sea’s role in the future of man-
kind. In an address presented on July 13,1966, President Lyndon B. Johnson took note of the
importance of this role. He portrayed our newly awakened scientific interest in the sea as
“a new age of exploration” and described the high adventure that still awaits those pioneers
who enter upon “our last frontier on earth”. Addressing himself in particular to a group of
youthful guests consisting of outstanding high school students, the President stated, “I hope
that there are among you some of the great oceanographers of tomorrow. You could not
choose, in my judgment, a more important or a more challenging career”.

Science and the Sea, a compilation of ten articles describing some of the practical aspects
of the marine sciences, is presented to acquaint both teacher and student with a few of the
realistic problems that face the modern oceanographer. The articles were selected on the basis
of applicability from a series of original papers specially prepared for presentation on the re-
verse sides of the Pilot Chart of the North Atlantic Ocean and the Pilot Chart of the North
Pacific Ocean. These charts are published monthly by the U.S. Naval Oceanographic Office
to provide mariners with a graphic synopsis of meteorological and oceanographic conditions

prevailing in the waters specified.

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CONTENTS

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OCEANOGRAPHY AND THE MARINER...........---.----seeeeeee eee 1
TREASURE FROM THE SEA ..... 1. ccc cece cece eet eect e teen n eens 9
BIOLOGICAL OCEANOGRAPHY ......-----eeeee reece eee teen eee e ees 17
DANGEROUS SEA LIFE ............ 0... cece eee eee ce cee eee ee eee tees 25
THE TITANIC—50 YEARS LATER...................0e eee ee cece ete ee ee 35
INUNTPLON RYN, TABU BINKOMOBINUA G5 cancoccgao obo capoodoDcoDUGoDGOBabeDaGb0ODG0DDEOE 45
UNDERWATER DISTURBANCES ................0 000s eee e eee erence eens 53
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WATER DENSITY AND ITS APPPLICATIONS .....................000-- 69
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OCEANOGRAPHY AND THE MARINER

A. J. Barther
Marine Sciences Department
U.S. Naval Oceanographic Office

Oceanography can be properly defined as a combination of sciences
which deals with physical, chemical, biological, and dynamic properties,
as well as other phenomena found in, on, and around the earth’s hydro-
sphere exclusive of stricily freshwater bodies.

HISTORY

Study of oceanography in the U.S. Naval Oceanographic Office
had its inception about the year 1842, at which time Lieutenant
Matthew Fontaine Maury was appointed Officer-In-Charge of the
U.S. Naval Depot of Charts and Instruments. It was the foresight
and persistent efforts of Maury during early attempts to collect world-
wide data pertaining to the oceans which led to such developments
as the Wind and Current Charts of the North Atlantic of 1847, origi-
nally presented as a series of six charts. Also collected were data
pertaining to best sailing routes, fog limits, ice fields and icebergs,
rain areas, feeding grounds of whales, and other information which he
deemed of interest and value to mariners.

In 1854, the Depot was redesignated the “‘U. S. Naval Observa-
tory and Hydrographical Office’. Congress separated the two
in 1866 to increase the responsibilities and scope of the latter by
authorizing The Hydrographic Office to carry out surveys, collect
information, and print every kind of nautical chart and publication
for the benefit and use of navigators generally.

Purchase of the copyright to The New American Practical Navi-
gator was one of the first acts of the new Office. Several volumes of
Sailing Directions had already been published. The Notice to
Mariners appeared in 1869. The first Pilot Chart was issued in
December 1883. Radio Navigational warnings were broadcast
in 1907, and the International Ice Patrol was established in 1912,
following the TITANIC disaster.

Maury’s tenure with the Hydrographic Office terminated in
1861, but his work in oceanography was furthered by his successor,
Captain Robert H. Wyman, Hydrographer, who reorganized the
Office in 1871 and created a department of meteorology. Though
seriously understaffed, the Division of Marine Meteorology managed
to produce Pilot Charts which were in high demand. In 1904, the
Hydrographic Office was relieved of all responsibility for collecting
ocean weather data by executive order of President Roosevelt. The
majority of meteorological data used in the construction of Pilot
Charts since that time has been furnished by the U.S. Weather
Bureau. Development of a new depth finder and use of aerial
photographs in 1922, led to improved charts and soundings.

In 1924, a conference of various Government agencies was
organized for the purpose of investigating the possibility and feasi-
bility of conducting a research expedition in oceanography with
Navy vessels. Though many representatives from branches of the
State, Treasury, War, and Navy Departments attended this con-
ference, nothing seems to have developed at this first attempt to
support an oceanographic program in the U.S. Navy. Investigations
begun in 1927 by the Committee on Oceanography of the National
Academy of Sciences—National Research Council resulted in the
recommendation that oceanographic research be undertaken by a
Navy vessel specially fitted for the work. These investigations
enabled the Hydrographic Office to acquire its first supply of ocean-
ographic equipment which was used only incidentally in the survey
work of the hydrographic ship, USS HANNIBAL, in 1931. Co-
operating observers on merchant and naval vessels also submitted
numerous oceanographic observations.

Late in 1945, with termination of the war, a conference was
convened for the purpose of determining views with regard to forma-
tion of a Division of Oceanography in the Hydrographic Office. The
Division became a reality on 1 February 1946 but got off to a slow
start due to demobilization and deployment of practically all ocean-
ographers to Bikini Atoll. The purpose of the Division was to
collect, codify, coordinate, and implement basic oceanographic re-
search for various government activities. It was also charged with
the responsibility of preparing charts, manuals, and other publica-
tions of an oceanographic nature for the Navy, Merchant Marine,
fishery industries, and airlines.

Many of Maury’s theories in oceanography have been long since
disproven. However, his methods of scientific approach to the
problems of navigation cannot be denied as having been the founda-
tion of oceanographic studies in the U.S. Navy.

GENERAL

Today the U.S. Naval Oceanographic Office makes hydrographic,
topographic, and geomagnetic surveys in international waters and
along foreign coasts. In addition, it occupies an important position
in oceanographic work. Because of its responsibilities for the safety
of ships and aircraft, the Oceanographic Office has a worldwide
interest in the oceans. Data are systematically collected from public
and private institutions and persons in all parts of the world.
Another responsibility of the Oceanographic Office is to foster inter-
national cooperation in the study of the oceans and to promote free
exchange with other hydrographic offices. The Oceanographic Office
Oceanographic Analysis Division prepares classified and unclassified
oceanographic charts, manuals, and special reports with the aid of
available data. The Oceanographic Prediction Division provides
ice, wave, and sea water temperature forecasts in addition to supply-
ing experimental ship routing services. The Marine Survey Division
performs oceanographic surveys in domestic as well as in international
waters.

Recent establishment of the National Oceanographic Data
Center administered by the Oceanographic Office, where all data are
processed and distributed to interested parties, will contribute greatly
toward achievement of the objectives of the science of oceanography.

TIDES AND CURRENTS

Increased interest in synoptic oceanographic conditions and
development of forecasting techniques has resulted in increased
basic and applied research in many fields of oceanography. Pre-
diction of tides and currents has been presented for many years by
means of tide tables and current charts.

Methods of air-sea rescue were studied thoroughly during World
War II for the purpose of locating life rafts and survivors of downed
aircraft. The principle consisted mainly of the application of
available data on surface currents and wind drift to determine the
probable direction and rate of drift of any object on the sea surface.

The chart on the reverse side of this article represents one of the
most comprehensive current prediction studies to date.

Current charts have been prepared to show general surface and
subsurface circulation of all oceans. However, more important
large scale harbor and coastal current charts have been prepared to
aid the mariner and engineer in circumventing navigational and
constructional hazards incurred by treacherous effects of tidal, rip,
overfall, and runoff currents produced by headlands, shoals, break-
waters, and the like.

Current measurements are determined by numerous methods
including calculations from ship navigation, subsurface tracking, and
by electronic or mechanical means, dyes, etc. Free-floating bottles
and cards are used to give general direction of currents when drift
rates are not a required measurement.

Tidal range can be predicted only by use of past conditions or
through complicated calculations which take into consideration all
major tide-producing forces. The latter system has been made rela-
tively easy by development of the tide predicting machine, which to
the present time has proven to be more practical than electronic
computers. It is hoped, however, at some time in the future to
convert the system to analog computer adaptation for more rapid and
reliable predictions.

Storm surges, often found piled on the normal tides, are more
difficult to predict in view of their relatively sudden occurrence.
Importance of the tides can be seen in the braking effect which they
have on the spinning of the earth. Across eons they have increased
the rotation period from four hours to twenty-four hours. Though
the change is not of sufficient magnitude or rate to be of concern to
man, it nevertheless takes place and will eventually result in a greatly
altered day consisting of longer periods of total light or darkness.

OCEANOGRAPHY AND THE MARINER

Tides are measured visually and mechanically with staffs and
gages at numerous coastal stations throughout the world. In certain
areas, they have been measured in open waters, e.g., stable platforms
located on shoals in the Atlantic Ocean and the Gulf of Mexico.
Measurements of sea level changes with precise surveying instru-
ments have revealed tidal components with periods greater than
those normally perceptible by human, mechanical, or electronic
means. A tautly anchored spar buoy has been used as an experi-
mental visual staff in the Gulf of Mexico. However, inherent
problems due to wind and current drag preclude the use of this
method in place of more precise measuring equipment. A variety
of glass capillary tubes has been used to measure tides in private
research projects.

The importance of tides and currents to the mariner cannot be
overemphasized. In areas where these factors exert their greatest
influences, ship’s officers should familiarize themselves with out-
standing oceanographic factors. Many ships have suffered damage
ranging from slight to heavy or have become total losses owing
to a lack of tidal knowledge. Good seamanship demands use of
up-to-date nautical charts and publications together with full com-
prehension of their meaning.

One might think of the great ocean currents as being nothing
more than great rivers of the sea since their lateral limits are rela-
tively well defined. However, general ocean currents have neither
beginning nor end and thus result in the formation of clockwise
patterns in Northern Hemisphere oceans and counterclockwise pat-
terns in Southern Hemisphere oceans. General ocean currents are
the most important controllers of climatic conditions over land areas,
and have become important factors in meteorological studies.
Thermal and chemical concentrate changes in seawater are brought
about by freezing, evaporation, heating, and precipitation; the first
two factors increase the density of sea water, while the last two
decrease its density.

Theoretically then, one would expect the more dense polar
waters to sink and replace the less dense equatorial waters which
would flow poleward on the ocean surface. This condition would
produce simplified ocean current patterns which could readily be
understood and predicted. However, the actual current pattern is
made complicated by the effects of wind and rotation of the earth
(Coriolis force). Ocean currents are the dynamic result of unbal-
anced physical conditions tending to right themselves in the direction
of equalization.

Navigational safety took a great turn after the sinking of the
TITANIC in 1912. Formation of the International Ice Patrol led
to collection of varied data such as temperature, current, ice drift,
and bathymetry in the North Atlantic. Benefits derived from the
many seasons that the Patrol has operated include the prediction of
ice limits and conditions not only for the safety of ships transiting
regular shipping lanes in higher latitudes but also the ice-transits of
supply and research ships in extreme latitudes. Since the greater
part of an iceberg or floe is submerged, the ocean currents are a
greater determinant of direction and speed of drift than is the wind
influence. Oceanographic ice forecasts have led to many successful
convoy transits through icebound waters and have undoubtedly
reduced ship damage and loss.

This aerial photograph shows the ‘'calving"’ of icebergs
from the Antarctic ice sheet

Project Polynya conducted at Thule Harbor in Greenland has
been successful in producing artificial water currents at dockside.
Compressed air is distributed through the water from perforated
tubes lying on the harbor floor. Lengthening the shipping season
by direct application of dynamic principles is of primary concern in
this experiment.

Many harbors, being located near or in river mouths, are
subject to heavy silting due to currents. Silting rates for dredging
purposes have been determined by oceanographic research projects
in many areas. Knowledge of silting, erosion, and current rates is
indispensable for the planning of breakwaters, piers, lighthouses, and
also various types of oceanic construction.

Currents are an important factor in the distribution of bio-
logical organisms, determining the quantity and area of shell and egg
deposition. Transportation of nutrients and plankton vital to the
majority of life in the sea is provided by currents, thus determining
which areas of the oceans will become commercially important.
Marine fouling growth rates also are regulated by the distribution
of these nutrients as well as by physical properties of sea water.

General surface current charts and some detailed information
concerning local currents are provided in the Sailing Directions pub-
lished by the Oceanographic Office. These publications also provide
corange and cotidal line charts, i.e., charts which show lines con-
necting points having equal heights and times, respectively, of tides
in any given area. All recent editions of Sailing Directions include a
rather comprehensive section on the subject of general oceanography
for the particular area covered by the publication.

SEA AND SWELL

Of all oceanographic parameters, probably the most familiar to
sailors are sea and swell. According to definition, ‘‘sea’’ is composed
of waves generated by local winds. These waves are relatively short
in period and generally advance in the same direction as the wind.
“Swell’’ consists of ocean waves which have advanced beyond the
area of their generation.

Neither of these parameters serves the mariner beneficially,
rather they are adverse under most conditions. Sea and swell
coupled with intense cyclonic winds are definitely a great cause of
severe damage to shipping and loss of life. Fire and explosion
damage, sometimes attributed to direct effects of rough seas, also
have been correlated with atmospheric thermal conditions. Other
forms of meteorological disturbances such as hurricanes and water-
spouts are responsible for more damage incurred by ships at sea.

Waterspout damage is caused by a combination of tornadic
winds, suddenly reduced atmospheric pressure, and the deluge of
water sometimes released. Although the funnel of a normal water-
spout is composed of small water droplets formed by condensation
from cooling due to atmospheric pressure reduction, it is believed
that the more severe storm spouts carry considerable quantities of
sea water up to fair heights.

Lack of knowledge concerning the structure and properties of
waves and swell has been-an obstacle to theoretical and practical
applications of oceanography in the reduction of ship motions, a
desirable goal for all oceangoing vessels. Benefits to be derived
from such studies include improvement of speed, cargo safety, pas-
senger comfort, and reduction of ship damage.

Each vessel will respond more violently to waves of certain
periods, since this is a function of ship dimensions and center of
gravity. When a ship encounters such wave conditions there is
little that can be done to alleviate the magnitude of the stress and
strain forces, outside of attempting to ease the ship’s headway by
speed reduction, by change of course, or by altering trim. Structural
failures are apt to occur and, theoretically, ships have disappeared
without a trace under such circumstances, especially when carrying
extremely light or heavy cargoes while subject to pounding.

The first organized attempts at overcoming hazardous ocean
conditions were made by Maury in 1847 by gathering ship logs and
collecting oceanographic data. With assemblage of these data in
the forms of wind and current charts, the mariner was provided with
the means to avoid hazardous areas and to follow best tracks.

By 1961, at least several commercial companies and two govern-
ment units predicted best routes for the mariner. Experimental
routing has been conducted by the Oceanographic Office since 1956.
Depending on the individual ship requirements, the predictors aim
is to forecast either a least-time track, a maximum passenger comfort
track, a maximum cargo safety track, or any combination of these

OCEANOGRAPHY AND THE MARINER

Care is taken to avoid crossing of or sailing opposite
standard tracks. Shipmasters and commands have written many
comments regarding the ship routing programs. Besides the ad-
vantages of more economical operations and time savings, routing
programs reduce worry on the part of the shipmaster by alerting
him to forthcoming weather conditions. These programs also enable
greater utilization of new crews.

Natural conditions and artificial methods exist for abating or
somewhat calming the high seas. The most important natural
abater is ice, which occurs only in higher latitudes. Hail, snow, and
seaweed also exert calming effects, though they are considerably less
than the effect of ice. Artificial methods of reducing wave height
include breakwaters and the distribution of storm oil.

By measurement and analysis, oceanographers have shown the
sea surface to be acomplex composed of many different wave trains
occurring simultaneously. Each of these trains has its own period,
height, length, and direction of travel. Waves are measured from
stationary platforms and along shores by means of electronic wave-
staffs, pressure diaphragms, radar, and with instruments similar to
tide gages. They can be measured from moving craft with sonic
surface scanners, inverted echo sounders, and with accelerometer
devices. Floating electronic wavestaffs and expendable accelerom-
eter devices have been used successfully in open-ocean measurement
of waves.

conditions.

PHYSICAL PROPERTIES

Until about a decade ago, physical oceanography was probably
one of the least understood science subjects. In general, its results
found most practical application in the solution of marine fisheries
problems. Therefore it was considered more of an adjunct to the
field of marine biology, and, for this reason, most of the earliest
advanced studies of physical oceanography stemmed from complex
investigations made by investigators more interested in the general
approach (classic oceanography). Specialized investigators were
interested in the geographic approach. More recently, physical
oceanography has evolved an aggregation of highly trained research-
ers, each a specialist in his own right. Because of the existence of
several similarities between oceanic and atmospheric problems, many
meteorologists have been inducted into and successfully adapted to
the field.

Some of the more common physical properties of sea water are
temperature, salinity, density, pressure, ice, water color, transpar-
ency, and sound velocity. Less commonly known or determined ones
are specific heat, osmotic pressure, eddy viscosity, electrical conduc-
tivity, etc. Development of instrumentation for use in securing
measurements of the most common of these parameters has been
fairly rapid in recent years. The least common parameters are
usually determined by complex mathematical calculation and formu-
lation from one of a combination of the common parameters.

Much greater improvement in future instrumentation will be
necessary before the study of physical oceanography can parallel the
pace of present-day meteorology. Original instrumentation, instru-
mentation in numbers, and the feasible means of utilizing this
instrumentation are needed before we will be capable of attaining
our desired degree of worldwide synoptic observations.

Surface temperatures are obtained by the simple means of a
scientific mercury thermometer, the bulb of which is immersed in a
small attached container filled with sea water by submersion. Some
injection temperature values are reported as surface values. How-
ever, since they are taken at various depths at engineroom intakes
on ships, submarines, and offshore structures, they are unreliable for
precise oceanographic work. Continuous recording of temperature
for industrial research purposes is made with a thermograph.

The present common method of obtaining deep sea temperature
data involves the use of paired specially constructed reversing ther-
mometers, one protected by enclosing it in a glass sheath and the
other unprotected. Through comparison of the two temperature
readings obtained after reversing the thermometers and application
of correction factors, one can readily determine the water tempera-
ture and correct depth at which the thermometers were actuated.
A bathythermogram is a record made with an instrument known as
a bathythermograph and consists of a continuous trace of tempera-
ture plotted against depth at a given location. BT’s are collected
by naval and merchant vessels the world over and forwarded to the
Oceanographic Office for processing, use, and distribution. Hundreds

of thousands have been collected and processed to date. However,
processing this type of data is very time-consuming. Serial vertical
temperature distribution values are also obtained by electronic
methods incorporating parallel-connected electrical resistors, the
values of which are directly dependent on water temperatures, e.g.,
the thermistor chain and the thermocline recorder. The latter is an
improvement of the former in that the quantity of measurable resist-
ance change is greater. Resistance thermometers operate on this
same principle, however, they are not as sensitive as the thermistor
chain or thermocline recorder.

Water temperatures have been obtained in the past with insulated
water bottles to depths of several hundred yards. Owing to the large
margin of error in this method, the reversing thermometer or ther-
mistor methods are preferred when measuring deep water temperatures.

On the basis of considerable temperature data, charts have been
constructed to indicate survival rates for immersed bodies.

Cargo temperature is dependent on temperature of the air and
sea water, particularly in instances of bulk liquids or highly porous
materials; passenger comfort is also to a degree dependent on air
temperature and thus indirectly on sea water temperature. Cargoes
with temperature values less than the dewpoint of the outside air
will suffer condensation damage if ventilated when such conditions
exist. In some cases, sea water temperature can either reduce endo-
thermic cargo reactions or, conversely, it can cause buildup of cargo
temperature. Cold spray or wash from stormy seas can reduce
weather deck temperaturés sufficiently to produce condensation
within warm holds, thus abetting deterioration and waste of cargo.

Salinity of sea water is based on the quantity of dissolved salts
contained in a given amount of sea water after certain chemical
changes have taken place. Direct determination of these values by
recommended procedure is rarely carried out at the present time,
because the method is too difficult and slow. Sea water composition
adheres to the Law of Constant Proportions, i.e., the total amount
of the major constituents in any two samples is always present in
the same relative proportions. Since chloride ions constitute more
than half of the total amount of chemicals in sea water, salinity
values can be empirically related to chlorinity once the latter has
been established by chemical means. A relationship also exists
between salinity and electrical conductivity values of sea water.
Based on this knowledge, an extremely complicated electronic
instrument has been developed and proven suitable for rapid pro-
cessing of salinity samples. However, the technical nature and
prohibitive cost of these machines have limited their distribution.
A smaller portable underwater version of this apparatus, the con-
ductivity cell, has been successfully used in many regional surveys.
By correlating water temperature and electrical conductivity values,
this instrument automatically furnishes the observer with immediate
values of salinity.

Temperature values go hand-in-hand with salinity values to
determine the extent and growth rate of marine fouling in all areas
by controlling the environment in which the organisms must live.
Certain combinations of temperature and salinity values can be
highly conducive to corrosion of any type of structure. In particular,
equipment constantly bathed in sea water is susceptible to adverse
corrosive, contractive, or expansive damage. Condenser failure is
usually due to corrosion of tubes and ferrules.

Temperature and salinity also combine with pressure effects to
form the density values of sea water—values so important in caleu-
lating loadlines for freshwater to salt water transits and vice versa.

Many cases of improper stowage have resulted in loss at sea or
serious listing after freshwater to salt water transits. Improper dis-
tribution of bulk cargo coupled with low-temperature conditions
have proven disastrous for ships in rough waters. Extra buoyancy
provided by empty fore and aft tanks and brittleness of metal pro-
duced by low temperatures have promoted cracking or complete
severance of tankers.

Density of sea water is an important factor of economy in
evaporator operation; the lower the density, the less the amount of
fuel that is required. Density of surface water can be measured
directly with a hydrometer. However, since it increases with rise
in pressure and salinity and decreases with rise of temperature, it
can also be determined directly for water beneath the surface from
these latter values by use of oceanographic tables.

Pressure can be used to measure sea and swell heights and periods.

Currently, importance of the least investigated physical proper-
ties of sea water to the mariner is little understood. At best, the

OCEANOGRAPHY AND THE MARINER

benefit to be derived from these is of indirect consequence in view of
the fact that the properties themselves are not too well understood.
Furthermore, as stated above, they are usually determined by com-
plex mathematical calculations or by tedious laboratory experiments
which always contain an inherent degree of error. If any of these
least commonly known properties can be considered to have the
slightest value to the mariner, it would definitely be indirect as
seen in application of the values of specific heat or heat fusion in
basic experimentation for ice-forecasting purposes. Another indirect
application is the use of thermal expansion in determination of
general ocean circulation.

Freezing of sea water takes place at lower temperatures than
does freezing of freshwater, owing to the presence of dissolved salts
which tend to depress the freezing point.

An ice-forecasting program has been pursued at the Oceano-
graphic Office since 1952. Depending on requirements, either short-
or long-range forecasts can be prepared, ranging in period from 5 to
30 days. The bases for these forecasts are extensive air reconnais-
sance missions and comprehensive reports of shore observers. Nu-
merous favorable post-operative comments have been received from
shipmasters directly concerned.

Water color may be caused by a variety of factors: sky cover,
water depth, and particle content of water to cite a few. Particle
content may consist of sediments, nutrients, or plant and animal
matter whether dead or alive. As observed from shore or on board
a vessel, water color may range from deep blue to intense green. In
some special cases, water color may appear brown or red, especially
in coastal waters. Open ocean water with a high degree of trans-
parency usually assumes a deep blue color owing to scattering of
light on water molecules or fine suspended particles. Greens occur
in a variety of hues ranging from yellow-green to blue-green, the
degree of tinting or shading being dependent upon the amount of
suspended material such as algae or sediment particles. Extraor-
dinary populations of minute plants and animals near the surface
can be responsible for red or brown water. Color variations occur
more frequently in coastal waters owing to addition of sediments
and nutrients by river effluent or by disturbance of bottom sediments
by wave action in shallow waters.

Transparency of sea water is closely linked with the distribution
of suspended particles and concentration of dissolved colored sub-
stances. High values of transparency have afforded many mariners
with a large margin of safety while navigating shallow hazardous
waters. Rate of progress during salvage work is highly dependent
on the amount of light penetrating the water. Little information is
available with regard to depths at which animal life in the oceans
can see, nevertheless, the distribution and color of various organisms,
including fishes, are apparently also related to the amount of light
at depths. The depths to which electromagnetic waves of various
lengths, especially heat and light rays, will penetrate are directly
dependent on this suspended or dissolved matter. Most of the radi-
ant energy received at the sea surface is absorbed or reflected in the
form of heat, thus becoming the basis for the study of the heat budget
of the sea. The temperature and vapor pressure at the interface
created by the sea surface and atmosphere play an important role in
determining the rate of heat exchange between the two. Extent of
cloud cover controls the amount of radiation gained or lost by the
sea. The rate at which the downward traveling radiation decreases
in water is determined by the “‘extinction coefficient”. This coeffi-
cient is of concern to the oceanographer in that it can be used to
calculate depths to which visible waves will penetrate. Measure-
ments of extinction coefficients are rare.

SOUND

Oceanographic research has considerably increased man’s under-
standing of sound in the sea, although many aspects of underwater
sound transmission remain to be investigated before full appreciation
of its use can be made.

It has been shown that sound velocity is dependent on values of
density and elasticity. Density, as stated above, can be measured
directly or determined by use of tables when values of temperature,
salinity and pressure are known. Elasticity is determined mainly
by pressure. Sownd intensity, or the sound pressure level at any
point, is dependent on the sound generating source and properties
of the medium.

Sound waves propagated in a homogeneous medium radiate out-

ward from the source in all directions. This spreading of the energy
is known as divergence and will result in reduction of the sound
intensity at any distant point as compared with the initial intensity
at the source, whether the distance travelled is from source to target
(ping) or from target to source (echo). Thus the greater the range,
the smaller the amount of energy imparted to a target surface or
returned as an echo.

Other factors contributing to range limitations are reflection
loss, reverberation, refraction, and absorption. Reflection occurs
whenever sound waves are obstructed by solid objects or sharp dis-
continuities, such as the hulls of ships, the ocean floor, and the sea
surface. If these surfaces are rough, sound energy will be scattered
in all directions. That part which is returned to the location of the
original sound source, thereby interfering with echo recognition, is
known as reverberation. The bottom effects are generally important
enough to be regarded as the controlling factor in echo ranging
whenever the depth of water is less than about 100 fathoms. At
short ranges (less than 1,000 yards), reverberation from the surface
forms the principal background in echo ranging and is usually the
controlling factor in the detection of small objects whenever the sea
is not calm. Suspended particles and bubbles also cause reverbera-
tion by scattering the sound energy as secondary wavelets and

SPREADING

REFRACTION
ULL LLL LLL

UMtirsrrerreerreenrrssibns

Factors affecting sound paths in water

reflecting part of it back to the sound source. Refraction is the
bending of sound rays owing to changes of velocity caused by varia-
tions of density in the transmission media. These variations occur
between water masses having different physical or chemical properties
and between dissimilar mediums. Bending of a sound beam always
takes place in the direction where velocity is lower. Absorption fur-
ther reduces ping and echo intensities when part of the sound energy
is converted to heat energy by friction caused by water viscosity or
by vibration of suspended particles such as bubbles.

Echo intensity can also be attenuated by soft forms of biological
growth ona target. Echo interpretation is further complicated by
surrounding sources of extraneous noises. These noises are known
as ambient noises and are classed in four categories according to their
source, viz., thermal, biologic, water, and artificial or man made.
Thermal noise is created by increased molecular activity of water
with increasing temperature and is characteristically more intense at
higher frequencies. Biologic noise emanates from numerous organ-
isms, primarily fish and shrimp. Water noise is, of course, produced
by wave and current action. Artificial noise originates from several
sources such as ship machinery, bow waves, wake, or perhaps shore-
based noise.

Whatever its source, ambient noise will tend to mask the echo
signal and, as a result, reduce the maximum range at which an
object may be detected or identified. In addition, when a vessel
backs down, drifts with the wind, or uses excessive engine or rudder
changes, little energy may return to the transducer because of bubble
formation around the transducer and may result in quenching.
Maintaining constant headway has been considered the best solution
for avoiding the problem of quenching.

Keeping in mind the factors which promote or deteriorate sound

OCEANOGRAPHY AND THE MARINER

propagation, we should now find it easier to comprehend the princi-
ples involved in the formation of sownd channels which exist through-
out the oceans. These channels are formed by a layer of water
having a negative (decreasing with depth) sound velocity gradient
overlying an adjacent layer having a positive sound velocity gra-
dient. In these particular circumstances, sound waves are confined
within these channels by refraction.

Discovery of the existence of such permanent sound channels in
the ocean and their ability to permit transmission of sound for great
distances led to the development of many methods of underwater
communications and navigational aids. SOFAR (Sound Fixing And
Ranging) was utilized during World War II for the purpose of loca-
ting survivors at sea. By means of triangulation, shore stations could
determine the approximate position of survivors by detecting sounds
of exploding preset depth bombs dropped into the vicinity of a
sound channel by the survivors. A variation of SOFAR, RAFOS
(SOFAR in reverse), later proved highly valuable for determining
approximate positions of vessels by use of a hydrophone lowered to
a sound channel to detect sound signals produced by known stations.
More recently, underwater methods of navigational aid have given
way to more accurate electromagnetic systems such as RAMARK
(RAdar MARK), RACON (RAdar beaCON), SHORAN (SHOrt
RAnge Navigation), HIRAN (HIgh precision shoRAN), electronic
position indicator (EPI), DECA, and RAYDIST. Inertial naviga-
tion has been of considerable value in submarine navigation.

Oceanography is likely to play an increasingly important part
in precise submarine navigation. The submarine navigator of the
future will have much use for charts depicting expected sonar
conditions based on thermal structure of the oceans, as well as charts
showing such fixed features as bottom topography, major currents,
and magnetic and gravity anomalies.

Shark impaled on SONAR dome

GEOLOGY

The greater percentage of geologic oceanography deals with the
study and analysis of nearshore and open ocean depths (bathymetry)
and sediment composition. Many other fields comprise the lot of the
ocean geologist and geographer, e.g., magnetics, gravity, seismism,
volcanism, and erosion. All involve long and costly investigation
programs, requiring numerous manhours, complex instrumentation,
ships, reinvestigation, and above all cooperation between the report-
ing mariners, investigators, and worldwide government and private
hydrographic and oceanographic offices and observatories.

The study of bathymetry is properly the lot of the hydrographic
surveyors, nevertheless, geologic oceanographers do construct numer-
ous special bathymetric charts in conjunction with bottom sediment
charts. All bathymetric charts are bound to contain a number of
obsolete soundings; constant attempts are made to revise them and
add to their worth by systematic hydrographic surveying.

Sudden shoaling also may be the result of volcanic action. In
1934, an area of discolored water with depth of 48 fathoms was
reported in the North Pacific. A volcano in this same area attained a

height of 150 feet above the sea within ten days in February 1946.
Volcanic action usually occurs along the concave sides of the great
ocean deeps, especially in the Pacific Ocean. Merchant and Naval
vessels should report all depth aberrations immediately to proper
port authorities for inclusion in the Notices to Mariners and Radio
Navigational Warnings.

Bathymetric charts have been made for most ocean areas,
however, information is very sparse in some of these. Usually only
a fraction of the total number of soundings obtained in a thorough
hydrographic survey are included in the final chart, though all are
used in its preparation. Sparse or unevenly distributed soundings
are indicative of an incomplete survey.

In deep oceanic areas, soundings taken about every half hour
or five to eight miles are sufficient for hydrographic purposes except
over the more outstanding features such as peaks and pinnacles.
Any prominent bottom feature in the ocean which can be determined
by fathometer readings can become a valuable aid to navigation if
its location is accurately determined and plotted. Proposals have
been made for the use of these prominent features as underwater
beacons for surface ship and submarine navigation and as anchoring
ground for deep water oceanographic telemetering instruments. Both
of these proposals will possibly become realities.

Importance of the geologic oceanographers work in bottom sedi-
ment and seismic studies can be seen in the development of harbor
and submarine natural resources. The construction engineer relies
heavily on geologic and geophysical surveys for determination of
bearing surfaces or bedrock depths for marine construction. The
petroleum engineer relies on sediment analysis and seismic soundings
to reveal the most probable oil-bearing strata and thus the area in
which marine drilling is most likely to be successful. Detailed
bathymetric and sediment charts can be used for selection of best
holding grounds and anchorages of vessels.

Submarine earthquake activity affects the mariner in several
ways: (1) interference with sonar operations, (2) disturbance of
biological activity, and (8) formation of so called ‘‘tidal waves”
(tsunamis). Other causes of extraneous underwater sound or motion
of this nature are volcanic activity, heavy surf, strong winds, and
landslides.

The study of magnetic anomalies, e.g., magnetic storms in rela-
tionship to radio communications and gravity surveys for the
improvement of navigational charts, properly fall into the category
of geophysics rather than geologic oceanography. However, these
subjects often require sufficient understanding by the oceanographer
for purposes of editing and incorporation in specially requested
studies. Prediction of penetrating ability and travel path of electro-
magnetic (including sonic) waves has not been too successfully
correlated with bottom sediment types. However, electrical con-
ductivity or its reciprocal, resistivity, measurements can be made
from the sea surface taking into account the varying conditions of
the stratified nearshore water, of which each layer has differing
temperature and salinity values, the saturated bottom sediments,

Part of the large variety of marine life taken off the bottom
of the ocean by an underwater dredge

OCEANOGRAPHY AND THE MARINER

the compacted and less porous buried deposits, and the bedrock.
Much work is needed in this area for the improvement of degaus-
sing techniques, sonar utilization, and minesweeping.

Marine geologists and geophysists conduct many other phases
of oceanographic research, most of which do not directly concern the
mariner. By studying the history of our planet as revealed by sedi-
mentary deposits and bottom topography, man is enabled to further
understand the history of the universe. Millions of years of erosive
activity on land have deposited unknown and untapped amounts of
mineral resources in the sea. These deposits become increasingly
important as our present natural resources are slowly exhausted.
Precise navigation, improved echo sounders, bottom photography,
acoustical probes, and long coring tubes have all aided in locating
and charting many areas having potential mineral reserves. Today,
large quantities of oil and sulphur are obtained from beneath the sea
floor. Magnesium, bromide, iodine, and a few other elements are
extracted in smaller quantities from sea water.

BIOLOGY

It has been estimated that at least a million vessels of various
sizes, and about four million men are engaged in some phase of the
marine fisheries industry. Of importance to this industry is that
phase of oceanography dealing with marine biology.

The endless search for dld and new forms of life in the oceans
has attracted freshwater biologists as well as marine biologists.
These scientists probing in the many divisions of marine biology are
constantly striving to discover and classify the numerous marine
organisms and to clarify the ecological structure of the communities
which they form. Working hand in hand, the taxonomists, ecologists,
geneticists, biochemists, physiologists, evolutionists, and students
of animal behavior are undertaking research problems which con-
tribute to our overall knowledge of the life cycle of the sea.

These scientists are attracted to the study of marine life mainly
by the unique research opportunities to be found in this field.
Animals living in a liquid world, eating and breathing in a manner
not too dissimilar to that of man but living under entirely different
environmental conditions foreign to and impossible for man, are the
basis for the never-ending research of marine biologists.

The possible variety of environmental conditions under which
the sea creatures exist are countless and include extreme variations
of temperature, pressure, salinity, light, nutrients, weather, and
currents. Of these, the distribution of vital nutrients is probably
the most important controlling factor in the ups and downs of the
commercial fishing industry.

The study of the relationships of organisms to environment is
known as Ecology. Much is known about these relationships, how-
ever, much more research regarding temporal and spatial distribution
of nutrients and animals is necessary if we are to make more extensive,
consistent, and complete charts of the ocean’s communities. For-
mulation of such charts will require large-scale international coopera-
tion. Simple observational methods of the past will not achieve
our end; prior research must be performed, particularly in the
solution of adequate technical sampling methods, both instrumental
and statistical.

The sea is considered an inexhaustible source of animal protein.
However, of the thousands upon thousands of species of animal life
contained therein, only about 300 species of fish and shellfish are
marketed by American fishermen. Sixty percent of the total annual
catch is composed of only 9 species, indicating the specialization in a
minority of what is actually available.

Much study has been conducted by biologists, physiologists,
and students of animal behavior in determining the response of
various marine organisms to applied artificial stimuli, especially
electromagnetic waves of heat, sound, and light. The nervous
system of a fish regulates its muscular response and can be controlled
by application of variable-frequency electric stimuli. Pure AC
electricity has been used successfully in whaling operations; undula-
ting current has proven efficient for capturing small fish. Fish
attracted by underwater light can be pumped aboard by suction
hoses. What new methods are awaiting discovery through basic
and applied research?

Worldwide surveys leading to complete oceanographic charts
will pave the way to better fishing methods by enabling us to predict
the times and places where fish will concentrate. They will also
provide an understanding of the ecological relationships between the

animals and the stimuli of their environment. Knowledge of prey,
predators, competitors, and diseases will provide us with the key to
increasing the number and possibly the size of fish in the sea. The
prey, being the food source of the various animals, is the most
important of the foregoing factors, but as yet little is known about
it in spite of the amount of research already performed. Little is
known regarding the distribution of plankton, i.e., organisms at the
mercy of the currents. Why are the apparent numbers and eventual
sizes of plankton in polar seas so much greater than those of plankton
in warmer seas? What determines the discrete, regular distribution
of plankton though they are at the mercy of the currents? What
determines the balance between the size and numbers of zooplankton
and phytoplankton? Open-sea waters are considered homogeneous
when compared with waters of the intertidal zone, yet plankton seem
to be more prolific in the latter environment. The phenomena of
“red tide’ in the Gulf of Mexico and “El Nino”, a warm current
counter to the Peru Coastal Current, are both only temporary
occurrences, yet each exerts a disastrous effect on the biological
communities in those areas. The “red tide’ virtually suffocates fish
by the millions, while useless organisms thrive. Beachside human
communities suffer the aftereffects of these dead fish. Though much
research has been performed on the “red tide’, no cure has been
found for the condition. ‘El Nino’’ has been studied less, but the
effects are the same with the exception that a side-effect, known as
“Callao painter”, is the production of hydrogen sulfide in sufficient
quantity to blacken the paint of entire ships. How many more
similar undesirable conditions exist unknown in the oceans?

Lower half of photo shows preventive effect of antifouling
paint applied to metal submersed for period of one year

Another important phase of marine biology which affects all
ships sailing in both fresh and saline waters is the problem of foul-
ing. Attachment, entanglement, and boring organisms and corro-
sion have long been the scourge of the mariner. Clogging of sea
chests and intake lines can lead to serious damage to other major
machinery and result in costly repairs. Fouling growth in lines can
effectively reduce heat transfer in condenser operations. Accumu-
lation of attachment fouling organisms on underwater portions of
hulls can effectively reduce ships’ speed.

Fouling also produces adverse conditions for the operation of
underwater sound equipment. All forms of marine life, whether
attached, free-swimming, or drifting reduce the efficiency of under-
water sound transmission by interfering with the normal path
of sound waves. Air bubbles entrapped by attachment fouling
organisms on sound domes and transducer plates can reduce sound
transmission by 30 percent, at the same time reducing echo intensity
by a factor of one half. The importance of such effects can be seen
in the application of sonar and fathometer equipment.

OCEANOGRAPHY AND THE MARINER

Few fouling organisms are found in fresh-water areas. For this
reason, ships transiting such water are provided with some degree of
temporary protection. Contrary to popular belief, marine fouling
organisms do not detach themselves from the hull of a ship which
enters freshwater; they are killed if they remain in it for a sufficient
period of time. Studies have shown that the layer of dead organisms
abets corrosion in some cases and delays it in others. In any event,
the layer does provide an excellent substratum for the attachment
of new organisms once the ship re-enters saline waters.

Growth and accumulation rates of fouling organisms are
dependent on seasonal distribution of environmental factors such as
temperature, salinity, sunlight, and nutrient material, all of which
control breeding rates, and consequently, egg production and spat
settlements. Through an understanding of the physiology of the
various fouling organisms, the marine biologist and chemist are able
to improve the effectiveness of fouling inhibitors.

Large ships enjoy considerable immunity from disablement by
entanglement foulers by virtue of their sheer power and size.
Smaller vessels, such as lighters and amphibians can become severely
entangled in areas where extremely dense plant growth exists.
Average size of the most troublesome entanglement foulers is only a
few feet, however, the giant kelp of the Pacific sometimes attains
lengths of several hundred feet. Growth of entanglement foulers
is most luxuriant where the substratum provides a good anchoring
ground for hold-fasts. Offshore rocky bottoms are typically good
areas of growth, especially when the nutrient supply is ample and
depths are sufficient to prevent or mitigate erosion due to excessive
wave conditions. All shallow inshore areas, regardless of the nature
of the substrata, are poor areas for growth if the bottom is subject
to continual adverse effects of high waves or strong currents. Most
of these entanglement foulers, so undesirable from the mariner’s
viewpoint, have been converted into edible forms, especially in
countries such as Japan.

One remaining aspect of the ocean included in the field of
marine biology is bioluminescence. Thousands of species of plant
and animal life possess light-bearing or light-producing organs. The
smallest of these forms of life, when disturbed within the water, can
produce intense concentrations of light. Depending on the organism,
involved, these light displays are classified as either glowing-ball,
sheet, or spark-type.

Bioluminescence occurs most frequently in warmer surface
water, but may be considerable under favorable conditions in cold
northern waters. Several occurrences of bioluminescent displays in
warm tropical waters have been attributed by shipmasters to high-
frequency radiation from radar equipment. Lack of research along
these lines prevents authentication of such reports. Of benefit to the
mariner is the outlining of shoals and reefs by breaking waves
containing these organisms. Much research on the physiology and
chemistry of bioluminescence has been performed for the purpose of
seeking-out uses for such manifestations. However, no valuable
application has been found to date other than as a source of “cold
light’”’. Moistened powder produced from the bodies of luminescent
marine animals served the Japanese as 2 wartime substitute for
artificial light for reading messages at night. Fishermen of Portugal
enhance the quality of bait by rubbing luminous exudate on it while
fishermen of the Banda Islands use the luminous organ of a fish as
an effective bait.

Color, transparency, and chemistry of sea water properly belong
to the regime of the physical oceanographer. However, since
these factors are of importance in understanding the relation between
plants and animals and their marine habitat, they are also measured
by the marine biologist during the course of his research.

THE FUTURE

Oceanography has had but a short life span in the United States.
Foreign scholars, however, have been actively engaged in the fields
of marine science for a considerable number of years. Through
their studies, we have come to understand some of the vast ocean’s
mysteries. Their research has given sufficient impetus to the
American school to enable it to grow from the handful of eight lab-
oratories in 1920 to the present number of about seventy. It would
be difficult, indeed, to predict the future course of marine sciences.
At best, the prediction will be inaccurate owing to the very nature
of research itself. Research and discovery in any field of scientific

pursuit must necessarily be limited to the ability, ambition, and
imagination of the individual scientist.

Due to the fact that oceanography is not a true science, but
actually entails a combination of all earth sciences, the promotion of
marine study has suffered greatly in the past if compared to other
fields. One may ask, “‘Why do we want to know about the ocean?”
Depending on one’s views, this question may be answered in any
number of ways. First of all, we want to study the ocean simply
because it is there and unknown. Its challenge is equal in our eyes
to the space problem; the adventuresome spirit of man does not rest
until he has discovered and understood that which is strange and
unfamiliar to him. Theoretically, all life including man arose from
the sea, yet many of us look upon it with a feeling of awe. We also
realize that the oceans hold the key to our past, present and future
in that our unknown history is locked securely in its mysterious
depths. By prying these secrets from the oceans, we can provide
ourselves with a great deal of knowledge concerning the ‘‘whys’’ and
“wherefores” of the oceans. Why do they exist? How long have
they existed? What purpose do they serve? How can we further
our utilization of them? On and on, many more similar questions
evolve in our minds. Slowly but surely with both good and bad
work, in difficult and trying situations, we will eventually force the
oceans to reveal its mysteries. To be sure, we can learn much of
the history of our planet by probing into space and going back in
time, but the best way would be to delve into the oceans on our
own earth. Through the ability to read the records which still lie
in the sediments, rocks, and chemistry of sea water, we can learn
much about the history of earth and of life itself.

Oceanography consists of much more than observing waves
from the shore or collecting shells on the beach. For years, man
has been limited to indirect methods of observing a small fraction of
what lies beneath the opaque mantle of the sea surface. Develop-
ment of skindiving equipment has enabled man to descend a short
distance into his former element to observe first hand the environ-
ment which seems so remote to him now. Perhaps he is looking for
the answer to what kind of life the fish lives, or could it in truth be
an evolutionary inclination to return to the protective bosom of the
sea? Man has surely exposed himself to numerous handicaps by
emerging from the sea and lives without hope of ever completely
conquering all the problems presented by his new environment.
New avenues of ocean exploration have been afforded with develop-
ment of underwater television and the bathyscaph. With the latter,
man has almost penetrated the full seven miles to the known
ultimate deeps. These research apparatuses have been in existence
for only a few years. Who can say what as yet undiscovered
apparatus lies in the future to serve man in his quest to better his
knowledge of the ocean?

Our present knowledge and theories are amazing, but new-found
answers in the future will be greater. We must explore and sample
many new regions—the plains, ridges, fissures, trenches, and shelves
which comprise the ocean floor. Revelation of ancient earth history
will lead to better understanding of our environment and enable us
to decipher the history of the planets. It is necessary and vital that
we study the waters and animal life in the ocean in order to solve
the origin and evolution of life on earth. We must find and study
the undersea rivers which have flow rates a thousands times as great
as the largest land rivers. We must find the way to determine the
number of fish in the sea and how to control their quantity, if we
are to increase their numbers. The welfare of many of the world’s
people is heavily dependent on the harvest from the sea. These and
many other problems of the economic and defense requirements of
society can be solved only by studying the oceans and the world
above and beneath them.

A third of all sunlight striking earth is used for evaporation
of sea water and a goodly portion of the remaining sunlight is absorbed
as heat by the water or reflected into the atmosphere. If we can
learn to control the distribution of this heat budget, understand the
storage of gas in the sea, and complete our knowledge of the air-sea
boundary and deep mixing processes, then we can possibly predict
and regulate climatic conditions.

Electronically-equipped, nuclear and diesel propelled sub-
marines have collected a considerable amount of oceanographic
data which have intensified our knowledge of the behavior of the
Arctie oceanic ice cover and have served as platforms for testing and
developing oceanographic instruments for the future. More stable
platforms such as the ARGUS ISLAND near Bermuda are excellent

OCEANOGRAPHY AND THE MARINER

observation points for detailed information at given locations. A tube-
shaped floating instrument platform (FLIP) is a novel vessel con-
taining a free-floating manned laboratory for the measurement of
parameters at various locations as it drifts with the currents. Like
the rocket which is the basic vehicle for space study, research ships
and platforms are the basic vehicles of the oceanographer. Combina-
tions of ships, aircraft, and towers at predetermined locations and in
sufficient numbers facilitate temporal as well as spatial observations
of the ocean environs.

In the future, we must strive to maintain constant rates of data
acquisition and instrument improvement. Complete gravity,
magnetic, current, physical property, biologic, and geologic surveys
will greatly enhance our knowledge and insure safety of surface and
undersea precision navigation.

The importance of domestic and international cooperation can-
not be overstressed. Though duplication of basic research is not

— —
——_ |
————

particularly harmful, much of the unnecessary duplication in basic
and applied research can be avoided by fostering good international
relations. We must continue to collect and disseminate information
gained in future oceanographic research through various agencies for
application and use in underdeveloped areas of the world.

One of the ultimate goals of the Oceanographic Office is to
provide worldwide oceanographic coverage comparable to that al-
ready provided by charts, Sailing Directions, and other navigation
aids. To this end, it encourages and will assist other U.S. agencies
in collecting additional data and in compiling all available infor-
mation including that obtained through liaison and exchange with
foreign sources.

It has long been hoped that the Oceanographic Office will eventu-
ally serve the same purpose for oceanography as it now does for
hydrography, as the Weather Bureau does for meteorology, and as
NASA does in the space program.

nis

“
iD etmmmaeTeRRET wy

aed,

USNS JAMES M. GILLISS (AGOR-4)—One of the principal Oceanographic
Research ships under technical control of the Oceanographer of the Navy.

TREASURE FROM THE SEA

J. W. Chanslor
Maritime Safety Division
U.S. Naval Oceanographic Office

The sea is “water” only in the sense that water is the dominant
substance present. Actually, it is a solution of gases and salts in
addition to vast numbers of living organisms, the majority of which
are quite minute. Since the beginning, materials in solution and in
suspension, carried by rivers, have been deposited in the oceans and
seas of the world. It is to the wealth related directly and indirectly
to these materials that this article is directed, rather than pirate
treasure.

CUBIC MILE

Few consequential resources ashore are so little developed as
those of the sea. Taken as a whole, the quantities of materials avail-
able from the sea are so gigantic that they can hardly be computed.
Listed are a few of the more abundant compounds that are present
in a single cubic mile of sea water. A cubic mile is a measure of
enormous size and one rather difficult to visualize. It may be of
some help, however, to point out that a body of water 26 miles long,
10 miles wide, and 3.3 fathoms deep would contain approximately
one cubic mile.

Approximate amount of minerals in one cubie mile of sea water

Sodium Chloride (common salt)............ 128,000,000 tons
Magnesium Chloride...................... 17,900,000 tons
Mapnesiumisulphatererererrer ee ee eee rete 7,800,000 tons
Calciumisulphateseereeereer eee rere rer re 5,900,000 tons
Potassiumisulp hate nnreee rer rete rie 4,000,000 tons
Calcium Carbonate (lime)................. 578,832 tons
Mapnesium|Bromidessrerees- ane eee 350,000 tons
IEYROTA ASE Pa obs Sh om en cot One e Cen S 300,000 tons
AS Gr OWNELUN ITN a cp reese hes eee rescue av fetes ohcvtooc crs, cueen 60,000 tons
IB OT OMe eteren ee fale iakc ras tekcitecpenr cen Seay say saseevage a seNae 21,000 tons
TORTS oe Beisel sola oe SOM er eS eee bes 6,400 tons
JEXA; SUV E Ap Gyo ch benatatota Een anc GH ease Bits eRe ee 900 tons
IGG 5 5 ciere gadlol cho.g ee OOD ore Mean 100 to 1200 tons
ESIGN Ops pb.g0 de 30 CHC T eae OO be DOS aaa 50 to 350 tons
Rulbidiuimmerteectaryessaegscre eisiee oh seis 2s 200 tons
Sil erin seein: ty sracyee Ee euce oye eieunersie zen up to 45 tons
Copper, Lead, Manganese, Zinc............ 10 to 30 tons
(COG -Gdnegsend qascsa a nesoen Soae hee aera up to 25 tons
WTR Oa occ cd seu cee apna Gace aera eeaeee etre 7 tons

In the above table, the first five items show what great quantities
of minerals can be extracted from sea water. With the exception
of sodium chloride, however, these minerals still exist in dilute
amounts compared with the medium in which they are suspended.
Nevertheless, it has been possible to extract some of these products,
such as sodium chloride, magnesium, and bromine from the sea.
Other minerals, such as potassium and iodine, can be obtained with
less expense from terrestrial salt deposits. These deposits of salt are,
of course, the remains of ancient seas. Consequently, when their
stocks are exhausted, we shall have to turn directly to the abundant
seas.

MINING THE SEA

It should not seem strange to consider the sea as a vast mineral
mine. For, our oceanic waters contain more minerals than have
ever been mined by man.

On land, when minerals are taken from mines, they are not re-
placed. And, as this ore is used up, industry is forced to use lower
and lower grades, making extraction more difficult and expensive.

Such, however, is not the case with our seas. For, as previously
mentioned, the sea is a great reservoir constantly receiving the pro-
ducts of erosion, decay, and runoff. Although in great dilution, here
is a source of almost limitless amounts of all the minerals and metals
we use.

Mining the endless resources of the sea is not nebulous hope, but
rather a growing actuality, with continued expansion—the frontier
of chemists.

SALT.—The most common product from the sea is salt or sodium
chloride. Every gallon of sea water contains just over a quarter
of a pound of common salt. Or, stated differently, each cubic mile
of sea water contains enough salt to supply the world’s needs for nine
years. Each year millions of tons are mined in places like San Fran-
cisco Bay, where sea water is trapped in shallow ponds and evaporated
by solar heat. The world uses some 35,000,000 tons of salt each year,
but only a comparatively small amount of this comes directly from the
sea. Salt mined underground such as in Kansas, Michigan, Ohio,
etc., is obtained from brine wells precipitated by ancient seas. Some
of these deposits, 350,000,000 years old, are occasionally 1,000 feet
thick and a mile or more below the present surface of the earth.

Salt is a prerequisite to good health, as well as a preservative
and condiment. Some of the earliest trade routes of the world were
established for the desire of this “luxury.’”’ When man’s diet con-
sisted of uncooked food, the fresh meat he consumed provided his
required salt. But, when he began to boil his food, a considerable
amount of the salt was lost. History does not clearly state when
man first began to gather salt from the sea, but records do indicate
that the Chinese obtained it prior to 1,000 B. C. by evaporation.

Upon the simple evaporation of sea water, the mixture of salts
that remains is not at all like the table salt to which we are ac-
customed. Sodium chloride has a brackish but not bitter taste. On
the other hand, calcium and magnesium salts are very bitter and
hence the higher their content in common salt, the more bitter its
taste. In addition to being quite bitter, calcium and magnesium
salts are highly hygroscopic, and salt in which their contents are
high is normally wet, refusing to “run.” Several different grades
of edible salt are manufactured, all predominately sodium chloride
but none pure sodium chloride. Various procedures are undertaken
during evaporation, giving different degrees of purification. Also,
other chemicals are added for special purposes.

MAGNESIUM.—The most spectacular treasure from the sea
is perhaps magnesium. The Dow Chemical Company began the
manufacture of magnesium from sea water at Freeport, Texas in
January 1941. This was the first time a metal had been produced
in commercial quantities from sea water. There are currently four
companies in the United States extracting magnesium hydroxide
from the sea.

To make metallic magnesium from sea water, it is necessary
to separate the magnesium from the sea water. This is accomplished
by treating the sea water with lime, precipitating magnesium as
“Milk of Magnesia.” The milk of magnesia is treated with hydro-
chloric acid and evaporated to dryness as magnesium chloride. This
salt is put through electrolytic cells where the electric current turns
the compounds into metallic magnesium. In a million pounds of sea
water there are approximately 1,000 pounds of magnesium.

Had it not been for World War II, the magnesium in the sea
might well have remained there. But, with the war came great
demands for metallic magnesium for use in incendiary bombs, flares,
ete. This new and sudden demand ran into millions of pounds per
year. A very significant contribution to winning the war can be
attributed to sea water magnesium, and the ability of the United
States to master conversion problems before its enemies did.

BROMINE.—Of the many elements present in sea water, the
first to be recovered systematically was bromine. Unlike many
products from the sea, there has long been a demand for bromine
compounds due to their sedative properties. They are also used
in photography and in the manufacture of certain dyes. Bromine
was formerly extracted from the ash of burned seaweed. Later it
was obtained from brine or salt deposits of ancient seas. The tech-
nieal experience gained by the Dow Chemical Company in the ex-
traction of bromine from brine wells, was of great value when the
demand for this product exceeded the supply.

During the 1920’s, the General Motors Corporation, while trying
to improve gasoline for use in more powerful internal combustion en-
gines, discovered that tetraethy] lead added to gasoline allowed much
higher compression ratios to be obtained and prevented “knocking.”

TREASURE FROM THE SEA

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10

TREASURE FROM THE SEA

This metallic lead, however, tended to build up on valves and exhaust
parts of the engine and a detergent was required to be mixed with
the lead for removal purposes. The first solvent used was a com-
pound of iodine, but it was soon apparent that iodine could not be
produced in the required quantities. It was found, however, that
bromine was equally effective in preventing lead build up. Anti-
knock gasoline was of far reaching importance and even with brine
well production of bromine, it became apparent that the demand
would exceed maximum production. From the inexhaustible sea
came the answer, for bromine exists in solution at the rate of 68
pounds per million pounds of sea water.

The procedure for extracting bromine from sea water is, theo-
retically, not difficult. Sea water is treated with sulphuric acid and
then chlorine is passed into it. The bromine is then free in solution,
and air is blown through the sea water carrying off the bromine
as vapor. This vapor is then absorbed by an alkaline solution, and
from this bromine can be recovered as required.

Approximately half of the bromine currently used in the United
States comes from the sea. Twenty cubic feet of sea water is pro-
cessed to obtain the bromine required for each gallon of leaded gaso-
line. To give some idea of the ability of the inexhaustible sea as
a source for bromine—if all the bromine now used in the United
States each year for gasoline came from the sea, one cubic mile of
sea water would last two years.

SULPHUR.—Sulphur deposits are basically salt pillars that
were thrust upwards from ancient sedimentary beds. As oxygen
and other elements were expanded the sulphur content remained.
In the more productive deposits, the domes are capped with lime-
stone, tending to seal them off. These sulphur deposits, however,
are rare, with less than ten percent of the 250 salt domes so far
discovered in the United States, suitable for commercial recovery.
Of the twenty successfully mined domes, eight are now exhausted.
And, as virtually all known salt domes within the proximity of
Texas and Louisiana have been examined for sulphur it is improb-
able that many, if any, new profitable sources ashore will be found.
Consequently, our need to again turn to the sea for supply, becomes
more apparent.

As a result of the constant search for new mineral reserves,
in June 1960 the world’s first offshore sulphur mine began operation.
Known as the Grande Isle Project, it is located in approximately
43 feet of water and seven miles off the coast of Louisiana. The
platform is the largest steel structure to ever be erected in the
ocean. This sulphur deposit is the third largest known in the United
States, varying from 220 to 425 feet in thickness and covering several
hundred acres.

The operation of a sulphur well whether drilled at sea or ashore
is basically the same. That is, hot water is pumped down to melt
the sulphur, which is then aerated with compressed air and forced
to the surface.

At the above offshore site, wells are drilled directionally i.e.,
laterally from the surface. Using this process, it is possible to drill
and operate over 100 wells from the one platform.

Coupled with a mining venture of this type is the hazard of
“subsidence”. The removal of thesulphur weakens the rock structure
sufficiently to cause collapse. As the upper sediments offer but
little resistance, the ocean bottom subsides. Such will eventually
be the case at the Grande Isle wells.

Sulphur was first commercially produced in Sicily during the
fifteenth century. But, the world did not begin its quest for the
product until 1735, when a process was developed to manufacture
sulphuric acid. Four-fifths of allsulphur now mined is utilized for
the manufacture of sulphuric acid. Today, this indispensable item
is used in the production of such items as drugs, detergents, rubber,
paper, petroleum and many others.

OIL.—The earliest use of oil is rather obscure, but it is known
that King Nebuchadnezzar used asphalt to surface the streets and
build the walls of ancient Babylon. The Assyrians and Persians
also used asphalt as a building material and ancient Egyptians
utilized pitch in the coating of mummies.

When the Jesuit missionaries came to North America they
found Indians using oil, scooped up from surface pools, as a fuel and
also as a medicine. The famed scout and frontiersman Kit Carson
collected oil from seepage pools in Wyoming and sold it as axle
grease, to pioneers.

11

Although oil was produced in Romania and Canada in 1857, it is
usually agreed that the beginning of the industry on a large scale
was in 1859 when Edwin L. Drake drilled his famous well near Titus-
ville, Pennsylvania. Commercial production of oil then rapidly spread
throughout the world.

The modern quest for oil is reminiscent of the old gold rushes,
with industry looking for “black gold” under the sea instead of
“yellow gold” in the California hills.

With the increasing lack of new oil prospects ashore, industry
began to look to the offshore tidelands as a source, and on 6 October
1937 the first offshore oil well in the Gulf of Mexico was “spudded
in”. This well is located approximately a mile off the coast of
Cameron, Louisiana and gauged some 22% barrels an hour, starting
the ever growing “forest” of platforms and derricks now located
in the Gulf of Mexico. After the completion of this first well, the
platform was enlarged and ten more directional producers were
drilled. These eleven wells are still producing today, having given
a yield of over four million barrels of oil.

Increasingly within the reach of modern floating drilling equip-
ment, great reserves of petroleum hydrocarbons exist in the
submerged lands of the Gulf of Mexico and the Caribbean Sea.
Along the islands stretching from Florida to Trinidad are subsea
pinnacles and shelves that may very well hold immense prospects.
Recently 21 salt domes were identified in the deepest part of the
Gulf.

Within the Gulf of Mexico and the Caribbean Sea bounded by
the 100-fathom curve, are approximately 300 million acres. Of this
vast area, only about 35 million acres off the coast of Texas and
Louisiana have been more than sparsely explored. Hence, one of
the “world’s largest deep hunting grounds.”

As a result of offshore deposits, the largest oil boom ever is
taking place off the coast of Louisiana, with approximately 90 drill-
ing rigs in operation and at a daily drilling expenditure of over
a million dollars.

Bottom supported drilling rig.

Courtesy Union Oil Co. of California.

The Gulf of Mexico has been called the proving ground for off-
shore drilling rigs, and the year 1963 saw the development of a new
trend in such rigs. This was the change from bottom supported
units to floating drilling units. It will be years before floating units
replace bottom supported units, but the trend has started and most
all new construction is directed toward the “floaters.”

TREASURE FROM THE SEA

Actually, the first offshore production came from wells slant-
drilled from the beaches of California, out under the Pacific. As
the ocean floor of the Pacific falls away quite steeply from the
shoreline, this leaves only a narrow band offered for prospecting.
It is primarily due to this type of submarine relief that deepwater
drilling techniques have developed more rapidly on the west coast.
In fact, it was here that the first floating drilling vessels were used,
rather than in the Gulf of Mexico.

The oil industry decision to build floating drilling rigs rather
than bottom supported units is based upon several factors, some of
which are:

a. The ability to drill in deeper water.

b. Mobility for foreign as well as domestic operations.

c. Less expensive to operate than some bottom supported units.

d. Those with a hull similar to a ship ean head into the sea

during severe conditions, thus minimizing roll and pitch.

Cuss III—a floating drilling vessel.

Courtesy Union Oil Co. of California.

The oil boom is not confined to the Gulf of Mexico, but is in
fact becoming world wide. To some extent, this has caused an
exodus of marine drilling rigs from the Gulf, to such places as Lake
Maracaibo (where there are approximately 4,000 offshore wells),
Cook Inlet, Alaska, the Gulf of Suez, the Persian Gulf, the Gulf of
Guinea, and many others.

Concerning foreign oil prospecting, the majority of interest
is probably now directed to the North Sea, a sedimentary basin
almost as big as Texas. A major discovery on the threshold
of the world’s thirstiest gas and oil market would be not only a
bonanza, but could also have a direct bearing on the European Com-
mon Market, as the holder of such a find would have a key to much
of Europe’s energy.

In 1960 Slochteren, Netherlands became the third largest gas field
in the world. And, these producing sands are the same ones that
have been discovered on the northeast coast of England. The ques-
tion as to whether these sands are also under the North Sea, is the
reason for great acceleration of oil prospecting in that area.

The prospects are so great in the North Sea that it will take
approximately three years of drilling to check the prime geologic
structures already located. With the ratification by Great Britain,
the 1958 Geneva Convention on the continental shelf became effec-
tive on 10 June 1964. This convention proclaims that the sea-bed
and subsoil of the submarine areas adjacent to the coast belong to
the coastal state as far out as the “depth of the superjacent waters
admits of the exploitation of the natural resources of the said areas.”
It contains also provisions for drawing of boundaries where the
claims of two or more countries overlap. Hence, the oil and gas
rights of the North Sea will be divided up among Belgium, Denmark,
England, France, Germany, the Netherlands, and Norway.

The greatest portion by far, of all geophysical prospecting has
been in the search for oil and gas geologic structures, with but a
small fraction of expended effort directed to solid minerals. In
petroleum exploration, the seismic reflection method is the most
widely used, with gravity, seismic refraction, and magnetic survey
methods following in that order. With the data provided by this

method it is possible to chart depths to subsurface interfaces with
accuracy exceeded only by measurements in wells. Similar to the
fathometer operation in many respects, the system depends on travel
times of elastic waves reflected back to the surface from different
earth formations.

SURVEY BOAT RECORDING BOAT SHOOTING BOAT EXAOSION
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Seismic reflection shooting offshore.

The advantage of the reflection method is that it permits charting
of many horizons from each shot, with the precision approximately
the same for the deeper horizons as for the shallow ones. In the
other mentioned methods, reliability decreases with increasing
depth.

With seismic reflection, depth determinations are not exact,
as sound velocity within various layers is not precisely known. This
inaccuracy, however, is not too important as it is the position of
local humps or domes in the rock layers that is sought by the
geophysicist. ;

DIATOMS.—As oil is referred to as “black gold”, so has diato-
mite, the lightweight remains of diatoms, been called “white gold.”
Diatoms are members of the yellow-green group of algae and are
the most numerous plants of the phytoplankton, sometimes amounting
to ninety percent of the total. There are many different species
of diatoms, all of which are unicellular and microscopic, with an
above average one measuring perhaps 1/200th of an inch. Although
they are a form of vegetation, diatoms possess no leaves, stalks or
roots. Rather, their most characteristic feature is a transparent
shell of silica, filled with the protoplasm of the cell.

Like plants ashore, diatoms are seasonal, with their numbers
fluctuating accordingly. It is seldom that thay are completely
absent from any portion of the surface waters.- Ordinarily, they
are more numerous near land as their required nutrients are nor-
mally more abundant in coastal waters. With the extended hours of
sunlight in the spring, occasionally their numbers become so vast
that they tend to change the very color of the sea. During these
times the waters may become green, brownish-green or even red,
and a single cup of sea water may well contain hundreds of thousands
of diatoms.

These silicified diatom skeletons, sinking to the ocean floors in
earlier eras, resulted in large deposits of packed diatomite. Today
these deposits are mined in places such as California, Nevada,
Oregon, Washington, Denmark, Finland, and France.

Due to its light weight in relation to bulk, industry has found
many uses for diatomite. Albert Nobel created dynamite in 1870,
by soaking nitroglycerine into diatomaceous earth. When made
into strainers, it is porous enough to let liquid flow through it, while
its lacy particles strain out bacteria. It is for this quality, that
drug firms use the product. It has also been used as a cigarette
filter, to strengthen concrete and to produce a flat or semigloss
finish in paint.

GOLD.—Concerning recovery from the sea, the only “trace
element” that has really attracted attention is gold. Just one of
our 300 million cubic miles of sea may contain as much as 25 tons
of this precious metal. But, it is in such minute particles that ex-
traction is not currently financially feasible. There have been a
few attempts, all of which met with failure. A minute amount was
extracted experimentally as a by-product of bromine production.
The final cost, however, amounted to approximately five times the
value of the gold recovered. Also, there was the unsuccessful at-
tempt in 1927 of the German METEOR expedition. This was the
German attempt to obtain sufficient gold from the mid-Atlantic
to pay off their war debt.

Research on gold extraction will no doubt continue, to some
extent. If an economic method is not found, scientists will still gain
other useful information from their efforts.

TREASURE FROM THE SEA

NODULES.—In 1870 the famed British oceanographic vessel
CHALLENGER dredged from the ocean bottom, lumps of a mineral
that to some extent resembled blackened potatoes. The assays
later proved the nodules to be rich in manganese, copper, cobalt,
nickel, and iron. Industry, however, failed to become interested.

More recently, during the International Geophysical Year, tre-
mendous quantities of these metal bearing nodules were rediscovered
on the ocean floor and interest concerning them has now been raised.
These ore nodules grow in layers like onions, have taken millions
of years to form and often have a small nucleus of clay, pumice or
glass. The majority recovered have ranged in size from a few inches
in diameter to two cubic feet. At least one, however, has been re-
ported to weigh almost a ton. The rate of growth is approximately
one millimeter in a thousand years. But, so many nodules are forming
continuously that they could supply our major needs and the growth
rate, though exceedingly slow, would exceed the rate of depletion.

Thus far, no one has mined nodules on a commercial basis,
although there are some companies at least investigating the possi-
bilities. Recovering these ore deposits promises to be an engineering
feat of gigantic proportions and may not be accomplished until
land deposits become exhausted, or nearly so. The engineering re-
ward, however, will be vast as it has been estimated that by
vacuum-cleaning a square mile of ocean bed surface, in a selected
area, the ore recovered could amount to 6,000 tons of manganese,
4,000 tons of iron, and 125 tons each of cobalt, copper, and nickel.
These are, of course estimates only. It has been further projected,
however, that the value of mineral deposits within one square mile
of ocean floor, might well amount to half a million dollars.

OTHER MINERALS.—Other similar treasure, in the form of
rich tin ore, lies off the coasts of Thailand and Indonesia. Also, there
is gold in the gravels and sands in the proximity of Nome, Alaska
and a barge dredging approximately $200,000 worth of diamonds
a month off the southwest coast of Africa.

M. V. Rockeater—first ship designed and built for mineral prospecting.

The first of its kind and owned by the Ocean Science and Engi-
neering Inc. of Washington, D. C., the newly completed ship ROCK-
EATER has just recently joined in the search for minerals off the
Diamond Coast of southwest Africa. It is employed by the De Beers
group, and will determine the value and extent of under sea diamond
deposits in that area. The ship is capable of prospecting either by
drilling geological core samples of hard rock, or by dredging and
processing large quantities of unconsolidated material. All dredging
and drilling is accomplished through a 7 by 11 foot center well, lo-
cated amidship at the point of minimum motion. This well is sur-
mounted by a 52-foot derrick.

For primary propulsion, ROCKEATER is equipped with twin
screws. In addition, it has a bow mounted propeller plus an addi-
tional outboard motor on the stern, for greater maneuverability.
All four propellers are controlled from a central steering console,
on which a “joy stick” directs ship movement in any direction. This
equipment is an extension of the “dynamic positioning” system used
in Phase I of the MOHOLE Project.

PEARLS

This “Gem of the Ocean” has been sought by man for thousands
of years. In the past, many civilizations have attributed powers of
romance and magic to the pearl, probably resulting in today’s
association of the pearl with love and marriage.

13

The origin of the pearl was for ages a mystery. The ancients
believed that at certain times oysters came to the surface and
opened their shells. Then the tear of an angel was deposited
within the shell, where it became a pearl upon crystallization.
The Greeks were of the belief that when lightning struck
the sea, pearls were created. And, after seeing oysters attached
to mangrove roots in the West Indies, Columbus suggested that dew
drops falling into the open shells, from the trees above, resulted in
the formation of pearls.

Pearls are found in many parts of the world and from a number
of different mollusks. They are produced in fresh water as well as
salt water. The majority of the more valuable pearls, however,
come from the oyster Margaritifera, that flourishes in tropical
waters. The pearl oyster is a distant relation to the edible oyster
and is more closely related to the mussel. As the common edible
bivalves do not produce nacreous pearls, one is not likely to find one
in a platter of oysters or clams on the half shell.

Essentially, a pearl is of the same substance as the “mother of
pearl” of shells. It is composed mostly of calcium carbonate and
held together by a tenuous network of organic conchiolin. They
are formed when a foreign substance is ingested accidentally into
the pearl bearing oyster. It is the oysters attempt to reduce irri-
tation and prevent itself from being harmed. If the shell of the
oyster is penetrated by a parasite, the oyster seals off the entrance
with a secretion that in time becomes a “blister pearl”. Blister
pearls are hence attached to the shell, but can be cut off. It is
the symmetrical or round pearl though that is so highly prized.
These are formed around a nucleus, which may be any small
irritant—a grain of sand, marine larva, or other debris.

The most valuable pearls are found near Ceylon and in the
Persian Gulf. The nucleus of these pearls is believed to be the egg
of a tapeworm, found in a certain ray. If the floating tapeworm
egg enters the oyster shell two possibilities exist. A ray may eat
the oyster, thus giving the tapeworm a chance to develop and hence
lay other eggs. Or, the oyster may deposit numerous layers of
nacreous material around the egg, thus forming a valuable pearl.

The demand for pearls has always exceeded the supply, as the
average find is only one pearl in a thousand pearl oysters. Actually,
in many areas the mother-of-pearl brought up by divers is worth
as much as, if not more than, the pearls.

A round pearl % inch in diameter will weigh approximately one
grain, a 4 inch pearl about 7 grains, and a ¥% inch pearl about 55
grains. The largest known pearl is the 1,860 grain pearl, in the Hope
collection. The general value of a pearl may be estimated by
establishing a base one-grain value for a pearl of the same shape,
color and luster, then multiplying this amount by the square of the
number of grains that the pearl weighs. For example, if the base
one-grain value is determined to be $1, then that would be the worth
of a 1-grain pearl; but a 2 grain pearl would be worth four times as
much, or $4, and a 10 grain pearl would be valued at $100.

The lack of pearls formed naturally in the sea, has led to the
development of cultured pearls. And, although the development
of cultured pearls has caused a drop in price of natural pearls, the
value of unusually large specimens remains high as cultured pearls
come from oysters that do not produce the larger gems.

Men have tried for centuries to discover ways to induce mollusks
to produce pearls. The earliest known cultivated pearls were pro-
duced during the thirteenth century by the Chinese, by hand
inserting irritants into fresh water mussels.

During the sixteenth century, the Chinese started inserting
small lead Buddhas into the mussels which resulted in Buddha-
shaped pearls. And, these pearl coated images are still, to some
extent, produced in the Orient.

A Swedish naturalist, Linnaeus, perfected a method for pro-
ducing pearls in 1761. His method was to drill a hole in the oyster
shell and with the aid of wire, push a small piece of limestone
through the opening.

Neither of the above two methods, however, produced round
pearls. The majority produced were “blisters”, or baroques
(misshapen pearls). This was due to the foreign object being
placed between the mantle and the shell. Symmetrical pearls are
produced within the connective tissues of the oysters body, rather
than next to the shell. Further, the pearl is produced within the
connective tissue only when the nucleus or irritant, on its entry into

TREASURE FROM THE SEA

the tissue, has been accompanied with epithelial cells. Epithelial
cells must be in contact with the pearl nucleus and these nacre
producing cells are found only on the outside of the oyster mantle,
ie. next to the shell. This is the theory on which the more than
100 pearl farms operate in Japan, the largest of which is the
Mikimoto Company. Kokichi Mikimoto, founder of the Mikimoto
Company, died a few years ago at the advanced age of ninety-five.
He often attributed his health and longevity to the fact that he ate
two crushed pearls for breakfast each day.

AMBERGRIS

The sole source of this treasure of the deep, is the sperm whale.
The fact that it is produced in the intestine of the sperm whale is
well known. The manner of formation, or how it is formed, how-
ever, is still a subject of debate and conjecture. Although ambergris
has been found in numerous places, the majority has been recovered
in the middle latitudes, as the sperm whale is basically a temperate
water animal.

When ambergris is ejected by the whale, it resembles black
stones. It is abominably malodorous, but as it spends more and
more time floating on the sea its odor improves somewhat. It
lightens in color also with age, fading to shades of brown and
eventually becoming a chalky white.

The uses of ambergris have been many and various throughout
the ages, with strange powers attributed to it. It has been used as
an aphrodisiac, a condiment in food, drink, tobacco and medicines.
Its current use, however, is devoted primarily in the manufacture
of perfumes. It is used as a fixative in the manufacture of only
the most expensive perfumes and it is for this reason that the scent
of perfumes made with ambergris will last much longer.

Most of the ambergris now comes from the whaling industry,
with ships and beachcombers reporting occasional finds. Sizes of
ambergris found vary from less than an ounce to some 982 pounds.
As the size of finds vary so does value, ranging from $2 to $9 per
ounce, in accordance with the market and quality. A further
example is a 151 pound 8 ounce chunk that sold in the United States
for $20,000.00. Although not as valuable as it once was, due partially
to synthetics, it does promise its finders a considerable reward.

AQUACULTURE

As the term implies, aquaculture is the cultivating and managing
of the ocean’s resources in much the same way foresters and
farmers husband the land’s resources. Aquaculture is a word not
too well known today, but a subject that has enormous possibilities
and is gaining world wide popularity. There is no doubt that further
improvements to increase yield will be made in agriculture. The
land area, however, is limited and hence must obviously limit the
quantity of food it can produce. This limit has been reached and
indeed has been exceeded in many locations of the world. Conse-
quently, our need to turn again to the sea, as aquaculture is the
means most conducive to conquering the world’s undernourishment.

Zooplankton feeding on phytoplankton, the basis of the sea’s food chain.
Enlarged about 15 diameters.

Oceanographers have calculated that approximately nine times
as much vegetation is available in our seas as is cultivated on land.
The main bulk of this vegetable life consists of microscopic plank-
ton, upon which zooplankton (small grazing sea animals) feed. And,
zooplankton in turn is eaten by fishes—a cycle similar to the one
on land in which grass is eaten by cattle and converted to beef.
Actually, this chain of life in our seas has its beginning with sun-
shine and the dissolved chemicals in the water, for it is upon these

14

that vegetable plankton prosper. The ocean currents and tides
tend to stir the plankton’s food supply of nutrients, with the
smallest changes in quantity of nitrogen or phosphorus having a
direct bearing on plankton population. Hence, this in turn, affects
the entire chain of life in the sea, as animal life is basically depend-
ent upon plant life.

The aquacultural concept has led scientists and oceanographers
to speculate regarding methods to herd fish, increase and improve
the stock and increase the richness of waters via forced upwelling.
For, where the waters are rich in nutrients there is a bloom of
plankton and hence a far heavier concentration of fish.

On land it takes considerable more acreage to raise a ton of
beef than it does to grow a ton of wheat or corn. Similarly, the
same situation holds in ocean pasturage. The advantages a farmer
gains by growing vegetables in lieu of beef are quite small compared
to those that could be gained were it feasible to harvest plankton
directly, instead of having the fishes harvest it for us. This is due
to the extended ladder of life in the sea, between plankton and man.
If man could harvest plankton directly, he could increase the
ocean’s food yield by as much as a thousand times. At each link
in the chain of sea life there is considerable waste, for whether it is
zooplankton feeding on vegetable plankton or large fish devouring
smaller ones, there is about 90 percent loss of energy or food. It
therefore follows that it takes approximately 1,000 pounds of plant
plankton to produce one pound of medium size fish with increasing
amounts for the development of larger fish such as tuna.

If man could bypass the process and go directly to the bottom
of the sea’s ladder of life, there would be a tremendous saving of
food materials. This currently is not economically feasible due to
the high cost of pumping and sieving. In addition, the final product
would be one barely palatable. So until a revolutionary technique
is developed, man will have to depend on the fishes of the sea for
conversion.

Even though we cannot yet economically harvest plankton, we
can aid in the growth of plankton and thus advance the fish harvest.
This can be accomplished by bringing to the surface the rich bottom
nutrients on which plankton flourish, i.e. by forced upwelling. Where
upwelling occurs naturally it causes plankton to bloom and fish to
congregate, a good example of which is the Grand Banks of New-
foundland. Here the Gulf Stream meets the Labrador Current,
causing a complex vertical circulation and produces an area of
constantly renewed fertility. Another example of copious sea life,
is off the coast of Peru. The prevailing winds along the west coast
of South America are offshore. Water thus is blown offshore and
is replaced by the nutrient rich deep waters of the north flowing
Peru Current. Consequently, upon reaching the Peruvian portion
of the Continental Shelf these waters produce sea life unsurpassed
elsewhere in the world—phytoplankton, zooplankton, fish and even
numerous sea birds are in abundance. Such are the possibilities of
aquaculture.

The farming phase of aquaculture also offers many possibilities,
for the most astonishing fact about sea life is the tremendous loss
of young. A single female Cod, for example, will produce from one
to five million eggs each season. For the species to continue in exist-
ence, only two of these eggs need survive to maturity. Here we
have a tremendous egg potential offset by enormous mortality. As
the eggs develop, they float to the sea surface and become a part
of existing plankton, which is destined to be eaten by other fishes.
After developing into small fry, the remainder tends to settle near
the bottom where they attain their best growth in five or six years.

There is little that can be done to cause more of the cod eggs to
grow into adult fishes, as they are affected by various factors. To
raise young fish in huge numbers artificially for transplanting with-
out providing additional food, would be similar to a farmer trying
to double his land’s yield by planting twice as many seeds. Life in
the sea exists almost entirely by cannibalism and the rate of
destruction would be high until the numbers of fish had been
reduced to the natural food level. Actually, if the majority of fish
eggs were not destroyed, the oceans would soon overflow with fish.
This point may be further stressed by using the oyster as an
example. For, if the progeny of a single pair of oysters survived
100 percent, in five oyster generations their combined bulk would
be equal to approximately eight times the size of the earth!

TREASURE FROM THE SEA

Electrical Fishing

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TREASURE FROM THE SEA

Pond culture has proven successful in several areas, with a yield
higher than that of agriculture. For instance, in China production
is said to be 5,000 to 7,000 pounds of fish per acre, compared to 800
pounds per acre for beef. Oyster cultivation, however, has been
one of man’s most successful attempts at aquaculture. The Romans
were among the first to try their hand at aquaculture some two
thousand years ago. Growing oysters were attached to ropes in
protected areas, while they were fattening. Today, where con-
ditions are favorable, oysters are cultivated in many areas of the
world.

One oyster will produce several million young of which only a
very few ever emerge as adults. Were this not the case, a few
oysters could, within a short time, produce enough food to feed
the entire world population. When the spat (young oysters) emerge
from the plankton stage, they settle to the bottom. If at this
critical period of their life they do not find sand, or a rock on which
to attach themselves they soon expire from silt and pollution. It is
at this most important phase of their life that man can best promote
their growth, for the numbers are few that ever find the necessary
type of bottom. For this reason, some states wisely require that
a certain percentage of marketed oyster shells be returned to the
growing areas.

FISHERIES

Fishing has been referred to as man’s oldest industry. It has
certainly provided him with a substantial portion of his diet since
pre-historic times. Currently seafood probably makes up less of
man’s diet than it did in earlier times, as fishery products now con-
stitute less than three percent of the world’s food.

In the less fortunate areas of the world, millions of people suffer
greatly from protein deficiency, due to their economic diet of rice
and other starchy foods. Fish from the sea, however, offers a thrifty
solution to this nutritional problem. For, fish is a concentrated
protein diet, with the advantage of holding all of the essential
amino acids.

In addition to the calorie producing foods, our body chemistry
requires other sources of energy such as vitamins and minerals,
which are all contained and well-balanced in seafood. Further, the
fat in fish provides vitamins A, D, & B complex; and it is now
believed that natural vitamins may contain beneficial qualities not
found in the synthetic product. Concerning minerals, fish contains
phosphorus, calcium, potassium, and magnesium along with adequate
quantities of iodine, iron and copper. So, not only is fish a most
palatable and economical food, it is also the most digestible form of
protein and a well rounded source of energy and health.

The remedy for protein shortages is in the sea and waiting
utilization. But, all too frequently the fish are scattered and so
far removed from the hungry mouths it is beyond the means of
economy to catch them. New devices and methods are sorely
needed, as very little has been accomplished of a radical nature,
concerning methods, in the past several hundred years.

A wide variety of new gear, with a completely new approach,
is presently being studied by scientists. They have discovered some
of the ways fish respond to what they feel, see, hear, and smell and
are taking advantage of these facts. One of the items receiving
interest is the tendency of fish to react to electric fields. A strange
fact concerning electrical fishing, is that fish line up with the field,
facing the positive pole. Upon becoming aligned with the electrical
fields of force, the fish then begins an inexorable move towards the
positive pole and so continues as long as the current persists. At or
near the anode electrode the fish becomes stunned and may be
scooped up. This process, although not yet too successful in salt
water, has been going on for some time in fresh water.

The basic reason for the lack of success in salt water is the
fact that salt water has less resistance than fresh water. Or,
stated differently, the higher the salt content of water the greater

16

the conductivity. This range of resistance is quite great, with a
minimum of 9 to 20 ohms per cubic inch for sea water and going
up to 1,000,000 ohms for pure rainwater.

As electricity takes the path of least resistance it can be seen
that it would bypass a fish with a resistance of perhaps 250 ohms
swimming in sea water of, say, 15 ohms. On the other hand, were
the fish swimming: in river water of 1,500 ohms resistance it would
quickly be effected. Consequently, to produce the required effect
in sea water, considerable more power is necessary.

The advantage of this process is that the size of fishes caught
can be controlled, as the larger the fish the less current is required
fer response. Other items include dye curtains, a net of sonar
transmitters that emit a repellent noise, gigantic nets that can be
closed before the fish become frightened, underwater television
cameras and many others.

Whatever improvements and advances are made in the near
future, commercial fishing will still largely be a matter of hunting
and finding the fish. It is therefore not only important that
catching methods be improved, but also the means of locating the
fish is of paramount importance.

To awaken the general public’s interest in the protein rich food
of the sea, marketing experts are continually at work. New
methods of packaging along with new products such as breaded
shrimp and fish sticks are now conveniently available at most grocers.

FRESH WATER

Of all the riches from the sea, the one that may well prove to
be of highest value to man, is water itself. For, neither industry,
agriculture nor man himself can long survive without this all
important element. In parts of the United States, North Africa,
Australia and Central Asia the need for fresh water is becoming
desperate. During the draught years several United States cities
place special restrictions on the use of water. An extreme example
of the lack of water was in Dallas, Texas in February 1957 when 5
gallon jugs of drinking water sold in grocery stores for $1.25.

So, where shall we get additional water? More reservoirs would
help, but a vast supply of water in a northern reservoir would be of
no value to the draught-stricken south. Again we should look to
the sea for help. Man has long been in quest for a means of irri-
gating deserts and arid lands. Several methods have been known
for years, but the problem has been not only to obtain fresh water
abundantly, but cheaply. The answer to this age-old problem will
probably be nuclear power. For, as has been the case with so many
subjects, “nuclear energy has been a solution in search of a problem.”

The Department of Interior has been conducting research on
obtaining fresh water from the sea, for more than a decade, and has
a few pilot plants in operation. In any event, the day is probably
not far off when deserts will bloom and arid countries will be able
to produce the crops that their populations so desperately need.

CONCLUSION

The Malthusian theories hold that the population of the world
tends to multiply faster than its means of subsistence can be made to
do, and that, unless an increase of population be checked by pru-
dential restraint, poverty is inevitable. The views of political
economist Rev. T. R. Malthus (1766-1834) might well have been
quite different if he could have forseen more of the capabilities of
our inexhaustible sea.

The potentials of Neptune’s treasure are vast. Minerals and
chemicals exist beyond one’s comprehension. Food is available in
quantities more than sufficient to lift all of the world’s wants. In
addition, if the power of the ocean’s currents, tides and waves could
be converted for use, it would be considerably more than all the
power currently produced.

Our conquest and understanding of inner space may well prove
more important to our very existence than the greatest of achieve-
ments in outer space.

BIOLOGICAL OCEANOGRAPHY

F. W. Fricker
Maritime Safety Division
U.S. Naval Oceanographic Office

Oceanography, a relatively new word in our vocabulary, has
been generally defined as the “‘application of the sciences to the
phenomena of the oceans’. Broadly speaking, oceanographic research
can be said to embrace four major scientific disciplines: biology,
chemistry, geology, and physics. Oceanography can, therefore, be
further defined as the corporate study of the biological, chemical,
geological, and physical components of the world’s oceans and
adjacent waters.

Biological oceanography specializes in the study of the living,
or organic, content of the sea, its myriad plants and animals. It is,
in its own right, a broad field of scientific effort embracing separate
disciplines of which morphology concerns the form and structure of
organisms, taxonomy their classification, physiology their functions,
and ecology their environmental relationships. Of these, ecology is
the dominant field in modern marine biology as biologists strive to
understand the complex interrelationships that exist between marine
organisms and their environment and between the organisms them-
selves. The importance of understanding these relationships is tied
to a number of existing and anticipated problems.

From an economic and social standpoint, the sea contains vast
quantities of foodstuff upon which much of the present world popula-
tion looks for sustenance. As the burgeoning population of the future
will place fantastic demands upon this source, scientists, industrialists,
and statesmen the world over have begun to focus their attention
upon the seas as a vast latent source of nutrients. To cultivate, foster,
reap, and conserve this fabulous natural resource is an important part
of biological research.

From the purely military aspect, the sea, as a three-dimensional
medium for naval operations, has assumed new significance.
Extensive efforts are being expended to find possible means of combat-
ing the limiting and damaging effects of marine organisms upon ships,
installations, and equipment; to investigate the source of the
scattering effect upon sonic impulses; to catalog the sounds created by
marine animals; to determine the predictability of bioluminescence;
and to explain numerous other phenomena which affect naval
operations.

In brief, biological oceanography is cast in an important role in
the conquest of earth’s last remaining frontier, inner space. To
highlight this role is the purpose of the following article. As a complete
monograph of the science is quite beyond the scope of a single article,
it has been limited to those facets of apparent interest to mariners.

BIOLOGICAL ASPECTS OF FISHING

It has been generally estimated that 10% of the world’s present
protein supply is comprised of aquatic organisms. Disregarding
possible inaccuracies in this rate, sufficient evidence now exists to
predict a much greater usage of seafood in the not-too-distant future.
Theoretically, the presumption that the sea can provide increasing
amounts of food is well founded. Scientists realize, however, that
fulfillment of this promise can only be achieved through progressive
advancements in fishery technology. Better conservation measures
must be instituted, new fisheries discovered, capturing techniques
improved, and the range of useful products widened to ensure that
the world’s fisheries keep pace with expected population demands.
The issues involved are essentially biological in nature and, certainly,
oceanographic in scope, for the development of rational theories
concerning present and future exploitation of oceanic resources must
be based on a more complete knowledge of the various organisms and
their interrelationships with environment.

Fish are very similar to land animals in that each kind has its
own preference of food and environment. Because of this, they tend
to congregate in regions where their particular food is most plentiful
and water temperature is agreeable. Most fish migrate during certain
seasons of the year along comparatively well defined routes, stimu-
lated by an unconscious urge to spawn, feed, or winter in a different
location. Many species tend to feed and migrate as a group, or shoal.
Obviously, a sound knowledge of the migratory cycles, routes, and
shoaling behavior of desired fishes is necessary in forecasting the most
favorable catch areas. Fishery charts, currently being developed on

IT

a worldwide scale, are largely based on this knowledge. As the many
species have varying habits, the task of collecting, collating, and
cataloging the required data is enormous. An example of the details
investigated as a result of research in this field is the recently de-
veloped theory that salmon migrations are initiated by the organism’s
preference for water of varying salinity, due to a change in the rate
of its thyroid activity.

Food is undoubtedly the most dominant influence in the lives of
fishes; and consequently, their behavioral patterns, as well as their
growth, are largely affected by the type, location, and abundance of
their food supplies. The fact that the world’s great fisheries coincide
with the areas of bountiful plankton growth is no mere accident. The
first link in the sea’s food chain is its drifting algae, or phytoplankton.
Feeding upon these vast quantities of microscopic plants are the
myriad zooplankton, tiny snrimplike creatures barely visible to the
naked eye. These creatures form the staple diet of most commercially
important fishes at some stage of their development. The fishes, in
turn, are preyed upon by larger predators, mammals, and birds, thus
completing the chain. As productive imbalances at any level of this
progression may adversely affect commercial production, intensive
studies of feeding relationships is an important part of fishery re-
search. The construction of rational methods of exploiting our
fisheries would be impossible without an understanding of the manner
in which a particular fish exploits its food resources and the nature
of the relationships between the fish and others which consume the
same food.

At the present time, the greatest danger resulting from a con-
stant expansion of our marine fisheries is that of overfishing. Biologi-
cally, overfishing is that condition created by excessive catches in
which the reproductive capacity of a remaining population of fish is
unable to compensate for the losses sustained. Economically, the
practice eventually results in a proportionate decline in catch per
effort expended, making further production of a fishery unprofitable.
While the latter condition probably prevents fishing of a species to
the point of extinction, it is of little consolation to the fisherman and
the conservationist. Although the imposition of conservation
measures rests with legislative bodies, the problems involved are
basically biological.

Ocean perch infested by parasitic copepods.

In addition to the adverse effects of overexploitation, there are
many natural conditions which affect reproduction and maturation
of marine organisms. Several bacterial and virus diseases attack
fish, and some fungi can kill them. Parasites do enormous harm, and
predators take a huge toll of commercial fishes. The amount of fish
consumed by piscivorous birds is very large, so that in areas where
they abound birds can cause serious losses to fisheries. Mussel
poisoning on our west coast results from periodic blooms of the plant
Gonyaulax, and a similar one-celled organism, Gymnodynium brevis,
has been associated with the fish killing ““Red Tide’’ along Florida’s
west coast. In the interest of enhancing our fisheries, biologists must
develop methods of reducing or eliminating these harmful elements.

Researchers are also combating relatively new threats to fish
suryival. Pollution of the seas by oil and other substances has a serious
adverse effect on fish by upsetting their metabolisms, contaminating
their food supplies, and destroying the reproductive qualities of spawn-
ing areas. The blocking of spawning grounds by dams, log rafts, and
debris has grave effects upon reproduction.

BIOLOGICAL OCEANOGRAPHY

Although the sea harbors at least 40,000 species of fish and an
even greater number of other aquatic organisms, only about 300 kinds
of fish and shellfish are utilized for food in the United States. Further-
more, of the nation’s total annual catch, 60% is composed of only
9 species. This overspecialization in only a few of the species available
places a severe limitation on the expandability of the source. It
appears evident that future demand will gradually necessitate a wider
usage of the many edible species now classified as commercially un-
important. Oceanography will play an important role in determining
the exploitability of new stocks.

Biological research has provided several methods of augmenting
existing stocks of commercial fishes. By artificially rearing fish in
controlled hatcheries and on fish farms, eggs and larvae can be pro-
tected from a number of adverse conditions, thus assuring a higher
rate of maturation. The productivity of a water-mass can also be
enhanced by artificially raising its food content, either by fertilization
to encourage the growth of organisms upon which the larvae feed, or
by introducing cultured fishfood into the area. Transplantation of
desirable species from one environment to another has, in many cases,
been successful.

To realize the full potential of harvest from our oceans,
however, effective methods of utilizing the many species inhabiting
the extensive geographic regions of our open oceans must be devised.
Many of these resources, like those of the tuna family, may form
natural aggregations only periodically, may make themselves avail-
able only seasonally to existing fishing systems, or may be widely
dispersed thoughout the sea. Exploratory expeditions conducted by
various nations have resulted in the discovery of several new offshore
fisheries of commercially valuable fish. It seems reasonable to assume
that many more await discovery in the vast reaches of our oceans.
However, economical exploitation of any new oceanic species must
be preceded by a careful appraisal of the creature’s shoaling, feeding,
spawning, and migratory habits so as to forecast and chart the areas
of highest concentration.

Equal in importance to the discovery and forecasting of their
aggregative traits, increased harvests of offshore species will require
vast improvements in capturing gear and techniques. Most methods
in use today evolve from systems designed to capture fish within
close proximity to land, relying on environmental features and bio-
logical characteristics of fish to form required concentrations. The
perfection and effective application of fishing gear is impossible
without a sound knowledge of the reactive processes of fishes, partic-
ularly their shoaling behavior and the characteristics of their sense
organs by which they orient themselves to fishing gear. The form,
size, color, and other properties of capturing gear, and the region in
which it is applied, have a definite bearing upon its effectiveness.

Refinements in fishing techniques may require the use of more
sophisticated capturing methods, to facilitate economical harvesting.
The attractive influence of strong artificial light upon fish is well
known, and fishermen the world over have exploited its use. Recent
experiments have further revealed that fish behavior is affected to
some extent by the color, as well as intensity, of artificial light.
Biologists have recently confirmed the fact that fish respond to an
electromagnetic field, first, by orienting themselves to the lines of
flux, then by swimming toward the anode. By placing an electrode
in front of a trawl, shoal fish can be attracted and guided into the
catching area. Furthermore, experiments show that by the use of
direct, alternating, or pulsating current, electrical fishing gear can be
made to frighten, block, or ‘‘fence”’ fish, or to narcotize or kill them.
Guiding herring into nets or traps by use of a wall or stream of air
bubbles has been experimented with and employed with some success.
Perfection of such techniques, however, will require a better under-
standing of the behavioral reactions of fishes to artificial stimuli.

FOULING AND DETERIORATION

Among the many important problems associated with marine
biology, none has greater economic significance than the control of
marine fouling and deterioration. Anyone familiar with the sea and
ships is well acquainted with the costly effects of marine growth on
ships’ hulls and salt water intakes. Equally important is the damage
of shore installations resulting from the penetration of wood, plastics,
concrete, and other structurally important materials by several
marine organisms. It has been conservatively estimated that the
annual cost to the Navy alone for the protection and maintenance of
ships, waterfront structures, and offshore equipment against biological

18

deterioration and fouling is approximately $100,000,000. Far more
importantly, however, uncontrolled fouling and deterioration by
Marine organisms can effectively reduce the combat readiness of
naval ships and shore facilities.

Sections of 6-inch pipe taken from over boiler on Navy ship.
The pipe is almost closed by marine-fouling growth.

The fouling of ship’s hulls is, of course, an age-old problem.
Man’s historic efforts to discourage marine growth has resulted in the
development of chemical agents which today, can protect hull surfaces
for as long as 24 months. The problem is far from solved, however,
for the development and use of submerged equipments vital to naval
operations and technological progress constantly introduce new
requirements for enduring antifouling agents.

The biological fouling of a sonar transducer can seriously impair
its effectiveness by attenuating sound transmission. In certain areas
of the world, critical fouling of unprotected surfaces can occur within
a few months, rendering sonars unfit for ASW operations. Some
success in developing reliable protective coatings for sonar domes has
been realized, but the problem is complicated by the requirement
that the agent used must not alter the equipment’s acoustic properties.

The growing use of underwater optical instruments presents
further complications. Complete fouling of an underwater television
lens can be accomplished in an incredibly short period of time.
Obviously, the lens cannot be painted with antifouling paint as in the
case of a ship’s hull. The development of durable but transparent
protective coatings is a necessary preliminary to the planned instal-
lation of submerged optical equipment such as television monitoring
stations.

Moreover, the proposed construction of large, stationary struc-
tures in relatively deep ocean waters for various military and commer-
cial projects creates additional fouling problems. Already, the
underwater structures used in the recovery of offshore petroleum
are approaching deeper waters. Because of the size and permanency of
proposed structures frequent maintenance will be impractical, if not
impossible. Therefore, anti-fouling agents of enduring effectiveness
must be developed. But little field data is available at the present
time to warrant the assumption that deep-ocean fouling will not
differ from that occurring in shallow coastal waters. For this reason,
far more data must be obtained about the ecology of fouling organ-
isms in the deep sea before reliable fouling deterrents can be developed.

Wood gribbles bore into a piling.

BIOLOGICAL OCEANOGRAPHY

Deterioration of submerged installations by marine organisms
is another serious threat to present and proposed marine operations.
Extensive destruction is caused by species of Limnoria, or gribbles.
These animals are related to the shrimp and lobster and are worldwide
in distribution. They are normally found attacking the surface of
submerged piling and other wooden structures in shallow water, but
materials other than wood, such as the gutta-percha insulation of
submarine cables in depths up to 360 feet, have been penetrated by
gribbles. Other crustaceans burrow into, and consequently weaken,
stone seawalls.

Certain mollusks, such as the well known teredo, or ‘‘shipworm’’,
relatives of the clam and oyster, attack submerged wooden structures
in harbors, or burrow into rocks and coral. Mollusks are also respon-
sible for destructive attacks on gutta-percha insulation of cables at
depths ranging from a few feet to 7,200 feet, causing physical damage
and short circuits. Others have been found to penetrate solid lead

sheathing of submarine power cables. Even concrete is not immune
to destructive attacks by these creatures.

7

Rock-boring bivalves, worms and sponges attack hard limestone.

Marine bacteria play a surprisingly important role in the deter-
ioration and fouling of materials and equipment in sea water and
marine sediments. These micro-organisms accomplish their destruction
in a number of ways. By forming over antifouling agents, to which
they are apparently immune, they provide a foothold for barnacles
and other fouling animals. Cellulose-decomposing bacteria cause
millions of dollars worth of damage to net cordage, seines, and lines
used by commercial fishermen. Also present in the sea are cellulose-
consuming fungi which infest natural fibers and woods. Rubber prod-
ucts such as hoses or gaskets, generally regarded as being impregnable,
have been found to be decomposed by the action of marine bacteria.
Sulfate reducing bacteria have been associated with the accelerated
corrosion of submerged metals. Here again, the problem of protecting
deeply submerged materials from the ravages of these organisms is
complicated by the fact that some bacteria actually thrive in deeper
water, reproducing only when subject to great pressures.

Even the color of materials used in underwater installations has
an influence on the attacks by marine fish. Attracted by its white
color, the polyethylene insulation of marine cables has been extensively
damaged by the nibbling of certain fishes. Biologists have suggested
a less attractive insulation color to reduce such attacks.

Vulcanized insulation of submarine cable slashed by shark
who left some imbedded teeth as evidence.

19

The fouling and destructive potential of a segment of the sea’s
population is, thus, clearly illustrated and defines present and future
requirements for more effective control. To meet the requirements
our understanding of the vital processes which govern the life cycles
and behavior of the offending organisms must be broadened. Ade-
quate knowledge of such processes should lead to the discovery of an
inherent weakness in each organism which is susceptible to external
control.

BIOLUMINESCENCE

A biological phenomenon well known to mariners is the relatively
common yet curious sight of luminescence in the sea. At first believed
to be caused by the presence of the element phosphorus within the
water, it has been known for almost two centuries that the phenom-
enon is biologically induced. In its most familiar form, luminescence
is observed as a bluish-green fluorescent glow in waters disturbed
by bow waves and wakes, and by cresting waves. Luminescent dis-
plays occasionally attain more spectacular proportions, however,
forming parallel bars, or ‘“‘wheel spokes’, of pulsating light extending
from horizon to horizon. Sometimes the wheel spokes appear to rotate
like a giant pinwheel.

A simplified version of the occurrence is that tiny plants and
animals, some even microscopic, exist in the near-surface regions of
the sea in countless numbers and react to various stimuli by emitting
light. The light emitting properties of many of these organisms permit
them to alternate, or flash, their light in a manner similar to the
common firefly. The rhythm of flashing depends in most cases upon
the kind of stimulation introduced. Some of the lowly dinoflagellata,
a group of single-celled organisms strangely cast on the borderline
between plants and animals, are known to possess this characteristic.
Since they abound in the upper portions of the oceans, dinoflagellata
are among the better known organisms responsible for the lumines-
cence observed by seafarers.

Because they often exist in huge concentrations, luminescent
organisms are capable of producing an amazing amount of light.
In certain geographic regions, agitation of the sea by the passage of
a vessel at night produces enough illumination on deck to enable one
to read. When the stimulation is passed through them in waves,
their rhythmic reaction may give the impression of a symmetrical swirl-
ing movement of light, thus creating the pinwheel illusion. The
parallel bar effect occasionally observed is accounted for by the move-
ment of the sea, which even under calm conditions, circulates
vertically in such a way as to concentrate the organisms in horizontal
streaks.

While surface displays are the most frequently observed, bio-
luminescence is not confined to the upper regions of the sea. Light
producing organisms have been found to exist at every depth. In
the blackness of the abyssal depths, where sunlight never penetrates,
the light produced by certain animals provides almost constant
illumination, to the mutual benefit of themselves and others not so
equipped. The fact that the latter creatures have well-developed
eyes, and are obviously dependent upon alien sources of light, is
evident of the close interrelation of these deep dwelling species. To
fully understand the significance of luminescence in the ecology of
marine life is a constantly expanding project for oceanographers.

A 6” slomiatoid fish taken in net tow at 2,000 feet (approx.)

To the casual observer, luminosity of sea water is but a harmless
manifestation of natural wonder. In the conduct of naval operations,
however, the phenomenon is viewed with a jaundiced eye. Observed
from the air, or from the bridge of a large vessel, the luminous wake
of a ship travelling at even moderate speeds can be detected for some
distance, clearly revealing its position and, roughly, its direction
and speed. During World War II amphibious landings and other
naval movements were, on several occasions, compromised by the
presence of bioluminescence. Consequently, another goal of the
oceanographer is to eventually establish a pattern of reoccurrence so
as to forecast the periods of luminescence in areas of projected naval
operations.

BIOLOGICAL

OCEANOGRAPHY

At night layers ascend and merge near the surface.

THE DEEP SCATTERING LAYERS

Another biological phenomenon which has gained increasing
importance to both mariner and oceanographer during the last two
decades is the sea’s “‘deep scattering layers (D.S.L.s)”. Briefly, these
are the horizontal sound reflecting bands that exist at various depths
over broad reaches of the world’s oceans. Mariners today are
probably quite familiar with the physical aspects of the D.S.L.s as
they often produce “false bottoms” on the recording traces of echo-
sounding devices. Indeed, it has been widely conjectured that
misinterpreted ‘‘echograms’”’ may have led to the charting of non-
existent shoals. Today, determination of the exact composition,
behavior, and distribution of the layers is a continuing oceanographic
project, for much more information is needed regarding their possible
influence on sonar systems.

Discovered by accident during World War II, the “‘layers’”’ have
a relatively brief but interesting history. A group of physicists experi-
menting with sonic submarine detection gear consistently, and annoy-
ingly, recorded echoes from a uniform layer some distance above the
sea’s floor. During daylight hours an exceptionally well-defined
layer was frequently observed at 150 to 175 fathoms. At night it
disappeared. The feature could only be attributed to a suspended
stratum of some sound reflecting, or scattering, agent, and thus
derived the name ‘“‘deep scattering layer’. The name was pluralized
after subsequent experiments revealed the existence of multiple
layers.

Soon after initial discovery, a causative solution was sought in
some physical property of the sea capable of producing the sonic
reflection. To this end, attempts were made to correlate the phenom-
enon with density discontinuities, or abrupt temperature differences,
in the sea. However, workers were unable to suggest any physical
effect that would account for the layers’ characteristic of ascending
to the surface at sunset and descending to depth at sunrise.

Observing the close parallel between this characteristic and the
diurnal vertical migrations of certain marine animals, biologists
postulated that the scattering layers were of biological origin. This
theory has endured the test of time and is universally accepted today.

On the basis of this correlation and later field experiments it was
concluded that huge aggregations of tiny planktonic animals were
reflecting some of the sonic impulses, or “pings’’, from sound appa-
ratus. The animals, it was suggested, rose to the surface at nightfall
to feed upon the abundant phytoplankton. At daybreak they would
again seek the darkness of depth, either through the fear of predatation
or their natural sensitivity to light. Further investigations have shown
that during the day the layers remain at depths roughly between

700 and 2,400 feet. At night they rise almost to the surface and
diffuse, or they may merge into a broad band as much as 500 feet
thick. Most places in the deep ocean usually have three layers, the
deepest at an average of 1,900 feet. Sometimes, sounding traces show
very diffuse layers that stay at the same depth day and night.

Tiny fish and crustaceans found in scattering layer. Shown at approximately
actual size are two forms of lantern fish, a euphausiid, and a sergestid.

From physical evidence as a result of sampling and bathyscaph
observations, many researchers are of the opinion that shrimp-like
crustaceans called ewphauszids and sergestids are the reflecting agents
in the layers. Others, however, argue that crustaceans rarely occur
in sufficient densities to produce reflection layers. In rebuttal, the
the latter workers suggest that fish and similar animals with swim
bladders, or gas filled bubbles, are the causative agents. Quantities
of myctophid or lantern fish, 2- to 3-inch predators which feed upon

BIOLOGICAL OCEANOGRAPHY

crustaceans, have been collected in net tows to reinforce this conten-
tion. At least one observer has concluded that concentrations of
tiny jelly fish equipped with gas-filled floats are the source of the
scattering layer.

The complexity of the problem is indicated by the apparent
likelihood that several agents are involved, for a single layer often
“splinters” during vertical migration into as many as four separate
elements. These elements never cross one another, each seeking a
precise depth as though adjusted to a particular level of twilight.
Because of this stratification, exact identification of each element is
dependent upon the selectivity of sampling devices which, at present,
leaves much to be desired.

The inevitable development of improved sampling techniques
and echo sounding apparatus will, undoubtedly, resolve the problems
of the deep scattering layers. But apart from the acoustical problems
they present, biologists view the phenomenon as a valuable ecological
tool for understanding the mass distribution of life within the sea.

NATURAL SEA NOISES

Marine animals contribute another source of acoustic interference.
Contrary to the belief that the sea was a silent environment, many
aquatic animals are now known to produce noises of widely varying
nature. At times, concentrations of animal sound-emitters can set
up a veritable clangor beneath the sea, and because of the diverse
properties of air and water, little of it ever reaches the casual listener
above the surface. Over hydrophones, however, these ‘“‘fishy’’ noises
ean be plainly heard and recorded. While the sea’s inhabitants are
apparently well adjusted to the condition (having no other choice)
such noises can have serious effects on naval operations.

The military implications of natural sea noises were not fully
realized until World War II, when their intensity and worldwide
distribution were recognized as limiting factors in anti-submarine
operations. Early researchers found that hydrophone reception was
decidedly hampered by the ambient noise level produced by animal
sound-emitters. Some of the sounds detected and identified as bio-
logical were remarkably similar to sounds characteristic of surface
and underwater craft. At least one organism, or group, produces a
sound like an unrythmic hammering on steel to the understandable
dismay of a hydrophone operator.

Mindful of the obvious operational and psychological stress the
noises placed on ship’s crews, the Navy initiated a program to record
and identify them. The object of the program was to train operators
of acoustic gear to discriminate between biological sounds and mechan-
ical sounds and to possibly redesign equipment to filter out undesir-
able sounds.

The problem of identification is complicated by the fact that,
over hydrophones, the sounds made by an individual animal may
differ from the effect produced by a group. Thus, the croaker often
makes a drumming sound, but the noise produced by a dense shoal
of croakers has been described as resembling that of a pneumatic drill
tearing up a pavement. In some instances their chorus becomes so
voluminous that it drowns out completely any ship or propeller
noise. The snapping shrimp, an inedible variety smaller than a man’s
little finger, produces a sharp ‘“‘snap” with its lobster-like claw, but
the over-all noise created by a large number of such animals is a con-
tinuous crackling noise similar to radio static.

In the effort to catalog marine animal noises, workers found it
necessary to correlate the sounds recorded with more familiar terres-
trial ones. Today, it is known that porpoises and whales whistle,
click, bark, and moan; barnacles slurp; black mussels crackle; toadfish
croak, growl, and whistle; weakfish, silver perch, and spot perch
produce a rapid, raspy croak; the Atlantic croaker, true to its name,
makes a similar, almost drumming sound at a slower rate; the northern
puffer or swellfish squeaks and coughs among other noises; the striped
barnfish coughs; and the striped sea robin makes a sound like finger-
nails being scraped over a drum. On the other hand, many fish have
been found to be practically mute, such as the flounder and mullet.

The manner in which the organisms produce their sounds is fairly
well known. Crustacea sounds are normally of the percussion variety,
such as the claw-snapping of shrimp. The noises made by free-swim-
ming fish are usually the product of their swim-bladder. This organ
varies in form with the species of fish, and the type of sound emitted
is a particular function of its size, shape, and the manner in which it
is vibrated. Fish also produce rasping, scraping, grinding, or whining
noises by either grinding their teeth or by rubbing their fins together.

21

The exact function of marine animal noises is still uncertain.
They appear in some instances to be associated with breeding and
spawning, in others to be defensive and protective. It seems likely
that sounds produced by at least some fish are used by them for
spatial orientation in a manner similar to sonar. It has also been
determined that some of the sounds made serve no useful purpose at
all, and in some cases even reveal the originator’s presence to a lurking
predator.

Marine biologists are particularly interested in determining the
exact biological significance of sounds and look upon the non-military
use of hydrophones as a valuable oceanographic instrument. It is
evident that if certain sounds are peculiar to certain animal groups,
underwater listening could be used to plot the distribution of such
animals. Moreover, by classifying the creature’s various sounds,
such as those made while spawning and feeding, and those believed
to be “‘emotional’’, biologists hope to broaden their understanding of
the behavioral traits of marine animals.

CORAL REEF BUILDERS

Probably no branch of oceanography involves as many of the
earth’s sciences as the study of the origin and development of coral
reefs. Primarily an active biological process, the building of a reef
embraces geological, chemical, and physical processes, the extent of
which varies with the location and type of formation under construc-
tion. While considerable work has been done in this field over the
years, there remain wide gaps in knowledge which impede progress,
particularly in the physiology and ecology of reef organisms.

Common sea coral

BIOLOGICAL OCEANOGRAPHY

Stinging coral

Elkhorn coral

Following World War II, a war fought in coral seas of which
little was known, a marked intensification of coral reef investigation
took place which has resulted in the acquisition of valuable biological
data. The importance of continued research lies not only in the fact
that the constantly growing reefs pose a serious threat to present
and future marine operations, but improved harbor maintenance and
the stabilization of many important islands may depend upon a better
knowledge of coral formation. The studies are also important in
expanding our knowledge of the general ecology of the sea, for as a reef
develops, other organisms become adapted to the environment,
thriving and contributing to a relatively ‘closed system” of existence.

The most important builder on a coral reef is a creature very low
on the scale of evolution known as a polyp. These animals cement
themselves to an underwater platform and proceed to secrete an
external layer, or skeleton, of calcium carbonate which, due to the
shape of the young polyp, produces a stony limestone cup. As each
polyp matures it grows in size and complexity of structure, branching
and multiplying to eventually form large masses of dense rock. At
certain times of the year, the polyps reproduce their kind by releasing
larva which are carried by the currents to other sites, where, if suitable
conditions of temperature and depth exist, a new reef is formed. It
has been estimated that billions of tons of rock are thus created each
year.
Corals are specialized carnivores, subsisting on tiny planktonic
animals which they capture with their paralyzing tentacles. Typical
reef building corals characteristically contain within their tissues
numerous algae cells which they are incapable of expelling. This
symbiotic relationship between animal and plants contributes

mutually to each other’s well being, the exact significance of which
is the subject of considerable controversy among marine biologists.
It appears evident that the relationship is beneficial, at least to the
host polyp, for the most vigorous coral growth occurs within the
lighted depths, from 20 to 30 fathoms, apparently due to the fact
that the contained algae, like all plants, require light for survival.

Coral growth is also dependent on other factors which include
favorable temperature, salinity, and nutrient value of the surrounding
water mass.

A secondary but integral part of reef construction are the various
calcareous algae which grow upon the reef. In the course of time,
these stony plants have a mortise-like effect upon the environment
that binds the reef mass together, contributing to its over-all strength.

Coral reefs are constantly subject to various forces that can
damage or weaken them. Erosion from the constant battering of the
sea can eventually cause massive breakage, and the deposition of
sediments on living coral beds results in eventual death of the beds.
A number of snails, worms, and barnacles bore deeply into the very
foundation of coral colonies. Naturally, a greater knowledge of the
effects of these forces is essential to present and future coral reef
studies.

THE HARMFUL AND USEFUL ASPECT
OF MARINE LIFE

Probably the most important problem that man associates with
survival at sea is the danger of attacks by obnoxious animals. Whether
this or other factors are the primary detriment to survival is debat-
able. The fact remains that sea life poses a serious threat to naval
operations involving swimmers and divers. Furthermore, as the
rapid advances in underwater equipment and techniques extend the
depth and range of such operations, there is a greater need for effective
deterrents against the threat.

The number of species of marine animals capable of harming man
has been estimated at more than 3,000, and these are separable into
three categories—poisonous, venomous, and carnivorous. The last
category is undoubtedly the most familiar for it includes the biters
such as the fearsome shark. For a man-in-the-water the fear of sharks
is well founded, for out of approximately 250 species that inhabit
the seas, more than 50 are known to be dangerous. Furthermore,
sharks are to be found in all oceans from 45° north to 45° south
latitude.

Because of the many attacks attributed to them, no other marine
animal has been more extensively observed than the shark. Over
the years, chemical repellent agents have been developed and used in
survival circumstances. Their effectiveness has been less than com-
plete, for incidents have been recorded in which sharks have demon-
strated unpredictably savage conduct in apparent disregard of the
repellents released.

Attacks by other marine carnivores such as the barracuda and
the moray eel present a physical, as well as psychological hazard to
many types of underwater operations. Venomous animals, such as
the stone fishes, sea snakes, and numerous invertebrates, and a variety
of stinging organisms represent a constant menace to the survivor at
sea or the unwary swimmer or scuba diver. The development of
truly effective defenses against all of these forms will require far more
ecological and behavioral information than is now available.

On the brighter side, however, there are good indications that
marine life itself can provide the answers to these and many other
problems. It has been observed that certain marine animals and
plants produce substances which either kill, repel, or confuse other
forms. By isolating and examining these substances, biologists hope
to discover more effective repellents or deterrents for use against
obnoxious animals.

Studies of the pharmacological properties of marine plants and
animals may open the door on a new family of drugs. The defensive
poisons exuded by many sea organisms are believed to be the source of
potent new drugs for possible use in the war against cancer as well as
other human diseases. Anti-cancer drugs are also being sought in the
tissues of shark brains.

Studies of the amazing swimming characteristics of certain
marine animals, such as the dolphin and seal, may provide information
useful in the design and construction of new hulls for surface ships
and submarines. Research on the swimming techniques of marine
animals indicates that many possess highly efficient propulsion
mechanisms, completely silent and accomplished without detectable

BIOLOGICAL OCEANOGRAPHY

SL a ater
Let Serf
4 Mesh a mas tr }

ne

Some obnoxious fishes: 1. Moray eel. 2. Parrot fish. 8. Sea bass, or grouper.
4. Barracuda. 5. Puffer.

turbulence. This phenomenon is of considerable interest to the Navy
in the development of future submersibles.

Biologists have determined that many kinds of marine animals
have the ability to detect and identify targets at great distances and
then swim toward them with unerring accuracy. Closely related to
this phenomenon is the ability of shoals of fish to perceive and respond
quickly to some sort of self induced signal. These signals suggest a
highly effective system of underwater communications. Research in
this field is expected to evolve new concepts of target detection and
identification, long range submerged navigation, and underwater
communications.

Many other unique capabilities of marine organisms are being
studied in an effort to create new, and improve existing, man-made
devices. Biologists are investigating how marine animals such as
whales, porpoises, seals, and numerous fishes can sound rapidly to
great depths without developing the bends and other diseases con-
tracted by humans under similar conditions. The remarkable process
by which some marine animals can replace lost or damaged parts of
their bodies may hold secrets of cell formation useful to medical
sciences. The anti-bacterial activity of marine algae may aid in the
development of new antibiotics. The possibility of emulating natural
processes of air purification by constructing analogues based on the

23

photosynthesis of algae is being investigated as a means of improving
submarine habitability. These are but a few of the potentially great
discoveries at hand, and, in every instance, success will depend upon
the systematic acquisition of fundamental biological data.

FIELD METHODS

A fundamental step in biological research is the collecting of
sample organisms for laboratory examination. In marine biology,
this step is complicated by the fact that the specimens must normally
be removed from a murky, three-dimensional medium, the sea. As
the objects of the search are, therefore, usually hidden from direct
view, they must be groped for in a manner vaguely comparable to
hunting for a button at the bottom of a well-stowed sea bag. The
search is, for the most part, dependent upon gear which can be lowered
to a desired depth from the deck of a ship.

The size, mobility, and natural habitat of a sought-for organism
determines the type of sampling gear to be used. Traditionally, the
basic gear is the net, with a number of variations. The free swimming
animals are sampled with gear similar to the trawls used by commer-
cial fishermen. Bottom dwelling organisms are collected by dredges
and grabs. A dredge is simply a bag-like net attached to a heavy
framework which is dragged along the sea’s floor. A grab consists of
a pair of heavy metal jaws, not unlike the construction workers’ “‘clam
shell’? shovel. Coring devices are used for collecting undisturbed
samples of bottom sediments. Because the microscopic nannoplankton,
such as the smaller diatoms, dinoflagellates, protozoans, and bacteria
pass through the finest nets, they must be collected in water samples
and then separated, usually by centrifuge, in a laboratory.

In sampling the zooplankton, as required in studies of the deep
scattering layers, specially designed nets are towed through the
water at a predetermined depth. The depth is maintained constant
by a paravane-like device attached to either the tow wire or the net.
Accurate quantitative samples require that the amount of water
filtered be known, and this is dependent on mesh size, area of filtering
surface, shape of net, area of opening, and the speed of the towing
vessel. A more modern innovation of this technique employs a meter
at the net opening which registers the amount of water that enters
the net during a tow. Of course, some means must be provided to
open and close the sampling device at any desired time and depth.

Because of their superior swimming ability, many of the larger
planktonic animals elude towed nets. Such losses can be reduced by
increasing the speed of the tow, but speed is limited by the strength of
available nets. To obviate many of the difficulties associated with
net tows samples have been collected by pumping them up, with
measurable quantities of water, through a hose from the required
depth and caught in filters aboard ship. A more recent variation of
this technique eliminates the hose and employs a submersible pump,
electrically controlled from deck, which is attached to a net and
lowered to a precise depth. A meter on the pump measures and
records the amount of water screened.

A multiple plankton sampler.

BIOLOGICAL OCEANOGRAPHY

A mechanical device known as a continuous plankton recorder is
used to supplement the data acquired by nets. The device is essen-
tially a torpedo-shaped tube about 3 feet long, and it is designed to be
towed behind a ship at full speed. The planktonic organisms enter
the machine through a front opening and come to rest on filtering
material which is slowly wound across the tube. The material, with
the plankton it has accumulated, is continuously rolled onto a storage
spool. Since the winding mechanism is actuated by an external pro-
peller, the speed at which the filtering material passes across the
opening is proportional to the speed of the towing vessel and, conse-
quently, the number of organisms collected can be related to the
distance traveled.

A specially equipped research vessel is required for most types
of plankton investigations. Unfortunately, these specialized ships
are too few in number to provide the numerous observations necessary
to chart the changing patterns of plankton distribution throughout
the world. To implement such a program the use of merchant ships
and warships is being contemplated for the systematic collection of
data along their normal routes. Automated instrument packages
operated from these “ships of opportunity” could yield valuable
biological data without affecting their routine or schedule.

Marine scientists are aware, however, that the classical methods
of data collection are not wholly sufficient for the needs of modern

Diver using underwater camera.

24

oceanography. For one thing, the depth at which existing sampling
gear can be effectively used is limited. For another, the remote
operation of such equipment, however precise, precludes any real
study of the overall environment, so important in ecological work.
To fully understand the nature of the deep, biologists must use all
of their senses, particularly that of sight.

In intertidal waters and on coral reefs, the work of both scuba
and “‘hard hat’’ divers are augmenting the data collected by instru-
ments. The use of remotely controlled, underwater cameras has
permitted biologists to observe bottom-dwelling organisms under
natural conditions. An even superior technique lies in the use of
underwater television cameras. In the abyssal depths of the sea,
observations from manned deep-diving vehicles such as bathyspheres
and bathyscaphs have contributed materially to our knowledge of
that region. But, because man is essentially a frail instrument, the
use of highly sophisticated robot vehicles will doubtlessly play an
important role in the future of deep-sea research.

EPILOGUE

The foregoing is a brief attempt to present some of the more
challenging projects in biological oceanography. If after reaching
this point the reader has concluded that the unsolved problems are
numerous, the objectives of the article will have been well served.
The very fact, however, that few of us entertain serious doubt that
these problems can be solved is a tribute to the present level of our
technology. But this is not to predict any forseeable end to such
problems, for historically, each success becomes a stepping stone
to greater achievement. The results of applied research today will be
merely the basic knowledge of tomorrow, as whole new concepts and
goals will undoubtedly come into focus. This, however, is a healthy
progression and one which will provide the necessary motivation
for continued effort.

The modern challenge to marine biologists is to understand,
explain, and predict the intricate interrelationships of life in the sea.
It is, of course, impossible to foretell the extent that this knowledge
will affect the future of mankind. That it will be profound appears
evident in the many imaginative programs being undertaken. The
ultimate goals are far reaching and constantly being extended as the
sciences adjust, almost daily, to an increasing awareness of the oceans’
great potential. Today, it seems reasonable to envision spectacular
achievements in inner space that will parallel those of outer space.

The present and future plans of the National Oceanographic
Program include the concerted efforts of many institutions, govern-
mental and private, toward common goals. The U.S. Naval Ocean-
ographic Office is an active participant in this great enterprise and
will play an important role in unlocking the door to that strange
world beneath the seas on which we sail.

DANGEROUS SEA LIFE

J. W. Lermond
Maritime Safety Division
U.S. Naval Oceanographic Office

Since the beginning of time the sea has stimulated the imagina-
tion of man. A most interesting part of this speculation has always
centered around dangerous marine animals. Ancient writings abound
with tales concerning legendary creatures of the deep. Early mariners
feared destruction of their vessels in a sea of imaginary monsters.
Picture and legend illustrate some of these ancient beliefs. Super-
stitions connected with the sea, outlining its mysteries and vastness
continue to influence our thoughts to the present time.

Legend and superstition concerning the sea were a part of the
religious life of each member of an ancient coastal tribe. The awe
inspiring power of the sea in its many moods held the ignorant in
reverent terror. Tribal taboos restrained the conduct of the indi-
vidual, thus protecting him from the more poisonous marine species
in the area. Veneration was but little short of worship and these
imagined beneficial elements later took the form of deities. Half-
human, half-fish gods and goddesses are depicted on many ancient
temples and were also used as figureheads on ships. Some were
beautiful, some were horrible, while a few, such as the Greek sea god
Poseidon, assumed human form. All seafarers came under the myth-
ical protection of Poseidon who ruled the waters in conflict with the
land deities. Poseidon’s uncontrolled stormy temper tantrums, sym-
bolic of great strength, could reportedly produce earthquakes or
control the shape of continents. Poseidon, of course, held full sway
over all marine animals, and the dolphin was symbolic of his pro-
tection.

Many persons and some nations depend upon the sea for food
and other necessities of life. Others must ply the sea lanes in pursuit
of a commercial existence. An increasing number fly above the
oceans to satisfy a variety of travel needs. Recent observation has
thus revealed a great many details concerning the sea and marine
animals. Concentrated efforts of many scientific investigations have
been devoted to study, to describe, and to tabulate present day
knowledge concerning the ocean and its inhabitants. The sea has,
notwithstanding all this effort, kept many secrets locked in the
gloomy depths beneath the surface. Present efforts in the field of
oceanography endeavor to reveal facts which have long been the
subject of theory or mere speculation.

Losses of surface vessels and aircraft during the last war, with
accompanying casualties due to nature’s perils, brought about a
greater interest in survival techniques. The reports of survivors,
rescuers, action reports, and original papers on survival were studied
in an effort to improve the situation of a downed aviator or ship-
wrecked mariner. After the war, the combined experiences and
researches on the subject were critically examined to improve the
various survival manuals. This work continues in an effort to per-
fect all details.

Survivors in life rafts narrated in detail every sight of a shark,
yet few stories were found of survivors being attacked or killed by
sharks. Off the coast of New Guinea, one flier was attacked by
a shark when swimming outside the coral reef and lost a leg; however,
he lived through the ordeal. Another story concerned a Navy plane
which had ditched. The pilot and gunner were kicking hard to keep
clear of the wreckage; perhaps the splashing attracted the sharks.
The gunner had removed his trousers and shoes and still wore white

25

shorts. Sharks nosed him several times and finally one bit his right
thigh. The bite was not clean; the man was pulled under but broke
free and bobbed to the surface, shouting for help and continuing to
splash in the water. The sharks continued to attack, biting and
pulling the gunner under the water until he was drowned. The pilot,
who survived to report this shark attack, said that the sharks kept pull-
ing at the bobbing body until it finally disappeared. The sharks then
followed the pilot, who splashed at them and finally hit one shark on
the snout. The shark turned quickly and struck the pilot in the face
with his tail. This broke the man’s jaw and caused abrasions on his
face. The sharks then left and were not seen again.

Survivors in life rafts reported seeing many sharks, few sharks,
or a single shark; yet a flier spent twelve days without seeing one.
Life raft survivors tied extra clothing on a line and used it as a sea
anchor; this sea anchor was attacked by sharks several times.

Other life raft accounts mentioned seeing large fish. One pilot
saw a 40-foot whale surface near him and spout into the air; the
same pilot glimpsed an 8-foot marlin which swam around his raft
several times. A sea turtle nosed the raft of another pilot for 15 to
20 minutes; the pilot did not hit the animal for fear his sudden
movement or that of the turtle would upset his craft.

Other survivors reported injuries from coral reefs in the form of
cuts and lacerations from walking or falling on the sharp edges.
Coral cuts are painful, difficult to treat, and usually slow to heal.
One survivor noted a method used by the natives in the treatment
of wounds sustained by coral. The acid juice of limes or other fruit
was used to apparently help dissolve the calcium carbonate of the
coral fragments left in the wound. While the lime juice itself was pain-
ful, such treatment seemed to promote healing. A flier reported that
sea spines could be removed much more easily after such treatment.

A review of the facts concerning wartime survival experiences has
shown many interesting details concerning dangerous sea life. The
objectives of this article are to present brief essential details concerning
habits and characteristics together with distribution and environment
data for the more dangerous species of sea life. In order to be of practical
value to those concerned, much technical detail had been eliminated, but
may be found in the many good books on the subject. A simple division
of material, suggested by the type of injury inflicted on humans, has been
followed. Marine animals that bite and a few that sting are described
and illustrated.

DESTRUCTIVE BITERS
SHARKS

Among the more dangerous marine animals, the shark, being
most numerous and voracious, has established a fearful reputation.
Through the years, however, much sensational journalism has been
lavished on sharks. Although found to be peaceful and retiring in
nature, investigation of the records and scientific evidence indicate
that only a score or less of the shark species, out of several hundred
known to exist, are likely to attack man. A knowledge of sharks
and their habits, if judiciously applied, may avoid an attack. Certain
rules of conduct should be carried out to avoid attracting or exciting
sharks.

DANGEROUS SEA LIFE

Nid IVNV

Nid 1vSyOd pug

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Nid 1wYOL03d

Nid 1WSYOd 3ST

STINLSON

26

DANGEROUS SEA LIFE

Adult sharks range in size from 18 inches to more than 50 feet
in length. The giant whale shark and many other species feed ex-
clusively on small marine organisms and do not ordinarily pose a
great threat to a man in the water. A great many sharks eat large and
small fish, including other sharks, seals, and a variety of organisms
or material, depending upon feeding circumstances. Many sharks
are too small or are equipped with inadequate teeth to be of any real
danger to a man in the water. Considering the feeding habits of all
sharks more than 4 feet in length and adequately equipped with
teeth, the situation may be considered dangerous for swimmers or
divers if blood or other attraction may be present.

Detection by sharks of blood, food, or injured animals in the
water has always posed a subject of considerable interest. Although
possessed of poor visual acuity and a low order of intelligence, a
shark’s ability to detect food is phenomenal. Detection is probably
accomplished by a highly developed sense of smell and an extremely
sensitive system for reception and detection of low frequency vibra-
tions in the water. Their ability to detect a disabled or wounded
animal at long range has been considered most uncanny.

In addition to these abilities and habits concerned with casual
eating, either alone or in small numbers, sharks have also demon-
strated unpredictably wild conduct, under circumstances involving
many sharks or much food. This may occur subsequent to an explo-
sion in the water, the sinking of a vessel, or crash of a plane. When
resorting to these mob tactics, sharks may be observed in a frenzy,
attacking vertically from the depths, dramatically breaking the
water, and snapping savagely at everything in sight. During this
most dangerous situation, nearly all repellant devices are ignored.
Sharks may be seen ripping and devouring each other, with one
unfortunate fish the target of attack by several larger ones. It is
under circumstances like these that sharks may attack one swimmer
out of many in the water and concentrate on this one to the total
exclusion of those attempting a rescue. This, however, cannot be
depended upon, and experienced divers explain that shark conduct
even under mob frenzy conditions is unpredictable. p

The danger of attack by sharks is greatest in tropical and sub-
tropical areas between Latitudes 30°N., and 30°S. Temperate waters
are generally considered to be free of shark attacks. However, this
is not always true, as the records prove. Certain shark species mi-
grate periodically into cooler waters in search of food. Areas which
have been found particularly dangerous are Australia, South Africa,
and the Pacific coast of Panama. Most recorded attacks have taken
place in water temperatures greater than 70°F., but fatalities have
taken place in temperatures of 60°F. or less. The season with the
greatest number of recorded attacks is during the summer, especially
from 3:00 p.m. to 4:00 p.m. daily. This is also the time when most
recreational bathers are attracted to the beach. Sharks are round-
the-clock eaters, however, and frequently feed during the hours of
darkness when the risk of attack may be even greater.

In considering those sharks most dangerous to man, members of
4 families are believed to be of greatest concern to divers or swimmers:

(a) The Mackerel or Man-eater Shark family (ISURIDAE)
(b) The Requiem Shark family (CARCHARHINIDAE)
(c) The Sand Shark family (CARCHARIIDAE)

(d) The Hammerhead Shark family (SPH YRNIDAE)

Four species are described and illustrated as being representative
of these families, but are not to be considered the only dangerous
members:

(1) White Shark, Carcharodon carcharias (Figure 1), is one
of the most dangerous of its kind. It is savage, aggressive, fast-
swimming; it has been known to attack boats. Numerous
human attacks are accorded to this species. Distinctive charac-
teristics are the lunate or moon-shaped tail fin and coarse serrate
teeth. Color is slate-brown, slate-blue, gray, or almost black
above, shading to dirty white below. The tips of the pectoral
fin are also black, usually with some adjacent spots black. They
may attain a length of 30 feet or more. Distribution is oceanic
—widespread in tropical, subtropical, and warm temperate belts
of all oceans.

(2) Tiger Shark, Galeocerdo cuvier (Figure 2), is sluggish in
character except in pursuit of food. The tiger shark when stim-
ulated becomes a vigorous and powerful swimmer. Attacks on
humans are credited to this shark, although it tends normally to
being a scavenger. Distinctive features are the very short snout
and sharply-pointed tail. It is colored gray or grayish brown,

27

and darker above than on the sides or belly. The oblique trans-
verse bars usually appear only in the smaller specimens. It
attains a length of 30 feet, but the largest recorded specimens
measured 18 feet. The tiger shark is widespread in the tropical
and subtropical belts of all oceans, both inshore and offshore
and is reported to be the commonest large shark of the tropics.

(8) Sand Shark, Carcharias taurus (Figure 3), is a shore
species which lives on or close to the bottom and is compara-
tively sluggish but has a voracious appetite. This shark, in
East Indian waters, enjoys a bad reputation, however, this is
not true of the North American species. Gill openings in front
of the pectoral fin, a second dorsal fin about as large as the first,
with the first dorsal entirely in front of the pelvic are distinctive
features. It is colored a bright gray-brown above, darkest along
the back with the snout and upper sides of the pectorals shading
to gray white on the belly. The body rearward from the pec-
torals is marked with round to oval yellow brown spots. The
sand shark may reach a length of 10 feet. It inhabits the west-
ern Atlantic from the Gulf of Maine to Florida and southern
Brazil, as well as the Mediterranean Sea, tropical West Africa,
Canaries, and Cape Verde Islands in the Eastern Atlantic. In
Argentine waters and the Indo-Pacific it is represented by simi-
lar species.

(4) Hammerhead Shark, Sphyrna diplana (Figure 4). This
powerful swimmer may frequently be seen at the surface, in-
shore, or far at sea and is definitely known to attack humans.
It is colored ashen-gray above, fading to white below. The
hammerhead is readily distinguished by the widely expanded
head with eyes at the outer edge. It may attain 15 feet in length
or more, and closely related species are distributed throughout
tropical warm temperate zones of all oceans, including the Medi-
terranean Sea.

The bites of sharks are almost always severe, and death is
usually due to loss of blood and to shock. Fifty to eighty percent of
those bitten may die. Severe skin abrasions are suffered by brushing
against the very rough, sharp skin of sharks. First aid requires
prompt and vigorous action to control the bleeding and shock. The
patient must be kept warm. Use of large gauze pressure bandages
held with elastic bandages may be best to control the bleeding.
Tourniquets have been described as dangerous and impractical for
use by the inexperienced person. Hospital or surgical treatment is
required. Intravenous fluids should be administered as soon as pos-
sible, while whole blood may be required later.

The prevention of shark bite depends mostly upon avoidance of
the contact. When sharks are present, persons should not dangle
arms or legs in the water. Injured swimmers should be removed
from the water quickly. If obliged to be in the water, the use of
dark clothing and equipment is preferred. All movements should be
slow and purposeful to avoid attracting sharks. Should sharks ap-
pear and individuals unavoidably remain in the water, they should
remain perfectly still. In a number of instances, curious sharks have
left the scene under these circumstances. In other cases, they have
been successfully thrust away by use of a large stick. In close con-
tact, some sharks have departed when struck on the snout, eyes or
gills. However, attempts to wound the shark may be useless and
may only aggravate the situation.

BARRACUDA

Barracudas are an extremely pugnacious and dangerous fish
which may attain a length of 6 to 8 feet. They have a large mouth
equipped with knife-like canine teeth, and, being swift swimmers,
strike rapidly and ferociously. They are feared more than sharks in
some areas of the West Indies.

Great Barracuda, Sphyraena barracuda (Figure 5), which is
found off Brazil, in the West Indies, and northward up to Florida,
appears to be the most feared fish. It is also known in the Indo-
Pacific area from the Red Sea to the Hawaiian Islands. Other
species are widely distributed throughout the tropical and subtropical
waters of the world. Among these species are some which differ
greatly in nature and size and are never known to attack man, how-
ever, none of them seems to exhibit any undue fear of man.

Barracudas are attracted by almost any bright or colored object
in the water and may attack indiscriminately. This is especially true
in murky water where it appears they are handicapped by poor vision,
but because of their predatory nature they attack anyway.

DANGEROUS SEA LIFE

Wounds inflicted by a barracuda differ from those of a shark by
the shape of the wound. The former leave straight row toothmarks,
while the latter take a U-shaped curve like that of the particular
shark jaw involved. Bites and wounds inflicted by the barracuda
should be treated with the same general care as shark bites previously
described. Hospital or surgical care will be required.

Prevention of attack appears to be one of respect and caution
when in waters known to be inhabited by this dangerous species.
Any shiny or bright object in the water will attract their interest
and attack may swiftly follow.

KILLER WHALE OR GRAMPUS

Killer whales usually hunt in packs of 3 to 30. The grampus is
a toothed whale, voracious enemy of all sea creatures, including its
own kind. Although measuring only 15 to 30 feet in length, they
may attack much larger whales, using wolf-pack tactics. Killer whales
are characterized by a bluntly rounded snout, high black dorsal fin,
white patch just behind the eye, and with a striking jet-black color
above, contrasting with snow-white underparts. These whales have
large conical teeth which interlock when the jaw is closed. They are
swift swimmers, the implacable enemy of seals, walruses, and even
penguins. Scientists regard this whale’s intelligence as being about
on the level with that of a domestic dog. Many remarkable experi-
ences have been described to illustrate the superior mentality of these
whales. They have been reported to collaborate with whalers in
obtaining their prey and to utilize wolf-pack tactics to harry larger
whales into shoal water where they may be easily killed.

The Killer Whale or Grampus ocra (Figure 6) is found in all
oceans and seas from the Barents Sea or Bering Strait to beyond the
Antarctic Circle. The only defense against this ruthless and fero-
cious killer is a hasty retreat. Divers should get out of the water if
killer whales are observed.

Figure 6. KILLER WHALE

28

TRIDACNA CLAMS

These giant clams abound in the reefs of Pacific tropical waters.
Specimens measure up to 4 feet in length and several hundred pounds
in weight.

This mullosk, named T'ridacna gigas (Figure 7), if prodded while
open, will close with a tight vise-like grip. Divers and others have
been reported trapped by the giant clam. Release can be gained by
inserting a knife between the valves and severing the 2 large trans-
verse adductor muscles which hold the 2 halves together.

MORAY EELS

Moray eels are possessed of powerful muscular bodies and may
attain a length of 10 feet. Their narrow jaws are armed with knife-
like canine teeth, well able to inflict severe lacerations or to hold a
bulldog-like grip until death. Morays are incredibly slippery and
difficult to handle. They dwell mostly on the bottom in crevices and
holes under rock or in coral.

Moray eels, of the family Muraenidae (Figure 8), of about 20
species, are largely confined to tropical and subtropical seas. Several
temperate zone species are known to exist in California and in Euro-
pean waters.

Because injury resulting from a moray eel bite is of the tearing,
jagged type, similar to that inflicted by the barracuda, the same
principles of treatment should be followed.

Avoidance or prevention of wounds from moray eels may be
accomplished by exercising due diligence and caution when exploring
crevices and holes under rocks or coral where eels may be lurking.
Hands and feet must be kept out of rock crevices. Although moray
eels are vicious biters, they have seldom been known to attack except

when .Provoked- MISCELLANEOUS

There are many other aggressive and dangerous marine animals
capable of causing serious wounds or abrasions. A downed aviator,
beached mariner, or diver must guard against becoming the target
for attack or inviting a rubbing acquaintance with the following types:

1. The Giant Devil Ray or Manta, Manta birostris may
reach a spread of 20 feet and a weight of 3,500 pounds. The
greatest danger is caused by the huge size of the manta and by
the cephalic fins covered with a coarse skin. This sharp skin is
capable of producing a severe abrasion on close contact. Active
curiosity while investigating air bubbles may lead the manta
into entanglement with air hose. Normally, the manta swims
or basks near or on the surface and feeds on plankton, small fish,
and crustaceans. Mantas may be observed in tropical seas as
they leap out of the water, and may be heard to fall back with
a resounding smack. Their color is reddish brown to black
above and light below.

2. Sea Lions are not usually ferocious, but during the
breeding season the larger bulls become irritable and may take
exception to any intruder. They may take a nip at a diver or
swimmer during this season, whereas ordinarily they are merely
curious.

3. Seabass or Grouper, Serranidae, may reach a length of
8 to 10 feet and attain a weight of 800 pounds or more. Because
they are unusually curious and bold, large groupers become a
potential hazard to divers or swimmers. Although not aggres-
sive, they are voracious feeders, possessed of a fearless attitude,

DANGEROUS SEA LIFE

and cavernous jaws. They may usually be found lurking around
rocks, caverns, or old wrecks.

MARINE ANIMALS THAT STING

The lethal abilities of stingrays were described in early Greek
literature. Numerous other references to the h. -n inflicted by the
stings of marine animals have been recorded in ancient literature and
in news reports of later years. While the stings of fish were being
analyzed as a recognized danger before the turn of the century, the
causes of many disabling occupational illnesses experienced by marine
workers remained obscure until fairly recent times. The sponge
fishermen’s disease, for example, has been found to be caused not by
the sponge but by the stinging tentacles of very small sea anemones
which adhere to the sponge.

A. Invertebrates

The poisonous invertebrate marine animals that inflict injury
by stinging may be divided into 4 main groups:

(1) The coelenterates, including corals and sea anemones,
jellyfishes, and hydroids.

(2) The molluses, including univalve shellfish and octopuses.

(3) The annelid worms, including bloodworms and bristle-
worms.

(4) The echinoderms or sea urchins.

COELENTERATES

Coral polyps and sea anemones of the coelenterate group are
often mistaken for sponges. In reality they are a more advanced
form of life. The coelenterates may be likened to an uncorked flex-
ible bottle, with a circle of tentacles at the mouth designed for capt-
uring food. The points of interest, however, are the remarkable
stinging cells which are used for the capture of food or as a defense
against enemies. This apparatus consists of a trigger hair which,
when touched, actuates a spine followed by a hollow-thread through
which a paralyzing drug is injected into the victim. The stinging
cells or nematocysts are the source of many illnesses encountered by
skin divers, sponge fishermen, and other marine workers.

Coelenterates are divided generally into 3 classes, examples of
which are as follows:

1. The hydroids, which are commonly encountered tufted
on pilings, seaweeds, or rocks. The more common types, all of
which possess stinging cells, are:

(a) Fire Coral, Millepora alcicornis, a false coral, some-
times called stinging coral, is generally found among the true
corals in warm waters of the tropical Pacific or Indian
Oceans, as well as in the Red Sea and Caribbean.

(b) Portuguese Man of War, Physalia physalis, also
called Blue Bottle, is often mistaken for a jellyfish. This
hydroid floats on the surface of the water in all tropical
oceans and the Mediterranean Sea. The stinging tentacles
may trail several feet down into the water.

2. Jellyfishes; this includes the large bell-shaped medusae
having 8 notches on the margin, and many other species which
ean be considered especially dangerous:

(a) Sea Wasp, Carybdea alata (Figure 9), inhabits the
tropical areas of all oceans.

(b) Sea Wasp, Chiropsalmus quadrigatus, is an especi-
ally dangerous inhabitant of Australian and Philippine areas
and the Indian Ocean. A less dangerous, but related form,
is found in the Atlantic Ocean.

(c) Sea Nettle, Dactylometra quinquecirrha, is a widely
distributed form which may be found as far north as New
England coastal waters, as well as in all tropical sea areas.

(d) Sea Blubber, Cyanea capillata, inhabits the North
Atlantic and Pacific to the Arctic Ocean. Other stinging
species of this genus exist southward into tropical areas.

3. The sea anemones and corals include venomous mem-
bers as follows:

(a) Elk Horn Coral, Acropora palmata (Figure 10),
inhabits the Florida Keys, Bahamas, and West Indies.

(b) Sea Anemones, Actinia equina, inhabits the Atlantic
from the Gulf of Guinea to the Arctic Ocean and the Medi-
terranean and Black Seas, including the Sea of Azov.

(c) Rosy Anemone, Sagartia elegans, inhabits eastern
Atlantic Ocean waters from Iceland to the African coast
and the Mediterranean Sea.

29

Coelenterate tentacles may be sticky for holding, or long for
entangling, and may be equipped with stinging cells. The stinging
cells, or nematocysts (Figure 11), are situated in the outer layers of
tissue on the tentacles and may be likened to tiny, diabolica] hypo-
dermic syringes and needles arranged to inject a paralyzing drug into
an unwary victim. They are elaborately armed weapons, cocked
and ready to fire on contact. Swimmers who brush against a jelly-
fish may be stung by literally thousands of tiny poison weapons or
minute sting organs.

Symptoms produced by coelenterate stings vary according to
kind or locality. Some persons react in different ways than others.
Wounds are primarily local skin irritations. A few are painful and
ulceration may follow. The sea wasp or Chiropsalmus is a most
venomous organism and can produce human death in 3 to 8 minutes.

Stinger symptoms vary and range from a mild prickly or stinging
sensation to a throbbing pain which may render the victim uncon-
scious. The pain may be localized or may radiate to the armpit, groin,
or abdomen. Local redness may be followed by inflammatory swelling,
blistering, or minute skin hemorrhage. There may be shock, mus-
cular cramps, loss of sensation, nausea, vomiting, severe backache,
frothing of the mouth, constriction of the throat, loss of speech,
difficulty in breathing, paralysis, delirium, convulsions, and finally,
death.

The usual treatment is directed toward relieving the pain, alle-
viating the effects of the poison, and controlling shock. Morphine
may be used to relieve the pain. Histaminics by mouth, or creams
applied locally, may prove valuable in treatment of the rash. Sooth-
ing lotions such as olive oil, ethyl alchohol, sodium bicarbonate, and
dilute ammonium hydroxide have been used. Artificial respiration,
stimulants, and other measures may be necessary. Specific anti-
dotes are not known.

Avoidance of original contact with the tentacles is important.
The tentacles may trail as long as 50 feet, so jellyfish must be given
a wide berth. Rubber suits or tight fitting woolen underwear have
proven to be useful protection. Dead jellyfish found on the beach
are also hazardous, as the nematocyst remain potent. Waters which
have been storm lashed may contain many shreds of tentacles which
can each inflict a wound. Swimmers or others, after contact, should
leave the water and seek treatment. Washing of the poisoned skin
area with dilute ammonia or alcohol, as soon as possible, will be
helpful. Mineral oil or baby oil may help to alleviate the stinging
sensations.

CORAL CUTS

Wounds inflicted by the stony corals are an ever-present annoy-
ance to marine workers in tropical areas. The calcareous, razor-sharp
edges produce wounds which are notoriously slow to heal. Coral cuts,
if left untreated, may, under adverse living conditions, become ulcer-
ous. Stinging cells, similar to those of jellyfish, may complicate the
conditions. Red welts and itching are often a primary reaction to
ordinary coral cuts.

Treatment involves prompt cleansing of the wound and removal
of particles. Application of antiseptic agents should follow. If the
case is severe, bed rest or elevation of the limb may be required.
Various poultices and applications have proven helpful in varying
degrees. Antihistaminic drugs taken by mouth or applied locally may
afford a measure of relief to the patient.

Activity carried out in the vicinity of coral requires the wearing
of appropriate protective clothing. Heavy shoes, gloves, and outer
garments will help to prevent contact.

MOLLUSCS

Typical members of this group that may produce a venomous
sting or bite, fall into 2 categories: (1) those with a spirally twisted
single shell, (Gastropods), and (2) those with no shell, such as the
octopus or squid, (Cephalopods).

GASTROPODS

The Gastropods or univalve molluses include land, freshwater,
and marine snails and slugs. They are characterized by a single
spirally coiled shell, or, as an exception, without a shell as is the
case of the slugs. Typically, a distinct head, 1 or 2 pairs of tentacles,
and a flattened fleshy foot exist. The shell or coned type are poten-
tially dangerous and may be of concern to those who work or live
near the beach. Cone shells of this type (Figure 12) have long been
collected because of the attractive patterns displayed. Of more than

DANGEROUS SEA LIFE

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30

DANGEROUS SEA LIFE

400 species, however, most contain a fully-developed venom appa-
ratus. Cone shells may be seen crawling along the sand or may be
found under rocks or near coral. Some of the more dangerous tropical
species are listed as follows:
(a) Court Cone, Conus aulicus, ranges from Polynesia to the
Indian Ocean.
(b) Geographer Cone, Conus geographus, inhabits the Indian
Ocean and the Pacific Ocean from Polynesia to east
Africa.
(c) Marbled Cone, Conus marmoreus, ranges from Polynesia
westward to the Indian Ocean.
(d) Striated Cone, Conus striatus, inhabits the area from
Australia to east Africa.
(e) Textile Cone, Conus textile, ranges from Polynesia to
the Red Sea.
(f) Tulip Cone, Conus tulipa, ranges from Polynesia to the
Red Sea.

The venom apparatus of cone shells lies near the shell opening.
The radular teeth are thrust into the victim, and the venom is be-
lieved to be forced under pressure into the wound opening.

The sting of a Conus usually produces a numbness or burning
sensation. The numbness and tingling may spread rapidly and
become particularly pronounced about the lips and mouth. Respira-
tory distress is usually absent. Paralysis and coma may follow. Death
miay be the result of heart failure.

Specific treatment for cone shell stings has not been discovered.
Efforts should be devoted to alleviating the pain, combating the
effects of the poison, and preventing secondary infection. The wound
should be promptly irrigated and washed clean with sterile saline, if
available. Suction may be applied to remove poison. A small inci-
sion may be required. A 30-minute soaking in hot water or hot com-
presses, according to location of the sting, has been recommended.
Under conditions of unfavorable delay in treatment, the administra-
tion of antibiotics may be desirable. The patient should be kept
warm and stimulants may be required. Early hospitalization and
treatment, as in the case of venomous fish sting, is recommended.
Cone shells, if still alive, should always be handled very cautiously

id stings.
to avoid stings CEPHALOPODS

Nautilus, squid (Figure 14), cuttlefish, and octopus (Figure 13)
are included in this group. Members are characterized by 8 or 10
tentacles around a muscular central body mass. A powerful, parrot-
like beak, concealed in the mouth, is used in conjunction with the
tentacles for tearing captured food. A well developed venom appa-
ratus exists. Fast movement through the water is accomplished by
water jet propulsion.

Because the octopus has been subjected to much publicity for
many years, it is now vastly over-rated as a hazard. Actually, the
octopus is timid and will usually hide in holes. They are curious but
very cautious. They are often found in the intertidal zone and most,
if not all, species live in depths of less than 100 fathoms. The actual
damage to be feared by humans is the danger from poisoned biting.
A relatively small octopus can cause as much damage as a large one
in this respect. Although some may attain an overall length of 25
feet, there is no reported increase in demonstrated aggressiveness.
They are normally a fearful sight, whether seen out of the water or
encountered while swimming.

Identification of the various species of Cephalopods is difficult.
The bite is similar for all species and usually consists of 2 small
puncture wounds, according to the size of the particular specimen.
A burning sensation with localized discomfort may later spread from
the bite. Bleeding is usually profuse and indicates that clotting has
been retarded by the poison. Swelling and redness commonly de-
velop in the immediate area. While recovery is fairly certain, a
fatality has taken place from the bite of a small unknown variety.

Treatment of wounds from octopus bites should be carried out
as for fish stings. Prevention of the bite relies on avoidance of the
octopus and the wearing of an outer cloth garment. Gloves should
be worn for handling the octopus, if handling is required. The best
method for killing an octopus has been described as a forceful stab
between the eyes.

ANNELID WORMS

Segmented seaworms possess tufted, silky, chitinous bristles in
a row along each side. Upon contact or stimulation of any kind,
the bristles rise on edge, the worm contracts and presents a defensive

31

armor of tiny spears to the intruder. The fine bristles penetrate the
skin in much the same way as prickly pear cactus spines. They are
difficult to remove and produce a burning sensation. Later, the area
becomes inflamed and may afterwards swell or become numb. Other
worm species have strong jaws, which inflict a painful bite. These
worms, up to 12 inches long, may be encountered under rocks or
coral.

Representative species of both types are illustrated as follows:

(a) Bristleworm, Eurythoe complanata (Figure 15), is found
in the Gulf of Mexico and throughout the tropical
Pacific area.

(b) Bloodworm, Glycera dibranchiata, is found on the Caro-
lina coast and northward into Canadian waters.

The bite of the bloodworm, round and with a red dot in the
center, may or may not penetrate the skin. The bite is usually
surrounded by a pale area, later becoming hot and swollen, and then
turning numb or itchy. A bristleworm contact, on the other hand,
produces inflammation, swelling, or numbness which may persist for
several days.

Since it is not definitely known whether the bite is poisonous or
not, all sea worm bites or stings should be treated in the same manner
as fish stings. Bristles are best removed with forceps, since scraping
may break the bristles off and complicate matters. An effective
method of removal is by the application of adhesive tape over the
bristles. After removal, the area may be treated with ammonia or
alcohol to alleviate the discomfort. Certain of the sea worms inflict
a painful bite and should not be handled, except while wearing pro-

tective gloves. ECHINODERMS

Most members of this division of sea life are characterized by
radial symmetry and may bear a rigid or semirigid skeleton of cal-
careous plates or spikes on a flexible body wall. Included are star-
fishes, sea cucumbers, and sea urchins.

Sea urchins occur in large numbers and variety in shallow coastal
waters. All possess spines, some long and slender, many with a poison
apparatus of some sort. Certain of the sea urchins are of prime danger
to the diver or swimmer. These may produce deep wounds and may
be difficult to identify until after a very painful encounter.

The spines of sea urchins vary greatly from species to species.
Most spines are solid, with blunt or rounded tips, and are not veno-
mous. Others, however, are long, slender, sharp, and hollow, permit-
ting easy, deep entrance into flesh. Because of extreme brittleness,
these spikes may be difficult or impossible to withdraw in one piece.
Some of these may be a foot in length and may secrete a deadly venom.

Distributed among the spine tips are small, delicate, globe-
shaped, seizing organs called pedicellariae. This globe-shaped head,
in one type, serves as a venom organ and is armed with a set of pincer-
like jaws for holding. A sense bristle, on contact, causes a small
muscle to contract, releasing venom. A function of the pedicellariae
is defense of the sea urchin. If an object contacts the extended organ,
it is immediately seized and poisoned. If the object is large and
strong, it will tear away from the urchin, but the pedicellariae re-
mains fast on the object and continues to poison for several hours
after being parted from the sea urchin.

Representative species, only a few, of the large numbers in
existence are:

(a) Long-Spined or Black Sea Urchins, Diadema setosum
(Figure 16), distributed throughout the Indian and West
Pacific Ocean areas northward to Japan and eastward
to Hawaii.

(b) Sea Urchin, Toxopneustes pileolus, inhabits the Indo-
Pacific area from East Africa to Melanesia and Japan.

(c) Sea Urchin, Toxopneustes elegans, inhabits Japanese
waters.

(da) Asthenosoma ijimai inhabits the Japanese area south-
ward to the Molucca Sea.

Penetration of the skin by the spines usually produces an im-
mediate and intense burning sensation. This is followed in a short
time by redness, swelling, and a generalized aching sensation. Mus-
cular paralysis has been reported and secondary infections may ensue.

The sting from sea urchin pedicellariae may produce immediate
distress and in some severe cases, death. The sting produces intense
radiating pain, faintness, muscular paralysis, loss of speech, and
respiratory distress. However, it may be of short duration, dimin-
ishing in 15 minutes and disappearing altogether in an hour.

DANGEROUS SEA LIFE

Sea urchin stings should be handled in the same way as other
venomous stings. Prompt attention must be given to the removal
of the pedicellariae, as it will continue to introduce venom if not
removed. Although the ordinary spines of some species may be
absorbed in the course of a day or two, most will require removal. A
purple discoloration in the area of the wound, due to a secretion of
the animal, is not a cause for concern.

Sea urchins with long needle-like spines should not be handled.
Special protection must be arranged as ordinary leather or canvas
gloves and shoes do not afford adequate protection. Marine workers
and others must exercise critical care in working at night without
adequate light. This is especially important in those areas where
the lethal species may be encountered.

B. Vertebrates
The vertebrate marine animals that inflict injuries by means of
venomous stings may be divided into 2 groups:
(1) Fishes, including a numerous and interesting variety.
(2) Reptiles, limited to a few sea snakes.

FISHES
Dogfish Sharks

The larger sharks, previously described, depend on speed or teeth
for defensive or offensive operations. Some of the smaller, less
powerful species are equipped with venomous spines for protection.
Many variations in poison spine arrangement exist in these sharks.
The common spiny dogfish, Squalus acanthias, is a small shark, up to
316 feet in length, found along both coasts of the Atlantic and Pacific
Oceans. Closely related spiny dogfish are found throughout the
temperate and tropical seas of the world.

DORSAL FIN SPINES

PECTORAL FIN SPINE (SERRATE)

\ CAUDAL SPINE ~
BODY SPINES
ANAL FIN SPINE
OPERCULAR SPINE

PREOPERCULAR SPINE

PELVIC FIN SPINE

COMPOSITE DIAGRAM
(showing injury-producing structures on body of fish)

Dogfish sharks may be recognized, in comparison to the larger
species, by the absence of the anal fin. Another feature peculiar to
all dogfish is, of course, the presence of two short, stout spines, one
situated immediately in front of each dorsal fin. Although dogfish
are somewhat sluggish, this does not prevent them from thrashing
around with much vigor when caught in commercial fishing nets. The
teeth of a dogfish are not feared too much, but the spines are capable
of causing painful wounds unless appropriate caution is taken. The
venom is a glistening white substance in a shallow groove of each
spine. The poison secretion enters the skin with the spine. These
smaller sharks appear to be dangerous only if handled and will not
attack.

The poison sting brings on an intense, stabbing pain, which
starts immediately and may last for 6 hours. Much redness and
severe swelling may follow and local tenderness may last for several
days. Treatment is the same as for any other venomous fish sting.
Some dogfish stings have been fatal.

Prevention of the sting depends, in most cases, upon adequate
care in handling the spiny dogfish. Removal of the fish from a net,
hook, or spear should be accomplished with caution. A sudden jerk
or reflex of the fish may drive one of the stings deep into the flesh of
the unwary.

Stingrays

Stingrays of many kinds are much feared inhabitants of coastal
areas. They form a serious menace to waders, not only because of
their abundance but also because of their habit of striking from a
concealed position on the bottom in shoal water.

Most rays have a sharp spine near the base of a whiplike tail.

32

The spines may be lost in an adversary but will be replaced. Deep,
glandular grooves of the spines contain poisonous tissues. While
some rays merely create a painful dirty wound, others may inflict a
mortal stab.

Rays inhabit tropical, subtropical, and warm temperate seas of
moderate to shallow depths. Their favorite areas are sheltered sandy
bays, lagoons, and river mouths. They may be seen lying in
shallow water, on top of the sand, or partly concealed in mud or
sand with eyes, spiracles, and tail exposed. They can dig in with
their pectoral fins for the purpose of concealment or in order to feed
upon worms, molluscs, and crustaceans.

Some rays are free swimmers, relying more upon speed for an
escape from an enemy than upon ability at concealment on the
bottom. Because most rays are scavengers by habit, they will
readily accept a baited hook and may frequently appear in the com-
mercial fisherman’s net, where they may cause as much trouble as
the dogfish shark. Sharks that commonly feed upon rays may be
branded with numerous “‘stings” imbedded in the skin area of the
shark’s head and jaws.

Stingrays ordinarily glide through the water by a rippling wing-
like motion of both fins. When at rest on the bottom they may,
quite suddenly, with a quick move of the wings, stir up enough sand
and mud to cover themselves, leaving only the eyes, spiracle, and
tail exposed. Under these conditions, water intake is by way of the
exposed spiracles located behind each eye.

Because of their flat shape, the weight of a person stepping upon
a ray serves both as a target and a dead weight necessary for lever-
age. Thus anchored, the ray whips the barbed tail with great force
and precision. At times the spines are found to be driven clean
through a foot or through the flesh and into the leg bone of the hap-
less victim.

Stingrays are a large group of venomous marine organisms to
which may be attributed several thousands reported attacks each
year. The rays may be divided into 7 families:

1. Dasyatidae—stingrays or whiprays
2. Potamotrygonidae—river rays
3. Gymnuridae—butterfly rays
4, Myliobatidae—eagle rays or bat rays
5. Rhinopteridae—cow-nosed rays
6. Mobulidae—devil rays or mantas
7. Urolophidae—round stingrays
Representative examples of some of these according to area are:
Diamond Stingray, Dasyatis dipterurus (Figure 17), British

Columbia to Central America.

Bat Ray or Spotted Eagle Ray, Aetobatus narinari (Figure

17), tropical or warm-temperate belts of the Atlantic Ocean,

Red Sea, Indian Ocean, and Pacific Ocean.

Round Stingray, Urolophus halleri (Figure 17), waters of
the Pacific between California and Panama.

The stingray wound usually causes immediate and severe pain.

DANGEROUS SEA LIFE

This pain has been variously described to be sharp, shooting, spas-
modic, or throbbing in nature. Swelling in the wound area is accom-
panied by an ashy appearance, which later turns red. Most wounds
occur on the feet or ankles, but fatal wounds have been inflicted to
chest and stomach areas.

Treatment, as described under venomous fish stings, should be
undertaken. Even a freshwater stingray may cause an extremely
painful wound with generalized symptoms as; fall in blood pressure,
vomiting, diarrhea, sweating, rapid heart beat, and paralysis. Death
may occur in severe cases.

Catfish

Catfishes of about 1,000 species may assume many different
sizes and shapes. Body shape may be elongated, almost eel-like.
Heads may be oversize in a variety of ways. The mouth is usually
provided with long barbels or feelers. The skin is thick and slimy,
without scales, although bony outer plates may exist in some species.

Venomous catfishes are provided with a stiff spine in the front
part of the dorsal and pectoral fins. Venom glands are located in
the outer skin or sheath of each. The venomous spine of the catfish
is additionally treacherous to the unwary because of a locking device
which maintains the spine erect when desired. Certain species have
recurved teeth on each spine. This makes venom absorption by the
victim more certain.

Although many freshwater catfishes are used for food, the salt-
water species are not often eaten. A representative marine species
of the catfish, Galeichthys felis (Figure 18), ranges from Cape Cod to
the Gulf of Mexico. Another catfish, Clarias batrachus, inhabits the
waters of India, the Netherlands Indies, and the Philippines. Cat-
fishes are abundant in rivers, estuaries, and the open reef areas;
they are also particularly numerous in certain large sandy bays.

The wound of a catfish spine is generally accompanied by an
almost instant stinging, throbbing, or scalding sensation. The pain
may radiate or may localize, numbing an arm or other parts. Certain
tropical species, such as the oriental catfish, Plotosus lineatus, is capa-
ble of inflicting a violently painful wound which may endure for 48
hours. A paleness about the wound area is followed by redness and
swelling. Gangrene may set in, or a secondary bacterial infection is
possible. Death may result from a catfish sting.

There are no known antidotes for this and other fish stings.
Care should be taken in handling marine catfish, especially those
having sharp, rigid fin spines.

Weeverfish
Weeverfish, all of the family Trachinidae, are a very venomous

fish of the temperate zone. They are small marine fishes, less than
18 inches in length, and inhabit mostly sandy or muddy bays. Be-
cause of an aggressive temperament, combined with a well-developed
poison apparatus, the weever presents a continuing source of danger
to divers or others. Weevers habitually bury themselves with only
part of the head exposed. Upon little or no provocation they dart
out with fins erect and gill covers expanded and strike with unerring
accuracy at any offending target.

The Great Weever, Trachinus draco (Figure 18), may be found
along western Africa, in the Mediterranean Sea, and in the vicinity
of the British Isles and Norway. The Lesser Weever, Trachinus
vipera, inhabits the North Sea, southward along the European Coast,
and the Mediterranean Sea.

The aggressive armament of the weever consists of venomous
dorsal and opercular spines. The dorsal spines, 5 to 7 in number,
are needle sharp and are equipped with a venom groove and thin
walled sheath. The blade-like opercular spine has an attached venom
gland. The venom is similar to some snake venoms and acts both
as a neurotoxin and a hemotoxin.

A weever wound normally produces instant pain of a burning or
stabbing type which gradually spreads in the affected part. Within
30 minutes, pain becomes severe and the victim loses consiousness.
Pain is usually severe to the extent that the victim may scream and
thrash about wildly. Other symptoms as, headache, fever, chills,
delirium, nausea, vomiting, sweating, loss of speech, palpitations,
and convulsions follow. Morphine often fails to give any relief.
Pain subsides in a few hours and redness and swelling then develop.
Secondary infections are common in cases not properly treated.
Recovery time extends to several months, depending upon the con-
dition of the patient and the amount of venom received. There are
no known antidotes for this and other fish stings. Immediate first
aid and treatment by a physician may save the patients life.

Since weevers are ordinarily encountered while wading, care
must be taken to avoid contact. Adequate footwear should be worn
where weevers are known to exist. The fish should neither be antag-
onized into an attack nor handled in a careless manner, even after
death. Scorpionfish

The scorpionfish family contain some of the most virulent of all
venomous fishes. The sting of any of these fish will produce serious
results, and a few of the Stonefishes, Synanceja (Figure 18), may
be ranked with the cobra in comparing the deadliness of the poison
secreted. These fish are divided into 3 main groups:

(1) Zebrafish, Pterois

(2) Scorpionfish, Scorpaena

Figure 18. Top-Great Weever and Spines.
Center—Catfish and Fin Spines.
Left—Deadly Stonefish and Sting.

DANGEROUS SEA LIFE

(8) Stonefish, Synanceja

Zebrafish are a beautiful and ornate shallow water fish of trop-
ical and temperate seas. They parade about coral reefs, spreading
their fan-like and lacy fins in much the same manner as peacocks.
They are found in pairs and present an invitation to disaster if
touched. Beneath the finery are hidden long, straight needle-sharp
fin spines which are a spectacular menace to anyone exploring trop-
ical coral areas. These fish are armed with as many as 18 potentially
lethal spines, each equipped with venom.

The scorpionfish are inhabitants of shallow water bays and reefs.
A habit of concealing themselves in crevices among debris, under
rocks, or in seaweed along with a nearly perfect protective coloration
makes this fish almost invisible. Upon discovery and removal from
the water these fish erect spiny fins and spread out gill covers in an
aggressive display.

Stonefish are encountered in tidepools and shoal areas. They
lie motionless while concealed or even partly buried and are fearless
or even disinterested in any careless intrusion. This presents a dan-
gerous situation to anyone with bare feet. The fish is equipped with
as many as 18 dorsal spines, 3 anal spines, and 2 pelvic spines; all
are short and heavy with enlarged venom glands. In natural con-
cealment, the fish looks like a piece of mud or debris.

Symptoms produced by all 3 types of scorpionfish vary in degree,
but the pain is immediate, sharp, and radiates. Pain may cause a
victim to thrash in a wild manner, scream, or lose consiousness. The
immediate wound area may be pale, surrounded by a zone or redness,
swelling, and heat. Paralysis of an entire arm or leg may result,
and intense swelling of a member may impair movements. Many
other symptoms may also be present. Death may be the result of
an encounter, or the victim may recover after months of treatment
but with general health impaired. Treatment, as for other venomous
fish stings, must be administered promptly.

Prevention of the sting, based on previous experiences, depends
upon the warning of individuals not to handle scorpionfish with un-
protected hands. Attraction of the uninitiated to touch the lacy fins
or the placing of hands or feet in crevices inhabited by the fish must
be prevented to avoid the danger.

Recommended treatment of Venomous
Fish Stings

Treatment of venomous fish stings should be directed to the

achievement of 3 objectives:
1. Alleviate pain.
2. Combat the effects of the venom.
3. Prevent follow-up infections.

The pain is generally a direct result of the damage caused by
the spine. Additional effects are produced by the venom and the
introduction of slime and foreign material. Certain stings, as in the
case of rays and catfish, may produce greater damage if spines are
recurved or barbed edges are present. Such wounds should be care-
fully washed out or irrigated with cold salt water or with sterile
saline, if available.

It is advisable in most cases to make a small incision across the
sting wound. Immediate suction for removal of poison and irrigation
should then be accomplished. Since fish do not inject venom in the
manner of snakes, results from this suction are not entirely
satisfactory.

Use of a ligature in the treatment of fish stings may help. The
ligature, if used, should be placed immediately between the sting site
and the body, as near the wound as possible. Adequate circulation
should be allowed periodically every few minutes. Hot soaking of
the wound site for 30 minutes to an hour should be maintained, with
the water as hot as the patient can bear without injury. Hot, moist
compresses may be used on areas not convenient for immersion. The
addition of epsom salts to the water is believed beneficial. Following
the soaking, a surgical removal of the lacerated or contaminated parts
should precede closure of the wound by sutures. A small drain may
be left for a day or two if the need is indicated by size or nature of
the wound. The wound site should be covered with an antiseptic
sterile dressing. Supportive measures, as described in ‘“‘THE SHIP’S
MEDICINE CHEST AND FIRST AID AT SEA” under shock,
should be attended to immediately. The patient must be watched
carefully for complications and prompt attention given as described.
The assistance of a physician should be obtained or medical advice
requested by radio.

34

Reptiles

Notwithstanding all that has been written concerning the sub-
ject of sea snakes, and the universal fear of most people concerning
them, there has always been a great deal of misunderstanding con-
cerning their actual existence. The sea snakes are closely allied to
the cobras and form a specialized group, adapted by structure and
habit to a marine existence. All are poisonous and many deadly,
however, they will not generally attack without provocation and have
often been described as docile in habit. Fishermen who unintention-
ally contact sea snakes in their work suffer most of the fatal bites.
Fatalities are quite common in the Gulf of Siam and the Philippines
area.

Figure 19. SEA SNAKE

Few sea snakes exceed 4 feet, but 10-foot specimens have been
caught. Color is dark above and light below with cross-bands of
black, purple, brown, gray, green, or yellow. All of the marine
species may be distinguished from the land forms by a paddle-shaped
tail. Any confusion with eels may be resolved by the fact that sea
snakes are true snakes, and their bodies are covered by scales. Eyes
are covered by transparent scales and have no lids. The tongue is
slender and forked. Hollow venom fangs are present.

Marine snakes inhabit sheltered coastal waters, particularly the
areas near river mouths. They penetrate upstream to the limits of
brackish water, and a few species are found in fresh water. They
tend to collect close along shore and among coral reefs in the breeding
season, when they are more active and sometimes become aggressive.
During this season, fishermen may net as many as a hundred at a
time. This presents an especially hazardous condition, since some
sea snakes have been reported to possess venom of a potency ex-
ceeding that of the king cobra.

Swimming is accomplished by a lateral undulation and use of
the oar-like tail. A peculiar ability to move backwards as well as
forward has been reported. Although sea snakes may float on the
surface for extended periods of time, they are also able to remain
submerged for hours. Most of their food is obtained underwater and
consists nearly entirely of fish swallowed headfirst. Many of the
items of food, such as eels and fish, are quickly killed by the deadly
first bite of the snake. Like many other marine animals, sea snakes
often feed at night and many are netted after dark when attracted
by artificial lights exhibited by fishing boats. Individual snakes are
frequently taken by line fishermen as they will readily accept the
baited hook.

The yellow-bellied Sea Snake, Pelamis platurus, ventures beyond
coastal waters and is the most widely distributed of all sea snakes.
It exists in East Africa and Asian waters northward to Siberia, Jap-
anese east coast, the Philippines, Oceania, and eastward to tropical
America. The sea snake Enhydrina schistosa (Figure 19) is a more
aggressive species which ranges from the Persian Gulf eastward to
the north coast of Australia. Other species, nearly 50 in number,
inhabit the tropical Pacific and Indian Oceans from the Persian Gulf
to Samoa. They also follow the warm currents northward into the
western Pacific to the Ryukyus and Japan. They are not known to
inhabit the Atlantic.

THE TITANIC—30 YEARS LATER

O. L. Martin Jr.
Maritime Safety Division
U.S. Naval Oceanographic Office

THE TITANIC — 15 April 1912.

The great bow knifed serenely through the calm, sunlit sea as
three mighty engines pushed the 46,000-ton titan through the water
at a speed well in excess of 23 knots. Double bottoms ran throughout
the full length of her 852-foot hull, which contained a massive colli-
sion bulkhead forward, followed by 16 watertight compartments
containing 11 decks. The passenger accommodations included
private promenades, exquisitely furnished suites, plush cabins, beau-
tiful lounges, a heated swimming pool, a gymnasium, and a hospital.
This was the ultimate in ship design: the safest, largest, swiftest, and
most comfortable vessel afloat. As she steamed majestically west-
ward across the North Atlantic on the evening of April 14, 1912, to
keep her lonely appointment with fate, everyone making this mem-
orable maiden voyage knew the TITANIC was unsinkable.

The CARONIA radioed that ice lay ahead; as the day wore on
messages from the BALTIC, the MESABA, and the AMERIKA
revealed the probability of an ice field, 12 miles wide and 70 miles
long, lying across the course of the TITANIC. Day faded into night,
and a bite was noted in the air as the ship neared the Grand Banks.
The CALIFORNIA reported icebergs dead ahead. Yet the TITANIC
steamed on with ever increasing speed as the First Officer slowly
paced the bridge, 90 feet above water. Twice the lookout, in the
crow’s nest, reported ice in the distance, but with speed unabated
the unsinkable ship steamed on. Meanwhile, the TITANIC’s

35

radio operator, when working Cape Race at 2300, heard the CALI-
FORNIA break in loud and clear and say, ‘‘We are stuck in the ice.”’
He answered, ‘‘Keep out, you are jamming my signals.” Tired
after a long day and irritated at the TITANIC’s rebuff, the radio
operator aboard the CALIFORNIA secured his set and turned in.

The goliath of the sea steamed on, unwittingly drawing ever
closer to her icy rendezvous with death. The lookout sighted another
iceberg ahead and notified the bridge. Instantly, the First Officer
reversed the port engine and put the rudder hard over in an attempt
to make as tight a turn to port as possible. Seconds ticked by, the
mighty bow swung safely past the ice but the advance of the vessel
carried her bodily forward against a knife-like protrusion, slashing a
300-foot gash in the hull well below the waterline along the starboard
side. However, the impact of the collision was so slight and the con-
cussion so muffled that only several of the stokers and engineers
realized the stark truth. She was doomed.

Upon reaching the bridge, the Captain received a full report
of the known facts, and immediately dispatched an officer below to
survey the damage. This officer upon finding ice on the foredeck
inspected the forepeak but found it dry. Working his way aft along
the starboard side he found the boiler room flooded and being aban-
doned, firemen scarcely having time to pull their fires. Water rushing
into No. 3 hold was already 20 feet above the keel. Returning to the

THE TITANIC—50 YEARS LATER

bridge, he informed the Captain that the ship would sink. Upon
learning the facts, the Captain ordered the radio operator to request
help from nearby ships. Fifty-eight miles away the CARPATHIA
heard, turned, and proceeded at full speed through the ice strewn
waters to the rescue. Soon the VIRGINIAN, the BALTIC, the
OLYMPIC, and Cape Race heard—then the whole world knew that
the TITANIC, with 2,224 persons aboard, was sinking. However,
salvation of the doomed passengers was only a few miles away —
aboard the CALIFORNIA, but her radio was silent and she did not
hear of the disaster so near at hand.

In the meantime, the Captain ordered the senior officers to clear
away the boats and prepare to abandon ship, while the junior officers
fired distress rockets from the flying bridge and attempted to raise an
unknown ship, possibly the CALIFORNIA, only a few miles away,
by blinker light. The stewards awakened the sleeping passengers,
assisted them into their lifejackets, and shepherded them to the
waiting boats. Meanwhile, several decks below, the immigrants,
closer to the rising water, fearfully realized the urgency of the situa-
tion. However, when the first lifeboat pulled away from the ship,
one hour after the collision, it was only partially filled. The first
class passengers on the boat deck, far above the water, were reluctant
to leave the warmth and security of the great unsinkable bastion of
strength for the flimsy protection of a small frail lifeboat tossing pre-
cariously on the icy seas far below.

Few realized there were only enough lifeboats to accommodate
about one-half the people on board. All the distress rockets were gone
and the attempt to contact the vessel so near, yet so far away, had
failed. At 0205 the last boat was lowered and shortly afterwards a
great wave swept over the boat deck. The tremendous screws were
now entirely out of the water and rising higher as the vessel settled
faster by the head. The forward funnel sheared off and tumbled into
the sea—the stern rose even higher. A great thunderous rattling
rent the air as the heavy engines, tearing away from their beds,
lurched forward and crashed downward through bulkhead after bulk-
head by the sheer force of their great weight. The seconds ticked
into minutes, and the minutes into an eternity, as the after 150 feet
of the stern hung vertically, then slipped beneath the cold desolate
waters of the North Atlantic.

Nature in the guise of a small iceberg had met man’s challenge
to flout her in 41°46’ north latitude, 50°14’ west longitude and in
only two and one-half hours defeated him at the cost of 1,517 lives
with the sinking of the TITANIC at 0222 on 15 April 1912.

THE GENESIS OF THE TRACKS

Tronic as it may be, the White Star Line, owners of the TITANIC,
was one of the first steamship companies to advocate lane traffic
across the North Atlantic Ocean as a safety measure for their pas-
senger vessels. Separate east- and westbound lanes were first pro-
posed after the disastrous ARCTIC-VESTA collision, during thick
fog off Cape Race in 1854. The following year, Matthew Fontaine
Maury, known as the “Path Finder of Seas’, then in charge of the
U.S. Navy Hydrographic Office, devoted a section of the 1855 edition
of his “Sailing Direction” to the proposal, specification, and justifica-
tion of separate lanes for east- and westbound passenger traffic.

Yearly, during the latter half of the nineteenth century, the
rising tide of immigrants created new demands on an already flour-
ishing trade route. Simultaneously, the advent of steam permitted
vessels to operate without benefit of the wind. Therefore, schedules
could be maintained, but the inefficiency of the early boilers, con-
suming enormous quantities of coal, required vessels to follow the
shortest distance between ports. Vessels sailed a great circle track
from Europe to a position southward of Cape Race, then rhumb-lined
to the various North American ports. This congested the bulk of the
North Atlantic traffic in the foggy and often ice-laden waters of the
Grand Banks.

At this time it was believed the paramount danger was from
collisions between vessels, not icebergs. However, early safety advo-
cates, in proposing a system of separate east-west lane routes clear
of major fog areas, minimized the iceberg threat. Maury’s westbound
or northern, route was about 100 miles southward of Cape Race,
cutting through the southern limits of the fog and ice area; although
slightly longer it offered far less fog, thus passages should be quicker.
The eastbound, or southern, route passed about 300 miles southward

36

of Cape Race, well out of danger, but was considerably longer than
great circle route. However, this route afforded the advantage of
following the easterly drift of the Gulf Stream and the improved
weather conditions usually prevalent in that area. A representative
of the White Star Line stated in Liverpool on 1 January 1876, at the
“North Atlantic Steam Traffic Conference,” that ships of his com-
pany had been complying with Maury’s trans-Atlantic lane recom-
mendations since 1874. He also strongly urged other steamship
companies to do the same as a measure of safety for the increasing
number of passengers carried across the North Atlantic each year.

The U.S. Navy Hydrographic Office launched a new service for
the mariner in December of 1883, with the inauguration of the
Pilot Chart series. These charts depicted in a nautical manner,
hydrographic, meteorological, and early oceanographic information
pertaining to the North Atlantic Ocean. Commencing with the May
1884 issue, the approximate calculated limits of ice for the month
and a safe track from New York to Northern Europe, skirting the
ice menace, were charted. The ice sighted during the previous month
was also shown. The Pilot Charts were the first to publicize the
seriousness of the ice menace in attempting to locate, identify, and
disseminate ice and weather information relative to shipping along
the critical routes adjacent to the Grand Banks. At once ship-
masters realized the value of this information. The increasing
demand to provide mariners with more up-to-date navigational
data created a new service from the fledgling Branch Hydrographic
Offices in Boston and New York. These offices collected daily ice
information from all possible sources and maintained a master ice
plot available to mariners prior to their sailings. The information
was also forwarded to interested steamship companies along the
eastern seaboard.

Meanwhile, delegates from 26 maritime nations met in Wash-
ington for the “International Marine Conference”’ of 1889 and pro-
posed that trans-Atlantic lanes be adopted on a voluntary basis by
the steamship operators. Representatives of the five principal trans-
Atlantic steamship companies met in 1891 and formally adopted
seasonal tracks to be followed by their vessels. During the ice season
these routes were considerably longer, but it was believed if a steam-
ship obeyed the Rules of the Road through the ice and fog areas of
the Grand Banks, the utilization of the proposed tracks would be
safer and more economical.

STUDY OF THE ICE

In the interest of gaining more scientific knowledge of the ice
menace of the North Atlantic, the Hydrographic Office dispatched
a team to the Newfoundland area to study the origin and drift of
icebergs. Lighthouse keepers, fishermen, and whalers were engaged
as voluntary observers to report regularly ice conditions to the Hydro-
graphic Office. The results of this study were published in 1890 as
H.O. Pub. 93, ‘Ice and Ice Movements in the North Atlantic Ocean.”

Today more thorough research has revealed that most of the
icebergs menacing the trans-Atlantic shipping lanes are products of
the Greenland Ice Cap. A stupendous mass of compacted ice and
snow covers the interior of Greenland, varying in thickness from several
hundred to several thousand feet. Although at an imperceptibly
slow rate, ice under great pressure attempts to flow outward and
downward to the sea level following paths of least resistance. Giant
rivers of ice called glaciers extend from the ice cap through the
coastal mountain passes and into the fjords. The flowing ice grad-
ually pushes the toe of the glacier farther and farther into the waters
of the fjord until the outer extremity of the ice becomes buoyant.
The internal stresses created by wave and tidal action causes the
buoyant portion to break off, or calf, and drift down the fjord into
the sea as an iceberg. Newly-calfed bergs may vary in size from
a few tons to hundreds of thousands of tons.

Each year a few bergs are spawned along the east coast of
Greenland; they usually drift with the East Greenland Current
toward Kap Farvel, and thence are carried by the West Greenland
Current along the eastern portion of Davis Strait and into Baffin Bay.
However, it is in this area along the west coast of Greenland above
68°30’ N. that the bulk of the icebergs sighted in the North Atlantic
are produced. Here about 100 tidewater glaciers spawn approxi-
mately 15,000 bergs each year. Glaciers may calf at any time but
most of the icebergs are produced in the warm summer months.

THE TITANIC—50 YEARS LATER

Once the icebergs are waterborne the long drift to the shipping
lanes is underway. First the icebergs drift northward with the West
Greenland Current into the Baffin Bay Basin, where they may spend
their first winter frozen in the ice. Thence, drifting westward across
Baffin Bay, they commence their southerly movement under the
influence of the Labrador Current. Many bergs that survive the
first winter ground and break up along the treacherous Labrador
Coast. The surviving icebergs may spend their second winter frozen
in the Davis Strait region and from there, as soon as the pack breaks
up in the spring, the remaining bergs drift southward with the
Labrador Current toward the Grand Banks.

In an average year, about 400 icebergs drift below the 48th paral-
lel with about 35 continuing their southerly drift past the Tail of the
Banks to menace the trans-Atlantic shipping lanes. Yearly vari-
ation is great. During the peak ice year of 1929 an estimated 1,352
icebergs drifted southward of the 48th parallel. Yet in 1958 only
one iceberg was observed. However, the following year, 1959, there
were 693 bergs in evidence. This variation has not been fully ex-
plained but is probably related to climatological conditions over the
entire iceberg-producing area and the distribution of pack ice in the
Davis Strait. Icebergs may be encountered any month of the year,
but in the Grand Banks area over 90 percent of them are encountered
from March thru July, which constitutes the usual ice season, with
the heaviest concentration from mid-April to mid-May.

icebreaker techniques, convoying, and towing in ice. A comprehensive
glossary of ice terms is also included in this reference.

Natural deterioration commences as soon as newly-calved ice-
bergs are waterborne. Melting processes are always at work. Al-
though nearly dormant during the winter months, they speed up as
the temperatures rise in the spring and reach an accelerated pace
when the bergs drift farther southward into the warmer waters off
the Tail of the Banks. In areas where the air temperature is well
above the water temperature bergs will melt faster above the water,
retaining their stability, and, as the bulk decreases, gradually rise
out of the water, leaving tell-tale encircling rings of former waterlines.
If the water temperature is high enough to melt the underwater por-
tion faster, bergs become unstable and frequently oscillate to new
positions of equilibrium, thereby creating new strains on protruding
portions that may cause them to calf off, thus inducing another shift
in the equilibrium of the berg. Sea water is the principle factor in
the natural disintegration of an iceberg. Therefore, the area of a
berg near the waterline is subject to the greatest melting, or actual
erosion, by the continuous wave action sloshing warmer surface
waters against the waterline of the berg, eating into cracks and crev-
ices, and undercutting the sides, thus creating new protrusions, new
strains, and renewed calfing. Melting of the underwater portion also
releases the innumerable tiny pockets of entrapped air which bubble
to the surface in an audible effervescent effect. Throughout their

The density of icebergs may vary slightly as galciers are com-
posed of compacted snow. In the upper layers of the Greenland Ice
Cap the entrapped air content may be as great as 50 percent of the
volume. But, by the time the ice has traveled along the glacier to
the sea, the great pressure has reduced the air content by volume to
somewhere between 7 and 15 percent and the density is about 0.899
as compared to a density of 0.917 for fresh water ice. The average
iceberg floating in sea water with a density of 1.028 will have about
87.5 percent of its mass below the surface of the water; therefore,
the portion above water represents approximately one-eighth of the
bulk of an iceberg. Arctic icebergs may weigh as much as about
1,500,000 tons, but icebergs found off the Grand Banks are seldom
larger than about 150,000 tons. Berg ice in solid condition, is very
hard and melts slower than artificially made ice, despite the general
appearance of softness. Icebergs are of a peculiar opaque flat white
color resembling snow, often with soft iridescent hues of green and
blue. The snowy appearance is caused by surface weathering and the
affect of the sun’s rays releasing innumerable air bubbles. Bergs may
be striped with blue or green veins of hard transparent ice which stand
out strikingly against the porous white background. Brown and
yellow patches, probably due to some form of planktonic life, may
appear on them. Rock and earth remnants of old glacial moraines
dart through the bergs in ribbons of brown, gray, and black.

An excellent and convenient reference on the formation, growth,
movement, and dissolution of ice in general can be found in Chapter
1 of H.O. Pub. No. 47, “Sailing Directions for the Northern
USSR.” This reference also discusses the hazards involved in
handling, maneuvering, and navigating a vessel in ice, as well as

Removing Nansen Bottle.

THE TITANIC—50 YEARS LATER

U. S. NAVAL OCEANOGRAPHIC OFFICE

WEEKLY ICE CHARTLET

NORTH ATLANTIC LANE ROUTES—UNITED STATES
In accordance with the North Atlantic Track Agreement, the Oceano-
graphic Office advises that Track “B” is effective as follows:
TRACK “B" (SOUTHERN)
From April Il to June 30, inclusive

EASTBOUND.—Cross long. 47°00’W., in lat. 40°30’N.
WESTBOUND.—Cross long. 47°00’W., in lat. 41°30’N.

The Weekly Ice Chartlets are issued each Wednes-
day during the annual ice season in the North Atlantic.
They are based primarily upon the twice-daily ice infor-
mation bulletins issued by the International Ice Ob-
servation and Ice Patrol Services. All ice information
received during the week (up to 1230 G.M.T. on the date
of publication) is included (for complete text, see reverse
side hereof).

Copies of Weekly Ice Chartlets are available at the
U.S. Naval Branch Oceanographic Office in Norfolk and
the Offices of the Collector of Customs in Chicago, Port-

KEY TO SYMBOLS

Estimated ice limits Apr. 20th
Sea ice limits.
Berg (with date sighted)
Growler (with date sighted)
Radar target (with date sighted)

LABRADOR

land, Boston, New York, Philadelphia, and Baltimore.
Copies may also be obtained from Oceanographic Office
Sales Agents in the above ports and from the Office
Services Officer, Eisenhower Lock, Massena, New York.

Radio ice information bulletins are issued twice
daily by the Oceanographic Office and are transmitted
at 0430 and 1630 G.M.T. by NSS (Navy Radio Wash-
ington) on the regular “‘Hydro’’ broadcasts.

A daily ice chartlet, with detailed text, is included
in the Daily Memorandum, (East Coast Edition).

NOTICE

Each issue of the Weekly Ice Chartlet
supersedes all previous issues.

April 20, 1965

nee

(ie Cae
2° NEWFOUNDLAND ot? ~))

50°

Published by the U. S. Naval Oceanographic Office, Washington, D.C., March 1965
under the authority of the SECRETARY OF THE NAVY

38

H, O. Misc. 11,845-B

THE TITANIC—50 YEARS LATER

life, icebergs continually emit weird sounds as if the ice is being
alternately contracted then expanded.

A warm rain will have a marked affect on the surface of an
iceberg. If the temperature becomes higher, melting water will
cascade from a berg as a brook hurtling down a mountain side,
cutting ever-deepening furrows into its surface. Possibly at night
with a drop in temperature, water that seeped into cracks and crev-
ices during the day may freeze. Sun’s rays produce still another
temperature gradient, causing a different amount of expansion to a
piece of ice that may already have internal stress caused by slight
variations in density and composition. These new forces, slight as

they may be, might possibly be enough to cause calfing along internal
natural cleavage planes. Although an iceberg in a solid state is almost
indestructible, when it becomes rotten it may be completely broken
up, under certain conditions, by relatively small external forces.

Drifting southward in the Labrador Current along the eastern
slope of the Grand Banks an iceberg is usually in water temperatures
lower than 35°F and disintegrates very slowly. In the mixed waters
off the Tail of the Banks the dissolution is accelerated by water
temperatures above 36°F. However, when the water temperatures
reach 50°F the change can be observed from hour to hour. In the
mixed waters southward of the Grand Banks the average medium-
sized berg will survive as a menace to navigation for a period of 12
to 14 days during April, May, and June, but no longer than 10 to 12
days thereafter. Should the same berg drift even farther southward
into the 65° to 70°F temperature of the Gulf Stream it would prob-
ably survive no longer than 7 days.

HISTORY OF THE ICE PATROL

The institution of an efficient patrol and warning system for the
critical iceberg area was evolved with the perfection of the marine
radio which enabled vessels to communicate freely with others within
a reasonable distance. Immediately after the TITANIC disaster,
upon the recommendation of the Hydrographic Office, the U.S. Navy,
in the interest of safety of life at sea, dispatched a cruiser on 19 May
1912 for patrol duty near the ice regions of the North Atlantic.
Primarily, the purpose of the patrol was to locate icebergs and field
ice nearest the trans-Atlantic shipping lanes, patrol along the
southern limits of the ice, and endeavor by radio communications to
inform ships in the vicinity and the Hydrographic Office of these
conditions. To cover effectively as large an area as possible, vessels
were requested to report by radio observed ice conditions to the
patrol ship. The Hydrographic Office and its Branch Offices in
Boston and New York promptly disseminated the daily reports along
the eastern seaboard. Circumstances did not permit the Navy to
undertake a patrol of the ice regions the following season. Conse-
quently, the 1913 patrol was carried out by revenue cutters of the
United States Treasury Department and by the British steam trawler
SCOTIA. The ice information received daily by the Hydrographic
Office was published in the Daily Memorandum and the Weekly
Hydrographic Bulletin and was also disseminated daily by the Branch
Office in New York.

The subject of protecting trans-Atlantic shipping from the ice
menace was thoroughly discussed by the first International Confer-

39

ence on “‘Safety of Life at Sea’’, convened in London on 12 November
1913 as a result of the TITANIC sinking. Representatives of the
various interested maritime powers signed an agreement on 20 Jan-
uary, 1944 providing for the inauguration of an international derelict
destruction, ice observation, and ice patrol service. This triple
service, consisting of two vessels, was conceived to patrol the ice reg-
gions during the season of danger from icebergs and attempt to keep
the trans-Atlantic lanes clear of derelicts during the remainder of
the year. The United States was invited to undertake the service
for which the expenses were to be defrayed in agreed fixed proportions
by the nations signing the agreement. Thus, the patrol became
international in character when the Revenue Cutter Service (now
the United States Coast Guard) began the 1914 patrol.

Upon the subject of trans-Atlantic lanes, the Conference also
adopted the following: “The selection of the routes across the North
Atlantic in both directions is left to the responsibility of the steam-
ship companies, nevertheless the High Contracting Parties undertake
to impose on these companies the obligation to give public notice of
the regular routes which they propose their vessels should follow, and
of any changes which they make in them. The High Contracting
Parties undertake, further, to use their influence to induce owners
of all vessels crossing the Atlantic to follow as far as possible the
routes adopted by the principal companies.’’

Each year as soon as reports from the northern waters indicated
icebergs were beginning to drift southward, a cutter would be dis-
patched to the Tail of the Banks. Arriving on station the Coast
Guard Cutter would notify the various radio stations and vessels in
the vicinity of the official commencement of the International Ice
Patrol. Thereafter, ice reports would be broadcast on several fre-
quencies twice daily and forwarded to the U.S. Navy Hydrographic
Office. Two cutters alternated in a continuous patrol, remaining on
station about 2 weeks each. The patrol located and guarded the
southern ice limits, giving particular attention to the critical ice area
between the Tail of the Banks and the westbound B-track, constantly
in use throughout the ice season. Serious ice conditions are likely
to be encountered any time northward of the 48th parallel, but this
is common knowledge to shipmasters sailing in higher latitudes;
so, for practical purposes, the surface ice patrol was conducted in
an area southward of the 48th parallel but northward of latitude
40°30’N. and between longitudes 48° and 54°W.

U.S. Coast Guard Cutter TAMPA

TECHNIQUES OF ICE DETECTION

Icebergs present no particular problem when they can be detected
in time. However, throughout the ice season the Grand Banks area
experiences some of the poorest visibility in the world. Detecting
and forecasting the drift of icebergs during extended periods of fog
has been a continuing problem for the Ice Patrol. Formerly, during
periods of reduced visibility, patrol cutters would stop their engines
and drift with the current in the vicinity of the icebergs they were
guarding. Often the patrol would lie-to at night as it was impossible
to search out bergs in the darkness.

Under excellent conditions a large berg may be sighted at a
distance of about 18 miles, but with a hazy horizon this distance can
be reduced to less than 10 miles, and in a light fog or drizzling rain the

THE TITANIC—50 YEARS LATER

detection range may fall to 1 mile or less. In dense fog, an iceberg
may not be seen until it is close aboard and then it will appear as a
luminous, white mass if the sun is shining or as a dark, somber mass
if the sun is not shining. Ona clear dark night an iceberg will seldom
be picked up at a distance greater than about 14 mile, but if a sea is
running, the wave action against the base might be sighted as far-
away asl mile. A moon in the direction of an iceberg may hinder
its detection, while the light from a moon on the opposite horizon
may produce enough of a blink to allow the berg to be seen up to 3
miles. Often an icefield can be detected by a yellowish glare, or ice
blink, in the sky above the field; should there be snow on the ice the
glare will be whiter. If an iceberg is in the process of disintegration,
its presence might be detected by the cracking, roaring sound as calfing
takes place.

An early method of iceberg detection was the echo, and under
proper conditions it is still useful. Sound is reflected off at the same
angle it strikes a reflecting surface; thus, unless striking a steep-
sided or cliff-like face, the sound may reflect aimlessly off in a useless
direction. If the echo bounces back, the approximate distance and
bearing of the iceberg can be obtained. Abrupt changes in air and
sea temperature or the salinity of the sea water cannot be assumed
as a reliable sign of the approach to ice. Temperature and salinity
changes as great as those experienced in the Grand Banks area may
be experienced in many areas of the ocean that are entirely ice free.
However, it has been noted that icebergs tend to remain in the cooler,
less saline waters of the Labrador Current.

Although the majority of the tremendous bulk of an iceberg is
submerged, early attempts to locate ice with a sonic fathometer were
unsuccessful. However, the fathometer was put to excellent use in
producing data for very accurate bottom contour charts of the area.
More recent Ice Patrol experiments proved that sonar can be useful
in detecting icebergs at relatively short ranges. Under favorable
conditions bergs may be detected at a range of about 3 miles and
growlers at about 14 mile.

Before the advent of early radio aids to navigation, accurate
positioning was frequently impossible as atmospheric conditions often
prevented the patrol from obtaining celestial fixes despite many
ingenious methods perfected in early patrols. Radio compass and
radio direction finder equipment made this task easier. Improved
methods and equipment, such as the electric salinity indicator,
increased the scope of the oceanographic work that could be under-
taken. After establishing the position of an iceberg the prediction
of its drift remained a challenging problem. The patrol vessels
maintained up-to-date isotherm charts by plotting the sea surface
temperatures received regularly from vessels within the affected area.
These isotherm charts show the surface distribution of the warm
Gulf Stream and the cool Labrador Current and give an indication
of the general drift of the surface waters. However, a prolonged
wind or severe storm can mix the surface waters so that the under-
lying general drift of the water mass will be impossible to determine.
Since the bulk of an iceberg is underwater it is the deeper general
movement of the water mass that asserts the greatest effect on their
drift.

Therefore, another method, involving the construction of a
dynamic current map depicting the unstable pressure conditions for
an entire water mass, offered a more reliable system of iceberg drift
prediction. This method required the undivided attention of a patrol
vessel for several days at a time, and was therefore impossible for
the Ice Patrol as constituted. The ‘International Conference on
Safety of Life at Sea,” held in London during 1929, considerably
broadened the responsibilities of the Ice Patrol, in requiring ‘‘a service
for the study of ice and current conditions.” Thus, from 1932 on,
a third vessel was employed each year for this scientific pursuit.

The construction of a current chart depicting the dynamic
topography of the sea surface adjacent to the Grand Banks is a
scientific achievement of the oceanographer. To be useful, the area
to be charted must be of sufficient size to portray a fair picture of
the current circulation. Many oceanographic stations (50 to 100)
are taken as quickly as possible, usually in rows radiating out per-
pendicular to the slope of the Grand Banks. The oceanographer is
able to compute the relative dynamic or pressure height in decibars
of a water column at each station from a deep isobathic plane to the
sea surface. In oceanographic work, water pressure or dynamic po-
tential is commonly expressed in decibar units. This unit is con-
venient because it is very close to the pressure exerted by 1 meter of

water. Thus the pressure height in decibars of a water column is
approximately the same as the depth of the column in meters.

Because sea water is not a homogenous substance, particularly
in the critical iceberg area near the confluence of the warm, salty
Gulf Stream and the cool, less saline Labrador Current, the computed
relative pressure heights in decibars will vary from station to station.
The oceanographer plots each station geographically with its cor-
responding pressure height, then by scribing a line through areas of
equal pressure heights he obtains a chart depicting the dynamic to-
pography of the sea surface. The resulting chart closely resembles an
isobar weather map and actually portrays Highs and Lows in the
pressure level of the sea surface. Thus, in the Northern Hemisphere,
the unequal water mass from the Highs, attempting to equalize the
depressions, flows counter-clockwise around the Lows similar to the
flow of an air mass around a barometric low. However, if the com-
plicated details of the water circulation are to be determined, oceano-
graphic stations must be placed much closer together than weather
observation posts, with the density of stations even greater along
the slope of the Grand Banks than in the deeper water off the Grand
Banks. Whereas, a weather map may be constructed in hours, and
is useful only for hours, the construction of a current map takes days
but it is useful far longer, as the rate of the everchanging water
circulation is slower than that of an air mass.

EARLY EXPERIMENTS IN ICEBERG DESTRUCTION

The shapes, sizes, heights above water, and depths below water
of icebergs differ tremendously, each variation contributing to the
many variable factors determining their drift. Observations have
shown that, with the best current charts available, drift predictions
are not always accurate. Consequently, if the rather short life span
of an iceberg in the critical area south of the Tail of the Banks could
be shortened by only a few days it would greatly, percentage wise,
reduce the time it is a menace to navigation. Experiments in arti-
fieally increasing the meltability or in the demolition of icebergs
have been carried out intermittently by the Ice Patrol since its
beginning. These experiments have included sound, gunfire, mines,
demolition charges, depth charges, and even fire hoses. All attempts
have had no real practical results. However, studies available
revealed that with the strategic positioning of half a ton of conven-
tional explosives about 2,000 tons of ice can be broken up, but this
could require upwards of a hundred charges to destroy a berg and
would be both physically and economically unsound. Melting by
heat would be equally impracticable as it would require the heat
energy contained in 2.4 million gallons of gasoline to melt a medium-
sized berg of 100,000 tons.

Plane and iceberg target after bombing

The Ice Patrol has long been aware of the experiments, results,
and theories of the late Professor H. T. Barnes, of McGill University,

THE TITANIC—50 YEARS LATER

using strategically placed thermite explosive charges on grounded
icebergs off Newfoundland. Large bergs were literally shattered by
a series of explosions and reactions. The thermite theory involves
the high temperature of combustion when thermite, an intimate
mixture of powdered aluminum and iron oxide, reacts to produce
molten iron. The high temperature gradient, though from a relatively
small heat source, may set up shock waves within the berg and
fracture it along planes of internal stress. Boarding an iceberg in the
open sea to plant the charges is not only very hazardous and fool-
hardy but frequently impossible.

INTRODUCTION OF ELECTRONIC AIDS

Throughout the war years of 1941 thru 1945 the Ice Patrol
was suspended as it had been between 1916 and 1918. However,
during the Second War many scientific advances were made, and
their application greatly increased the efficiency of the post war
International Ice Patrol. During the absence of a surface patrol,
aerial observation flights of the ice area were successfully flown.
After the resumption of the regular ice patrol in 1946, aircraft contin-
ued to play an ever increasing role. Equipped with radar for probing
areas of reduced visibility and Loran for a system of precise position-
ing, aircraft were able to systematically search the ice areas quickly
and fairly thoroughly. Patrol planes flying set patterns at an alti-
tude of 500 to 1,000 feet, cross and recross the ice area on parallel
courses about 25 miles apart, while obtaining Loran fixes at 3 to 5
minute intervals. These ice observation flights have been so effective
that during light ice years continuous surface patrols are unnecessary.
Normally preseason ice observation flights begin in January and
continue until the commencement of a continuous surface patrol.
Flights are resumed after the surface patrol is terminated.

Yearly the number of vessels equipped with radar increases.
Consequently, since 1945, the Ice Patrol has conducted continuing

Boarding party preparing iceberg for thermite charge.

41

research programs in iceberg detection by Radar. These experiments
prove radar is useful in detecting ice, but the atmospheric conditions
over the Grand Banks that create a need for radar often cause sub-
normal propagation of radar waves. The research indicates there is

no preference to the frequency of the equipment as ice is not fre-
quency sensitive and the response of ice to S- and X-bands is the
The effect of fog on either band is negligible, but rain can

same.

Aerial ice observer.

ae |

THE TITANIC—50 YEARS LATER

effectively hide dangerous growlers on the X-band. The reflective
quality of an iceberg is very low, about 60 times less than that of
a ship of equivalent physical cross sectional area. Due to the shape
and irregularity of the reflecting surfaces of icebergs, their range of
detection by radar varies greatly. An observant radar operator, ex-
perienced in ice detection, is a definite advantage. Often, even with
the expert use of the FTC and STC anti-clutter devices, dangerous
growlers can be lost in the sea return when a moderate sea is running.
If ice is not picked up beyond the area of sea return it will not be
spotted and the maximum range for the detection of a growler is
only about 4 miles. Usually, better results can be obtained from a
sector scan of a particular area, say 30° on each side of the bow,
than a general scan, and nearby ice which may not appear on the
minimum range setting often will appear on the intermediate or
maximum range settings.

RADAR IS AN EXCELLENT AID FOR ICE DETECTION
WORK BUT EVEN WITH DILIGENT USE IT WILL NOT AS-
SURE A SAFE PASSAGE THROUGH THE ICEBERG AREA
OF THE NORTH ATLANTIC.

RECENT EXPERIMENTS IN ICEBERG DESTRUCTION

Although not primarily concerned with iceberg destruction, the
Ice Patrol, despite the previous unsuccessful attempts, evaluates
each new technique or theory that might hasten the disintegration
or melting of an iceberg. The highly successful aircraft offered a
practical approach to utilizing the thermite theory of ice destruction.
Therefore, aerial bombing experiments were conducted on selected
icebergs with thermite type bombs in June 1959. Each bomb con-
sisted of clusters of incendiary bomblets and was designed to open
about 100 feet above the target and spread the destructive power of
the thermite bomblets over a wider area. Sixteen out of the twenty
bombs dropped scored hits, but no icebergs were destroyed. The
heat, spread over too wide an area, did not deliver the concentrated
high temperature source necessary to the thermal stress theory of ice
demolition. The following year, 1960, high explosives were substi-
tuted for the thermite and twenty 1000-pound bombs were dropped
on a single iceberg for a total of 18 hits. The iceberg at the con-
clusion of the bombing was estimated to be one-fourth to one-third
smaller. Although natural deterioration was in progress throughout
the eight days of the experiments, the bombs were believed to be a
factor in the reduction of the size of the iceberg.

The Ice Patrol felt that before further bombing experiments
were conducted the thermite theory should be re-evaluated. Due to
the great danger involved in boarding icebergs in the open sea this
had not been done previously, but permission was obtained from the
Canadian Authorities to conduct the experiments in the sheltered
waters of Bonavista Bay. Forty 28-pound thermite charges and
related ice equipment were obtained for this experiment. A small
tabular berg was boarded and a 196-pound thermite charge planted.
The resulting explosion, aside from calfing a few small bergs around
the waterline, appeared to have little effect on the berg. Nearby,
a large pinnacle berg was boarded and a second charge of 560 pounds

Spreading carbonblack on iceberg.

42

of thermite was planted at the base of the pinnacle. There was a

magnificient display of smoke and molten iron hurled hundreds of
feet into the air, but the iceberg remained virtually unchanged.
This experiment showed that this type of detonation will not neces-
sarily cause the disintegration attributed to the thermite theory.

Iceberg 12 hrs after spreading carbonblack.

Practice bombs filled with carbonblack, sand, ground clay, iron
fillings, and oil were also dropped from a patrol aircraft, but the
results were unsatisfactory. However, the small tabular berg used
in the first thermite experiment was reboarded on 10 June, in the
middle of the afternoon, and 25 pounds of carbonblack were spread
manually with fiber brooms over half of the iceberg. Five hours
later the berg underwent major calfing, and on close inspection the
following morning, it was found to be less than 1/8 its previous size.
The calfing of the iceberg after the carbonblack experiment could be
coincidental; further experiment will determine the feasibility of
this type of deterioration.

WIND EFFECT

For years the draft-height ratio for icebergs was believed to be
about 5 or 6 to 1, but recent wire drags and submarine observations
reveal a much smaller ratio. The approximate ratios for the various
types of icebergs are 7 to 1 for flat tabular bergs, 3.5 to 1 for spher-
ical shaped bergs, 2 or 3 to 1 for pinnacled bergs, and 2 to 1 for
drydock type bergs with the average ratio for all bergs somewhere
near 3.5 to 1. If the mean draft of icebergs is not as great as originally
estimated then the effects of surface winds on their drift should be
greater than previously believed. Therefore, in 1960, the Ice Patrol
conducted experiments to establish the proper relationship between
the wind and berg drift. Results obtained indicated that winds
between 10 and 50 knots imparted a drift velocity in knots of
0.023 that of the wind speed and in a direction 50° to the right of
the direction of the wind.

THE TITANIC—50 YEARS LATER

Ye
,

BANKS
GRAND

TITANIC SANK 1912

43

THE TITANIC—50 YEARS LATER

TODAY

The present seasonal trans-Atlantic lane routes were last revised
by the “North Atlantic Track Agreement’’ of January 1950. The
1960 convention for the ‘Safety of Life at Sea’’ reaffirmed the basic
concepts of the 1950 agreement, with a new provision, when ratified,
requiring mandatory lane compliance by vessels in the converging
areas. The present routes, consisting of tracks A, B, and C to and
from U.S. ports and tracks D, E, F, and G for Canadian ports,
together with the general instructions for their use are printed each
year on the back of the North Atlantic Pilot Chart for April. The

effective tracks each month appears on the face of the Pilot Chart
for that month. Alterations to the effective tracks deemed advisable
by the steamship companies composing the North Atlantic Track
Agreement are published by the Hydrographic Office.

Radio Station NIK, Argentia

The Ice Patrol cooperates closely with the Canadian Department
of Transport which, in conjunction with its Meteorological Branch,
maintains an “Ice Central Office ’’ at Halifax to support its ice-
breaking operations and to assist shipping in Canadian waters,
particularly in the Gulf of St. Lawrence and Straits of Bell Isle.
Ice experts consolidate the information obtained by observers
aboard the 10 Canadian Icebreakers, regular aerial reconnaissance,
commercial shipping, and lighthouse keepers. Up-to-date charts
depicting detailed ice conditions for the entire area of operation are
maintained and a radio facsimile is broadcast to shipping and other
interested parties. An ice forecasting service is also provided, and
an ice information officer is stationed at Sydney, Nova Scotia to
assist shipping and to act as a liaison between the shipping interests
and the ice-charting and forecasting service.

Each year throughout the ice season, bulletins from the
Commander, International Ice Patrol (NIK) are broadcast twice
daily at 0048 and 1248 GMT by the U.S. Coast Guard Radio

44

Argentia, Newfoundland (NIK). Broadcasts are preceded by the
general call CQ on 500 ke. with instructions to shift to a receiving
frequency usually either 155, 5320, or 8502 ke. The bulletins are
transmitted at 15 words per minute and repeated at 25 words per
minute. If necessary, special ice bulletins, preceded by the Inter-
national Safety Signal TTT, may be broadcast in addition to those
regularly scheduled. Normally, merchant ships call NIK on 500 ke.
or 8 me. Ships usually work 425, 448, 454, or 480 kc., or their
assigned working frequencies, and NIK normally works 432, 8734,
or 12718.5 ke. When on station the surface patrol vessels (NIDK)
will relay messages between the ships and NIK if necessary.

All vessels are requested to report any ice sighted in the area
between latitudes 39° and 49°N. and between longitudes 42° and
60°W. Also at 4-hour intervals, reports of the ship’s position, course,
speed, visibility, sea temperature, and weather conditions are desired.
These reports by shipping are of the utmost importance to the
International Ice Patrol during periods or reduced visibility when
aerial ice observation is rendered ineffective. Reports aid the Ice
Patrol in relocating drifting ice, effectively planning and concentrat-
ing ice observation flights in areas of suitable visibility, and con-
structing isotherm charts employed in estimating ice melting rates
and detecting shifts in the branches of the Laborador Current.
Weather conditions are useful in estimating set and drift of bergy
bits and field ice and in determining the necessity for special warnings.

To facilitate the correct evaluation, ice reports to the Patrol
should include (1) the type of ice sighted (Note.—If a radar target,
report it as such.), (2) the position of the ice (not the position of the
ship), (8) sea temperature at the closest point of approach to the ice,
and (4) weather and visibility conditions. When impracticable to
send reports promptly every 4 hours, vessels are requested to prepare
the scheduled reports for later transmission as a late report is much
better than no report.

Again this year, as in 1961, the International Ice Patrol
contemplates regular daily transmissions of ice conditions by fac-
simile. The time and frequencies of the transmissions will be
indicated in the regular ice bulletins. These facsimiles will represent
true ice conditions and limits instead of the synoptie view offered by
the ice bulletins.

Throughout the ice season the U.S. Navy Hydrographic
Office repeats the ice information bulletins over Navy Radio Wash-
ington (NSS) on the twice daily Hydrolant Broadcast at 0430 and
1630 GMT. Before the commencement and after the termination
of the International Ice Patrol, all reports of ice sightings should be
addressed to the U.S. Navy Hydrographic Office, Washington, D.C.
The information will then be broadcast to shipping on the Hydrolant
schedule. -

Fifty years have passed since that fateful night when the
TITANIC went down with such an appalling loss of life. Today,
thanks to the International Ice Patrol, thousands of ships annually
traverse the Grand Banks region in perfect safety. Since the
inception of the Patrol, not a passenger has lost his life in the area.
Truly it can be said that those who lost their lives in the world’s
greatest maritime disaster, did not die in vain.

NATURAL PHENOMENA

G. E. Buckwalter
Maritime Safety Division
U.S. Naval Oceanographic Office

Mariners, by the very nature of their calling, have excellent
opportunities for vubserving natural phenomena which may be of great
value to the astronomer, oceanographer, und meteorologist. The
scientist that delves into the secrets of nature depends upon accurate
data obtained from all sources, but observations of phenomena from
remote areas of the world add significantly to the sum of man’s
knowledge particularly when geographic distribution studies of the
occurrences of such phenomena are made. Also, such observations
may give the clues to unlocking the secrets of nature.

Observations of phenomena in the marine environs reported by
mariners to the U.S. Naval Oceanographic Office are not only useful
in studies made by this office but are forwarded to the various
government agencies and institutions having related interests.
Mariners are therefore encouraged to forward observations con-
cerning natural phenomena, as well as other hydrographic
observations.

The following are selected examples of natural phenomena to
which mariners have contributed significant knowledge as well as
being of general interest. Inquiries concerning them have been
received from time to time.

ABNORMAL REFRACTION

Deceptions of vision at sea are produced by abnormal refraction
of light which in the more extreme cases give rise to false images
of land, ships, or other objects. Generally, abnormal refraction at
sea is due to an inversion of temperature in a layer of air, the varia-
tions in density thus produced causing the light rays to be bent
considerably in excess of normal conditions.

The most frequent and most favorable conditions for excess
refraction, under which most of the more fantastic forms of mirage
and distortion take place, occur when a layer of warm air is in
contact with cooler water. The air next to the surface of the sea is
cooled, and consequently the upper layers are warmer than the lower
so that instead of the usual decrease there is an increase of tem-
perature with height. Most refraction phenomena are formed at the
boundary between this cold dense layer of air at the surface of the
sea and the less dense warm air above. This condition is identical
to that which is responsible for the formation of most sea fog;
therefore, the presence of fog is an indication that excessive refrac-
tion is likely to be encountered.

Similar inversions may be caused by the presence of cold air over
warm water. A marked difference between air and sea tempera-
tures is therefore another guide to the presence of excessive
refraction.

Although abnormal refraction is not restricted to particular
geographical areas, certain regions of the globe are so situated with
respect to general meteorological conditions as to be more favorable
than others for the occurrence of abnormal refraction phenomena.
The polar coasts are among the most favorable of these regions be-
cause of the frequently prevalent marked difference between sea
and air temperatures. In polar regions excessive visibility or some
form of mirage is often manifest when comparatively warm and
light winds blow over the cold ice surfaces or when cold winds blow
over open water. A milder temperature over open water than over
the ice-clad adjacent shore also leads to refraction phenomena.

CEILING OF INVERSION

SS See

Seat) Gale!

Mirage

Figure 1

DIAGRAM ILLUSTRATING THE CONDITIONS UNDER WHICH SUPERIOR MIRAGES MAY BE FORMED OFF
LARGE ICE MASSES. THE INVERSION LAYER HAS BEEN WARMED ADIABATICALLY IN DESCENDING
THE GLACIER SURFACE THE DUST-FREE NATURE OF THE AIR LEADS TO GREAT UNDERESTIMATION
OF THE DISTANCE OF THE COAST

45

In the polar regions the most common forms of abnormal refrac-
tion are looming and superior mirage. Looming is the apparent
raising of an object above the horizon. It is quite common at sea
especially in high and middle latitudes, and results in the appearance
of distant objects which in many instances may actually be below
the normal horizon at the time of observation. There are two types
of looming. In one case, the object (island, iceberg, ship) is seemingly
increased in elevation though not in size; in the other case, the ob-
ject appears to be enlarged and brought much nearer to the point of
observation.

The atmospheric condition that produces looming is one in which
there is an abnormal decrease in the density of the air from the
surface upward and hence a greater than normal downward curvature
of the paths of light rays. The more rapidly the density decreases
with elevation, the more unnatural and impressive becomes the
phenomenon. If the rate of this decrease is variable at low elevation,
the shape of the looming object is distorted, and strange bulging,
thinning, flattening, or pointing may occur. Thus, a distant rounded
peak might loom in its natural shape, appear with perfectly flat
summit, or with a misshapen summit drawn much nearer the observer
than the base. Likewise, the appearance from the masthead may
be different from that at deck level.

Superior mirage is the apparent reflection from a more or less
mirror-like atmospheric condition where there is a pronounced tem-
perature inversion at a distance of several feet above the surface.
This inversion introduces an abnormal change in density, and extra-
ordinary refraction results. Its most frequent appearance is that
of an inverted image above the object, but under suitable conditions
a second mirage is seen erect, close above the inverted one. Some-
times the object is not observed directly and the inverted image or
the upper erect image of an object below the horizon may be seen.

The formation of superior mirage is illustrated in figure 1. It is
best and most frequent in Arctic and Antarctic regions but it may be
observed down to middle latitudes. As with looming, the condition
requisite for its formation is a warm layer of air existing over the
sea at a suitable height, that is, an inversion of temperature. The
only difference between this and the condition necessary for looming
is that for superior mirage there must be a more sudden change
from cooler to warmer air at a certain height.

The observer on a ship near land usually sees mirage as an un-
natural image of the coastline, single, double, or triple, or as an
appearance of the coast much nearer to him or farther from him
than it actually is.

At sea, ships and icebergs are the mirage subjects more generally
seen. Ocean fog is also associated with mirage since the temperature
and humidity variations which favor condensation of moisture as
fog in the air are often factors in causing mirage. An attendant
mirage is, of course, not observable while dense fog actually ob-
structs the vision, but mock fog or the typical refraction band is
often seen under such conditions and may lead to the recording
of damp, or true, fog which does not exist.

The not uncommon phenomenon of mirage has been responsible
for many false estimates of remoteness of newly discovered land
features which have been seen by explorers within the polar regions,
combined as it has been with the underestimates of distance due to
the unusual clarity of the atmosphere. In many cases of snow-
covered lands, there is not enough individual character in the coastal
features to permit identification from different ship positions, and
in such cases coasts have frequently been placed upon charts on the
basis of the direction and estimated distance from positions offshore.
These estimated distances are often as much as 40 to 50 miles too
low because of atmospheric clarity alone, and can be as much as 300
miles too low as a result of the existence of a superior mirage.

As already indicated, abnormal refraction can be recognized only
by its effect on the appearance of land, or such objects as ships, or
icebergs. Temperature inversions may also give rise to abnormal
dip of the horizon, which may seriously affect the accuracy of sextant
observations. The navigator should therefore always be on guard
against such a possibility whenever there is a chance that a tem-

NATURAL PHENOMENA

perature inversion may exist. If the motion of the ship permits use
of a bubble sextant, it can be quickly determined whether the appar-
ent horizon is appreciably displaced.

AURORAS

Auroras are caused by positively charged atoms, mainly hydro-
gen atoms, together with electrons emanating from the sun and
entering the earth’s atmosphere at speeds exceeding those of
meteors. Auroras differ in color, form, motion, time of occurrence,
and geographical distribution. They are associated with other
phenomena, such as sunspots, magnetic storms, and ionospheric
storms.

The auroras commonly occur only in high latitudes, both northern
and southern. Occasionally they are visible from middle and low
latitudes far beyond normal limits. They present a rare spectacle
of great beauty and mystery to inhabitants of non-polar areas.
Observations of these phenomena have been made in India (latitudes
19°N. to 36°N), in the West Indies, and Aden (latitudes 10°N. to
24°N.), as well as regions closer to the poles.

AURORAL FORMS (see Fig. 2).—The Homogeneous Arc, as the
name indicates, appears as a segment of a circle across the sky,
usually nearly at right angles to the meridian. The lower edge is
more sharply defined than the upper, but there is no apparent fine
structure. It may be high or low in the sky. The sky below the are
is sometimes very dark; this is called the dark segment. When
several ares appear they are closely parallel. The lower border, in
most instances, becomes more luminous before the appearance of
rays. Sometimes only short lengths of arcs appear. In this case,
definite east-west motion may be apparent. Single narrow arcs, 1°
to 2° in width, are sometimes about twice the usual height.

A more irregular form of are with folds has been called a
Homogeneous Band. It may move east-west with an undulating
motion, or it may oscillate in a north-south direction. The are may

RAYED ARC

become very bright or have a red lower edge and may change sud-
denly into ray forms.

The Rayed Arc has the same elongated shape as the homogeneous
arc, but it is composed of rays arranged side by side. Sometimes the
homogeneous characteristic is retained; in others only the rays are
present. When the rays are short and curves are present, they are
commonly called Rayed Bands. Sometimes the rays become long
and the rayed are shows folds moving as though blown by wind;
these have been called Draperies. They sometimes move as a whole
and finally break up into groups of long rays. Whenever ray forms
approach the magnetic zenith, they appear to converge to form a
radiant crown or Corona. When a ray form moves over the mag-
netic zenith it appears as a thin band of light containing many bright
points (rays seen end on). Rayed arcs are characterized by rays
standing side by side in a pattern elongated at right angles to the
individual rays.

A Ray is the term applied to isolated individual rays or narrow
masses or bundles of rays. They may be present with other forms,
but the rays do not appear connected. Observation of rays is im-
portant because they are usually high above the earth. Rays appear
quite straight, like searchlight beams, and may be from 2° or 3° to
over 60° in length. The width varies from a few minutes to many
degrees-of are. The vertical edges are quite sharply defined. The
brightness usually varies from a low value at the top to a maximum
value about one third of the way from the bottom. Sometimes the
rays are very bright at the bottom and decrease in intensity gradually
upward.

The Pulsating Arc consists of a homogeneous arc or a part of a
homogeneous are which changes in light intensity, fading and
brightening in a rhythmic fashion. Each pulsation may last from a
few seconds to a few minutes. This form often drifts along slowly.

The Pulsating Patches or Spots are any diffuse patch or spot,
not in are form, which pulsates in brightness. They may be red in
color.

FLAMES

SPOT OR PATCH

PULSATING ARC PULSATING SPOT

HOMOGENEOUS ARC

Figure 2 Auroral Forms

46

NATURAL PHENOMENA

The Flaming Aurora comprise a quick moving form of waves of
luminosity moving toward the zenith, or of invisible waves which
cause segments of arc, bands, or patches to appear and disappear
rhythmically but always with an upward motion. One form con-
sists of ares which extend upward out of a quiet arc. Another type
occurs when these waves move up ray forms giving the impression
of flames. They often appear near the peak of a display, though
may be seen several times in one night.

The Glow form is a faint luminosity, which, when seen near the
north horizon, resembles dawn. When appearing high in the sky it
resembles a translucent veil. It occurs alone only at the beginning
and end of displays. However, after other forms become prominent
it is easily overlooked. The activity of an auroral display often ends
in a glow which may persist for several hours.

A Patch or Spot consists of patches or spots of diffuse light with
the edges more well defined than the edge of a glow form. The patch
or spot is usually whitish but may be a deep red in color.

BIOLUMINESCENCE

Bioluminescence, often incorrectly termed phosphorescence, is
the production of light by living organisms in the sea. Bioluminescent
displays must be triggered by some physical,chemical, or mechanical
stimulus. Generally, these displays are stimulated by surface wave
action, ship movement, fish and whale movement, subsurface waves,
upwelling, eddies, physical changes in sea water, surfs, tide rips,
and others.

In most cases bioluminescence is a reaction between luciferin
and oxygen in the presence of luciferase. Luciferin is a heat stable,
easily oxidized compound. Luciferase is an enzyme which accelerates
the reaction. Bioluminescence may be produced by secretions of
specialized glands, or by symbiotic bacteria.

Sketch of a phosphorescent wheel

Marine displays are generally grouped in three general categories:
(1) sheet-type, often appearing as a sheet-like glow extending for
several miles over the sea surface; these are caused by tiny one-
celled animals, protozoans; (2) spark-type, observed as innumerable
flickering points of light; these are caused by minute shrimplike
crustaceans; (3) globe-type, observed as glowing balls of light
produced by jellyfish and tunicates when drifted together in groups
in the sea.

Numerous reports concerning these phenomena have been re-
ceived from ships throughout the world. Some of the descriptive
terms submitted by observers are as follows: “appeared as shoal
water, low-lying fog bank, broad belts, narrow belts, ribbons, rivers,
milky patches, bars moving at great speed, flashing spots, white
water, beams of light, like a search light, patches resembling pack
ice, pale blue—horizon to horizon, millions of electric lights, starry
sky, round blobs, cloud-like patches, continuously changing form,
large anti-clockwise pinwheels,” and many others.

47

BURNING CLIFFS

Along the western shore of Franklin Bay, Northwest Territories,
Canada, the coast is backed for several miles by a range of steep
hills known as “Smoking Hills” or “Burning Cliffs”. The cliffs range
from about 300 to 500 feet in height and are in places composed of
bituminous alum shale. Their name is from the burning mineral
deposits which emit clouds of smoke and steam, particularly in
spring and summer.

Some areas of the cliffs burn in places for years. At night the
fires are visible a considerable distance to seaward and resemble
numerous camp fires. The fires burn out in some places and start up in
others. The burned out areas cause the cliffs to be washed and
undercut by the sea in places.

The smoke has a sulphurous odor but the fires are reportedly not
of voleanic origin. The water in the streams and ponds along this
coast is mostly undrinkable because of the alum content and other
mineral salts.

DESTRUCTIVE WAVES

Unusual sudden changes in water level can be caused by seismic
sea waves or violent storms. These two types of destructive waves
have become commonly known as tidal waves, a name which is
technically incorrect as they are not the result of tide producing
forces.

Seismic Sea Waves are set up by submarine earthquakes. Many
seismic disturbances do not produce sea waves and often those
produced are small, but occasional large waves can be very damaging
to shore installations and dangerous to ships in harbors.

These waves travel great distances and can cause tremendous
damage on coasts far from their source. In 1946, one originating in
the Aleutian Trench caused $25,000,000 damage in the Hawaiian
Islands 2,200 miles away.

The speed of seismic sea waves varies with the depth of water,
reaching 300 to 500 knots in deep water of the open ocean. They can-
not be detected in the open sea from a ship or from the air because
their length is so great, sometimes a hundred miles, as compared to
their height, which is usually only a few feet. Only on certain types
of shelving coasts do they build up into waves of disastrous
proportions.

There is usually a series of waves with crests 10 to 40 minutes
apart, and the highest may occur several hours after the first wave.
Sometimes the first noticeable part of the wave is the trough which
causes a recession of the water from shore, and persons who have
investigated this unusual exposure have been engulfed by the on-
coming crest. Such an unexplained withdrawal of the sea should be
considered as nature’s warning of an approaching wave.

A warning system has been organized in the Pacific with its
center in the Hawaiian Islands. Improvements for rapid determina-
tion and reporting of earthquake epicenters are being made, but no
method has yet been developed for determining whether destructive
waves will be generated.

Stormwaves.—A considerable rise or fall in the level of the sea
may result from strong winds and a sharp change in barometric pres-
sure. In cases where the water level is raised, higher waves can form
with greater depth and the combination can be destructive to low
regions, particularly at high stages of tide. Extreme low levels can re-
sult which are considerably less than those shown on nautical charts.
This type of wave occurs especially in coastal regions bordering on
shallow waters subject to tropical storms.

Seiche is a stationary vertical wave oscillation with a period
varying from a few minutes to an hour or more, but somewhat less
than tidal periods. It is usually attributed to external forces such
as strong winds, changes in barometric pressure, swells or seismic
sea waves disturbing the equilibrium of the water surface. Seiche
occurs both in enclosed bodies of water and is superimposed upon
the tides of the open ocean. When the external forces cause a short-
period horizontal oscillation of the water, it is called Surge.

The combined effect of seiche and surge sometimes makes it
difficult to maintain a ship at its berth alongside a pier even though
the water may appear to be undisturbed. On occasion ships have
incurred damage or caused damage to pier facilities after mooring
lines have been parted repeatedly under such conditions.

Since prediction of this phenomenon is nearly impossible, mariners
should be alert to the ship’s behavior at all times especially in strange

NATURAL PHENOMENA

ports and should take measures to prevent damage to the ship or
property. :

Tide Bores.—The tide bore may be defined as a sudden rise of
tide which rolls up certain rivers and bays in the form of a breaker.
Bores form a hazard to shipping and generally occur in a shallow
estuary where the range of tide is high. The high water moves
inward at greater speed than the preceeding low water because of
the greater depths at high water. When the high water overtakes
the low water an abrupt front is formed.

An example of this phenomenon occurs in the Seine River, France,
where it is known locally as a “mascaret”. This wave takes the form
of a fairly abrupt front the slope of which varies between 1/100 and
1/150, and the height from 3 to 614 feet. This front travels upstream
with a velocity of 22 to 25 feet per second and is followed by wave
undulations of 2 to 3 feet high and a few score yards in length. This
phenomenon is dependent on numerous factors and can be consider-
ably lessened or even entirely suppressed by prevailing atmospheric
conditions or hydrologic conditions of the river.

The impact of the mascaret on a ship at her mooring results in a
more or less alternating force; generally, the maximum influence of
this force takes place at the passage of the wave front and is directed
upstream attaining a value nearly equal to the product of the dis-
placement of the vessel by the slope of the wave (i.e. approx. 1/100
to 1/150 of the vessel’s displacement). The following undulating and
downstream forces, however, produce both upstream and downstream
forces comparable to that produced by the initial wave front.

Thus the vessel experiences violent alternating forces attaining
scores of tons with a period of some 10 to 20 seconds.

Moorings should therefore be such as to introduce opposing
reactions to the movement of the vessel before any appreciable
speed is obtained resulting in a considerable amount of kinetic
energy. Mooring lines should also have the ability to stretch to allow
for the lifting of the vessel as the tide rises.

Traditional mooring lines (wire hawsers, hemp ropes, etc.) are
not suitable since they are not sufficiently elastic to be hove taut
to limit the movement of the vessel at low tide and to subsequently
undergo a rapid change of height. Furthermore, as it is not possible
to balance the tension of each mooring line there is the risk of
breaking one after the other when subjected to the forces generated
by the mascaret.

The Port of Rouen Authority reeommends employment of nylon
springs shackled to customary mooring lines, particularly on wire
hawsers. These nylon springs should be 26 to 32 feet in length and 3 to
4 inches in diameter. The lines are hove as taut as possible at low
water. When conditions allow, both anchors should be laid out with
slightly taut chains to increase the ship’s resistance to the wave
front. Ships should not use engines as this increases the downstream
force. The nylon springs should not be in contact with bollards or
bitts but should end in metal thimbles.

Glacial Wave.—Lituya Bay (58°38’N., 137°39’W.), on the south-
east coast of Alaska, is a deep indentation with a narrow entrance.
The shores are backed by high peaks from which glaciers descend to
the water. This bay, on several occasions, has been subjected to
waves and water movements of exceptional amplitude.

Discovered in 1786, by La Perouse, the bay then appeared to
offer sheltered anchorage, but that explorer lost two small craft with
crews sent to reconnoiter the area. The craft were lost from being
thrown against the reefs by the strong tidal currents which attain
rates of up to 12 knots at the entrance.

On the evening of July 9, 1958 an earthquake in Alaska caused
an enormous mass of ice to break off Lituya Glacier and to fall into
the bay. The resulting wave swept the shores to a considerable
height. The few witnesses reported that the cataclysm caused the
water to attain heights of 492 feet (150 meters) at certain points on
the coast, more than twice that height southward of Lituya Glacier,
and 164 feet (50 meters) on Cenetaph Island within the bay.

Such heights had remained an enigma for oceanographers; but
several observations made by the U.S. Geological Survey and the
U.S. Coast and Geodetic Survey, and taking into consideration
similar phenomena, permitted the idea that such heights were not
exaggerated.

The complete disappearance of two Indian villages, mentioned
by La Perouse, were reported in 1853 or 1854 by hunters. A wave
of great amplitude was reported in 1936; and prior to 1958 a geologist

48

noticed that the trees around the bay shore grew according to the
age of the trees with marked delineations or bands on the hillsides
to a height of 393 feet (120 meters). The most recent boundary and
age group corresponded with the wave of 1936, and the second age
group corresponded to the winter of 1853-54.

Returning to the bay after July 9, 1958 the geologist discovered
that the mountainsides he had previously observed as completely
covered with trees, and the slopes descending to the shore were bare
to heights of 1,640 feet (500 meters). He noted also that the rock
fissures were clear of accumulated debris.

The observations were confirmed by aerial photographs taken
after the quake. The photos indicated that some great masses of
ice had fallen into the bay in addition to large avalanches. Photo-
grammetric measurements also indicated that the sea wave of 1958
exceeded the 1,280 foot (360 meter) level.

HISTORY OF A DISAPPEARING ISLAND

Faleon Island (Fonua F’ou).—This voleanic feature, located at
20°19’S., 175°25’W., in the Tonga Islands, has a history of appearance
and submergence and has changed in size and form on several known
occasions.

In 1865, the H.M.S. Falcon, from which it derives its name, ob-
served it as a breaking reef. The H.M.S. Sappho observed smoke
rising from the reef in 1877.

Birth of an island

In 1889, the H.M.S. Egeria, a surveying ship, surveyed the area
and found an island 114 miles long north to south, one mile wide and
wedge-shaped with a 153 foot-high hill at the southern part. The
island was formed of loose voleanic ash and cinders which were
constantly slipping down, as the sea action undermined it. It was
estimated that two-thirds of the island had worked away since 1885.
No growing coral was found. It soon dispersed entirely. The Egeria
was able to anchor off all but the east side.

In April 1894, the area was observed at a distance of 2 miles and
the only visible relief was a low streak of black rock. In December
of the same year voleanic action and a new crater was observed to
have formed with the resultant island 3 miles long and 14% miles
wide. It was 50 feet high with a hot surface. It was reported in
July 1898, that Falcon Island had disappeared completely and that in
its place was a shoal about 100 yards in extent with the sea breaking
heavily on it. Discolored water was also observed about 1 mile
southward of the breakers. Again in April 1900, it appeared above
water and was estimated to be about 9 feet high at its northern end.
The SS Cormoran could find no above-water features in the area in
1913.

The location of Falcon Island was examined by the H.M.S.
Veronica in 1921. A very heavy swell, discolored water, rips, and a
continuous breaker was observed at the southwest part of the area.
The breaker was found to be caused by a rock about 15 yards in
diameter, mottled green, covering and uncovering. The bottom was
visible for some distance from the rock. It was estimated that in
calm weather the rock would have had a depth of about 3 feet over it.

In October 1927, Falcon Island erupted again. It was examined
by the H.M.S. Laburnum which cruised around it and found the

NATURAL PHENOMENA

island as it was originally charted in size but about 305 feet high.
It was erupting once every 20 minutes. It commenced to erupt in
the middle, then ejected smoke and vapor, then was enshrouded by a
bank of smoke that billowed to over 4,000 feet in the sky. The
Premier of Tonga landed on the island in June 1928, and hoisted the
Tongan flag. In October of the same year the height of the island
was observed to be 405 feet with steam emitting from the crater.
In 1930, the height was again reported as 475 feet.

In 1936, the H.M.S. Leith steamed around the island about
\% mile off. The north side rose in a gradual slope to its 200-foot
summit, falling in a perpendicular cliff at its southern end. Little
voleanic activity was apparent, but eruptions were observed every
15 minutes from a submarine crater off the southeast end. The
island was about 11% miles long, north to south,and about % mile
wide.

In 1937, the H.M.S. Achilles passed 1 mile northeastward of the
island and reported no sign of volcanic activity. In June 1938, the
H.M.S. Leith estimated the height to be about 30 feet about % mile
from its southern end but with no activity. The MV Mawi Pomare
observed the island in March, 1941, emitting jets of steam.

Little is known of its activity during World War II. In February
1949, the H.M.N.Z.S. Hawea reported that the island had again dis-
appeared, and that the least depth found in the vicinity was 9
fathoms.

In 1959, it was again reported that no above water features were
visible in the vicinity of the island.

LOCUST RADAR TARGET

In July of 1959 at the Strait of Bab El Mandeb, at the south-
eastern entrance of the Red Sea, a ship observed a radar target at
a distance of about 10 miles. Visually the target appeared asa
sandstorm approaching from northwestward and to be about 8 miles
long northeast to southwest, about 6 miles wide, and oval in shape.
The target advanced until the ship was in the midst of a hugh swarm
of locusts. The target moved southeastward until it disappeared at
a distance of about 10 miles.

In the Middle East swarms of locusts are known to migrate from
Africa into Asia Minor plaguing crops and other vegetation since
Biblical days.

METEORS

Interplanetary space is by no means empty. As the earth revolves
around the sun, it swims through an ocean of rarefied gas, thinly
strewn with solid objects that range in size from dust specks to
minor planets. Both the zodiacal light and the outermost part of
the sun’s corona are interplanetary solid particles illuminated by
sunlight. But the most familiar indications that space between the
planets is not empty are the meteors seen as the earth collides with
small bodies.

Meteor Swarm

THE EARTH IS REPRESENTED MOVING IN ITS ORBIT AMONG THE PARTICLES IN SPACE. AN OBSER-
VER IS LOCATED ON THE FORWARD—MOVING SIDE OF THE GLOBE AFTER MIDNIGHT, AND
THEREFORE ENCOUNTERS A GREATER NUMBER OF SPORADIC METEORS.

Astronomers have recently realized that the solid grains in our
solar system are of two very different kinds. One variety consists
of bits of stone and iron, which travel around the sun in nearly
circular, low-inclination orbits, in the same direction as the earth.
These are regarded as debris from collisions of asteroids, or perhaps
material from a planet between Mars and Jupiter that long ago
broke up (or failed to form). Any meteor observed brighter than
Venus is probably the result of one of these asteroidal fragments

49

passing at high speed through the earth’s atmosphere.

The second kind of particles moving in orbits like those of
comets. These include almost all the fainter meteors that we see.
Several of the prominent annual meteor shows are caused by objects
moving in the same orbits as known comets; thus it is definitely
established that the Perseid meteors seen about August 12th each
year are debris of Comet 1862 III. The fact that the Perseids appear
every year means that fragments have spread out along the entire
orbit, forming a ringlike stream that the earth cuts through each
August.

At the height of the Perseid shower, a naked-eye observer may
count a meteor per minute that is a member of the shower. All
Perseid paths, if extended backward across the sky, originate in the
same radiant (actually a small area rather than a point). This isa
perspective effect; the Perseids are actually moving along widely
separated parallel paths in spacé as they come into the earth’s
atmosphere.

The number of distinct showers is large but indefinite. Every
gradation exists between conspicuous rich showers and others so
sparse that they contribute less than one meteor an hour.

If we imagine the sporadic meteors to result from a random scat-
tering of particles, moving at random in a swarm through which the
earth is moving at an orbital speed of 62,000 miles per hour, then we
can deduce that during the night the number of meteors visible per
hour should increase steadily from dusk to dawn. At sunset we are
on the trailing edge of the earth, and can see only those meteors
moving fast enough to overtake our planet. But as night progresses,
the earth’s rotation carries us around until near sunrise, we are on
the leading edge of the planet. Then the hourly rate of meteors
becomes much greater because head on collisions occur, and slow
moving meteors are overtaken by the earth.

This picture is valid even though the motions of sporadic meteors
are not quite random. Those going around the sun in the same
direction as the earth tend to have shorter periods and low inclina-
tions; those traveling the other way have longer periods and high or
low inclinations.

For many years astronomers debated whether these were visitors
to our solar system from interstellar space. The practical criterion
for recognizing such an intruder is high velocity. An object at the
earth’s distance from the sun is traveling in a hyperbolic (open) orbit
only if its velocity exceeds 42 kilometers a second. Since we observe
from the earth, which moves at 30 kilometers a second, a meteor
found to move significantly faster than 72 kilometers a second must
be an interloper in the solar system.

SS

ECHO BALLOON SATELLITE

PHOTO BY TERRY :SCHMIE

TSE courtesy sky PUBL cox

Photo of meteor trail

Accurate velocities for thousands of individual meteors have
been obtained from modern photographic and radar observations, but
so far not a single certainly hyperbolic case has been established.
Interstellar meteors are extremely rare and are not within present

NATURAL PHENOMENA

ranges of detection. Less than 30 years ago it was widely believed
on the basis of visual observations that most, if not all, sporadic
meteors were of interstellar origin.

The development of photographic equipment has enabled astrono-
mers to accurately compute the paths, entering velocities through
the atmosphere, and the radiant points of meteors. In addition, the
deceleration of meteors by air resistance can be evaluated accurately
enough to indicate the density of the upper atmosphere.

Another breakthrough was scored soon after World War II,
when radar observations began in England and Canada. Whena
meteoric object traverses the earth’s atmosphere, a cylinderical
column of ionized gas is produced which is a good reflector for radio
waves. The echo is strongest from the point where the column is
perpendicular to the line of sight. With a three-station system, it is
possible to obtain excellent determinations of velocities and radiants
of individual meteors.

Radar techniques can record meteors several magnitudes too
faint to be photographed. Furthermore the radar observations can
be continued around the clock, irrespective of daylight or clouds.

NATURE'S LIGHTHOUSES

On the island of Tofua, in the Tonga or Friendly Islands of the
South Central Pacific Ocean, an area noted for its voleanic activity,
is an extremely active voleano which is used as an aid to navigation.
By day it emits smoke for 5 minutes out of every 10 and by night
it displays flaring flames. Although there are other volcanic islands
in that area that spew forth fire and smoke, none have the regularity
of Tofua. Captain Bligh observed this phenomenon while adrift in
the Bounty’s longboat, and he recorded it in his logbook on April 28,
1789.

Another of nature’s lighthouses in the Pacific has been used as
an aid to navigation for years. This voleano’s name is Izaleo and its
location El Salvador. Blazing regularly every eight minutes, it was
once known as the “Lighthouse of the Pacific”.

NATURE’S TOWBOAT

In the Dardanelles, below the surface current, a more dense sub-
surface counter-current enables fishermen to give their boats a tow
against the surface current by lowering their nets into the deeper
sub-surface current.

In the Black Sea the precipitation and runoff exceed the evapo-
ration, thus giving rise to a low density, low salinity, surface layer.
As a result, the surface waters of the Black Sea flow out through
the Bosporus and the Dardanelles, whereas the Mediterranean waters
flow into the Black Sea along the bottom, thus explaining the above
phenomenon.

A REEF THAT EXPLODED

In Erin Bay, about 114 miles off the southwest coast of Trinidad,
a reef, known as Despatch Reef, has an interesting and explosive
origin. On November 11, 1911, a submarine disturbance caused an
island about 8 acres in extent to be raised 12 feet above sea level
where there had previously been 6 to 10 feet of water. Fishermen
who observed the phenomenon noticed that several days before the
eruption the sea in the vicinity was churning violently and the air
smelled of sulphur.

At 6 P.M. on the 11th a rumbling noise as of distant thunder was
heard coming from a mound that had risen above the surface of the
sea and which was emitting dense black clouds of smoke billowing sky-
ward. The clouds were followed by a great blaze of flame rising
300 or more feet in the air. The color of the flame was reported
blue to straw-colored and the duration was from 7 to 10 minutes.
The flame was visible in Port-of-Spain more than 50 miles away
where residents assumed there had been an explosion in developing
oil fields of the area. The newly arisen island existed for several
months, but the wind and eroding action of the the sea soon worked
the apparently soft structure back into the sea. Today, on Oceano-
graphie Office Chart No. 1963, there appears only the notation of a
submerged reef in the vicinity of Despatch Reef.

Subsequent investigation of the phenomenon by Mr. Ralph Arnold,
an American geologist and petroleum engineer, suggests the follow-
ing sequence of events and theory of origin.

No recent voleanie rocks or other evidence of true volcanic
activity are known on Trinidad. The porous sand beds and lenses

containing petroleum gas, in many occurrences under enormous
pressure, are associated with oil-bearing strata, especially along the
anticlines or lines of disturbance. Mud volcanoes and pitch cones
are found inland of Erin Bay and yield gas and muddy and oily
water discharging continuously, intermittently, and occasionally,
briefly and violently.

The appearance of the island was first heralded by an escape of
gas from the apex of the anticline or line of disturbance coincident
with the reef in Erin Bay. This was followed by the upwelling of
the reef accompanied by a fracturing of the rocks and rapid eject-
ment of mud with minor amounts of fragmental material through
a more or less well defined vent or crater. Two cones 20 to 30 feet
high rose above the surface of the island and served as vents at the
time of the explosion. During the height of the eruption when large
quantities of hard rock fragments were being ejected, sparks were
probably formed by the striking together of some of the rocks, and
the petroleum gas thus ignited.

Following the destruction of the main cone several mud flows
continued to be pushed upward from below the surface. Gas con-
tinued to escape from numerous small vents on the island but
lessened as several days passed. This resembled large gas voleanoes
in behavior which erupt periodically as the subterranean gas pres-
sures build up, eject, and subside.

The presence of oil sand in the ejected material on the island
and the presence of petroleum gas odor clearly demonstrated that
source of gas was from the oil- and gas-bearing strata which under-
lies that area of Trinidad. In summary, the explosive origin of
Despatch Reef was the result of a violent eruption of petroleum gas.
The phenomenon was clearly non-voleanic in origin. The unusual
features of this gas volcano were its large size as compared with
similar cones of this character, its submarine origin, and the fact
that the gas which caused the eruption ignited during its escape.

RED TIDE

In recent years this phenomenon has occurred off the coasts of
several countries including India, Australia, Peru, and the United
States. This scourge to sea life is caused by asmall organism known
as a dinoflagellate. Although classified among the algae, the power
of movement places the creature between the animal and vegetable
kingdoms.

Under suitable environment these organisms reproduce so
rapidly that as many as 60 million may be contained in a quart of
sea water, producing a deadly effect on other sea life. In vast
numbers they give the water a reddish color but observations indi-
cate other colors such as yellow, yellow-brown, or olive-green occur.

Scientists have advanced the theory that after heavy rains the
run-offs in certain coastal regions contains phosphates and vitamin
Bl2 which together with a lowering of the salinity and with
favorable temperature enable the dinoflagellates to multiply at in-
credible rates.

DEPT. OF INTERIOR PHOTO

Fish killed by red tide

It is suspected that these creatures secrete a poison as deadly as
botulinum, which is claimed to be the most poisonous substance
known. This secretion kills fish, turtles, and other marine life;
causes inflamation of lungs and throats to humans swimming in such

NATURAL PHENOMENA

waters; and causes other unpleasant conditions at resort areas.

Research on this problem has added to knowledge of substances
which attack the nervous system. New weapons against human
disease may well be developed by medical science as a result of
research in this phenomenon.

THE SARGASSO SEA

The central part of the Atlantic Ocean has remained the subject
of myth and legend for a longer period than any other part of the
ocean. The term “Sargasso Sea” is derived from the name given by
the early Portuguese navigators. “Sargacao” so-called from the fact
that the berries found on the weed resemble grapes (sarga). It was
traversed by Columbus as he sailed westward and the masses of
weed, supposedly hampering the progress of the ships, nearly caused
a mutiny among his crew.

Whether the Sargasso Sea was known prior to the discovery of
America is still open to question. There are grounds for believing
that the Phoenicians were acquainted with its presence. Before the
beginning of the Christian era there are references to the sea west
of the Pillars of Hercules (Gibraltar), and certain parts of the sea
are represented as being unnavigable because of the seaweed. Also,
there is a record of this fact that a Portuguese sailor told Columbus
that one of the obstacles to be overcome in the westward voyage
to India was weeds. To Columbus, however, must be credited its
discovery and the first authentic record of the occurrence of gulf-
weed in this area. On his first voyage westward he encountered
Sargasso Weed for a number of days; and likewise on his return
voyage. In his log, it is noted that Columbus carefully recorded the
occurrence of this brown, floating weed.

Gulf Weed

Viewed from a small vessel, such as that used by Columbus and
other mariners of his time, the patches of Sargassum undoubtedly
looked vastly more formidable than they really were. This region
is one of light winds; hence the sailing vessel made slow progress.
It is therefore little wonder that stories developed of widespread
distribution of the thickly-matted weed impeded the progress of the
vessels. These stories, it is interesting to note, originated not with
Columbus, but with his followers. Columbus himself records the
occurrence in an accurate manner.

The increased knowledge of the ocean banished many of these
myths concerning ships enmeshed in seaweed, being forced into the
center of the mass, and gradually disappearing. With this increase
in knowledge, many theories have been advanced to account for the
existence of the Sargasso Sea. A Major Rennel observed “that the
waters of the Atlantic have a greater tendency toward the middle of
the ocean than otherwise and this seems to indicate a reduced level
forming a kind of hollow space or depressed surface”. Another
theory, according to Findlay, was that it ‘Is the vortex of an im-
mense eddy and which is caused by the influence of the trade winds
and the Gulf Stream”, while others maintain that it is a raised sur-
face kept in position by the currents surrounding it.

A considerable portion of knowledge concerning the Sargasso
Sea is to be found in the records of the Challenger Expedition of 1873.
Many studies have been made since that date of the physical,
chemical, and biological nature of this oceanic area. But that ex-
pedition undoubtedly gave the first systematic study of the region.

Following the work of the expedition, O. Krummel (1891),
O. Wings (1923), and A. E. Parr (1939) wrote interesting and
informative papers concerning the Sargasso Sea. The basis for

51

Krummel’s investigations was provided by the records of floating
weeds observed from German ships crossing the North Atlantic and
entered in their log books as required by “Deutsche Seewarte” over
a period of many years. From these data regarding floating weeds,
he plotted the frequency of observations and the boundaries of the
Sargasso Sea and subdivided it into more or less concentric regions
showing various degrees of frequency of the floating weed. Wing's
material, on the other hand, consisted of actual samples collected by
various Danish research and merchant ships. Parr also collected
samples during hydrographic cruises to Central American waters.
His very extensive work covering his observations of the Sargasso
Weed is contained in the Bulletin of the Bingham Oceanographic
Collection, Volume 6, Article 7, issued December 1939, in New Haven,
Conn.

The Sargasso Sea is oval in shape and extends from about lat.
25°N. to 30°N., between long. 40° W. to 73° W. Isolated patches and
streamers of weed are frequently encountered outside these limits,
and the entire area shifts a few degrees to the north and south
during yearly cycles. As can be seen from the charts, the Sargasso
Sea is the center of the oceanic circulation and is an area of weak
and variable currents. It is bounded on the south by the North
Equatorial Current, flowing westward; on the west and north by the
Florida Current and the Gulf Stream, flowing northward and east-
ward; and on the east by the North African Current.

The temperature of the sea water is high while the decrease in
temperature is small compared with other parts of the ocean. Its
position in the lower latitudes, coupled with the freedom from
strong currents, permits the radiation from the sun to maintain a
relatively high water temperature in the surface layers.

The waters of the Sargasso Sea are characterized by relatively
high salinity, 36-37 parts per thousand, as compared to 35 parts per
thousand in the South Atlantic. The area is situated at a con-
siderable distance from any coast, thus there is no dilution by the
less saline discharge from continental rivers. As this is a region of
high temperature, conditions are favorable for evaporation and in-
creased salinity. This latter factor is further augmented by the
relatively high percentage of sunny days.

The waters of the Sargasso Sea are very transparent. Again
this is a combination of factors such as lack of continental sediments
reaching the region, and the relatively small quantity of plankton,
the microscopic organisms, plants and animals, which abound in
other parts of the sea. The color is a very deep blue contrasted to
the green or greenish blue, characteristic of the open ocean.

Sargassum Weed, or “Gulf Weed” as it is commonly known to
seamen, is not native to the Sargasso Sea, although for many years
it was thought to be so; it being assumed that it grew on the bottom
and then, becoming detached, floated to the surface. It is now well
established, however, that Sargassum, a brown algae, grows along the
coast and is loose, reaching the Sargasso Sea by way of the Florida
Current and the Gulf Stream. These plants are kept afloat by air
bladders and grow vegetatively, propagating by fragmentation, but
apparently do not form fruiting bodies. These floating masses
form a characteristic environment with numerous associations in-
cluding other plants (algae) and animal forms.

The weed is generally found floating in little islands or bunches,
not matted but with branches loosely intertwined, varying in size
from 1 and 2 feet to 2 and 3 yards in diameter. When a wind of low
force is blowing, the weed patches are usually formed into long
lanes or streamers. The spacing of the lanes of wind-driven
Sargassum is an indication of the depth of the mixed layer and
isothermal water. The general color of the weed is olive, the younger
branches being more golden olive with decaying parts dark brown.

One estimate of the quantity of Sargassum has been made.
Nets were towed for a known length of time and distance and the
resultant catch weighed. On the basis of these observations the
aggregate amount of this weed in the Sargasso Sea is estimated to
be about 20,000,000 tons.

Sargassum affords protection to swarms of minute crabs, fish,
and other animals, not usually found in the open sea. These animals
are an excellent example of “protective coloration”. Their color
allows them to blend in with the gulfweed in such a manner that
only the closest scrutiny reveals their presence. The animals are
very abundant, and represent a large number of species.

NATURAL PHENOMENA

UPWARD-FLOWING WATERFALL

At Rathlin Island, off the north coast of Ireland, a small stream
normally falls from bare cliffs into the sea. The source of the
stream is a small lake on the island. With northerly winds of over
45 knots in force, this stream has been observed to be blown back
from the cliffs toward its source. From 3 miles offshore under these
wind conditions the water of the stream appears as cloudy mist bil-
lowing high in the air before drifting downward and settling in a
turbulent mist.

WATERSPOUTS

Mariners have faithfully observed and reported waterspouts over
the years, and oceanographers and meteorologists have a continuing
interest and need for information concerning them.

Waterspouts are the result of meteorological conditions and do
not affect them. Thunder and lightning, which often occur with
this phenomenon, evidence the state of the atmosphere that is likely
to generate electrical storms and waterspouts.

This phenomenon occurs more frequently in the tropic zones but
also occurs in the temperate zones and have been observed off the
coast of England.

Tornadoes and typhoons have their special seasons, and follow
fairly stable patterns of activity. Waterspouts, however, are quite
unpredictable. They are irregular in their occurrence, are generated
in gales or calms, and form over warm and temperate waters. They
move with, against, or across the winds, rotate both cyclonicly and
anticyclonicly, and move with varying speeds from slow to rapid,
and range from moderate to strong in force.

The size of waterspouts varies from high and narrow to low and
wide. They have been observed from 10 to 5,000 feet in height and
from 10 to 500 feet in width. Duration averages about 30 minutes
but some lasting up to an hour have been observed.

A waterspout may be simply defined as a column of water over
the sea sustained upright by a whirling circular wind movement.
Shaped often like an inverted cone they appear to descend from
heavy cumulonimbus clouds until they meet a cone of spray raised
from the sea, forming a column or spout of water between the sea
and cloud. The funnel point seems to descend slowly and at the
point of contact with the sea appears agitated with a cloud of spray
forming.

The occurrence of any waterspout depends to a large extent on
local unstable atmospheric conditions. In many cases the cause is
the importation of air of much lower temperature than the sea sur-
face over which the air passes. It is believed that the interior and

exterior parts of water spouts have opposite circulation, and that
the descending central currents of rain precipitate
virtually empty core of the spout.

Sometimes waterspouts dissipate quietly, but there is generally
some agitation. The lower part breaks releasing a torrent of fresh
and salt water accompanied by sleet, snow, or hail, the weight of
which can cause considerable damage.

around the

Waterspout

UNDERWATER DISTURBANCES

O. L. Martin Jr.
Maritime Safety Division
U.S. Naval Oceanographic Office

This article is being published to create a measure of seaquake con-
sciousness in the minds of watch standers so that they will be in a posi-
tion to recognize and therefore be more able to cope with the forces acting
upon a ship during an underwater disturbance. The article rs not
intended to alarm the mariner about a natural phenomena which, al-
though of considerable interest, may never be experienced to a degree which
could cause distress.

INTRODUCTION

Slowly pacing the wing of the bridge, the mate watched the sun
rise above the horizon as the ship steamed eastward in a slight south-
westerly sea at a speed of 17 knots. Morning stars placed the ship
approximately 20 miles off the southwest coast of Central America
in 2,000 fathoms of water. Suddenly, there was a thunderous boom,
the ship commenced to shake violently and seem to rise up in the
water. Although the fathometer registered no bottom, the ensuing
vibrations became so severe that the engines were stopped; the mate
was certain the ship had grounded. An inspection of the hull, bilges,
and machinery revealed no apparent damage. However, the master
believed that the ship had at least struck a submerged object with
such force that there must be underwater damage to the hull. Subse-
quently, the ship was drydocked, at considerable expense, only to
find no evidence of underwater damage.

Later, an investigation of seismographic data provided by the
U.S. Coast and Geodetic Survey disclosed that a few seconds before
the vibrations commenced aboard the ship a strong earthquake oc-
curred under the ocean floor about 35 miles southeast of the ship.

EARTHQUAKE HISTORY

Psychologically, an earthquake affects man in a rather strange and
awesome manner. When the earth begins to lurch beneath his feet
and he realizes that “terra firma” is a rather ambiguous term, his
first impulse is usually to run. Often, this sudden undulation of the
earth’s surface subjects man to nausea and headache. Even the
equilibrium mechanisms in his ears and eyes can be affected in such
a manner that small vibrations in solid structures are magnified to
the extent that if real the structures would be torn asunder. Broken
columns and sheared arches of ancient ruins are majestic witnesses
to catastrophic earthquakes of the past. Throughout recorded his-
tory, man has wondered about the cause and effect of the earth-
quakes that have continually plagued him. Two thousand years ago,
the Chinese devised primitive instruments for detecting distant earth-
quakes. Other civilizations, particularly the Japanese, meticulously
recorded the observed effects in the shaken area of each earthquake.
These studies, although useful, revealed little of the geography,
geology, and mechanics of earthquakes. Man did not begin to compre-
hend the nature of earthquakes until an English geologist and mining
engineer named John Milne founded modern seismology.

Milne, already an engineer of considerable renown, accepted in
1875 a position as professor of geology and mining at the Imperial
College of Engineering in Tokyo. Immediately upon arrival in
Japan he was greeted by an earthquake and at once became involved
in earthquake research.

Literally, an earthquake is a shaking of the earth in which the
ground surface moves back and forth, side to side, and up and down.
If man could detach himself from the earth and remain suspended
above the affected area, it would be simple to determine the relative
magnitude and direction of ground motion during an earthquake.
This is impossible. However, Newton’s “First Law of Motion”
states that a body at rest will remain at rest until acted upon by an
external force. Thus, as with a pendulum, if the connection between
a body and the earth is as loose as possible, the movement of the
earth will exert a minimum external force on the body. Then, when
an earthquake does occur, the body will tend to remain stationary
while the earth moves beneath it. Milne incorporated this principle
in the instrument he developed to scientifically detect and record
local ground movements caused by the Japanese earthquakes. Basi-
cally, the instrument, firmly secured to the ground, consisted of the
loosely connected body (pendulum) to which a marking pen was at-
tached in such a manner that it lightly scribed a line on a contin-

53

uously moving roll of paper powered by a clock mechanism. Thus,
when earthquake vibrations moved the paper in relation to the mark-
ing pen, Milne was able not only to obtain a written record of these
vibrations in the form of jagged lines, but he was also able to deter-
mine the time of the movements.

Normally, seismographic stations are equipped with 3 instru-
ments—2 orientated at right angles, to record movements from east-
west and north-south directions, and 1 to record the vertical move-
ments. Thus, a record can be obtained of all 3 basic earthquake
movements. Modern engineering and electronics have greatly im-
proved todays’ seismographs permitting even more detailed study of
the phenomena. Each variation in the jagged lines as recorded on
seismograms have meaning to the seismologist who can, by comparing
the seismograms of a single distant earthquake from several stations,
determine the location of its epicenter and the depth beneath the
earth’s surface (hypocenter) at which the original fracture occurred

Milne did not actually invent the seismograph, the principle and
idea had been advanced about 1830, but he did develop and field
test a very practical instrument by setting up a network of seismo-
graphic stations throughout Japan. Data obtained from the network
enabled him to determine the geographic positions of the epicenters
for 8,331 earthquakes in the next 8 years. When the earthquake
epicenters were plotted, he discovered they fell in a relatively narrow
belt along the East Coast of Japan, and that the interior of the Islands
were relatively free of earthquakes. Upon returning to England, in
1885, Milne presented his findings to the Seismological Society, where
they created such a great interest that a new science was launched—
the study of earthquakes by an interpretation of the shock (seismic)
waves they generate in the earth.

Milne proposed, and by the turn of the century had in operation,
a world wide system of 34 seismographic stations. The information
obtained from these stations enabled him to chart areas of earthquake
activity throughout the world; basically the seismic zones he charted
are unchanged today. Milne furnished the tools and established the
methodology of the new science, but discoveries and advancements
came fast as man began to seismically probe the interior of the earth.
By 1907 the velocities of the seismic waves in the earth’s mantle
were accurately known and the existence of a core had been discov-
ered. Soon Andrya Mohoroviae discovered that a discontinuity
formed the lower boundary of the crust, and by 1913 Beno Gatenberg
had determined the radius and nature of the core. Only in this cen-
tury, with the aid of seismology, has man been able to investigate
earth beneath its surface to study scientifically the nature of its in-
terior.

MANTLE

OUR QUAKING EARTH

UNDERWATER DISTURBANCES

Today, scientists generally agree on the concept of the structure
and nature of the earth as an elastic sphere slightly flattened at the
poles with an equatorial radius of 3,444 miles. The mean rigidity of
the earth is of about the same order as that of steel, and it consists
of 3 principal parts—the crust, mantle, and core. The crust is an
encircling outer shell of heterogenous rock varying in thickness from
about 6 miles under the oceans to 15 or 20 miles beneath the conti-
nents, but increasing to as much as 30 miles under some mountain
chains. The irregularity of the base of the crust is, possibly, the
principal departure from the spherical symmetry in the physical pro-
perties of the earth. Below the crust is the mantle, believed to be a
thick massive shell of dense fine-grained rock that has solidified from
a hot molten condition. The thickness of the mantle is about 0.45
of the earth’s radius and its volume accounts for approximately 85
percent of the earth’s mass; for practical purposes, the mantle may
be considered concentrically homogeneous. Inside of the mantle is
the core, a hot dense molten sphere with a radius about 0.55 that of
the earth’s. Apparently, the core has no rigidity and its exact content
is unknown, although it reacts to many investigations in the same
manner as would a highly compressed ball of molten nickel-iron.

Over long periods of geological time, stresses build up within the
rock structure of the crust and upper mantle. If the pressure in-
creases slow enough, the confined rocks will bend and flow like plastic,
and the rock structure will adjust itself to the changing stress. How-
ever, when pressure is applied too fast or the structure is rigid enough
to resist slow deformation, the stress will accumulate until the elastic
limit of the rock mass is reached. When this happens, somewhere
the rock will break. The accumulated pressure will be released in-
stantly and the energy transformed into shdck (seismic) waves. This
is the mechanics of an earthquake.

How the pressure originates is unknown. Many theories have
been advanced but none satisfies the scientist completely. The pres-
sure seems to be connected, in some manner, to the expansion and
contraction of the rock mass due to differential heating. The weight
of the material above induces another pressure, but this can be
calculated. In the crust this pressure increases one atmosphere
(14 psi) for approximately each 13 feet of depth. However, the rate
of increase is more rapid at greater depths and the pressure at the
center of the earth has been estimated to be as high as 57 million
pounds per square inch. Under great pressure within the earth’s
mantle, the rocks seemingly become stronger and far more plastic,
tending to distort rather than break. Although most of the earth-
quakes occur within 25 miles of the earth’s surface, some have oc-
curred as deep as 390 miles, which seems to be the floor of earthquake
action. The pressure as this depth is estimated to be about 3!.
million pounds per square inch, and possibly beyond this point the
rock mantle becomes so plyable it will not fracture.

TECTONIC EARTHQUAKES

The majority of earthquakes involve a relative movement of
rock masses along either side of a fracture or fault plane in the earth’s
crust. When this relative movement is in a vertical direction, there
will be either an elevation or depression of one of the faces. Should
an entire crustal block be defined by faults, the entire block may rise
or fall as a unit. More often however, only one side of the crustal
block will move, resulting in a tilting or folding of the crust. Fre-
quently, the relative movement along the fault is in a horizontal
direction resulting in a twisting effect or horizontal displacement.
Earthquakes involving this sudden crustal movement are called tec-
tonic because they are structural in nature. Normally, in a tectonic
earthquake the area of greatest shock intensity lies along or parallel
to a fault. Often tectonic earthquakes occur in groups with the epi-
center of each subsequent quake migrating along parallel to the fault.
The perceptible effect tends to travel great distances down the fault,
but decreases rapidly as the perpendicular distance from the fault
increases. Although tectonic earthquakes may occur in regions of
voleanic activity there is no correlation between the two. The con-
trolling factor determining the magnitude of a tectonic earthquake is
the relation between the size of the rock mass and the relative dis-
tance of movement. Ina tremor the displacement may be slight, but
visible evidence on the surface have indicated abrupt displacements
on the order of 50 feet after some major earthquakes.

During most earthquakes, the maximum intensity of observed
vibrations occur in an elliptical area enclosing the epicenter, which
normally lies along the major axis of the ellipse near one end. Usually,

54

the orientation of this axis is parallel to major structural trends or
faults in the area. The intensity of an earthquake is represented by a
roman numeral rating (I to XII) on a descriptive scale that indicates
the physically perceptible earthquake motion and is based solely on
the effects observed on people and inanimate objects such as buildings
and their contents. The area representing the highest intensity is
called the meizoseimal area and outside this area, usually elliptical, the
intensity falls off rapidly in a uniform manner. Each earthquake
will have several intensity ratings from the highest in the meizoseimal
area to the lowest rating where the motion is barely perceptible on
the outer fringes. Scientifically, an earthquake is described by its
magnitude which is derived instrumentally, from the seisomogram,
and is a logarithmic measure of the total earthquake energy released
at the focal point. There is only one magnitude for an earthquake.

PROFILE

ARC TECTONIC FEATURES

Although the mechanics are similar, there are two distinct clas-
ses of tectonic earthquakes—the arc and block types. Are tectonics
constitute the majority group, but most of the knowledge of this type
is derived from the analysis of instrumental findings recorded at great
epicentral distances. However, on-the-spot observations of earth-
quake mechanics including studies of the visible results in the meiz-
oseimal area are plentiful from regions of block tectonics. Therefore
present earthquake theories are based primarily on information ob-
tained from this type. Block tectonics are dominant in California
and New Zealand and probably in most regions where only shallow
earthquakes occur, as along the Mid-Atlantic Ridge. In sections of
Japan, Peru, the Philippines, and North Island (New Zealand) both
types occur. The remainder of the seismic activity throughout the
world is predominantly arcuate. Arc tectonic are three-dimensional
in scope and require a profile view as well as a plan for their study.
Normally, they are associated with certain geological features usually
found in the following order, beginning on the outside of an are and
traveling toward the center:

A. A deep oceanic trench or trough.

B. The principal tectonic line, with a narrow belt of shal-
low earthquake epicenters along a non-voleanic up-folding or
rise of the earth’s crust which may form a submarine ridge or
possibly emerge as a chain of small islands.

C. A belt of earthquake originating at a depth of approxi-
mately 40 miles.

D. The principal structural are, often consisting of large
islands or even a coastal mountain range containing active vol-
canoes, and a belt of earthquakes originating at depths of 60
miles or more.

E. An inner structural are of older mountains, extinct vol-
canoes, and earthquakes originating at depths between 120 and
180 miles.

UNDERWATER DISTURBANCES

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55

UNDERWATER DISTURBANCES

F. A belt of deep focus earthquakes originating at depths
between 200 and 400 miles.

When the associated hypocenters of a typically active are system
are plotted in profile on a cross sectional chart showing the relief, they
seem to dip under the arc, frequently under a continent, at an angle
of approximately 45 degrees. The epicenters of the large shallow
earthquakes (B) are usually on the landward side of the foredeep,
but the epicenters of the deep shocks (F) may fall hundreds of miles
away. In South America the epicenters of many of the deep shocks
are well to the east of the Andes.

The chief characteristics of block tectonics are frequent shallow
quakes from which are features are absent. The activity consist of
relative displacements of blocks, separated by large faults which are
often nearly straight and dip almost vertically into the earth.

DEEP FOCUS QUAKES

Most earthquakes occur in the earth’s crust, but some originate
in the rock mantle at depths as great as 390 miles, which seems to
be the floor of earthquake activity. The mechanics of an earthquake
are the same regardless of the focal depth, however, the surface af-
fects in the meizoseismal areas differ greatly. A deep focusquake does
not create a well-defined meizoseismal area, instead there may be
several seemingly unrelated geographical areas of equal intensity at
varying distances and bearings from the epicenters. Yet in areas
closer to the epicenter the earthquake may be imperceptible. The
instrumental magnitude of two earthquakes, one normal and one
deep focus, may be the same, but the intensity in the meizoseismal
area will decrease as the depth of the hypocenter increases.

VOLCANIC EARTHQUAKES

There is still another class of earthquakes whose mechanics are
somewhat different. They are caused by the pressure of the confined
gases or forces brought into play during the swelling and contraction
of molten volcanic lava which may result in an explosion, tension
fracture, or fault within the structure of the voleano itself. Therefore,
volcanic earthquakes are dependent on voleanism and may be defined
as the transient elastic vibrations caused by forces originating in the
magma chamber and conduits of a voleano. The focal depth of this
type earthquake is very shallow. Frequently, the hvpocenter is within
the voleanic cone structure itself. Voleanic earthquakes may be of
considerable local intensity, often resulting in extensive damage to the
flank of a voleano, but their total energy is slight and they are usually
imperceptible a few miles away. A tectonic earthquake of equal epi-
central intensity would be perceptible at great distances.

EARTHQUAKE GEOGRAPHY

The world chart showing the geographical distribution of seismic
activity reveals that the earthquake epicenters fall in narrow belts
and zones easily correlated with certain geological features as high
mountain chains, oceanie trenches, ridges, and rises. Normally,
where there is high-relief there is increased seismic activity, indicating
that high seismic activity is related to crustal disturbances of the
recent geological past. The highest mountains and deepest trenches
are probably products of fairly recent geological time. Crustal
irregularities as great as these would be equalized by geological pro-
cesses within a single epoch if stress were not continually at work to
maintain them. Earthquakes are indications of these stresses.

Possibly, the present world chart of the seismic zones, even
though unchanged since Milne’s time, merely represents a fleeting
geological snapshot of temporary or unusual seismic conditions.
Man’s instrumental records span only a few short years of the hun-
dreds of millions of years of geological time, and the evidence found
in rocks indicate the tectonic geography of the earth has changed
considerably during the past eons.

At present over 1 million perceptible earthquakes occur each
year, of which at least 700 are strong enough to cause damage in
their meizoseimal area. Fortunately, as the magnitude of earthquakes
increase the relative frequency with which they occur decreases.
Earthquakes as well as volcanoes are usually located close to large
bodies of water. Therefore, it is not surprising that three-quarters
of the world’s earthquakes occur under the ocean floors. The North-
ern Hemisphere is more susceptible to seismic activity than the

Southern Hemisphere. The area below 30° South Latitude represents
one-fourth of the earth’s surface, yet less than 10 percent of our

56

earthquakes occur in this area. Earthquakes are unknown on the
continent of Antarctica.

The Pacific Ocean is ringed by a system of active volcanic and
seismic belts and has a branch that extends into the East Indies.
Another branch extends eastward across Central America into the
West Indies. This system accounts for four-fifths of the world’s
earthquakes. Another belt extends from the Mediterranean region
of Southern Europe across Southern Asia and down the Himalayan
Mountains into Southeast Asia. Active belts are also found in the
oceans along the Tonga Trench, down the Mid-Atlantic Ridge, and
southward from the Central Indian Ocean with a branch swinging
westward across the South Atlantic towards the Sandwich Trench
and another branch swinging eastward south of Australia.

PROPAGATION OF SEISMIC WAVES

When a rock mass fractures, the earth reacts to the resulting
seismic waves as an elastic solid, propagating them to all parts of
the earth, both through the interior and over the surface. Four
elementary types of seismic waves are generated, each having its
own characteristic type of motion and velocity that is’ easily disting-
uishable on seismograms.

The primary wave or P wave, sometimes called the longitudinal
wave, is the faster of the two body waves that travel through the
interior of the earth. Its velocity varies from about 4 to 7 knots per
second, depending on the nature and density of the material trav-
Because of the variations in density, the path of the P wave
through the earth is not a straight line cord but a concave curve bent
toward the center of the earth, and it requires approximately 20
minutes for it to travel to the opposite side of the earth. The P wave
has a period of about 1 second and travels through the earth in a
manner similar to that of a sound wave. Thus as it radiates out from
the focal point, the particles of earth immediately ahead of the wave
front are compressed forward away from the hypocenter along the
path of travel. Then as the wave front passes there is a slight dila-
tion of the ground and the earth's particles move back along the path
of travel toward the hypocenter.

The secondary body wave or S wave, commonly referred to as
a sheer or distortional wave, travels through the earth at velocities
about 0.6 that of the P wave and follows the same general path.
However, there must be rigidity in the material through which the S
wave travels, and there is no evidence that it penetrates the core.
The propagation of the S wave is similar to that of a light wave or
to the transverse vibrations of a taut string. Therefore the earth’s
particles are displaced in a direction that is perpendicular to the
direction of travel from the focal point. Whenever a body wave
traveling through the earth strikes a region of abrupt density changes,
as at the earth’s surface, the bottom of the crust, or even the surface
of the core, part of the wave energy tends to be reflected in new and
complex wave forms, or even transposed into waves of the opposite
type. Thus a sheer wave may be changed into a longitudinal wave
or vice versa.

The other 2 basic types of seismic waves are the Love and the
Rayleigh surface waves which are created when the P wave reaches
the earth’s surface; they account for most of the visible ground
movement in the immediate epicentral area. The speedier Love
wave with a velocity of approximately 214 knots per second is a sheer
wave propagated in a horizontal plane in a manner similar to the way
in which a wave travels down a garden hose when it is shaken from side
to side. The velocity of the Rayleigh wave is only slightly lower than
that of the Love wave and it creates a vertical wave motion on the
earth’s surface like the wave that travels down a carpet when one
end is shaken up and down.

ENGINEERING SEISMOLOGY

Man’s increasing knowledge of earthquakes and the specialized
field of engineering seismology enables architects and engineers to
design and build structures with inherently greater earthquake resis-
tent qualities. Structures built to withstand great downward or
gravitational forces with little thought of a vertical thrusting from
beneath or the sheering effect of horizontal twisting may crumble
during an earthquake, while properly designed structures closer to
the epicenter escape relatively unscathed. Within a structure, the
tempo of earthquake shaking in relation to the natural period of
vibration of the structure is very important; if the frequency of the
induced vibration happens to be the same as the natural frequency
of the structure the resulting movement will be the sum of the two

ersed.

UNDERWATER DISTURBANCES

vibrations and create a greater amount of movement. This condition
is called resonance, and the probability of damage from shaking is
greater when this occurs than if the two components are completely
out of phase. Another closely related phenomenon is when two
adjacent structures having different natural periods of vibrations get
out of step and tend to batter each other down when shaken by an
earthquake.

SEAQUAKES

The mechanics of an earthquake are the same, regardless of
whether occurring under a land mass or the ocean floor. Earth-
quakes ashore are sometimes called land quakes and the seismic
vibrations frequently felt aboard ships are commonly referred to as
seaquakes. Although the majority of the world’s earthquakes occur
under the ocean floors, the mariner is in a position far superior to his
land bound brother. A ship built to withstand the rigors of the sea
and remain a cohesive unit regardless of the direction from which an
external force is applied becomes ‘‘earthquakewise”’ an engineering
marvel. The intensity of shipboard seismic effects varies greatly,
but an analysis of ship reports describing seaquakes in view of local
geological conditions and available instrumental data reveals several
interesting generalities that are in line with the facts associated with
land quakes.

The principal seismie effect aboard ship is the jackhammering
vibrations induced on the hull by the arrival of the P wave. Upon
entering the less dense water from the sedimentary covering on the
ocean floor this compressional-type wave is bent by refraction and
deflected almost vertically to the sea surface at 0.8 knot per second.
Frequently, the first P waves to arrive on the surface of the sea are
not strong enough to be felt aboard ship, and will pass into the
atmosphere above the sea to create a sound wave. When the fre-
quency of the sound wave is high enough to be audible a loud bomb-
bing noise will immediately preceed the actual vibrations. Sound is
not heard in all earthquakes, and it is possible under certain condi-
tions to have the sound without the vibrations.

The duration of these vibrations may vary from a fraction of a
second to several minutes. Ship reports indicate a usual duration
of between 15 and 60 seconds. When the P wave arrives at the sea
surface its period is short and amplitude very low. Normally, the
amplitude is so small there is no indication of a disturbance by the
appearance of the sea surface. Yet this wave front simultaneously
striking the complete under water portion of the hull produces enough
energy to cause severe vibrations. Rarely have these vibrations
damaged ships, but a report from a ship off Point San Telmo,
Mexico, stated that on 15 April 1947 earthquake vibrations caused a
well-secured deck cargo of heavy steel prefabricated construction
sections to walk 6 inches.

The intensity of shipboard vibrations are determined by internal
as well as external factors. Internal variables that affect this vibra-
tion include the type and construction of the ship, the nature and
amount of cargo on board as well as the manner in which it is stowed,
and under certain conditions the position in which the cargo-handling
gear or other heavy equipment is secured. Among the external fac-
tors the magnitude of the earthquake, determining the amount of
energy released, and the depth of the original fracture (hypocenter)
are very important. Frequently, the perpendicular distance to the
fault along which the original fracture occurred may be more impor-
tant than the epicentral distance. Again at sea, as in a land quake,
the earthquake energy tends to travel great distances down or paral-
lel to the fault with little loss of intensity, but the perceptibility tends
to fall off rather rapidly as the perpendicular distance from the fault
increases. Although weather has no bearing on the origin of an earth-
quake, the effects (vibrations) on a ship may be magnified by un-
favorable weather conditions.

Occasionally, there is a weaker but definitely distinguishable
second set of vibrations closely following the original jolt. This is
not a twin quake but the arrival of part of the energy from the slower
S wave. When this sheer wave strikes the density discontinuity at
the ocean floor part of the energy is reflected back into the earth and
part of the energy is transformed into a compressional-type wave and
deflected almost vertically into the less dense water. There is an
energy loss in this transformation, but the arrival of the S wave under
the hull is quite perceptible under proper conditions. If a vessel is
in the immediate epicentral area of a shallow quake, the arrival of the
second group will only tend to intensify the original vibrations and

57

may not be detected. When the epicentral distance is too great the
arrival of a weak second group may be imperceptible. However,
there is a definite area between the two extremes in which the arrival
of the S wave group is easily distinguishable.

MEXICAN EARTHQUAKE OF JUNE 1932

An excellent example of the varied manner in which individual
ships, located at random, about the epicenter of an earthquake are
affected is available from the review of the ship reports describing
their experience during the large shallow Mexican earthquake of 3
June 1932. Although slight motions were felt throughout the early
morning hours in the mountainous area behind Manzanillo, it was
not until 10h 36m 50s GMT (03h 6m 50s Local Time) that the prin-
cipal shock occurred. The epicenter, located about 30 miles inland
near 19.5°N., 104.3°W. fell in the chain of voleanic mountains that
traverse Mexico in an east - west trend and are, probably, a conti-
nental continuation of the long straight Clarion Fracture Zone that
originates in the Central Pacific and passes through the volcanic
Revilla Gigedo Islands before emerging on the Mexican Coast.

During the early morning hours of 3 June 1932, the SS SOLANA
was steaming through a smooth sea with light variable winds in
18°30’N., 104°08’W., at 1037 GMT she was violently shaken for
about 7 seconds. The ship was then about 60 miles 170° from the
epicenter in approximately 800 fathoms of water and did not detect
any change in the state of the sea. The perpendicular distance to
the fault zone was also about 60 miles.

A few miles to the southwestward in 18°20’N., 104°382’W., the
MV SEVENOR experienced at the same time less severe vibrations
but of a longer duration (1 minute). The SEVENOR was approxi-
mately 70 miles 191° from the epicenter and the perpendicular dis-
tance to the fault zone was between 65 and 70 miles. The ship
reported a calm sea and slight westerly swells and detected no no-
ticeable change in the surface of the sea.

Conditions aboard the MV NORTHERN SUN in 19°56’ N.,
106°14’ W. were entirely different. Although the vessel was 115
miles 285° from the epicenter the perpendicular distance to the prob-
able fault zone was probably not more than 10 miles. Vibrations,
commencing at 1039, continued for 3 minutes and became so violent
that the engines were stopped. Before the earthquake, the sea had
been smooth with a slight westerly swell, but by 1046 GMT the swell
pattern had changed and the sea was confused.

Farther to the northward in 20°28’ N., 106°20’ W., the SS ARJ-
ZONAN commenced to vibrate at 1039 GMT and continued to do
so for about 75 seconds. The ship was about 130 miles 297° from
the epicenter with a slight southwesterly sea and did not notice any
change in the state of the sea. The perpendicular distance to the
fault was probably somewhat over 40 miles.

Cabo San Lucas

MEXICO

The after shocks continued for many days. Ship reports indicate
that during the next 36 hours several strong underwater disturbances
were experienced in the area. The MV SILVERWILLOW in 18°45'N.,
104°34’W. began to vibrate dangerously in every part and at the

UNDERWATER DISTURBANCES

same time partook an uneven short pitching motion followed by
heavy rolling. The disturbances commenced at 0530 GMT on 4
June and the rolling continued for 15 minutes. Seven hours later at
1245 GMT in 19°31’'N., 105°45’W. the crew aboard the SS TALA-
MANCA heard a loud noise like distant gunfire, then experienced
severe vibrations, and at 18337 GMT 2 similar reports were heard
about 10 seconds apart but there were no apparent vibrations. How-
ever, 20 minutes later the sea surface was littered for 5 or 6 miles
with small white oval objects. Several hours later in 19°28’N.,
106°06’W., the SS HANOVER reported at 1205 ship’s time (prob-
ably 1905 GMT) 2 violent shocks that rocked the ship like a nearby
explosion. Fifteen minutes later 2 more shocks were experienced
with only slight vibrations.

The main quake created considerable damage throughout the
country side behind Manzanillo and inundated the immediate coastal
area with a minor tsunami. Tide gages in Hawaii recorded a 214-foot
wave and 12 hours after the earthquake the boxlike harbor of Pago
Pago, over 4,400 miles southwestward of the epicenter, experienced a
series of sea level fluctuations on the order of 8 feet for over an hour.

DOMINICAN EARTHQUAKE OF AUGUST 1946

Another interesting earthquake occurred on 4 August 1946 when
the northeast coast of the Dominican Republic was shaken by a de-
structive quake at 17h 51m 05s GMT. The epicenter was located
in deep water about 9 miles eastward of Cape Samona. Forty miles
westward of the epicenter in the bight of Escocesa Bay an 8-foot
tsunami surged ashore destroying the town of Matanzas. Four miles
northward of Cape Viejo Frances Light, or about 43 miles north-
westward of the epicenter, the sea around MS CAMCA became
confused at 1310 ship’s time and commenced to boil violently, the
ensuing vibrations aboard ship became so turbulent the engines were
stopped and all machinery secured. The disturbance continued for
10 minutes, during which time an enourmous cloud of dust was ob-
served rising from the shore behind Cape Viejo Frances. Approxi-
mately 30 minutes later the water was observed to be boiling again,
but this time to the northward of the ship. Probably, there is no
connection but it is interesting to note that approximately 214 hours
earlier, while steaming northward through the Yucatan Channel, the
SS SAMUEL F. DEWING encountered similar areas of turbulent
water in an otherwise calm sea at 0915 (local time) near 21°12’N.,
86°16’W. The disturbance appeared close ahead and when the ship
entered the area the bow took a 30 degree sheer to starboard despite
attempts to check her. Although the fathometer was in constant
operation no bottom trace was recorded, but in 1960 a ship did report
414 fathoms in this general area.

During a seaquake the water mass in the ocean is seldom affected
but areas of boiling water, seiches, and tsunamis have been started
by earthquakes. Areas of boiling water that are occasionally sighted
by ships during and after seaquakes could be of volcanic origin, but
may have mechanics similar to earthquake fountains and sand blows
that occur ashore during seismic disturbances. This phenomena can
produce at great epicentral distances fountains 6 to 8 feet high that
flow up to 3 hours after the earthquake. The alternate tension and
compression applied to the ground during the passage of seismic waves
may open fissures and suck all the ground water into the opening, then
the same force closes the fissures and forces the water out. Under
the ocean a related mechanism would create a boiling effect on the
surface without an appreciable rise in water temperature, and the
unlimited supply of sea water would allow for an earthquake fountain
of staggering proportions.

Another unusual phenomenon is the seiche, a standing wave
that has its crest at one end and its trough at the opposite end of an
enclosed or partially confined body of water, and may even occur as
lateral oscillations in rivers, canals, and ditches. It is only necessary
that the limits of the enclosure define a natural period of oscillation.
Earthquakes are a comparatively rare cause of seiches which are usu-
ally set up by prolonged winds, currents, or tides. Seiches in harbors
have been started by the arrival of tsunamis. True earthquake
seiches have been set up in graving docks and castle moats by the
arrival of seismic waves through the interior of the earth. Regardless
of the cause, it may become impossible to hold a ship alongside a
dock during such a disturbance.

TSUNAMI

Many coasts of the world, notably those bordering the Pacific

58

Ocean, have been swept by giant waves surging ashore as high as 60
feet above normal tide levels. Although often referred to as tidal
waves, they are not associated with the tide in any manner but are
somehow related to tectonic earthquakes and are actually seismic
sea waves, commonly called tsunamis. The mechanics of a tsunami
are not fully understood. These waves usually originate in the vicin-
ity of deep ocean trenches after strong earthquakes, and often travel
undetected across thousands of miles of open ocean before devastat-
ing an exposed coast, island, or harbor. Block tectonics ashore have
produced vertical displacements of many feet over hundreds of square
miles. Tectonics of this nature under the sea floor would produce
an instantaneous movement of a tremendous mass of sea water which
would immediately fan out from or pour into the epicentral area with
great momentum, depending on whether the crustal block was raised
or lowered. Occasionally, tsunamis are created by earthquakes whose
epicenters are on shore. Possibly, the vibrations of the seismic wave
passing through the sedimentary covering on the sides of trenches
and continental slopes are great enough to create great submarine
landslides which would again displace a tremendous amount of water
in a relatively short time. There are also recorded instances where
submarine voleanic explosions and glacier break-ups have created
this type of wave in localized areas. There is some thought of the

possibility of a tsunami being created by a mechanism related to the
seiche being formed in deep trenches or troughs.

Once a tsunami is spawned it travels across the open seas at
speeds approaching 400 knots and because of its low wave height
(2 to 3 feet), tremendous distance between crest (100 miles or more),
and unusually long period (12 to 40 minutes) is very inconspicuous.
When a tsunami enters shoal water it conforms to the same physical
laws that govern wind-driven waves, but because of its great forward
speed in deep water, the slowing of bottom drag is relatively much
greater than for a wind-driven wave. Therefore its forward speed
rolls the wavefront over itself to greater heights than is possible with
a wind-driven wave.

Usually, the first indication in a harbor or along an exposed
coast of a tsunami is a slight, often unnoticeable, rise in the water
level, only to be followed immediately by a noticeable withdrawal of
the water, which returns several minutes later to a height well above
normal tide level. The initial wave is seldom the highest, the crest
is usually reached between the third and eighth wave. Once the crest
is reached the wave begins to subside slowly, sometimes requiring a
day or more. Because of a tsunami’s long period and delayed crest,
there is frequently enough time to take evasive action if it is initiated
immediately upon noticing the first indications.

There are no known seismographic characteristics by which the
seismologist can determine if a particular earthquake will create a
tsunami; fortunately few do. However, once spawned these waves
can be so destructive that a Seismic Sea Wave Warning System was
organized and is now in operation in the Pacific Area. The system
consists of strategically located seismographic stations, tidal stations,
a communication system, and a Control Center. Each seismographic
station is equipped with specially designed instruments and they are
located throughout the Pacific in such a manner no really strong
earthquake will go undetected. The tide stations are equipped with
Seismic Sea Wave Detectors that produce an audible alarm on the

UNDERWATER DISTURBANCES

arrival of waves with periods between 10 and 40 minutes. A high
priority radio system permits rapid collection and dissemination of
tsunami information by the Control Center at the Honolulu Mag-
netic Observatory. SEISMO is the characteristic identifying sym-
bol for this type radio traffic.

UNCHARTED OBSTRUCTIONS

Since the advent of the fathometer the mushrooming supply of
new sounding data adds daily to man’s increasing knowledge of the
topography of the ocean floors. No longer is the bottom of the ocean
believed to be as monotonously void of irregularities as is its surface.
Man realizes the magnitude and grandeur of many bottom irregular-
ities are unmatched anywhere on earth. However, even today vast
reaches of the ocean floors remain inadequately surveyed, averaging
in some areas only one sounding to many square miles of ocean floor.
Consequently, within these areas, particularly where irregularities
exist, must lie countless uncharted shoals and banks. Today the
increasing drafts of ships and operational depths of submarines
greatly magnify the importance of these uncharted shoals as dangers
to navigation.

Modern charts carry many doubtful shoals and reefs that mar-
iners have encountered in the past. Many of these obstructions have
been confirmed but others defy confirmation. Frequently, there is
an astounding similarity between the reports of vessels encountering
uncharted obstructions and the reports of vessels undergoing a seismic
disturbance. A similarity also exists between ships reports describing
distant reefs and rocks awash and vessels reporting early stages of
submarine voleanics. A comparison of the chartlet showing the earth-
quake belts of the world and the chartlet showing concentrated areas
of unconfirmed obstructions reveals a remarkable analogy. For this
reason observers should always include the precise GMT of an obser-
vation when reporting a suspected obstruction.

SUMMARY

Psychologically, the mariner’s sensation of grounding is common
to most seaquake reports.

A seaquake will affect each ship differently. The type, construc-
tion, and amount of cargo are internal factors affecting the intensity
of the vibrations.

Seaquake vibrations may become severe enough to warrant
stopping the engine and securing machinery.

Frequently, there are two distinct series of closely related vi-
brations, representing the arrival under the ship of the P and S waves,
respectively.

Usually shipboard vibrations cease with the terminaton of the
seaquake, but, under unusual conditions, vessels have been known to
undergo unexplained heavy rolling or pitching motions for several
minutes after the original disturbance ceased.

Visibly, the state of the sea is unchanged during a seaquake.
However, areas of turbulent water and locally confused seas are
occasionally encountered during seismic disturbances, and this con-
dition may exist for some time afterward.

Marine life can be destroyed by a seaquake.

There is no correlation between weather and earthquakes, but
the condition of the sea at the time of a seaquake may have a bearing
on the shipboard intensity of the vibrations.

Sound may precede the perceptible affects of a seaquake.

Although the epicenter of an earthquake is ashore the effects
may be perceptible aboard ship.

Almost all seaquakes are the result of tectonic earthquakes.

The mechanies of tectonic earthquakes are the same whether on
land or under the sea. When the rock structure deep within the earth
is rigid enough to resist slow deformation by changing stress patterns,
the stress will accumulate until the elastic limit of the rock mass is
reached, then somewhere along a fault plane the structure will snap,
instantly readjusting itself to a condition of no stress.

Geologically, earthquakes are associated with high relief as
mountain chains and deep oceanic trenches.

Exactly what triggers an earthquake is unknown and they can-
not be predicted.

Tectonic earthquakes tend to occur in swarms, with the epicenter
of each subsequent quake migrating parallel to a fault or major struc-
tural trend.

Earthquake energy at sea or ashore tends to travel considerable
distances down or parallel to the fault with little loss of energy, but

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the intensity tends to fall off uniformly, rather rapidly as the perpen-
dicular distance to the fault increases.

A study of the chart showing, approximately, the fault zones in
the earth’s crust and earthquake epicenters for the world will give the
mariner an indication of the areas in which he may expect to encounter
seaquakes.

The tsunami chart depicting the coasts that have been inundated
by these waves will also furnish the mariner an indication of the gen-
eral areas in which tsunamis may be encountered.

Tsunamis tend to originate near deep ocean trenches and are
somehow connected to tectonic earthquakes that usually have their
epicenter on the landward side of deep oceanic trenches.

The most probable explanation of the creation of a tsunami calls
for the vertical displacement of a block of the earth’s crust under the
sea. However, the epicenter of an earthquake does not have to be
under the ocean to create a tsunami.

Fortunately, earthquakes rarely produce tsunamis, but there is
no known method to foretell which earthquake will produce a tsunami.

Usually, the first noticeable indication of an approaching tsunami
is a lowering of the water level along an exposed beach or harbor.

At sea a tsunami is almost imperceptible, although thousands of
miles from its origin a tsunami may surge ashore as high as 60 feet
above normal tide level.

The period of a tsunami in deep water is between 12 and 40
minutes and its height is under 3 feet. The wave length or distance
between successive tsunami wave crests may be 100 miles or more
and it may reach forward speeds in excess of 400 knots.

The first wave of a tsunami is seldom the greatest. Usually, the
crest is reached between the 3rd and 8th wave. Therefore, there is
frequently enough time to take precautionary measures, if the action
is initiated immediately.

Obey local tsunami warnings issued by competent authorities
and work your vessel into deep water when possible.

Sediment

iin
pata

Bs
py

-RUSTAL FEATURES.

SEAQUAKES

Seaman’s Description Shipboard Effect

Weak seaquake........... Slight vibrations, normally felt in ex-
ceptionally fine weather only, as the
vibrations would be lost in an easy roll.

Moderate seaquake.......

Rather strong seaquake....

Strong seaquake..........

Very strong seaquake......

Damaging seaquake.

UNDERWATER DISTURBANCES

Noticeable vibrations and jolts resem-
bling an anchor running out or a moored
vessel bumping the dock. Squeaking of
interior bulkheads.

Pronounced vibrations, sharp jolts as if
a heavy lift was dropped on deck, a
collision, a grounding, or casualty to
the screw or tail shaft. Unusual jump-
ing of suspended objects and pronounced
squeaking throughout ship.

Severe vibrations, similar to a rather
strong seaquake but much stronger and
may require stopping the engines, steer-
ing may become difficult, wheel hard to
hold, unsecured objects walk or topple
over.

Violent vibrations, crew may have dif-
ficulty in keeping their feet. Objects may
Jump out of their sockets; heavy and
even well-secured objects may shift their
position.

..The ship may be thrown about in the

water with such force that mast, booms,
superstructure and machinery as well as
the hull may be damaged. It is possible
for seams to be opened to such an extent
that flooding cannot be contained and
vessel sinks.

60

CONCLUSION

Although seaquakes are occasionally experienced by the mariner,
factual information on the phenomenon readily available to him remains
almost non-existent. Until recently, little had been done in this field
since the German scientist E. Rudolph conducted a thorough study of
hundreds of reports from ships encountering seaquakes. However, the
value of his work decreased with the advance of seismology which enabled
scientists to determine the epicenter of an earthquake regardless of its
location. Instrumental locations and the precise GMT of strong shocks
throughout the world are available from the Seismology Division of the
U.S. Coast and Geodetic Survey. Today scientists are utilizing floating
seismographs as well as instruments located on the ocean floor in their
ceaseless search for knowledge.

Despite scientific advances, ship reports of seismic disturbances are
still valuable even more so when analyzed in conjunction with instru-
mental data. The mariner’s navigational ability and physical condi-
tioning to the movement of his ship should allow him to observe and report
accurately and objectively any seismic activity encountered. Include in
the report the name, tonnage, type of vessel, and amount of cargo on board,
the position, the GMT, and the duration of the disturbance. A brief
description of the observed effects aboard the ship and on the surface of
the sea together with the weather would complete the report. Reports
received in the U.S. Navy Hydrographic Office will be forwarded to the
cognizant authorities and, if requested, the mariner will be furnished the
particulars of the quake he experienced.

PERU CURRENT

J. W. Lermond
Maritime Safety Division
U.S. Naval Oceanographic Office

122) 20) 110° 100° 80°

90°
So

NS S e SS
SHES
io ~~. —-
» —
‘ coLomprs |
te Fis Ye 8 ~
Te > XN \ :
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( -, Galapagos Is. AY Ss SS
STs :

ECUADOR 2Quito s~

a‘ 2 Guayaquil Soe |
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Pedr ws wpe mer ~ Cap cod sf a |

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Sala y Gomez I.

* Easter I.

> Valparaiso
oSantiago

The striking phenomena exhibited by the Peru Current, previ-
ously named Humboldt Current, can be readily recognized by the
mariner if he is sufficiently aware of the material signs of its existence.
Such recognition will contribute to successful ability in navigating
along the coasts of Chile, Peru, and Ecuador. The utilization of a 10
to 25-mile per day current, or its avoidance by a change of route, can
add up to a considerable saving in fuel and time. A more certain knowl-
edge of the sets and drifts will also contribute to safety in navigating
these waters. A description of the current, its physical characteristics,
the abundant and visible marine organisms that live within it, and the
sea birds which abound above it, are all worthy of note. All of these
resultant phenomena which are easily observed by the mariner, con-
tribute to identify the presence or absence of the stream inshore or to
point out its location offshore. The following paragraphs will outline
the history of the current and some of its more outstanding visible
features, their causes and effects.

The first recorded reference to conditions off the west coast of
South America dates from the discovery in 1522 of the territory of
Biru, from which the present state of Peru derived its name. The
chronicler, Pedro de Cieza de Leon (1553), compiled a list of sailing
directions in which he said:

“The time for navigating is during the months of January, Feb-
ruary and March, because in this season there are always fresh
breezes from the north and the vessels make short passages;
which during the rest of the year the south wind prevails along
the coast of Peru.”

Jesuit Father Joseph de Acosta (1608) stated that the northerly
winds were troublesome and were the attributes of El] Nifo. This was

61

PERU CURRENT

a first reference to the countercurrent. Augustine de Zarate, who was
sent to Peru by the King of Spain soon after Pizarro’s expeditions,
gave a more complete report on conditions without however under-
standing their cause. Later accounts by early English voyagers were
mostly concerned with piratical adventures. Frezier, an experienced
observer, described a passage from Callao to Valparaiso (1717) as
follows:
“The Regularity of the Winds at E.S.E. and S.E. and the
Breezes at S.W. along the coast of Peru, made the Navigation
so tedious, before the Method was found of running out to sea,
that Ships were six or seven months of sailing from Lima to La
Conception, because they only advanced by the Help of some
small Northern Blasts and the Land-Breezes, during the night,
and some part of the morning. This shows that the Want of
understanding Natural Philosophy among Sailors is a greater
Evil than is imagined.”

Alexander von Humboldt was the first (1802) to take the temper-
ature of the coastal current and to make strictly scientific observa-
tions. He demonstrated that the temperature decreased approaching
the coast from seaward and concluded that this represented a flow of
cold water from high latitudes.

De Tessan (1844) partially solved the problem with his suggestion
of an upwelling of the lower layers as an explanation of the low tem-
perature. Many scientists have since contributed to the description
and store of facts concerning the phenomenon now named the Peru
Current, in accordance with modern usage and a more geographical
designation.

Sailing directions and other manuals of navigation describe the
Peru Current as part of the counterclockwise system of currents in
the South Pacific. At a mean latitude of about 50°S. the surface
water, encouraged by the west-wind drift of sub-antarctic latitudes
moves eastward and later sets in an oblique northeast direction toward
the west coast of South America and thence as a cold current north-
ward along the coast to the Galapagos Islands. The current follows
the trend of the coast in a general north and north-northeast direction,
varying slightly under the influence of the wind. The width of this
stream is about 120 miles at the latitude of Valparaiso. Temperatures
in the current range from 39°F. in latitude 47°S. increasing to 52° F.
off Valparaiso (Lat. 33°S.), 57°F. off Coquimbo (Lat. 30°S.), and
64° F. near Arica (Lat. 18°30'S.). The average velocity is about 15
miles per day. The drift along the Peruvian Coast is about one knot
or less between Arica and Pisco (Lat. 13°30'S.), with a westerly set
felt at times. The greatest strength is attained between Paita (Lat.
5°S.) and the Galapagos Islands where vessels have occasionally been
set 50 miles to the west-northwest in 24 hours. Seasonally under the
influence of a northerly wind, a southerly set is experienced inshore
in certain areas. This same northerly wind can bring torrential rains
to an otherwise arid coast and can cause the inflow of warmer equa-
torial water as far south as Salaverry (Lat. 8°S.) with an accompa-
nying widespread mortality of fish and birds. Curving westward
near Cape Blanco the stream passes the Galapagos Islands and joins
the South Equatorial Current.

The surface movements of sea water are due primarily to mete-
orological causes. Ocean currents are produced mostly by the agency
of the wind. The center of the semi-permanent anticyclone in the
South Pacific is located off the north coast of Chile near Lat. 30°S.,
Long. 90° W. Its position is relatively stable. On the southern side is
the zone of westerlies, northward that of the Southeast Trade Winds;
on the east and west are the coastwise winds, influenced by the usual
offshore and onshore daily alternations. This ocean wind system tends
to blow counterclockwise around a high pressure area of prevailing
tranquility in which deep transparent blue water and a clear horizon
are a marked characteristic. This is the “Great South Sea’’ named
Pacific by Magellan because of the steady gentle winds that drove his
fleet across the wide waters.

On the southern edge of this South Pacific expanse, the west wind
drift along the edge of the sub-antarctic convergence, and the result-
ing effect of these cool waters on the greater part of the west coast of
South America, determine the kind of climate that will prevail. The
drift also determines what fish will exist in the waters and the kind of
birds in the air above. It has also determined the economic circum-
stances of life ashore.

The surface waters in the Peru Current are relatively low in
temperature close to shore, with progressively rising temperature off-
shore. There is a remarkable uniformity of low temperature extend-
ing northward through the greater length of the current, which is not

62

ordinarily affected by latitude or season. This condition is made
possible mostly by an upwelling from cooler intermediate layers of
water and not to the northerly flow of surface waters. Otherwise
these surface waters would gradually warm as they flowed northward.
The inevitable result of the meteorological circumstances along the
coast accelerates a flow of surface water offshore which results in a
vertical circulation described as upwelling. One process in upwelling
has been attributed to deviation, in which divergence of surface water
offshore is a result of the earth’s rotation. Another process would be
the effect of offshore winds and ocean drift.

Upwelling along the coast is the cause of the varied marine life
of this area. It brings to the well-illuminated upper layers the inex-
haustible store of nutrient salts from the ocean depths, upon which
the plant elements depend for life. This rich life gives to the coastal
water its typical greenish color in contrast to the indigo or blue of the
open ocean.

Recent current and temperature studies reveal the upwelling as
practically limited to the upper 100 to 150 fathoms. Surface temper-
atures close to shore along the coast range between 58° F. and 64° F.
and average about 18°F. lower than latitude alone would indicate.
The atmospheric temperatures as a result are maintained at a similar
unchanging low average all the way up the coast from about latitude
38°S. to the Gulf of Guayaquil.

The drift north, strong inshore and diminishing offshore, is the
most evident feature of the Peru Current. The decrease in northerly
set offshore is accompanied by an increasing westerly set. Upwelling
off both Chile and Peru is the final evidence of the movement offshore
of surface layers. Frequent observations of countercurrents close
inshore are associated with the usual coastal eddies due to contours
of the coast and variations with the season.

The Peru Current, off Punta Aguja (Lat. 6°S.), normally swings
to the west and converges with the Equatorial Countercurrent run-
ning east. The line of convergence marked by a tide rip may run in
an irregular line from Punta Aguja to the Galapagos Islands. The
Equatorial Countercurrent normally turns northward along the coasts
of Ecuador, Colombia, and Central America but seasonally it swings
to the south during January to March and as a result a countercurrent
of warm water moves down the coast of Peru, displacing the ordinarily
cold water of the Peru Current. This influx of warm water named
“El Nino” may reach as far south as Salaverry (Lat. 8°13'S.). This
is a drastic temperature reversal and is associated with widespread
mortality in littoral invertebrates, fish, and birds. A common result
of this disturbance to the planktonic life is observed in the extensive
discoloration of the water. The phenomenon is always accompanied
by marked changes in the fauna of the sea, including the disappear-
ance of the typical cool water birds, and the invasion of the region by
equatorial species.

A similar current change occurring farther south in latitudes 8°S.
to 13°S. during the months of April through June is called ‘‘Aguaje”
and is caused by an inshore movement of outlying warmer water.
After the occurrence of the “‘Aguaje’’, penetration and warming in
shallow water by the sun, hastens decomposition of the plankton
in such a manner as to discolor the ocean and produce hydrogen sul-
phide in a quantity sufficient to poison fish. This is but one of the
several causes contributing to the widespread mortality.

Along the northwest extension of the current (Lat.3°S.), towards
the Galapagos Islands, maximum velocity is reached. The cool green-
ish water mixes with the warmer blue waters of the South Equatorial
Current, often forming distinct bands or stripes. These mixing zones
often prove very rich in sea life. Conditions are also favorable for sea
birds. This is in marked contrast to the barren ocean areas offshore
and northward.

The climate of the coastal region of Peru is arid with prevailing
winds of small force from the southeast quadrant. Here, as on the
northern coast of Chile, the cool waters of the Peru Current produce
a stable condition of the atmosphere with considerable cloudiness but
no rainfall of consequence. On the coast there are no storms and no
sudden changes of temperature although the sky is frequently cloudy
and threatening. The immediate coast of Peru has a regular alter-
nating breeze locally called virazén which blows toward the land in
the daytime, and terral which blows toward the sea at night. Farther
offshore, the southeast trades always prevail.

Air temperature over the current is affected by the cool water
from the upwelling. Conditioned by the hydrography of the sub-
marine areas, the sharpest lowering of temperature corresponds in posi-
tion with the ocean deeps close inshore or where the continental shelf

PERU CURRENT

is reduced in width. A marked similarity or uniformity of temperature
exists from north to south. Temperature observations at Valparaiso
and Paita with a difference of latitude of 28° show a temperature
difference of less than 5° F. A comparison of temperatures between
places on the shore and those a short distance inland also reveal the
effect of the ocean on the climate.

The morning mists are the product of the abrupt cooling of air
in contact with the sea at an hour when the land breeze still holds.
These mists, or Gartias as they are known locally, extend all along the
coast of Peru and northern Chile. The inability of the air to bring
rain is explained by a lack of evaporation from cool water to cool air
and also by the fact that the onshore breezes, which would be expected
to bring rain, are deflected upward by the coastal mountains but suf-
ficient change in temperature to cause condensation does not occur.
It is estimated that air in this area at 65° F. may be warmed 25° F. by
the land it is blown against. It would then take an ascent of nearly a
mile to cool the air 25° F. thus leaving it at the same temperature at
which it started and with no progress toward condensation. This
arid condition persists for decades, with an appearance of rain, but
no rain. It is amazing to encounter a pall of low cloud or an overcast
sky, with ports hidden in fog, but at the same time encountering ex-
treme evidences of aridity in the coastal areas. The coast appears
like a desert under a humid sky. The fog forms over the upwelling
stream of cold water and gathers on the seaward slopes of the coastal
hills.

ZONE OF SUBDUED COASTAL MOUNTAINS
ZONE OF COASTAL TERRACES wet SEAWARD
N ECT,

DRY LANDWARD
DRY UNDERNEATH OG ASPECT

GARUAS

Morning garuas are produced by the abrupt cooling of air in contact with the
sea at an hour when the land breeze still holds. The air drifts landward with
the onshore wind and mist gathers on the seaward slopes of the coastal hills.
The gartias descend at night nearly to the surface and all but disappear dur-
ing the day, or they may extend indefinitely westward.

The rain making conditions in this area are in such fine balance
that only a slight interference with the existing conditions might cause
a deluge that could lay the coast in ruins. Mud-walled houses and
sun-dried brick buildings would crumble in a heavy rain and the dry
alluvial valley lands would become mighty rivers. Fertile tracts
would be washed into the sea or be covered by sand.

Fortunately these conditions are infrequent and take place only
in a small area along the north coast of Peru where tropical conditions
temporarily blanket the area during the seasonal invasion by the
countercurrent.

MARINE LIFE

The divisions controlling the distribution of animals in land areas
are mountains, deserts, broad rivers and other abrupt lines govern-
ing changes in temperature or rainfall. The ranges of fish and marine
invertebrates can likewise be correlated with the temperature and
chemical content of the sea water. Ocean birds, like land birds, are
bound in the same way to their own type of conditions, if not for their
whole life then for at least a part of it. Few sea birds can long survive
a marked change in sea temperatures and salinity. The unique and
limited areas of change in the oceans provide barriers and invisible
walls controlling bird existence.

Water temperature appears to be the principal limiting factor
governing the distribution of sea birds. The control is bound up with
a long sequence of conditions related to temperature, rather than a
simple direct relationship. Temperature range is an important event
in the life cycle beginning with the phenomena of sunlight and photo-
synthesis and ending with the nature and quantity of organisms upon
which birds feed. Temperature is the most important factor of sea
water in relation to sea life. Salinity and density factors as controlled
by current and climate are only further complications in the relation-
ships. Studies of conditions at the north end of the Peru Current have
revealed some of the secrets in these relationships in which birds are
adjusted and respond quickly to periodic changes in the character of

63

sea water. Groups of birds retreat or advance with a change of con-
ditions and areas are invaded by a different species.

ANIMALS living
on algae

Carnivorous ANIMALS

CORPSES AND
EXCRETA

SEA-LIFE CIRCUIT

The ultimate source of food for all marine life is the microscopic
plant life obtaining sustenance from the nutrient elements in the sea
water. Tissue thus built up then becomes food for small crustaceans
and certain fishes which are in turn consumed by birds and other ani-
mals. Microscopic plants number tens and hundreds of thousands
per quart of sea water. Existing principally within 50 fathoms of the
surface, the dead remains settle and decompose in the lightless depths.
The enriched water from the decomposition is then recirculated to the
surface and made available for further profuse development.

Decomposition of animal and plant remains by bacteria brings
derivatives of the body substances to a soluble condition in water,
from which some may be removed for use by other advanced forms.
An ordinary circuit in this chain of events would be: diatom—cope-
pod—herring—cod (or bird)—bacterium—sea water—diatom. The
diatoms are one of the basic connecting links and surpass a thousand-
fold in bulk the productiveness of all other aquatic plants. They may
be likened to a pasture in the sea and, although available everywhere,
are most profuse in waters of low temperature. They are an abundant
source of food for all marine animals.

Low temperature and low salinity, usually associated with the
southern oceans, create an abundance of life far in excess of that in
warm sea water. The food substances of ocean life such as carbonic
acid, nitrites and nitrates of calcium and magnesium, phosphates,
silica and other elements, all exist in very small quantities everywhere.
The living substances incessantly use up the elements. Sea water of
low temperature, being more favorable to a high gas content and
richer in mineral compounds, support a more abundant plankton
growth. Co-existing generations in these low temperature areas assist
in the creation of a more generous growth and aid in factors tending
toward a longer life span leading to complete development.

Zones of distinctive conditions, each with a typical amplitude of
temperature, salinity, and condition for the support of plant and
animal life are defined geographically. These zones succeed one an-
other from polar latitudes and are named Antarctic, Sub-Antarctic,
Sub-Tropical, and Tropical. Hydrological circumstances within each
zone bear an interesting relationship to the distribution of sea birds.
The relationship of phosphate to plankton abundance, the distribu-
tion of plankton in general, and the color of sea water in relation to
the contained life, are indicated by the number of sea birds.

Discontinuities of temperature and salinity in the open ocean
behave more or less as though separated by a wall and are the physi-
cal basis for the zones of convergence. Surface layers of water are
inhabited by organisms not characteristic of near-by zones. Parts of
these convergencies are shaped and stretched as though by pressure,
and although influenced by surface topography, these boundaries are
seldom controlled by relationship to latitude alone. Such a diversion
can be observed in the South Pacific where the Sub-Tropical conver-
gence shapes northward in the vicinity of latitude 30°S., longitude

PERU CURRENT

90°W. Bottom contours at great depth may assist the course of
convergence. These are physical boundaries and can be detected
with a thermometer by the sharp change in temperature. They can
be as easily detected by the distinction of life within the water.

Within the Antarctic Zone, surface water temperatures 30°F. to
38°F., the food of birds, as well as of whales and some seals, consists
mostly of “‘krill’’, the Norwegian whaleman’s name for the euphau-
sian crustaceans or oppossum shrimps. Although there are many
kinds of euphausid, the species Euphausia superba has been found
most abundant in the stomachs of penguins, petrels, seals and whales
of the far south. The exclusive food of penguins is swarms of this
form of “krill” which in turn subsist largely on diatoms, the predom-
inant microplankton of the area. The body growth of the birds and
whales are thus only one step removed from the organic fixation of
the radiant energy of the sun by the phytoplankton.

Re ie Edward Is)

= South Sandwich

—-». Balleny Is- o
~~

Emerald I.
.Macauarie |.

ede I. sheets 1
Stewart I

Wchaiten Is. WwW

W, 180° E,

“ih

ANTARCTIC CONVERGENCE

The Sub-Antarctic Zone, surface water temperatures 38°F. to
58°F. is almost entirely within the belt of westerly winds and is an
area of much deeper and warmer surface water. Salinity and temp-
erature decrease with depth in this area and there is a constant tend-
ency toward upwelling and vertical mixing. The unstable conditions
of rough weather tend toward less production of phytoplankton.
Munida, known by the southern whalemen as “‘lobster krill”, make up
the predominant bird-whale-feed in this zone. These creatures occur
in enormous abundance. Munida gregaria sometimes color the sur-
face of the ocean a bright red. They appear in vast numbers far north
in Peru Current waters and form a substantial part of the food of gulls,
cormorants, petrels and penguins.

An impressive description of marine life in profusion living in
nearly perfect conditions in the Peru Current has been recorded by
R. E. Coker as follows:

“Tn contrast to the barrenness of the coast [of Peru] there is a
peculiar wealth of certain forms in the open ocean. The great
red seas, formed sometimes, at least, of myriads of microscopic
dinoflagellates, are of common occurrence........ Sometimes,
too, great areas of the surface of the sea are reddened by the
vast numbers of small crustacea (Munida) which then play a
part of great importance as food for the fishes and for the
guano-producing birds. More striking still are the immense
schools of small fishes, the ‘‘anchobetas’”’ (Engraulis ringens
Jenyns), which are followed by numbers of bonitos and other
fishes and by sea lions, while at the same time they are preyed
upon by the flocks of cormorants, pelicans, gannets, and other
abundant sea birds. It is these birds, however, that offer the

64

most impressive sight. The long files of pelicans, the low mov-
ing black clouds of cormorants, or the rainstorms of plunging
gannets probably cannot be equaled in any other part of the
world. These birds feed chiefly, almost exclusively, upon the
anchobetas. The anchobeta, then, is not only... .the food of
the larger fishes, but, as the food of the birds, it is the source
from which is derived each year probably a score of thousands
of tons of high-grade bird guano. . .No more forcible testimony
to its abundance could be offered than the estimate, made
roughly, but with not wide inaccuracy, that a single flock of
cormorants observed at the Chincha Islands would consume
each year a weight of these fish equal to one-fourth of the en-
tire catch of the fisheries of the United States.”

The Sub-Tropical Zone, surface water temperature 58°F. to
73° F., show an increase in salinity and a striking decrease in nutrients.
Oxygen in the surface layers decreases from about 80 percent of satu-
ration in 28°S. to about 40 percent at the Equator. These waters are
not favorable for diatom growth except where replenished by up-
welling such as exist along the Peruvian Coast where conditions remain
constantly favorable. The volume of plankton diminishes under these
adverse conditions in the Sub-Tropical Zone and the collective popu-
lation of surface organisms may be no more than ten to each quart.
The diatoms are replaced by less well known varieties and likewise
the pelagic crustacea, so important to life in the southern zones, are
replaced by copepods. Therefore the abundance, if available, becomes
sporadic. The Portuguese man-o-war appears in this zone. Flying
fishes and dolphins replace the immense schools of small fishes of the
colder waters. The numbers and types of sea life near the surface
diminish greatly.

The Tropical Zone of surface waters, temperatures 74°F. to
84° F., differs little with that of the Sub-Tropical. Salinity is at a
minimum because of heavy rainfall and low evaporation. Waters
of greater density and salinity are observable below the surface layer.
There are no detectable phosphates and but minute quantities of
nitrate nitrogen. Bird life in these climes is regarded as land bound
rather than pelagic except for flock or single migrations.

Next to the extraordinary abundance of marine life in low south-
ern latitudes, the most evident characteristic of the Peru Current is
the unequalled northward distribution of Antarctic and Sub-Antare-
tic types of birds and mammals. Examples in this category are many
Peruvian species with distinctly subpolar affinities such as:

(a) The Southern Kelp Gull (Larus dominicanus), a Sub-
Antarctic sea bird of cireumpolar range, which breeds in
numbers on Tierra del Fuego and upon other heavily-glaciated
ice-covered islands, such as South Georgia and Kerguelen.
This bird also extends its breeding range along the tropical
western coast of South America practically as far as the Peru
Current is in contact with the land. Its northernmost breed-
ing station, on Lobos de Tierra (Lat. 6° 25'S.) is one of its cen-
ters of maximum abundance.

(b) The White-breasted Cormorant, or Guanay (Phalacroco-
rax bougainvillei), first in importance as the Peruvian guano
bird, is a member of the well-defined Antarctic branch of the
cormorant family. Its closest kin are the cormorants of the
Strait of Magellan, New Zealand, Sub-Antarctic islands, and
the shores of the Antarctic Continent, but its relationship with
the other cormorants of South America or with those of the
Northern Hemisphere is distant. The range of the Guanay
extends along the west coast of South America from central
Chile to within six degrees of the Equator.

(c) Diving Petrels (Pelicanoididae) are representatives of a
typical Sub-Antarctic family of marine birds. They breed
along the western coast of South America from Cape Horn to
the northern islands off Peru (Lat. 6°25’S.). Diving Petrels
do not breed north of about latitude 37° S. in any other
part of the world.

(d) Penguins (genus Spheniscus) are found along the west
coast of South America southward of latitude 6° S., and also an
endemic species (S. mendiculus) resides on the Galapagos
Islands at the Equator.

(e) The Southern Sea Lion (Otaria byronia) is a permanent
resident along the west coast from Cape Horn to northern Peru,
and again a representative of the same genus occurs at the
Galapagos Islands.

(f) The rare Southern Fur Seal (Arclocephalus australis),
sometimes sighted at Independencia Bay (Lat. 14°10’S.),

PERU CURRENT

~ Figure 3. PERUVIAN PENGUIN,
Nino'', walks upright with great dignity, standing about 27 inches high,

weight about 9 pounds.

Figure 3) COE

Figure 1. WANDERING ALBATROSS, Diomedea exulans, ‘'Cape
sheep’, weighs about 13 pounds with a wing spread of eleven feet. The
birds are white with slate brown wing tips and trim with a buff-yellow beak
and blue-gray legs and feet. This is a southern hemisphere albatross which
nests mostly on glacial Antarctic islands such as South Georgia. A gifted
and beautiful aerial performer often seen far at sea. King of the air, the
albatross is one of the largest sea birds, and also of all flying birds, the
condor being heavier but with lesser wing-spread.

Spheniscus Rombo lain “Pajaro =

The bird has gray feathers with a black band
across a white breast and has a black bill and blackish brown feet.
penguin lacks any ability whatever _in the air but exhibits incredible skill

The

-

Figure 2. PERUVIAN PELICAN, Pelicanus occidentalis thagus,

~~ “‘Aleatraz"’, a large ungainly bird weighing about 16 pounds; has pearly

65

gray plumage with a white head, black or orange-yellow pouch with greenish
bill and lavender-gray legs. May hurtle into the water with a resounding
splash or may swim and scoop while fishing. The bird gives the impression
of being shy, stupid and at times awkward or impractical; is most conspicuous
among the flock birds on the coast for its size as it is the largest. This bird
does not stray out of sight of the coast and has never been sighted off the
outlying islands.

PERU CURRENT

Figure 4. PIQUERO. Sula variegata, “The lancer’’, weighs about 4
pounds, is white-headed and white-bodied with variegated white and brown
wings and back, purple-blue bill and blue-gray legs. This bird is the noisiest
and most numerous of the guano birds at the Peruvian islands and is a swift
and active flyer and a powerful diver. The lancer descends straight from the
blue, vanishes in a jet of foam in a spectacular plunge as he fishes for
anchovies in the cool current.

aT / = %
od / F 2 , re

Figure 5. GUANAY. PhalacrocoramnGateainle? “Pato yeco’™',
“walks erect, about 20 inches high, weight about 4% pounds. A long-winged,
ng-billed, cormorant with glossy green and blue-black neck and back and
lossy white breast, having pink feet. The bird has a conspicuous naked skin
: area about the eye. A very capable and strong flyer, feeding exclusively
______ upon sea-surface organisms, the Guanay is ranked first in importance among
= the famuos guano birds of Peru.

it _ ot ’ - = =.
= ay. ye a | = Ss
SN i ee ee
ecu Ghee RA ee

— 7
Qos “hemes ye ay Sess Thee

66

PERU CURRENT

formerly ranged from Cape Horn to northern Peru and the
Galapagos Islands, or throughout the path of the Peru Current.
This genus is one that has successfully jumped the northern
barrier of tropical surface waters, as a related species (Arctoce-
phalus townsendi) is now a resident of the lower California
coast and inhabits Guadalupe and the San Benito Islands
(beyond Lat. 28° N.).

The Peru Current is a narrow stream and the composite range of
endemic marine fauna of the Peruvian Coast is likewise a narrow rib-
bon in the ocean, hugging the shore as it projects toward the Equator
from the far south. A voyage offshore across the Peru Current reveals
the change in fauna, which is closely correlated with the changes in
surface temperatures. A few miles offshore the plankton, sea lions,
penguins, cormorants, kelp gulls, and Sub-Antarctic petrels, with
thousands of fish species, all disappear, and another oceanic region
with a totally different fauna appears.

The following species are considered native to the Peru Current:

SOUTHERN DERIVATIVES
Peruvian Penguin (Spheniscus humboldti)
Peruvian Storm Petrel (Oceanodroma tethys kelsallz)
Eliot’s Storm Petrel (Oceanites gracilis gracilis)
Potoyunco (Pelicanoides garnotit)
Guanay (Phalacrocorax bougainvillez)

PAN-TROPICAL DERIVATIVES
Alcatraz (Pelicanus occidentalis thagus)
Piquero (Sula variegata)
Peruvian Tern (Sterna lorata)

PROBABLE NORTHERN ORIGIN
Gray gull (Larus modestus)

DOUBTFUL SOURCE
Markham’s Storm Petrel
Hornby’s Petrel
Belcher’s Gull
Inca Tern

The birds of Sub-Antarctic affinities which extend their breeding
ranges northward into the Peru Current are as follows:
Magellanie Penguin (Spheniscus magellanicus)
Sooty Shearwater (Puffinus griseus)
Frigate Petrels (F regatta)
Red-footed Cormorant (Phalacrocorax gaimardi)
Tern (Sterna hirundinacea)

(Oceanodroma markhami)
(Oceanodroma hornbyi)
(Larus belcheri)
(Larosterna inca)

The area of the Peru Current is visited by many varieties of birds
from distant parts of the Pacific during the various seasons, but the
native species, found only in the waters off the coast between Ecuador
and Chile, are more abundant and noticeable. Included among the
migrants are certain species of Antarctic and Sub-Antarctic alba-
trosses, petrels such as Daption, Priocella, Macronectes, Procellaria,
and Oceanites oceanicus, as well as forms of the skua (Catharacta).
There are also seasonal migrants from the outer Pacific such as the
Sooty Tern (Sterna fuscata). Migrants from the Galapagos Islands
and tropical waters to the north are the albatross from Hood Island
(Diomedea irrorata), a Gadfly Petrel (Pterodroma phaeopygia), the
Blue-faced Booby (Sula dactylatra), the Swallow-tailed Gull (Creagrus
furcatus), the Royal Tern (Thalasseus maximus), and at intervals a
tropic bird (Phaethon aethereus). Casual visitors from the Northern
Hemisphere include petrels such as Loomelania melania, gulls like
Larus pipixcan and jaegers, and phalaropes from the Arctic interior
of North America.

67

The Peru Current, besides being responsible for the dramatic
distribution of cold Antarctic water, with a biologic cycle of its own,
has yet another unique item of interest worthy of note. This is guano,
a by-product of the cycle, the importance of which was long over-
looked. Guano, although mentioned in the Royal Commentaries of
the Inca and known by the early conquerors, was neglected as an
item of world trade, until Humboldt advised its use as a fertilizer soon
after 1800. Introduced into the United States by 1825 and England
by 1840, the first users were fearful of its potency because of the aston-
ishing results from its application as a fertilizer. After repeated ex-
periments it came into general use as a safe and cheap fertilizer. Some
early estimates describe guano as being 33 times more effective than
any other equivalent.

Soon after 1847 it was a principal industry in Peru, amounting
to nearly three quarters of Peru’s annual income. By 1874, in spite
of early predictions of an inexhaustible supply, most of the original
accumulations had been removed. Less worthy deposits have been
found around rocky islands in other parts of the world, but none com-
pare with the quality or size of the Peruvian deposits. This is no
doubt due to the peculiar aridity of the climate of Peru which pre-
served the deposits without loss.

Huge profits from the guano trade were realized in the early days.
Profits from a single trip by a sailing vessel at this time amounted to
as much as $10,000. Hundreds of vessels loaded at the coastal islands
each year. Rapid exploitation with no attempt at conservation soon
depleted first deposits. Four decades later, after implementation of a
government program for conservation of both producing birds and
deposits, the industry had become permanent. The Compania Ad-
ministradora del Guano in Peru is the official agency controlling and
operating the producing islands. The extraordinary commercial
success of the company is no doubt due to the wisdom of the admini-
strators who have conducted the industry with reference to the wel-
fare and perpetuation of the valuable sea birds. A rotating extraction
schedule is followed which provides for non-molestation of the birds
and will in time restore the balance so blunderingly upset during the
total exploitation era. Guano-fever burned as fiercely as gold-fever
in the early days and the islands were a focus of greed and corruption
that is now almost forgotten. Misery and slavery were attached to
a commercial enterprise represented by the towering spars of sailing
ships from the ends of the earth, whose skippers were greedy for the
stinking dust from these remote Peruvian islands.

Excavating guano in the Chincha Islands about 1860. The layers here are
nearly 800 feet thick.

PERU CURRENT

Another interesting by-product of the Peru Current is the un-
usual nitrate wealth of the north Chile desert. Nitrate beds are found
on the upland plain behind the coastal range between latitudes 19°S.
and 26°S. One theory is that the substance owes its origin to ancient
huge deposits of the guano of sea birds; later to be acted upon by
water and sun in the presence of quantities of sea weed. Some of
these beds are still the breeding grounds of many sea birds. Numer-
ous petrel mummies are unearthed during present day mining opera-
tions. Geologic changes in the history of this unstable coast could
well account for the present location of these inland beds far above the
sea. Regardless of their origin the nitrate fields are the basis for an
important industry in Chile. An average income of over twenty mil-
lion dollars gold has been realized by Chile in export taxes alone from
this source. For many years the nitrate trade accounted for half the
total value of the export trade.

The foregoing is but a short description of the peculiar conditions
found on this strange coast, with its odd interrelations of industry and
nature, where a mountainous desert borders the ocean for 2,000 miles.
Here rain threatens but never falls. Here the ocean current is cold
and mostly vertically disposed. Here birds (penguins) fly under water
instead of in the air.

The bird life and some of its spectacular features in this area have
been aptly described by the talented Dr. Chapman as follows:

“As for the birds, who can describe them in their incalculable
myriads? Visible link in the chain of life that begins with dia-
toms nourished by the cool, highly oxygenized waters of the
Humboldt Current, they animate both the air and the sea.
No other coastline of similar extent can show an avian popu-
lation equalling that of the waters off Peru.

“Whichever way one looked from our anchorage at Salaverry,
birds could be seen in countless numbers fishing in dense, ex-
cited flocks, passing in endless files from one fishing ground to
another, or massed in great rafts on the sea. Toward the shore
long, waving whip-like streamers and banners passed in end-
less undulating lines sharply silhouetted against the coast range.
“Seaward, like aerial serpents, sinuous files crawled through the
air in repeated curves lost in the distance, while low over the
water processions passed rapidly, steadily, hour after hour,
with rarely a break in their ranks during the entire day. At
times the flocks were composed of Cormorants with, at inter-
vals, a white-bodied, brown-winged Booby. At others, they
were composed of Boobies accented, here and there, by a Cor-
morant.

== : - dull blue bill and bright blue legs and feet.
water, is a buffoonish sort, curious and unafraid, and is the least important of the guano producers

BLUE-FOOTED BOOBIE,

68

“When the birds stopped to feed, the scene commanded the
untiring and often excited attention of every passenger aboard
the ship. The Cormorants fished from the surface in a sea of
small fry. Swimming and diving they gobbled voraciously
until their storage capacity was reached. Then they floated
in dense, black masses waiting for the processes of digestion
to give space for further gorging.

“The Boobies fished from the air, plunging into the water with
great force from an average height of 50 feet, to disappear in a
jet of spurting spray as they hit the surface. In endless cata-
racts they poured into the sea. It was a curtain of spearheads,
a barrage of birds. The water bacame a mass of foam from
which hundreds of fishers took wing at a low angle to return
to the throng above and dive again; or their hunger satisfied,
they flew by thousands to some distant resting place. It is
difficult to understand why the birds near the surface were not
impaled by their plunging comrades.

“But the most amazing maneuver in all this astounding spec-
tacle was the instantaneous disappearance from the air of flocks
of 500 to 1,000 Boobies that chanced to pass over a school of
fish. Then as one bird, they plunged seaward and the sky,
which a moment before seemed full of rapidly flying birds, was
left without a feather. This evolution, the most surprising I
have ever seen in bird-life, was witnessed repeatedly during the
day. When we left [Salaverry] late in the afternoon there was
no apparent decrease in the numbers or activities of the winged
fishers; but I could look at them no longer without a feeling
of confusion and dizziness; for the first time in my life I had
seen too many birds in one day!”

Sources of information include the following:

Ocean Birds of South America, 1936, Robert Cushman Murphy.
The Oceans, 1942, Sverdrup, Johnson and Fleming.

Variations in Behaviour of the Peru Coastal Current—with an
Historical Introduction, 1936, E. R. Gunther, The Geographical
Journal.

Notes on the Findings of the ‘William Scoresby” in the Peru
Coastal Current, 1937, R.C. Murphy, The Geographical Review.

Sula nebouxii, ‘‘Camay'', an ungainly bird weighing
about 4 pounds, of brown and white somewhat streaked appearance, with white underbody,

This bird dives and glides to great depths in the

WATER DENSITY AND ITS APPLICATIONS

J. W. Chanslor
Maritime Safety Division
U.S. Naval Oceanographic Office

The sea is a wilderness full of secrets, upon which man has sailed
since the earliest times. Even in these days of accelerated scientific
achievement, mysticism of the sea remains. The purpose of this
article is to touch upon one facet of the phenomena of nature—
density of sea water and its applications to mariners.

Some of the complexities discussed include changes in draft, due
to changes in density, currents affecting a voyage, causes of harbor
siltation, and the explanation of certain related phenomena observed
at sea.

The density of sea water depends upon three variables: salinity,
temperature, and pressure. At constant temperature and pressure,
density varies with salinity or, because of the relationship between
this and chlorinity, with the chlorinity. Density and specific gravity
are virtually identical numerically. A temperature of 32°F and
atmospheric pressure are considered standard for density determina-
tion. The effects of thermal expansion and compressibility are used
to determine the density at other temperatures and pressures. And,
the density at a particular pressure is quite important in its relation
to ocean currents.

The greatest changes in density of sea water occur near the sur-
face where the water is subject to influences not present at depths.
At the surface density is decreased by precipitation, runoff from
land, melting of ice, or heating. When the surface water becomes
less dense, it tends to float on top of the more dense water below.
There is little tendency for the water to mix, so the condition
is one of stability. The density of surface water is increased by
evaporation, formation of sea ice, and cooling. If the surface
water becomes more dense than that below, it sinks to the level at
which other water has the same density. At that level it tends to
spread out to form a layer or to increase the thickness of the layer
below it. The less dense water rises to make room for it, and the
surface water moves in to replace that which has descended. Thus,
a convective circulation is established. It continues until the density
becomes uniform from the surface to the depth at which a greater
density occurs. If the surface water becomes sufficiently dense, it
sinks all the way to the bottom. If this occurs in an area where
horizontal flow is unobstructed, the water which has descended
spreads to other regions, creating a dense bottom layer. Since the
greatest increase in density occurs in polar regions, where the air
is cold and great quantities of ice form, the cold dense polar water
sinks to the bottom and then spreads to the lower latitudes. This
process has continued for a sufficient length of time that the entire
ocean floor is covered with this dense polar water, thus explaining
the layer of cold water at great depths in all the oceans.

Changes in salt content of ocean waters, with position, depth,
and time, are brought about in the main by greater evaporation
taking place in subtropical latitudes and greater precipitation in the
polar seas. In the equatorial region surface water increases in
salinity because of evaporation but decreases in density because of
rise in temperature.

As the density of sea water depends on temperature and salinity,
all processes that alter the temperature or the salinity influence the
density. The water of the greatest density is formed in high latitudes.

Generally, density is a physical property possessed by solids,
liquids, and gases. It is defined as mass per unit volume. Although the
quantities, temperature and pressure, have only small effects on
density in the laboratory, these factors must be given close atten-
tion in oceanography. In the oceans density is further complicated
by the effect of salinity.

The fact that density is an inverse function of volume indicates
that an increase in volume will cause a corresponding decrease in
density, whereas a decrease in volume will cause the density to in-
crease. It logically follows that whatever factors cause the volume
of some quantity to undergo a change will also cause density to
undergo an inverse change, other factors being constant. The fol-
lowing explanations show how a change in pressure, temperature,
or salinity bring about a change in density.

Pressure: —Though, as a general rule, liquids may be considered
incompressible, such an assumption cannot be made when consider-

69

ing a unit volume of water at oceanic depths. Due to increase of
pressure with increasing depths, a small volume of water carried
from the surface down to some point beneath the surface will be
compressed, or stated differently, will be caused to occupy a smaller
volume. This decrease in volume causes an increase in density if the
mass of the sample remains constant without a change in tempera-
ture. Thus, the effect of pressure is to bring about a change in vol-
ume and thereby influence the density as described.

lass slide in bathythermograph.

Smoked glass slide

Temperature: —Like pressure, the effect of changes in tempera-
ture changes the volume of a sample of water; however, unlike
pressure, the variation of volume with temperature is direct, causing

WATER DENSITY AND ITS APPLICATIONS

volume increases with increasing temperature. The net result of an
increase in temperature causes a decrease in the density if other fac-
tors remain constant.

Salinity: —Salinity differs from the other factors in that its
variation essentially involves a change in mass of a given volume.
Increasing the salinity of a sample of water is much the same as
adding mass to volume which increases the density.

DENSITY AT VARIOUS TEMPERATURES

For some practical uses of density, it is more important to know
the density at the temperature apt to be encountered than at the
standard temperature. Figure 1 provides for converting density at

TEMPERATURE IN DEGREES FAHRENHEIT
30 eS ee a0 eee 45 ee SOS i Ty

1.032072 ease Ty
40 30 0 S ge
70340 03 3 oars 4 Sx >

1.0300

1.0280

1.0260

1.0240

1.0220

1.0200

1.0180

1.0160

10140

DENSITY AT 59°F (15°C)

1.0120

1.0100

1.0080

1.0060

AAAI LAMAN AAAI ADA DAALD LANA AADAD ADI AT ALOT ADO AT RONG TAD AA AOR IDAADORADANROARORDADAAIAO DOOD OANIODOALONADADADODADANDANL
‘o
%,
Xe

a
J ele,
\ ‘A, \O
AULT SUUSUUUC UCC C NUON UL EU EEE Pu ET PEPEE EET

Figure 1. Sea water density at various temperatures.

59°F. (15°C.) as published in U.S. Coast and Geodetic Survey Pub-
lication Nos, 31-2 and 31-4 (Density of Sea Water, Atlantic Coast,
North and South America, and Density of Sea Water, Pacific Coast,
North and South America and Pacific Islands). As it is intended
for use with true density rather than observed hydrometer readings,
no glass correction was included.

To convert a density at 59°F. to density at another temperature,
enter the graph horizontally from the left with the known density
and downward from the top with the desired temperature; the posi-
tion of the point of intersection of the curves gives the density at
the desired temperature. Interpolate between curves when necessary.

Example: If certain water has a density of 1.0274 at 59°F.
(15°C.) what would its density be at a temperature of 79°F.? En-
tering the graph from the side and top with these values, it is found
that the point of intersection lies about 4/10 of the way between
curves 1.0240 and 1.0250, so that the density at 79° F. is 1.0244.

DENSITY AND OCEAN CURRENTS

When the surface water in a particular area is heated until it is
warmer than the water around and underneath it, the heated water

70

expands so that the surface of the sea is slightly elevated in the
center of the warm spot. Immediately, the water begins to flow
downward in all directions away from the center. Cooler and denser
water then presses up against the warmer and lighter water,
buoying it up. Circulation therefore continues until there is an even
distribution of density and pressure.

The rotation of the earth causes all these movements to be de-
flected to the right (in the Northern Hemisphere). This results in
a whorl of clockwise water movements spreading out from the warm
center. Under ordinary circumstances, this eddy of warm water can
be expected to spread until the density differences are equalized.
The process is retarded, however, by the tendency of the water par-
ticles to be deflected more and more to the right, so that at the edge
of the eddy the movement follows very nearly a circular path.

The sinking of cold or saline water produces a somewhat similar
current pattern, but in the opposite direction. If the surface water
in a particular area is cooled sufficiently to make it denser than the
water underneath, it will sink until it reaches a level of its own den-
sity. As it does, the sea surface is depressed, and warm surface
water flows in from all sides to take its place.

All these factors are interrelated—the difference in density
between the warm water above and the colder water below, the
slope of the thermocline (as influenced by latitude), and the velocity
of the current produced. The relationship can be expressed by a
mathematical formula, so that by measuring the vertical density
structure of ocean waters, it is possible to determine the direction
and velocity of currents. Current systems are commonly studied
in this way, for actual measurements of the currents are very in-
accurate unless the vessel is equipped for anchoring in deep water,
and even then measurements are difficult and laborious. The prin-
ciple of determining ocean currents from the density structure of
the sea, which is generally known as the Bjerknes Circulation Theory,
is one of the most important contributions to modern oceanography.

While the mathematical relations of currents with the density
structure of the water are always about the same, the casual rela-
tionships are often inextricably mixed. The wind may set upa
current, and the transport of water that results will cause the den-
sity surfaces to slope. Contrariwise, density slopes that result from
heating or cooling processes will cause a current to be formed. Often
both processes are involved, and some of the most powerful ocean
currents are those in which the prevailing winds and the density
distribution work together.

In examining the currents it is worthwhile to compare them
with the wind systems of the world which are similar in many re-
spects and are, to a large degree, responsible for the general pattern
of the currents. This is particularly true of the west wind drift in
the Antarctic and of the North and South Equatorial Currents which
lie in the trade wind belts. The latter currents form part of the
great eddies centering in the mid-latitudes, clockwise in the Nor-
thern Hemisphere, and counterclockwise in the Southern, corre-
sponding to the prevailing wind direction. As they are primarily

p)

Se Se

Figure 2. Diagram of typical circulation, wind driven eddy
and subpolar convergence.

WATER DENSITY AND ITS APPLICATIONS

Recovering the bathythermograph.

wind-driven, they are swiftest at the surface. In the main thermo-
cline and the upper part of the deep water layer, horizontal eddy-
type motion gradually decreases with depth, giving way to slower
deep water transport. These eddies, together with the sinking centers
in higher latitudes, set the dominant pattern of the current systems
of each ocean basin. Figure 2 is a diagrammatic representation of
the scheme of circulation, showing the density structure and the
direction of the currents in a combined wind-driven eddy and sinking
center. In the eddy currents centering in mid-latitudes, the density
surfaces slope downward toward the right in the Northern Hemi-
sphere and to the left in the Southern. Thus, in the center of
the eddies, layer depths are greater than around the outer edges
of the currents. Hence, where these currents border on the equa-
torial doldrum belt the thermocline is shallow and echo ranging
conditions are relatively poor. Sinking ordinarily occurs in a band
a few yards wide and perhaps as much as several miles long. This
phenomenon has been observed by surface vessels. It has the choppy
appearance of a tide rip and may be full of seaweed and other debris
brought into it by the converging surface currents. The downdrift
is strong enough to carry down debris of slight buoyancy, and the
surface currents may be strong enough to hold a drifting vessel in
the convergence in spite of a crosswind.

Such convergences are probably important from the standpoint
of diving operations. Submariners use the term fresh pocket for a
place where the vessel suddenly and for no obvious reason begins
to sink and requires reballasting. This can happen any time when a
submarine goes too near the lower limit of a supporting density
gradient. Varying thickness and amount of temperature change
in the thermocline are no doubt responsible for some instances re-
ported. On the other hand, sometimes the submarine sinks very
rapidly and checks its descent with great difficulty and at a dan-
gerous depth. In such a case it may have encountered a convergence
in which there is no increase in density with depth, but also a down-
ward current of water comparable to downdrafts in the air that

71

cause airplanes to lose altitude. From what is known about the
shape of these convergences, it seems likely that a submarine held
in one for any length of time has come into it on a nearly parallel
course and should therefore change course about 90 degrees to escape.

DENSITY AND COASTAL CURRENTS

Very marked currents are produced by the melting of ice in salt
water. In the North Atlantic the arctic water of low salinity derived
from melting ice flows southward as the Labrador current, hugging
the right-hand shore. The deflection to the right owing to the earth’s
rotation causes it to set into the bays on the Canadian coast. On the
south-east coast, so many wrecks have occurred near Cape Pine and
St. Shots Cove that mariners have believed there was a local mag-
netic disturbance. Such is not the case however, because these
disasters were mainly due to the effect of the density currents men-
tioned in the Sailing Directions for Newfoundland (Pub. No. 14).

Because of land drainage the density of coastal water is usually
less than at corresponding depths offshore. Along any coast where
there is a significant amount of freshening due to land drainage,
there is a general tendency for the fresh water to move offshore
on the surface and the denser (more saline) water to move in under-
neath. Thus, the salinity of the surface water increases from the
shore seaward, and there is an increase in salinity from the surface
downward. This is an unstable condition in that the density sur-
faces slope downward in an inshore direction; and the unequal pres-
sure gives rise to currents which, in general, behave according to
the principles of the circulation theory.

Since the density surfaces slope downward toward the shore, the
directions of the currents are roughly parallel to the coast, with
the coast on the right-hand side of the direction of flow in the Nor-
thern Hemisphere and on the left-hand side in the Southern Hemi-
sphere. As a result of this prevailing condition, the Northern
Hemisphere coastal currents on the west side of the oceans are

WATER DENSITY AND ITS APPLICATIONS

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RIVER MERSEY

usually south-flowing and relatively cold. Salinity is responsible for
the density gradient that sets up the current, since, from the stand-
point of temperature alone, the inshore water obviously would be
heavier rather than lighter.

Along the east side of the oceans, coastal density currents
generally flow northward and are warmer than the offshore water.
Thus, both temperature and salinity contribute to the density gradi-
ent between inshore and offshore water.

Exceptions to the above occur where the Continental Shelf is
narrow and where little river water is brought down to the sea. In
such cases local winds and seasonal variations in rainfall are impor-
tant in determining whether or not a typical coastal current will
develop. For example, on the east coast of the United States there
is a well-developed coastal current as far south as Fort Pierce,
Florida. Beyond that point the shelf narrows rapidly and the coastal
current, known as the Florida Countercurrent, becomes weak and
sometimes nearly nonexistent. The coastal water off Miami is
slightly cooler than the offshore north-flowing Florida Current. It
is also slightly fresher, enough so that the countercurrent generally
flows during the wetter months of the year. During the spring
and summer months, however, steady southeasterly breezes carry
the Florida Current close inshore and the coastal current is obliter-
ated entirely or driven below the surface where it can be detected
only by a subsurface method.

The extent to which a current parallels a coast depends, in con-
siderable measure, on the difference in density between inshore and
offshore water. When the density difference is slight, the current
may frequently be sét onshore or offshore. The directions that it
takes will be dependent to a large degree on the bottom topography.
Frictional retardation by bottom particles in contact with a current
not only affect its velocity but also its direction. The tendency is

Figure 4.

for the normal twisting to the right (in the Northern Hemisphere)
to be accentuated as the current moves over a shoaling bottom and
to be lessened over a deepening bottom. Thus, when the water is

relatively homogeneous, it is common to find an inshore set towards
reefs and islets.

DENSITY AND SAFE CHANNEL DEPTHS

Density is an element which must be reckoned with when chan-
nel depths become a factor for entering port. The relation between
salt water loaded draft and required channel depth is a problem not
understood by all mariners. Several factors unite to increase the
channel depth requirements over the salt water loaded draft,
Figure 3.

As shown in the table, the salt water loaded draft for a 28,000
DWT vessel is approximately 33 feet 5 inches. Upon entering fresh
water a ship of that tonnage will sink approximately one quarter
inch for every foot of draft in salt water, or about 8 additional inches,
due to water density variation. In addition, to improve steering
characteristics she will be trimmed with a “drag” of approximately
3 inches for each hundred feet of length, or 1 foot 8 inches. A ves-
sel sets at a depth determined by the relation between her average
density and the density of the water she displaces. When underway,
however, a “bow wave” is formed which starts moving away. The
vessel itself moves forward steadily into the space previously occu-
pied by the wave. Hence, a vessel underway moves in an artificial
wave trough created by her own bow. She therefore rides some-
what lower than when at rest. This effect of depression varies
with speed and form of the hull. The effect is accentuated in shal-
low water, and when the vessel occupies a considerable part of the
channel cross-section the effect is greatly increased. When this is
the case, the water velocities alongside and under the vessel are

WATER DENSITY AND ITS APPLICATIONS

accelerated. The flow lines which this water follows interact with
the channel bottom and cause a marked increase in the “squat” or
“bottom effect”. A 2-foot minimum bottom clearance is a require-
ment for safety. This is a precaution for avoidance of screw dam-
age from sunken logs or other debris possibly carried into the chan-
nel. Further, it helps to minimize displacement of bottom sand by
the propeller, which might easily scoop out a foot or two of sand and
pile it up a short distance away to ground the next vessel passing.
It can therefore be seen that a 28,000 DWT supertanker or bulk
carrier with a 33-foot 5 inch sea water draft would require a 40-foot
channel for safe navigation in fresh water.

In actual practice of seamanship, mariners usually use the hy-
drometer for measuring the specific gravity or density of waters to
predict draft. The density of fresh water is 1000, and the average
density of sea water is about 1025 ounces to the cubic foot. In some
areas of exceedingly high salt content, such as the Suez Canal, the
hydrometer will often float at 1040 or even higher. The water used
for determining specific gravity should be drawn in a bucket from
over the ship’s side, well away from any overboard discharge pipes,
and its temperature immediately observed and recorded. The
instrument should be spun slightly in the center of the bucket so
that the scale will quickly loose any vertical motion, and be read
before the turning motion has entirely ceased.

Samples of the mechanics involved to determine draft frequently
found on U.S. Coast Guard examinations follow:

Problem:—Find the draft to which a ship must be loaded along-
side a pier where the density of the water is 1006, that she may float
at a draft of 20 feet in sea water.

Average density of sea water......... 1025
Wrattratiscamaserte serve ernie lols sie a _X20
Density of water at pier........ 1006) 20500 (20 feet

2012_

380

Inchesiper!footue. cco ees seme ee x12
Density of water at pier........ 1006) “4560 (4.5 inches

4024

5360

5030

330

Answer:—The ship must be loaded to draw 20 feet 4.5 inches.
Hence, she would rise 4.5 inches on passing into sea water.

Problem:—A vessel’s draft is 24 feet 6 inches at a dock where
the hydrometer floats at 10. What will be her draft when she gets
to sea where the hydrometer floats at 25?

Rule:—As the difference between salt water and fresh water is to
the difference between salt water and the water in which the ship

is being loaded, so is the allowance in fresh water to the required
allowance.
Solution:— As 1025: 1010:: 24 ft. 6 in.: draft at sea.
Draft at sea = 1010 x 24.5
1025
Densityzatepien 4a eeeeaeeeet
Drattga Gaplece serene
Density of sea water........ 1025) 24745 (24 ft.

4245

Imches}pemtooteeeeee eee eee eee x12
Density of sea water........ 1025) 1740
1025

7150
7175

Answer:—24 feet 1.7 inches

(1.7 inches

73

REQUIRED CHANNEL DEPTH

. Salt water loaded draft
. Added draft in fresh water

33 feet 5 inches
8 inches

. Drag (trim down at stern)

. Open water “squat” at 10 knots

. Added “bottom effect squat”

. Minimum safe bottom clearance

TOTAL CHANNEL DEPTH REQUIRED

Figure 3. Typical depth requirement.

DENSITY CURRENTS AND SILTATION

Density currents in relation to the siltation of docks are of prime
importance in many areas. An example of this is the siltation
problem in Queen Elizabeth II Dock on the River Mersey in England.
As shown in Figure 4, the lock and dock are alongside the Manchester
Ship Canal with the canal having separate entrance locks. The dock
is designed for the use of oil tankers and will accomodate ships of
650 feet in length. The lock connecting the dock with the River
Mersey is fitted with sliding caisson gates and prevents run-in at
spring tides. A typical salinity at high water springs is 26 parts
per thousand by weight (26 °/o. ) and the estuary tidal range at East-
ham is approximately 30 feet. Water levels in the Queen Elizabeth II
Dock as well as the Manchester Canal are maintained slightly above
the average of high water spring tides. Fresh water tributaries
constitute the primary source of water for the canal, supplemented
to some extent by run-in at high spring tides through the locks at
Eastham. Water level in the dock is maintained by the use of bal-
ancing culverts which supply water from the relatively fresh canal.
An average salinity in the dock is 21°/.o, about 5 °/o. less than that
in the estuary, but differences of up to 9°/oo have been noted.

The origin of siltation has two possibilities: from the balancing
culverts connected with the canal or through the lock connected
with the River Mersey. Investigation has proved, however, that a
negligible amount of silt enters from the canal.

Conditions outside the lock are very favorable to continuous silt
settlement from suspension. A mobile layer of unconsolidated silt
with very high concentrations of solids has frequently been ob-
served just outside the lock entrance. As the bed level of the
estuary in this proximity is somewhat higher than that of the lock
the mud layer gravitates, to some extent as a turbidity current,
into the lock when it is opened. The effect of differences in salinity
or density, however, is of somewhat greater interest. Locking op-
erations are normally undertaken during the period of high water.
However, this is also the time of the maximum difference in salinity
between the lock and estuary.

When the outer lock gate is opened, denser and more saline
water near the bed flows in carrying a large quantity of mud in high
concentration. Consequently, there is a corresponding outflow of
less saline and relatively clean water over the top of the more dense
water and into the estuary. On completion of this process, the outer
lock gate is closed and a similar condition develops when the inner
lock gate is opened into the dock. That is, silt is carried into the
dock by the strong in-flowing density current near the bed.

The rate of siltation in the dock varies from 3,000 to 8,000 cubic
yards per week. This high rate of siltation is further complicated
by the difficulties involved in using dredgers in an oil dock.

Several solutions have been suggested to help alleviate the situa-
tion. The most promising appears to be the use of vertical jets just
outside the outer lock gate. These jets would be brought into action
prior to the time the outer gate is opened. The mud lying in high
concentrations near the bed would be carried in suspension in the
upper layers of the water and, on opening the outer gate, would be
carried away from the lock by the out-flowing surface current.

The fluctuation of water density is the prime factor in the
siltation of tidal basins open to an estuary. Usually, the estuary
water is heavy with silt in suspension, concentrations being particu-
larly high in the lower layers during the early stages of flood tide.

WATER DENSITY AND ITS APPLICATIONS

Similar to the preceding example, the main in-flow takes place at
the bed with heavily silt-laden water being carried into a relatively
quiet basin, and deposition ensues naturally.

At sometime during the rising tide the salinity in the estuary
exceeds that of the basin, with salinity increasing continyously until
high water. This density difference tends to increase the inertia
forces and thus strengthens the silt-bearing flow into the basin.
Conversely, during the latter part of the ebb the salinity of the basin
exceeds that of the estuary and the out-flowing density current
assists the normal ebb flow from the basin. However, the total out-
flowing current is not sufficient to remove the silt deposited during
the rising tide.

DENSITY AND SUBMARINE APPLICATIONS

As an instrument designed for subsurface operation, submarines
are required to dive from the surface into deeper layers of water.
If the temperature and salinity of sea water were uniform from sur-
face to bottom, these operations would be relatively simple. These
two variables, however, change to cause varying densities which
complicate subsurface operation. Such a complication is the de-
crease in buoyancy of a submarine at great depths, caused by hull
compression. This must be compensated for by adjustments in bal-
last which the submarine must make under water. The presence of
a density gradient serves to complicate this adjustment.

In addition to this, strong density gradients may hamper the
ascent or descent of a submarine as well as impair the attempt to
remain in balance or trim at a particular depth. The effect of
density can very well be seen when one considers that a change in
density of 0.001 changes the buoyancy of a fleet-type submarine by
as much as 5,400 pounds. A change in salinity of one part per
thousand alters the density by 0.00078 and thus changes the buoyancy
of the submarine by 4,200 pounds. The role of density is of critical
importance in certain phases of submarine operations.

Early investigations of sound conditions in the oceans led to the
development of the bathythermograph, and it quickly became appar-
ent that the whole problem of sound transmission in sea water was
highly complex. Echo and listening ranges might be limited by any
one of half a dozen or more factors. Much research was necessary
before it was possible to devise a simple and accurate method of
translating the basic temperature-depth curve of the bathythermo-
graph into a practical prediction of sonar conditions.

74

Basically, bathythermograph literature is divided into two main
groups, prediction manuals and charts.

Prediction manuals are designed so the probable limits of sonar
ranges can be determined from any particular bathythermogram to
enable efficient tactical operations. The submariner obtains informa-
tion useful to him on the best depth for evasion, probable ping,
listening ranges, and the most efficient diving procedure. Perhaps
the most important use is for predicting ballast adjustments so that
diving can be accomplished as quietly as possible and with a mini-
mum of lost time.

The above-mentioned charts include sonar charts showing average
echo ranging conditions, average diving conditions, and bottom
sediment charts for shallow water sonar work. Charts on average
conditions are of less tactical value than a bathythermogram
obtained at the time and place needed because conditions are
generally too variable to permit accurate predictions on the basis of
averages. On the other hand, they provide a perspective unobtainable
from a small number of bathythermograms and hence are useful not
only to the observer for determining how often bathythermograph
readings should be made but also for more strategic purposes. It is
generally agreed that submarines can change depth more quickly
and more silently if the diving officer understands the changes in
density in the superficial layers of the ocean.

Maintaining efficient diving operations would be simple if the
buoyancy of sea water was uniform. Since it is not, the variations in
density that occur make each dive a separate problem requiring
slightly different tactics. For example, if the submarine is in trim
at periscope depth, its overall density is approximately the same as
that of the surrounding sea water. Consequently, it has no great
tendency either to rise or sink and such small movements as occur
are readily corrected with slight changes in the angle of the diving
planes. As the vessel travels at periscope depth it may move into
water of greater or lesser density. An increase in temperature makes
the water expand so that it is lighter. As density also depends on its
salt content, changes in density require reballasting to bring the
submarine back into trim. These lateral density changes are
relatively slight in most cases, however, and it requires no great
effort to keep the vessel on a horizontal course.

If a submarine in trim at periscope depth dives in water of
uniform density it gradually gets out of trim because the increasing
pressure at greater depths compresses the hull, making the submarine

WATER DENSITY AND ITS APPLICATIONS

less buoyant. Therefore, under these conditions, a submarine must
pump ballast during the dive in order to maintain trim. The amount
of water to be discharged depends on the size of the submarine and
on its compressibility, the latter varying with the type of construction
and, to a lesser extent, with individual vessels.

As previously pointed out, temperature may decrease from the
surface downward or in the water underlying a mixed surface layer.
With decreasing temperature the density would increase downward.
The sea may be thought of as a series of horizontal layers, one below
another, in which the density is either uniform or increases down-
ward by a greater or lesser amount.

A layer of increasing density gives a diving submarine more
support and tends to counteract the compression effect. It is
conceivable that the two effects may just balance, so that a diving
submarine will remain in trim all the way down. On the submarine
bathythermogram card, Figure 5, are printed isoballast lines, which
show the amount of temperature change with depth that will, by its
effect on the density of the water, exactly balance the compression
effect of a submarine of the type for which the card was prepared. In
any layer where the temperature-depth trace parallels the isoballast
lines, the diving submarine will remain in the same state of trim
throughout the layer. If the temperature is more nearly uniform, so
that the trace crosses the isoballast lines toward the right, a diving
submarine will get heavier and will have to discharge ballast to re-
gain trim. In a strong gradient that crosses toward the left, it will
be light and will have to flood ballast.

DEGREES FAHRENHEIT
30 40 50 60 7

30

OEPTH IN FEET

Figure 5. Submarine bathythermogram showing effect of
temperature gradients on ballasting operations.

DEGREES FAHRENHEIT
30. 40 50 60 70 80 90
T | ‘a y

OEPTH IN FEET

40

0 70 80

Figure 6. Submarine bathythermogram showing diving
operations in a mixed layer with an underlying
negative gradient.

75

It is common to find temperature conditions in the sea of the
kind shown in Figure 6, in which there is a surface layer of mixed
water and an underlying layer with a sharp decrease in temperature.
Suppose a submarine is in trim at periscope depth (Position A) and
makes a dive with no ballast changes. As it goes through the mixed
layer it gets heavier and sinks more rapidly. But the temperature
gradient below gives it more buoyancy again, and it finally comes
to trim at Position B, where the temperature trace intersects the
same isoballast line that passed through Position A. This is an
example of a very quick and efficient,dive that makes full use of
temperature and density conditions. It would be much less efficient
to dive in trim, discharging ballast while in the mixed layer, and
flooding again below it. However, if there were no temperature
gradient below the mixed layer, it would be more efficient, as well
as safer, to remain more or less in trim all the way down. Thus, the
correct diving procedure depends on knowledge of the vertical
temperature structure of the water. The above example is simplified
as it is not commonly possible to dive without making any ballast
changes at all. Nevertheless, the general principle holds in almost
any case. It is possible to dive more efficiently in water of known
temperature structure than in an unknown situation, because when
the diving officer knows the total amount of ballast change that will
be needed, he can make the proper adjustments at an even rate
through the entire operation. Hence, he will not be stopped by a
sharp density gradient or forced to increase the noise output of the
submarine in the effort to get through the layer. The time saved
during such a dive may be as much as 10 or 15 minutes.

To obtain proper knowledge of the temperature structure of the
water, it is necessary for the submarine to make frequent exploratory
dives. Density conditions are best coped with in an emergency if a
recent “BT” record is available. How often such dives are needed
depends on the variability of temperature conditions where the
submarine is operating.

The usefulness of density layers is too obvious to escape any
submariner. For them it is a fortunate coincidence that from both
the acoustic and diving standpoints density layers provide the best
possible protection in evasion. The so-called “layer effect” reduces
the echo and listening ranges. A submarine submerged well below
the top of a density layer is more difficult to detect. It is also
apparent that a submarine in the middle of such a layer requires little
effort to maintain constant depth. If it rises it will be in water of
less buoyancy and will tend to sink again. If it goes deeper it will
encounter more buoyant water. Hence, it is not only easy to maintain
quiet operation, creeping or balancing with the motor stopped, but
it is also easier to maintain control of the ship.

THE GULF STREAM

E. E. Watson
Queen’s University, Kingston, Ontario

Anyone who has sailed from the eastern coast of the United
States to Bermuda or the West Indies will recall the startling tran-
sition from the cold, dull coastal water to the deep blue waters
of the Gulf Stream. The air becomes warmer, and the breeze
freshens; the roll of the ship has increased, but, above all, one is
fascinated by the intense blue of the water. The white air-bubbles
along the ship’s sides and in its wake enhance the depth and purity
of the color. Something yellow is floating on the surface, and
as we come closer it turns out to be astray bit of Sargassum weed.
Soon we see more and more of this brightly colored weed, float-
ing in patches or in long streaks. Columbus thought this weed
grew on rocks or submarine ledges, and this idea persisted for a
long time, but we know now that it is a pelagic perennial which
grows fresh, greenish shoots at one end while withering to a
brown color at the other. It is kept afloat by berry-like bladders
which contain air. This Sargassum or gulf weed is found over
a large area of the North Atlantic, but does not reach the North
American coast. It is first noticed in any quantity as we approach
the Gulf Stream. The most marked characteristic of the Stream
is its blue color, flecked with the yellow of the weed, for there
are no “landmarks” at sea to tell the casual observer that he is
not only being driven through the water by the ship’s engines or
sails but is carried by the water itself in a northeasterly direction
at a speed which may be as great as 4 knots. For a modern
liner making 20 to 30 knots such a current is of no great impor-
tance, even though it may be about 60 miles wide, but for a sailing
vessel it was, and is, a serious navigational influence.

Owing to its effect on the course of ships, considerable knowl-
edge of the surface characteristics of the Stream has been accu-
mulated, but it is only in recent years that we have learned much
about its sources, the mechanism of its propulsion, and the trans-
fer of moisture and heat to and from the atmosphere above it.
Popular conceptions of the Gulf Stream are somewhat vague
and often incorrect. Along the Atlantic seaboard any unusual
weather condition is sure to be blamed on the Gulf Stream, espe-
cially a long hot spell such as was experienced in the summer of
1949. Since on the eastern side of a continent the weather
moves from land to sea, the oceanic conditions are more likely to
be influenced by the weather coming from the land than the other
way round.

HISTORY AND THE GULF STREAM

Before describing the Gulf Stream and its problems according
to modern oceanography, one may approach the subject from
an historical point of view. On Columbus’ first voyage in 1492,
when nearing the Bahamas, he was influenced by the flight of
birds (the fall migration by way of Bermuda to the West Indies)
to change his course from west to west-southwest. Had he not
done so his landfall would have been Eleuthera Island, and he
would have sailed through Providence Channel straight into the
Gulf Stream. He might then have made the coast of Florida or
have been swept along the coast of Georgia and the Carolinas,
if lucky enough to survive. There would have been no gold from
Hispaniola, and the history of the Spanish conquistadors in the
Caribbean might never have been written. It is a striking fact
that the eastern coast of the present United States was not dis-
covered by a direct voyage from Europe. In 1498 John Cabot
discovered Newfoundland and pushed southward around Cape
Breton. These explorations were continued by his son Sebastian,
but how far down the coast he penetrated is uncertain. Even
before the Cabots fishermen may have known the Nova Scotian
and New England shores, but they would have been interested in
the fishing banks rather than the shore, and hence disinclined to
publish their knowledge. Probably the first thorough exploration
of the coast was'‘carried out by Giovanni Verrazzani, a Florentine,
on behalf of Francis I of France. In considering the possible
effect of the Gulf Stream on the early explorations, it is worth
while to look at some of the details of Verrazzani’s voyage. He

76

left the isle of Madeira (which is almost at the same latitude as
Bermuda) in January 1524, and sailed due west. By 20 February,
a month later, he had traveled about 1,600 miles when he was
“overtaken by a tempest.’’ Unfortunately his account does not
state the direction in which he was blown nor the duration of
the tempest. After this he changed course to west by north, and
25 days and 1,300 miles later he discovered a new land. His land-
fall must have been near Charleston, S. C., or Savannah, Ga. This
means that he must have crossed the Gulf Stream where the
flow is rapid, so that he must have been carried north for ‘many
leagues.” It is hard to understand how he reached the coast at
the same latitude as his starting point, Madeira, unless his mid-
Atlantic storm carried him southward, though not so far as to
land him on the Bahamas. Verrazzani sailed up the coast as far
as Cape Breton, landing at many points. In 1562 Capt. John
Ribault, again on behalf of the French, sailed directly from the
Brittany coast to the west “to prove a new course which hath
not been yet attempted.” It was thought that this could not be
done, for lack of favorable winds, but Ribault wished to avoid the
more southerly route because of possible unpleasantness with the
Spaniards. He succeeded in reaching the coast of northern
Florida directly, but gives no details of his voyage. It is note-
worthy that none of these explorers knew that he had crossed the
Gulf Stream. No wonder the early maps of North America were
distorted!

Not until two centuries later do we find what is probably the first
scientific reference to the Gulf Stream. This occurs in a letter
sent by Benjamin Franklin to the secretary of the British Post
office,' much of which is quoted below:

Craven Street, October 29, 1769

Sir: Discoursing with Captain Folger . . . I received from him the
following information, viz.: . . . that the whales are found generally
near the edges of the Gulph Stream, a strong current so called, which
comes out of the Gulph of Florida, passing north-easterly along the
coast of America, and then turning off most easterly, running at the
rate of 4, 34, 3 and 2% miles an hour; that (people concerned in the
whale fishery) . . . cruise along the edges of the stream in quest of
whales ... ; that they have opportunities of discovering the strength
of it when their boats are out in pursuit of this fish, and happen to get
into the stream while the ship is out of it, or out of the stream while
the ship is in it, for then they are separated very fast, and would soon
lose sight of each other if care were not taken; that . . . they fre-
quently . . . speak with ships bound from England to New York,
Virginia, etc., . . . and it is supposed that their fear of Cape Sable
shoals, George’s Banks, or Nantucket shoals, hath induced them to keep
so far to the southward as unavoidably to engage them in the same
Gulph Stream, which occasions the length of their voyages, since . . .
the current being 60 or 70 miles a day, is so much subtracted from the
way they make through the water.

At my request Captain Folger hath been so obliging as to mark for
me on a chart the dimensions, course, and swiftness of the stream from
its first coming out of the Gulph . . .; and to give me withal some
written directions whereby ships bound from the Banks of Newfound-
land to New York may avoid the said stream, and yet be free of danger
from the banks and shoals above mentioned With much
esteem, I am, etc.

In a later paper, written in 1785, Franklin said that he had
been prompted to write this letter by the observation that the mail
packets from Falmouth to New York were generally a fortnight
longer in their passages than merchant ships from London to
Rhode Island. The chart referred to in his letter was ‘engraved
and copies were sent down to Falmouth for the captains of the
packets, who slighted it however.” It is amusing to note that
then, as now, sea captains were suspicious of any new scientific
procedure or information, particularly when coming from a
landsman, despite the fact that their navigation is entirely de-
pendent on accurate scientific instruments and calculations.

Carl Van Doren, ed., Benjamin Franklin's Autobiograhical Writings
(New York: The Viking Press, 1945), pp. 191-2.

THE GULF STREAM

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THE GULF STREAM

About a century later, in 1860, a map was published by Matthew
F. Maury, in his Physical Geography of the Sea, showing the cur-
rent system of the North Atlantic. It contains gross errors,
which must be attributed to his difficulty in obtaining information
from those seafarers who would have it. For instance, the
northern limit of the Gulf Stream is shown close to Cape Cod and
the Nova Scotia shore and above the Grand Banks, whereas it
never reaches George’s Bank, which lies to the east and south of
Cape Cod, nor does it ever flow onto the Grand Banks, a fact
which even then would be known to all fishermen in those regions.

A more accurate knowledge of the Gulf Stream was not ob-
tained until physical oceanography had been established as a
science in the present century. The real beginning of oceanog-
raphy was the Challenger expedition of 1872-76, but the cost of
oceanographic research has made progress very slow. As in
other branches of science a great impetus to development has come
with each war. After 1920 the technique of sounding was revo-
lutionized, with sonic depth finders replacing the old sounding
wire. During the second World War the bathythermograph for
temperature measurements became standard equipment for de-
stroyers and submarines, and submarine warfare in general made
it necessary to know what was happening within the ocean waters
as well as on their surface. Scientific explorations of the Gulf
Stream were initiated by the German and Norwegian oceanog-
raphers, but since the founding of the Woods Hole Oceanographic
Institution in 1930 by a Rockefeller endowment much more infor-
mation has been obtained about the Stream.

WHAT DRIVES THE GULF STREAM?

There are two major causes for the ocean currents in a large
basin such as the North Atlantic—unequal distribution of density
and the friction of the permanent wind systems. With the north-
east trade winds blowing across the southern part and the prevail-
ing westerlies across the northern part, one would expect that a
large clockwise circulation of the water would develop, provided
that no internal forces arose to prevent this motion. The friction
of the wind seems to be the most important factor in determining
the motion of this gigantic North Atlantic eddy, but the distribu-
tion of density complicates the details of the motion. Fresh
water is added to the surface by the great rivers, and more heat is
absorbed from the sun in the tropics than in higher latitudes.
The process of evaporation influences both salinity and tempera-
ture. When the sea surface is warmer than the air above, it loses
heat rapidly to the air and this air rises with turbulence, some-
times producing thunderstorms. But when the water is colder
than the air the reverse process does not take place, because the
air that is chilled does not rise and mix with that above it, so that
heat transfer downward is very slow and inefficient. Evaporation
utilizes heat while condensation releases heat. The greatest
evaporation occurs, not when the air is hot, but when cold air
flows over warm water. It may be surprising that in middle and
higher latitudes, where the sea surface in winter is warmer than
the air, the evaporation is greatest in the winter, not in the sum-
mer. This illustrates the intricate relationship between the phys-
ical conditions in the ocean waters and the meteorological condi-
tions. Two seasonal factors that influence the oceanic circulation
are the influx of cold but fresh water from the melting of ice in
the polar regions, and the winter cooling of the surface waters
along the coast, which so increases the density that the surface
water sinks and the whole column of water is overturned and
thoroughly mixed. To understand the structure of the Gulf
Stream it is necessary to look briefly at the dynamics of ocean
currents in general. Owing to the rotation of the earth, there is
an apparent force which tends to deflect a moving mass of water
to the right in the northern hemisphere. A steady state of flow
can be achieved only if there is a horizontal pressure-gradient to
oppose this, and in turn this pressure gradient can be produced
only by a distribution of density such that the lighter water is on
the right with the isobaric surfaces sloping upward to the right
of an observer looking in the direction of the stream. This means
that the ocean surface above a current is not level, but for a cur-
rent of 2 knots in latitude 45° the slope is only a rise of 1 centi-

79

meter in a distance of 1 kilometer, or one in 100,000.

With this background we may examine the Gulf Stream system,
first as regards its horizontal distribution and then its internal
structure. The North Equatorial Current is driven by the north-
east trades towards the Caribbean and joins a branch of the South
Equatorial Current which has crossed the Equator. Thus the
water entering the Caribbean contains some water of South At-
lantic origin, while the water flowing north of the Greater Antilles
is the same as that of the Sargasso Sea. The current driven
through the Yucatan channel has only one outlet, between Florida
and Cuba. This outflow is the genesis of the Gulf Stream system.
Only a negligible portion originates in the Gulf itself. The term
“Gulf Stream system” is now used to include the whole northward
and eastward flow beginning at the Straits of Florida and includ-
ing the various branches moving across the North Atlantic from
the region south of the Newfoundland Banks. The system is
subdivided into the following parts: (1) The Florida Current,
from the Straits of Florida to Cape Hatteras, where the current
swings outward from the continental slope. Beyond the straits
the water from the Yucatan channel is joined by the Antilles Cur-
rent, but the name Florida Current is retained up to the cape.
(2) The Gulf Stream from Cape Hatteras to a point east of the
Grand Banks at about longitude 45°, where the stream begins to
fork. This terminology is a restricted use of the popular term,
but is essential for clarity. (3) The North Atlantic Current,
from this point east and north, including the several] branches.
In this region the main current is often masked by erratic wind-
drift surface-movements, commonly known as the North Atlantic
Drift. The major branches are the Irminger Current, flowing
west below Iceland; the Norwegian Current flowing north
through the Norwegian Sea into the Polar Sea; and an irregular
branch which flows towards the Bay of Biscay. The Irminger
Current joins the East Greenland Current and can be detected by
its salinity (35 per mille?) as far south as Cape Farewell. The
Norwegian Current is warm enough to keep the port of Hammer-
fest, though well within the Arctic Circle, from ever being closed
by ice.

To return to the Florida Current: The energy of the flow is
derived from the difference in sea level between the Gulf and the
Atlantic coast, the difference being 19 centimeters between Cedar
Keys and St. Augustine (on opposite sides of Florida). This
difference of level is probably maintained by the trade winds.
Because of the flow through the straits the lighter water must be
found on the Cuban side and the sea surface there should be
higher. It is in fact about 45 centimeters higher, and the possi-
bility of direct measurement here corroborates our indirect meth-
ods of calculating velocities in the ocean from the distribution of
density. The direct current measurements of Pillsbury, made
from the survey vessel Blake in the years 1885-89, are among the
classical data of physical oceanography, since they provide a test
for indirect methods which can be applied elsewhere in the ocean.
The transport of water through the Straits of Florida is about 26
million cubic meters per second. On its left the shallow coastal
water is at rest and the transition to the blue water of the stream
is so sharp that it appears as a line from horizon to horizon. The
Antilles Current brings in about 12 million cubic meters per
second, and as the current moves toward Hatteras more water is
drawn in from the Sargasso on the right.

Beyond Hatteras the Gulf Stream swings away from the coast,
and on its left are the coastal waters over the shelf and a slope
water with temperatures of 4°-10° C. Here great seasonal vari-
ations occur, and eddies from the Gulf Stream intrude. Off Ches-
apeake Bay the transport of the stream has increased to about
75-90 million cubic meters per second, so that a great deal of
Sargasso water and deep water has been added, but at the tail of
the Grand Banks the transport has fallen off to less than 40 mil-
lion cubic meters per second, showing that water has been dis-
charged southward from the stream. The dynamics of this flow
are not properly understood, though several theories have been
propounded. An interesting point is that precise leveling along
the eastern coast shows that sea-level increases from Florida to

> 35 parts of salt in a thousand by weight.

THE GULF STREAM

Nova Scotia by 35 centimeters. There is a discrepancy between
the results of precise leveling and “oceanographic leveling” based
on the current and mass distribution: The piling up of water
along the coast takes place in the shallow coastal water only and
does not extend beyond the continental slope. At the edge of the
shelf the level sinks to the value suggested by the oceanographic
data, and consequently a current flows to the south along the con-
tinental slope, following the contour lines. This current, flowing
in the opposite direction to the Gulf Stream, lies between it and
the coast. At the tail of the Grand Banks the Gulf Stream comes
into close propinquity with the Labrador current, which flows
south past Newfoundland and on to the banks. The warm mois-
ture-laden air from over the Gulf Stream is chilled as it passes
over the cold surface water of the Labrador current, thereby pro-
ducing the abundance of fog for which the region is noted.

As to the internal structure of the Gulf Stream, the main char-
acteristic is that the stream is by no means a surface current, but

80

extends to great depths. The speed decreases from the surface
downward, but it is still significant at a depth of 1,500 meters
(nearly 5,000 feet). The flow of water in the surface layers is
only a small part of the total transport of the stream, and this fact
modifies the common concepts of the stream which are based on
surface phenomena. If we examine a vertical section of the
ocean from the eastern end of Long Island to Bermuda, we find
that at any level except near the surface, the temperatures rise as
we go across the stream. Thus at a depth of 500 meters (1,640
feet) the temperature rises from 6° to 16° C. This means that
the water which is moving rapidly, and which therefore consti-
tutes the stream, is on the average colder than the Atlantic water
on its right. The oceanographer may be forgiven if he dislikes
the popular concept of the Gulf Stream as a river of warm water
running through the ocean.

Copyright Queen's Quarterly 1950
(Reprinted from Queen's Quarterly, Vol. LVII, No. 1, 1950).