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[Number, 19; total area, 10,859 square miles.] 

National parks in 
order of creation. 


Area in 

Distinctive characteristics. 

Hot Springs 

Middle Arkansas 



Northwestern Wyo- 


Many hotels and boarding houses 20 bath- 
houses under public control. 

More geysers than in all rest of world together 


Middle eastern Cali- 


Boiling springs Mud volcanoes Petrified for- 
ests Grand Canyon of the Yellowstone, re- 
markable for gorgeous coloring Large lakes 
Many large streams and waterfalls Vast wil- 
derness, greatest wild bird and animal preserve 
in world Exceptional trout fishing. 

The Big Tree National Park 12 000 sequoia trees 


Middle eastern Cali- 


over 10 feet in diameter, some 25 to 36 feet in 
diameter Towering mountain ranges Start- 
ling precipices Cave of considerable size. 

Valley of world-famed beautv Lofty cliffs Ro- 

General Grant 


Middle eastern Cali- 


mantic vistas Many waterfalls of extraor- 
dinary height 3 groves of big trees High 
Sierra Waterwheel falls Good trout fishing. 

Created to preserve the celebrated General Grant 

Mount Rainier 

West central Wash- 


Tree, 35 feet in diameter 6 miles from Sequoia 
National Park. 

Largest accessible single peak glacier system 28 

Crater Lake 

Southwestern Oregon 


glaciers, some of large size 48 square miles of 
glacier, 50 to 500 feet thick Wonderful sub- 
alpine wild flower fields. 

Lake of extraordinary blue in crater of extinct 

Wind Cave 

South Dakota 


volcano Sides 1,000 feet high Interesting lava 
formations Fine fishing. 

Cavern having many miles of galleries and 


Southern Oklahoma 

numerous chambers containing peculiar forma- 

Many sulphur and other springs possessing 

Sullys Hill 

North Dakota 


medicinal value. 
Small park with woods, streams, and a lake Is 

Mesa Verde 

Southwestern Colo- 


an important wild-animal preserve. 
Most notable and best preserved prehistoric cliff 


Northwestern Mon- 

1 534 

dwellings in United States, if not in the world. 
Rugged mountain region of unsurpassed Alpine 


Rocky Mountain. . . 



North middle Colo- 




character 250 glacier-fed lakes of romantic 
beauty 60 small glaciers Precipices thou- 
sands of feet deep Almost sensational scenery 
of marked individuality Fine trout fishing. 

Heart of the Rockies Snowy range, peaks 11,000 
to 14,250 feet altitude Remarkable records of 
glacial period. 

Three separate areas Kilauea and Mauna Loa 


Lassen Volcanic... 

Mount McKinley . . . 

Grand Canyon 


Northern California. . . 
South central Alaska.. 

North central Arizona. 
Maine coast 




on Hawaii, Haleakala on Maui. 

Only active volcano in United States proper 
Lassen Peak 10,465 feet Cinder Cone 6,870 
feet Hot springs Mud geysers. 

Highest mountain in North America Rises 
higher above surrounding country than any 
other mountain in the world. 

The greatest example of erosion and the most 
sublime spectacle in the world. 

The group of granite mountains upon Mount 


Southwestern Utah. . . 


Desert Island. 
Magnificent gorge (Zion Canyon) depth frum 800 


to 2,000 feet, with precipitous walls Of great 
beauty and scenic interest. 

Bancroft Li 



United States Geological Survey. 

The purpose of this paper is not so much to elucidate any special 
problem connected with the many interesting geological questions to 
be found in the Yellowstone Park, as to offer such a general view of 
the region as will enable the tourist to understand clearly something of 
its physical geography and geology. 

The Yellowstone Park is situated in the extreme northwestern portion 
of Wyoming. At the time of the enactment of the law establishing this 
national reservation the region had been little explored, and its relation 
to the physical features of the adjacent country was little understood. 
Since that time surveys have shown that only a narrow strip about 2 
miles in width is situated in Montana and that a still narrower strip 
extends westward into Idaho. 

The area of the park as at present defined is somewhat more than 
3,300 square miles. 

The Central Plateau, with the adjacent mountains, presents a sharply 
defined region, in strong contrast with the rest of the northern Rocky 
Mountains. It stands out boldly, is unique in topographical structure, 
and complete as a geological problem. 

The central portion of the Yellowstone Park is essentially a broad, 
elevated, volcanic plateau, between 7,000 and 8,500 feet above sea level, 
and with an average elevation of about 8,000 feet. Surrounding it on 
the south, east, north, and northwest are mountain ranges with culmi- 
nating peaks and ridges rising from 2,000 to 4,000 feet above the general 
level of the inclosed table-land. 

For present purposes it is needless to confine ourselves strictly to legal 
boundaries, but rather to consider the entire region in its broader physical 

South of the park the Tetons stand out prominently above the sur- 
rounding country, the highest, grandest peaks in the northern Rocky 
Mountains. The eastern face of this mountain mass rises with unri- 
valled boldness for nearly 7,000 feet above Jackson Lake. Northward 



the ridges fall away abruptly beneath the lavas of the park, only the 
outlying spurs coming within the limits of the reservation. For the 
most part the mountains are made up of coarse crystalline gneisses and 
schists, probably of Archean age, flanked on the northern spurs by 
upturned Paleozoic strata. To the east of the Tetons, across the broad 
valley of the Upper Snake, generally known as Jackson Hole, lies the 
well-known Wind River Range, famous from the earliest days of the 
Rocky Mountain trappers. The northern end of this range is largely 
composed of Mesozoic strata, single ridges of Cretaceous sandstone pene- 
trating still farther northward into the regions of the park and protruding 
above the great flows of lava. 


Along the entire eastern side of the park stretches the Absaroka 
Range so called from the Indian name of the Crow Nation. The Absa- 
roka Range is intimately connected with the Wind River Range, the two 
being so closely related that any line of separation must be drawn more 
or less arbitrarily, based more upon geological structures and forms of 
erosion than upon physical limitations. 

The Absarokas offer for more than 80 miles a bold, unbroken barrier; 
a rough, rugged country, dominated by high peaks and crags from 10,000 
to 11,000 feet in height. The early trappers found it a forbidding land; 
prospectors who followed them, a barren one. 

At the northeast corner of the park a confused mass of mountains con- 
nects the Absarokas with the Snowy Range. This Snowy Range shuts 
in the park on the north and is an equally rough region of country, with 


elevated mountain masses covered \\ith snow the greater part of the 
year, as tin- name would indicate. Only the southern slopes, which rim 
in tlu- park region, come within the limit of our investigation. Here the 
rocks arc mainly granites, gneisses, and schists, the sedimentary beds, 
for the most part, referable to the pre-Cambrian series. 

The Gallatin Range incloses the park on the north and northwest. 
It lies directly west of the Snowy, only separated by the broad valley 
of the Yellowstone River. It is a range of great beauty, of diversified 
forms, and varied geological problems. Electric IVak, in the northwest- 
ern corner of the park, is the culminating point in the range, and affords 
one of the most extended views to be found in this part of the country. 



Archean gneisses form a prominent mass in the range, over which occur 
; ies of sandstones, limestones, and shales, of Paleozoic and Mesozoic 
age, representing Cambrian, Silurian, Devonian, Carboniferous, Trias, 
Jura, and Cretaceous. Immediately associated with these sedimentary 
beds, are large masses of intrusive rocks, which have- played an impor- 
tant part in bringing about the present structural features of the range. 
They are all of the andesitic type, but show considerable range in 
mineral composition, including pyroxene, hornblende, and hornblende- 
mica varieties. These intrusive masses are found in narrow dikes, in 
immense interbedded sheets forced between the different strata, and as 
laccolites, a mode of occurrence first described from the Henry Mountains 
in Utah, by Mr. G. K. Gilbert, but now well recognized elsewhere in the 
northern Cordillera. 


We see then that the Absarokas rise as a formidable barrier on the east- 
ern side of the park, the Gallatins as a steep mural face on the west side, 
while the other ranges terminate abruptly, rimming in the park on the 
north and south, and leaving a depressed region not unlike the parks of 
Colorado, only covering a more extended area with a relatively deeper 
basin. The region has been one of profound dynamic action, and the 
center of mountain building on a grand scale. 

It is not my purpose at the present time to enter upon the details of 
geological structure of these ranges, each offering its own special study 
and field of investigation. My desire is simply to call attention to their 
general features and mutual relations. So far as their age is concerned, 
evidence goes to show that the action of upheaval was contemporaneous 
in all of them, and coincident with the powerful dynamic movements 
which uplifted the north and south ranges, stretching across Colorado, 
Wyoming, and Montana. This dynamic movement blocked out, for 
the most part, the Rocky Mountains, near the close of the Cretaceous, 
although there is good reason to believe that in this region profound 
faulting and displacement continued the work of mountain building well 
into the Middle Tertiary period. 

Throughout Tertiary time in the park area, geological history was char- 
acterized by great volcanic activity, enormous volumes of erupted mate- 
rial being poured out in the Eocene and Middle Tertiary, continuing with 
less force through the Pliocene, and extending into Quaternary time. 
Within very recent times there is no evidence of any considerable out- 
burst; indeed the region may be considered long since extinct. These 
volcanic rocks present a wide range in chemical and mineral composi- 
tion and physical structure. They may all, however, be classed under 
three great groups andesites with basalts, rhyolites, and basalts fol- 
lowing each other in the order named. In general, the relative age 
of each group is clearly and sharply defined, the distribution and mode 
of occurrence of each presenting characteristics and salient features fre- 
quently marked by periods of erosion. 

Andesites are the only volcanic rocks which have played an important 
part in producing the present structural features of the mountains sur- 
rounding the park. As already mentioned, they occur in large masses in 
the Gallatin Range, while most of the culminating peaks in the Absarokas 
are composed of compact andesites and andesitic breccias. On the other 
hand, the andesites are not confined to the mountains, but played an 
active role in filling up the interior basin. That the duration of the 
andesitic eruptions was long continued is made evident by the plant 
remains found in ash and lava beds through 2,000 feet of volcanic 

In early Tertiary times, a volcano burst forth in the northeast corner 
of this depressed area not far from the junction of the Absaroka and 
Snowy Ranges. While not to be compared in size and grandeur with the 


volcanoes of California and the Cascade Range, it is, for the Rocky 
Mountains, one of no mean proportions. It rises from a base about 
6,500 feet above sea level, the culminating peak attaining an elevation of 
10,000 feet. This gives a height to the volcano of 3,5<x> iVrt from base- 
to summit, measuring from the Archean rocks of the Yellowstone Valley 
to the top of Mount Washburn. The average height of the crater rim is 
about 9,000 feet above sea level, the volcano measuring 15 miles across 
the base. The eruptive origin of Mount Washburn has long been recog- 
nized, and it is frequently referred to as a volcano. It is however simply 
the highest peak among several others, and represents a later outburst 
which destroyed in a measure the original rim and form of an older 
crater. The eruptions for the most part were basic andesites. Erosion 
has so worn away the earlier rocks, and enormous masses of more recent 
lavas have so obscured the original form of lava flows, that it is not easy 
for an inexperienced eye to recognize a volcano and the surrounding peaks 
as the more elevated points in a grand crater wall. By following around 
on the ancient andesitic rim, and studying the outline of the old crater, 
together with the composition of its lavas, its true origin and history may 
readily be made out. It has been named the Sherman volcano. This 
old volcano of early Tertiary time occupies a prominent place in the 
geological development of the park, and dates back to the earliest out- 
bursts of lava which have in this region changed a depressed basin into 
an elevated plateau. We have here a volcano situated far inland, in an 
elevated region, in the heart of the Rocky Mountains. It lies on the 
eastern side of the continent, only a few miles from the great Continental 
Divide, which sends its waters to both the Atlantic and Pacific. 

After the dying out of the andesitic and basaltic lavas, followed by a 
period of erosion, immense volumes of rhyolite were erupted, which not 
only threatened to fill the crater but to bury the outer walls of the vol- 
cano itself. On all sides the andesitic slopes were submerged beneath the 
rhyolite to a height of from 8,000 to 8,500 feet. This enormous mass of 
rhyolite, poured out after the close of the andesitic period, did more than 
anything else to bring about the present physical features of the park table- 
land. A tourist visiting all the prominent geyser basins, hot springs, Yel- 
lowstone Lake, and the Grand Canyon and Falls of the Yellowstone, is not 
likilv to come upon any other rock than rhyolite, excepting, of course, 
deposits from the hot springs, unless he ascends Mount Washbuni, A 
description of the rhyolite region is essentially one of the Central Plateau. 
Taking the bottom of the basin at 6,500 feet above sea level, these acidic 
lavas were piled up until the accumulated mass measured 2,000 fee t in 
thickness. It completely encircled the Gallatin Range, burying its lower 
slopes on both the east and west sides; it banked up all along the \YI-M 
flanks of the Absarokas, and buried the outlying spurs of the Teton and 
the Wind River Plateaus. 


The Central Plateau covers an area approximately 50 by 40 miles, with 
a mean altitude of 8,000 feet. It is accidented by undulating basins of 
varied outline and scored by deep canyons and gorges. Strictly speak- 
ing, it is not a plateau ; at least it is by no means a level area, but a rugged 
country, characterized by bold escarpments and abrupt edges of mesa- 
like ridges. But few large vents or centers of volcanic activity for the 
rhyolite have been recognized, the two principal sources being the vol- 
cano to which reference has already been made and Mount Sheridan in 
the southern end of the park. Mount Sheridan is the most commanding 
peak on the plateau, with an elevation 10,385 feet above sea level and 
2,600 feet above Heart Lake. From the summit of the peak on a clear 
day one may overlook the entire plateau country and the mountains 
which shut it in, while almost at the base of the peak lie the magnificent 
lakes which add so much to the quiet beauty of the region, in contrast 
to the rugged scenery of the mountains. From no point is the magni- 
tude and grandeur of the volcanic region so impressive. The lava flows 
bounded on the east by the Absarokas extend westward not only across 
the park, but across the Madison Plateau, and out on to the great plains of 
Snake River, stretching far westward almost without a break in the con- 
tinuity of eruptive flows. Over the central portion of the park, where 
the rhyolites are thickest, erosion has failed to penetrate to the under- 
lying rock. Even such deep gorges as the Yellowstone, Gibbon, and 
Madison Canyons have nowhere worn through these rhyolite flows. In 
the Grand Canyon of the Yellowstone the andesitic breccias are found 
beneath the rhyolites, but the deepest cuts fail to reveal the underlying 
sedimentary beds. Although the rocks of the plateau for the most part 
belong to one group of acidic lavas, they by no means present the 
great uniformity and monotony in field appearance that might be ex- 
pected. These 2.000 square miles offer as grand a field for the study of 
structural forms, development of crystallization, and mode of occur- 
rence of acidic lavas as can be found anywhere in the world. They 
vary from a nearly holocrystalline rock to one of pure volcanic glass. 
Obsidian, pumice, pitchstone, ash, breccia, and an endless development 
of transition forms alternate with the more compact lithoidal lavas 
which make i'r> the great mass of the rhyolite, and which in colors, 
texture, and structural developments present an equally varied aspect. 
In mineral composition these rocks are simple enough. The essential 
minerals are orthoclase and quartz, with more or less plagioclase. 
Sanidine is the prevailing feldspar, although in many cases plagioclase 
forms occur nearly as abundantly as orthoclase. Chemical analyses, 
whether we consider the rocks from the crater of Mount Sheridan, the 
summit of the plateau, or the volcanic glass of the world-renowned 
Obsidian Cliff, present comparatively slight differences in ultimate com- 


I have dwelt SOUK what in detail upon the nature of these rocks for 
two reasons: First, because of the difficulty met with by the scientific 
traveler in recognizing the uniformity and simplicity of chemical com- 
position of the rhynlite magma over the entire plateau, owing to its 
great diversity in superficial habit; second, on account of their geolog- 
ical importance in connection with the unrivaled display of the gey- 
sers and hot springs. That the energy of the steam and thermal 
waters dates well back into the period of volcanic action, there is in 
my opinion very little reason to doubt. As the energy of this under- 
ground heat is to-day one of the most impressive features of the 
country, I will defer commenting upon the .geysers and hot springs 
until speaking of the present condition of the park. 


Although the rhyolite eruptions were probably of long duration and 
died out slowly, there is, I think, evidence to show that they occupied 
a clearly and sharply defined period between the andesites and late basalt 
eruptions. Since the outpouring of this enormous mass of rhyolite 
and building up of the plateau, the region has undergone faulting and 
displacement; immense blocks of lava have been lifted bodily, and the 
surface features of the country have been modified. Following the rhy- 
olite came the period of late basalt eruptions, which, in comparison with 
the andesite and rhyolite eras, was, so far as the park was con- 
cerned, insignificant, both as regards the area covered by the basalt 
and its influence in modifying the physical aspect of the region. The 
basalt occurs as thin sheets overlying the rhyolite and in some 
937 20 2 


instances as dikes cutting the more acidic rocks. It has broken out 
near the edge of the rhyolite body and occurs most frequently along the 
Yellowstone Valley, along the western foothills of the Gallatin Range 
and Madison Plateau, and again south of the Falls River Basin. 

After the greater part of the basalt had been poured out came the 
glacial ice, which widened and deepened the preexisting drainage 
channels, cut profound gorges through the rhyolite lavas and modeled 
the two volcanoes into their present form. Over the greater part of the 
Cordillera of the central and northern Rocky Mountains, wherever the 
peaks attain a sufficiently high altitude to attract the moisture-laden 
clouds, evidences of the former existence of local glaciers are to be 
found. In the Teton Efange several well-defined characteristic glaciers 
still exist upon the abrupt slopes of Mount Hay den and Mount Moran. 
They are the remnants of a much larger system of glaciers. The park 
region presents so broad a mass of elevated country that the entire 
plateau was, in glacial times, covered with a heavy capping of ice. 
Evidences of glacial action are everywhere to be seen. 

Over the Absaroka Range glaciers were forced down into the Lamar 
and Yellowstone Valleys, thence westward over the top of Mount Everts 
to the Mammoth Hot Springs Basin. On the opposite side of the park 
the ice from the summit of the Gallatin Range moved eastward across 
Swan Valley and passing over the top of Terrace Mountain joined the 
ice field coming from the east. The united ice sheet plowed its way 
northward down the valley of the Gardiner to the Lower Yellowstone, 
where the broad valley may be seen strewn with the material trans- 
ported from both the east and west rims of the park. 

Since the dying out of the rhyolite eruptions erosion has greatly modi- 
fied the entire surface features of the park. Some idea of the extent 
of this action may be realized when it is recalled that the deep canyons 
of the Yellowstone, Gibbon, and Madison Rivers canyons in the strictest 
use of the word have all been carved out since that time. To-day 
these gorges measure several miles in length and from i ,000 to i ,500 feet 
in depth. 

To the geologist one of the most impressive objects on the park pla- 
teau is a transported bowlder of granite which rests directly upon the 
rhyolite near the brink of the Grand Canyon, about 3 miles below the 
falls of the Yellowstone. It stands alone in the forest, a long way from 
the nearest glacial bowlder. Glacial detritus carrying granitic material 
may be traced upon both sides of the canyon wall. This massive block, 
although irregular in shape and somewhat pointed toward the top, 
measures 24 feet in length by 20 feet in breadth and stands 18 feet above 
the base. The nearest point from which it could have been transported 
is distant 30 or 40 miles. Coming upon it in the solitude of the forest 
with all its strange surroundings it tells a most impressive story. In 


no place are tin evidences of frost and fire brought so forcibly together 
as in tlu Yellowstone National Park. 

Since the close of the ice period no geological events of any moment 
have brought about any changes in the physical history of the region 
other than those produced by the direct action of steam and thermal 
waters. A few insignificant eruptions have probably occurred, but they 
failed to modify the broad outlines of topographical structure and pre- 
sent but little of general interest beyond the evidence of the continu- 
ance of volcanic action into quaternary times. Volcanic activity in the 
park may be considered as long since extinct. At all events indications 
of fresh lava flows within historical times are wholly wanting. This 


is not without ink-rest, as evidence of underground heat may be ob- 
served everywhere throughout the park in the waters of the geysers 
and hot springs. All our observations point in one direction and lead 
to the theory that the cause of the high temperatures of these waters 
must be found in the heated rocks below, and that the origin of the 
heat is in some way associated with the source of volcanic energy. It 
by no means follows that the waters themselves are derived from any 
deep-seated source; on the contrary, investigation tends to show that 
the waters brought up by the geysers and hot springs are mainly sur- 
face waters which have percolated downward a sufficient distance to 
become heated by large volumes of steam ascending through fissures 
and vents from much greater depths. If this theory is correct it is but 


fair to demand that evidence of long-continued action of hot waters 
and superheated steam should be apparent upon the rocks through 
which they passed on their way to the surface. This is precisely what 
one sees in innumerable places on the Central Plateau. Indeed, the 
decomposition of the lavas of the rhyolite plateau has proceeded, on a 
most gigantic scale, and could only have taken place after the lapse of 
an enormous period of time and the giving off of vast quantities of heat, 
if we are to judge at all by what we see going on around us to-day. The 
ascending currents of steam and hot water have been powerful geo- 
logical agents, and have left an indelible impression upon the surface 
of the country. The most striking example of this action is found in 
the Grand Canyon of the Yellowstone. From the Lower Falls for 3 miles 
down the river abrupt walls upon both sides of the canyon, a thousand 
feet in depth, present a brilliancy and mingling of color beyond the 
power of description. From the brink of the canyon to the water's 
edge the walls are sheer bodies of decomposed rhyolite. Varied hues 
of orange, red, purple, and sulphur-yellow are irregularly blended in one 
confused mass. There is scarcely a piece of unaltered rock in place. 
Much of it is changed into kaolin; but from rhyolite, still easily re- 
cognized, occur transition products of every possible kind to good porce- 
lain clay. This is the result of the long-continued action of steam and 
vapors upon the rhyolite lavas. Through this mass of decomposed 
rhyolite the course of ancient steam vents in their upward passage may 
still be traced, while at the bottom of the canyon hot springs, fumaroles, 
and steam vents are still more or less active, but probably with dimin- 
ished power. 

Still other areas are quite as convincing, if not on so grand a scale, 
as the Yellowstone Canyon. Josephs Coat Basin, on the east side of 
the canyon, and Brimstone Hills, on the east side of the Yellowstone 
Lake, an extensive area on the slopes of the Absaroka Range, both 
present evidences of the same chemical processes brought about in the 
same manner. It is not too strong a statement to make to say that the 
plateau on the east side of the Grand Canyon, from Broad Creek to 
Pelican Creek, is completely undermined by the action of superheated 
steam and alkaline waters on the rhyolite lava. Similar processes may 
be seen going on to-day in all the geyser basins. A long period of time 
must have been necessary to accomplish these changes. The study of 
comparatively fresh vents shows almost no change from year to year, 
although careful scrutiny during a period of five years detects a certain 
amount of disintegration, but infinitely small in comparison with the 
great bodies of altered rock. This is well shown in a locality like the 
Monarch Geyser in the Norris Geyser Basin, where the water is thrown 
out at regular intervals through a narrow fissure in the rock. 

The Grand Canyon of the Yellowstone offers one of the most impres- 
sive examples of erosion on a grand scale within recent geological times. 


It is self-evident that the deep canyon must be of much later origin than 
UK- rock through which it has been worn, and it seems quite clear that 
the course and outlines of the canyon were in great part determined by 
the easily eroded decomposed material forming the canyon walls, and 
this in turn was brought about by the slow processes just described. 

The evidence of the antiquity of the hot spring deposits is, perhaps, 
shown in an equally striking manner and by a wholly different process 
of geological reasoning. Terrace Mountain is an outlying ridge of the 
rhyolite plateau just west of the Mammoth Hot Springs. It is covered 
on the summit with thick beds of travertine, among the oldest portions 
of the Mammoth Hot Springs deposits. It is the mode of occurrence 
of these calcareous deposits from the hot waters which has given the 
name to the mountain. Lying upon the surface of this travertiqe on 
the top of the mountain are found glacial bowlders brought from the 
summit of the Gallatin Range, 15 miles away, and transported on the 
ice sheet across Swan Valley and deposited on the top of the mountain, 
700 feet above the intervening valley. It offers the strongest possible 
evidence that the travertine is older than the glacier which has strewn 
the country with transported material. How much' travertine was 
eroded by the ice is, of course, impossible to say, but so friable a material 
would yield readily to glacial movement. 

Still another method of arriving at the great antiquity of the thermal 
energy and the age of the hot spring formation is by determining the 
rate of deposition and measuring the thickness of the accumulated sinter. 
This method, although the one which would perhaps first suggest itself, 
is, in my opinion, by no means as satisfactory as the geological reasoning 
already given. It is unsatisfactory because no uniform rate of deposi- 
tion can be ascertained for even a single area, like the Upper Geyser 
Basin, and it is still more difficult to arrive at any conclusion as to the 
growth of the sinter in the past. Moreover, it is quite possible that 
heavy deposits may have suffered erosion before the present sinter was 
laid down. It however corroborates other methods and possesses the 
advantage of being a direct way. 

It may be well to add that there exists the greatest contrast between 
the deposits of the Mammoth Hot Springs and those found upon the 
plateau. At the Mammoth Springs they are nearly pure travertin*., 
with only a trace of silica, analyses showing from 95 to 99 per cent of 
calcium carbonate. On the plateau, the deposits consist for the most 
part of siliceous sinter, locally termed "geyserite." The reason for the 
difference is this: At the Mammoth Hot Springs the steam, although 
ascending from fissures in the igneous rock, comes in contact with i he- 
waters found in the Mcsozoic strata, which here form the surface rocks. 
The Jura or Cretaceous limestones have furnished the lime held in solu- 
tion and precipitated on the surface as travertine. On the other hand, 
the mineral constituents of the plateau waters are derived almost 


exclusively from the highly acidic lavas, which carry but a small 
amount of lime. 

Deposition of sinter from the hot waters of the geyser basins depends 
in a great measure on the amount of silica held in solution, which varies 
considerably at the different localities and may have varied still more 
in past time. The silica, as determined by analyses, ranges from 0.22 
to 0.60 grammes per kilogram of water, the former being the amount 
found in the water of the caldron of the Excelsior Geyser and the latter 
at the Coral Spring in the Norris Basin. Analysis shows that from 
one-fifth to one-third of the mineral matter held in solution consists of 
silica, the remaining constituents being readily soluble salts carried off 
by surface drainage. A few springs highly charged with silica, like the 
Coral, deposit it on the cooling of the waters; but such springs are 
exceptional. At most springs and geysers it results after evaporation, 
and not from mere cooling of the water. It seems probable that the 
nature and amount of alkaline chlorides and carbonates present influ- 
ence the separation of silica. Temperature also may in some degree 
influence the deposition. My friend, Mr. Elwood Hofer, has called my 
attention to an observation of his made in midwinter, while on one of 
his snowshoe trips through the park. He noticed that certain over- 
flow pools of spring water, upon being frozen, deposited a considerable 
amount of mineral matter. He has sent me specimens of this material, 
which, upon examination, proved to be identical with the silica depos- 
ited from the Coral Spring upon the cooling of the water. Demijohns of 
geyser water which have been standing for one or two years have failed 
to precipitate any silica. Quite recently, in experimenting upon these 
waters in the laboratory, it was noticed that on reducing them nearly 
to the freezing point no change took place, but upon freezing the waters 
there was an abundant separation of free silica. The waters frozen in 
this way were collected from the Coral Spring. Xorris I'.asin. and the 
Taurus Geyser, Shoshone Basin. 

Again, there is no doubt that the algous growths flourishing in the hot 
waters of the park favor the secretion of silica and calcic carbonate and 
exert a potent influence in building up both the sinter and travertine 
deposits far greater than one might at first be led to suppose. These 
processes of assimilation are steadily taking place without interruption, 
as all algae act as geological agents. The silica and lime brought to the 
surface by hot springs is, upon the death of the algae, transformed into 
sinter and travertiiu-. becoming rock masses, which later show scarcrlv 
any sign of their origin from plant life. Tourists are seldom aware that 
the harmonious and brilliant tints are due to vegetable growths. 
<U -velop equally \\vll in the waters of all basins and upon the 

Urnuvs of Mammoth Hot Springs. \VaU-r boils in tin- t'pjx i G 
r..sin at 198 F., and rudimentary organisms appear at about 185 F., 
although no definite line can be drawn beyond which all life ceases. 



These low vegetable organisms occur in nearly all pools, springs, and 
running water upon the plateau. Wherever boiling waters cool to the 
latter temperature algae make their appearance, and with the lowering of 
temperature on exposure to air still more highly organized forms gradually 
come in. It is believed that at about 140 F. conditions are favorable 
for a rapid development of numerous species. Many forms of algae 
flourish within restricted ranges of temperature, and the different species 
possess characteristic colors and habits of growth dependent upon such 
changes of temperature. After a little experience it is quite possible, 
upon noting the nature of the plant life, to make a sure guess as to the 
temperature of the water in which the species grow. As water in the 
geyser pools and caldrons frequently stands at or near the boiling point, 
no life exists at the centers of discharge, but with a rapid lowering of 


temperature algae appear, with corresponding changes of color, in the 
shallow pools and overflow channels. In the geyser basins the first 
evidence of vegetation in an overflow stream consists of creamy white 
filamentary threads, passing into light flesh tints, then to deep salmon. 
With distance from the source of heat the prevailing colors pass from 
bright orange to yellow, yellowish green, and emerald, and in the still 
cooler waters various shades of brown. This, of course, is a simple stats- 
ment of phenomena which really display highly complex conditions. 
No two pools or overflow channels are quite alike in their occurrence 
either as regards flow of water or development of algae. 

Several methods have been devised for ascertaining the growth of 
deposition of the geyserite. One way is by allowing the water to trickle 
over twigs, dried grasses, or almost anything exposing considerable 


surface, and noting the amount of incrustation. This way gives the most 
rapid results, but is far from satisfactory and by no means reproduces 
the conditions existing in nature. Other methods employed are placing 
objects on the surface of the water or, still better, partially submerging 
them in the hot pools, or again by allowing the water to run down an 
inclined plane with frequent intervals for evaporation and concentration. 
The vandals who delight to inscribe their names in public places have 
invaded the geyser basins in large numbers and left their addresses upon 
the geyserite in various places. It is interesting to note how quickly 
these inscriptions become indelible by the deposition of the merest film 
of silica upon the lead-pencil marks, and, at the same time, how slowly 
they build up. Names and dates known to be 6 and 8 years old remain 


perfectly legible, and still retain the color and luster of the graphite. 
That there is some increase in the thickness of the incrustation is evident, 
although it grows with incredible slowness. Mr. Weed tells me that he 
has been able, in at least one instance, to chip off this siliceous film and 
reproduce the writing with all its original distinctness, showing conclu- 
sively that a slow deposition has taken place. Pencil inscriptions upon 
the siliceous sinter at Rotomahana Lake, in New Zealand, are said to be 
legible after the lapse of 20 or 30 years. It is easy to see that various 
ingenious devices might be planned to estimate- the rate of deposition, 
but in my opinion none of them equal a close study of the conditions 
found in nature, especially where investigations of this kind can be 
watched from year to year. All observations show an rxcrnlin^lv slow 
building up of the geyserite formation. This is well seen in the repair 



going on where the rims surrounding the hot pools have been broken 
down, and where it might be supposed that the building-up process was 
under the most favorable conditions; yet, in a number of instances, I can 
see no appreciable change in three or four years. Revisiting hot springs 
in out-of-the-way places after several years' absence, I am surprised to see 
that objects that I had noted carefully at the time remain unchanged. 
Taking the entire area of the Upper Geyser Basin covered by sinter, I 
believe that the development of the deposit does not exceed one-thirtieth 
of an inch a year, and this estimate I believe to be much nearer the 
maximum than the minimum rate of growth. Supposing the deposit 
around Castle Geyser to have been built up with the same slowness as 


observed to-day, and assuming it to grow at the rate given one-thirtieth 
of an inch a year it would require over 25,000 years to reach its present 
development. This gives us a great antiquity for the geyserite, but I 
believe that the deposition of the siliceous sinter in the park has been 
going on for a still longer period of time. It is certain that the decom- 
position of the rhyolite of the plateau dates still further back. 

From a geological point of view, there is abundant evidence that ther- 
mal energy is gradually becoming extinct. Tourists revisiting the park 
after an absence of two or three years occasionally allude to the springs 
and geysers as being less active -than formerly and as showing indica- 
tions of rapidly dying out. It is true that slight changes are constantly 
taking place, that certain springs become extinct or discharge less water, 


but this action is fully counterbalanced by increased activity in other 
localities. Close examination of the source of the thermal waters fails 
to detect any diminution in the supply. Moreover, it stands to reason 
that if the flow of these waters dated geologically speaking far back 
into the past, the few years embraced within the historical records of 
the park would be unable to indicate any perceptible change based upon 
a gradual diminution of the heat. 

The number of geysers, hot springs, mudpots, and paintpots scat- 
tered over the park exceeds 3,000, and if to these be added the fumaroles 
and solfataras, from which issue in the aggregate enormous volumes of 
steam and acid and sulphur vapors, the number of active vents would 
in all probability be doubled. Each one of these vents is a center of 
decomposition of the acid lavas. The following list comprises the prin- 
cipal geysers known in the Norris, Lower, and Upper Geyser Basins. 


Black Growler, 






Minute Man, 
Monarch , 

New Crater, 





Great Fountain, 

Pink Cone, 

White Dome, 
Young Hopeful. 





Bee Hive, 










A comparative study of the analyses of the fresh rhyolite, the various 
transition products, and the thermal waters points clearly to the fact 
that the solid contents of these waters are derived for the most part from 
the volcanic rocks of the plateau. During the progress of tin \\ork of 
the Geological Survey in the Yellowstone Park tin-re have been collected 
from many of the more important localities samples of the waters, which 
have been subjected to searching chemical analyses in the laboratory of 
the survey, by Messrs. F. A. Gooch and J. E. Whittle 11 

Cub (Big), 



Cub (Little), 










Old Faithful, 



















They are all siliceous alkaline waters holding the same mineral con- 
stituents, but in varying qualities. Silica forms the principal deposit, 
not only immediately around the springs but over the entire floor of 
the basins. The carbonates, sulphates, chlorides, and traces of other 
easily soluble salts are carried off in the waters. Oxides of iron and 
manganese and occasionally some calcite occur under certain conditions 
in the caldrons of the hot springs or immediately around their vents. 
Concentrations from large quantites of these waters fail to show the 
presence of even a trace of copper, silver, tin, or other metal. Nearly 
all the waters carry arsenic, the amount present, according to Messrs. 
Gooch and Whitfield, varying from 0.02 to 0.25 per cent of the mineral 
matter in solution. 

Among the incrustations found at several of the hot springs and geysers 
is a leek-green amorphous mineral, which proves on investigation to be 
scorodite, a hydrous arseniate of iron. The best occurrence observed is 
at Josephs Coat Springs, on the east side of the Grand Canyon of the 
Yellowstone, where it occurs as a coating upon the siliceous sinter lining 
the caldron of a boiling spring. Analysis shows a nearly pure scoro- 
dite, agreeing closely with the theoretical composition: 

Ferric oxide 34-94 

Arsenic acid 48. 79 

Water 16. 27 


Alteration of the scorodite into limonite takes place readily, which in 
turn undergoes disintegration by the wearing of the water, and is mechani- 
cally carried away. So far as I know, this is the only occurrence where 
scorodite has been recognized as deposited from the waters of thermal 
springs. Although pure scorodite is only sparingly preserved at a few 
localities in the Yellowstone Park, it is easily recognized by its charac- 
teristic green color, in strong contrast with the white geyserite and yellow 
and red oxides of iron. After a little practice the mineral green of scoro- 
dite is not easily mistaken for the vegetable green of the algeous growths. 
The latter is associated everywhere with the hot waters, while the former, 
a rare mineral, is obtained only in small quantities after diligent search. 
In America traces of arsenic have been reported from several springs in 
Virginia, and quite recently sodium arseniate has been detected in the 
hot springs of Ashe County, N. C. Arsenical waters of sufficient strength 
to be beneficial for remedial purposes and not otherwise deleterious are 
of rare occurrence. In France the curative properties of arsenical waters 
have been long recognized, and the famous sanitarium of La Bourboule, 
in the volcanic district of the Auvergne, has achieved a wide reputation 
for the efficacy of its waters in certain forms of nervous diseases. Hy- 
geia Springs carries 0.3 of a grain of sodium arseniate to the gallon. The 
Yellowstone Park waters, while they carry somewhat less arsenic than 
those of La Bourboule, greatly exceed the latter in their enormous 


overflow. . It is stated that the entire discharge from the springs of La 
Bourboule amounts to 1,500 gallons per minute. The amount of hot 
water brought to the surface by the hot springs throughout the park is by 
no means easily determined, although during the progress of investigations 
I hope to make an approximate estimate. According to the most accu- 
rate measurements which could be made, the discharge from the caldron 
of the Excelsior Geyser amounted to 4,400 gallons of boiling water per 
minute. The sample of the Excelsior Geyser water collected August 
25, 1884, yielded 0.19 grain of sodium arsenate to the gallon. It is 
impossible to say as yet what curative pioperties these park waters may 
possess in alleviating the ills of mankind. Nothing but an extended 
experience under proper medical supervision can determine. 

Changes modifying the surface features of the park in recent times are 
mainly those resulting from the filling up with detrital matenal of the 
valleys and depressions worn out by glacial ice, and those produced by 
the prevailing climatic conditions. Between the park country and what 
is known as the arid regions of the West there is the greatest possible con- 
trast. Across the Central Plateau and the Absaroka Range the country 
presents a continuous mountain mass 75 miles in width, with an average 
elevation unsurpassed by any area of equal extent in the northern Rocky 
Mountains. It is exceptionally situated to collect the moisture-laden 
clouds, which coming from the southwest precipitate immense quantities 
of snow and rain upon the cooled tableland and neighboring mountains. 
The climate in many respects is quite unlike that found in the adjacent 
country, as is shown by the meteorological records, the amount of snow 
and rainfall being higher, and the mean annual temperature lower. 
Rainstorms occur frequently throughout the summer, while snow is quite 
likely to fall any time between September and May. Protected by the 
forests the deep snows of winter lie upon the plateau well into midsum- 
mer, while at still higher altitudes, in sheltered places, it remains through- 
out the year. By its topographical structure the park is designed by 
nature as a reservoir for receiving, storing, and distributing an excep- 
tional water supply, not exceded by any area near the headwaters of the 
great continental rivers. The Continental Divide, separating the waters 
of the Atlantic from those of the Pacific, crosses the park plateau from 
southeast to northwest. On both sides of this divide lie several large 
bodies of water, which form so marked a feature in the scenery of the 
plateau that the region has been designated the lake country of the park. 
Yellowstone Lake, the largest lake in North America at this altitude 
(7,740 feet) and one of the largest in the world at so high an elevation 
above sea level, presents a superficial area of 139 square miles, and a 
shore line of nearly 100 miles. From measurements made near the 
outlet of the lake in September, 1886, the driest period of the year, the 
discharge was found to be i ,525 cubic feet per second, or about 34,000,000 
imperial gallons per hour. 



The following publication may be obtained free on written application 
to the Director of the National Park Service: 

Rules and Regulations, Yellowstone National Park (issued yearly). This pamphlet 
contains general information of interest to the tourist. 


The following publications may be obtained from the Superintendent 
of Documents, Government Printing Office, Washington, D. C., at the 
prices given. Remittances should be made by money order or in 

National Parks Portfolio, by Robert Sterling Yard. 260 pages, including 270 illus- 
trations. Pamphlet edition, loose in flexible cover, 35 cents; book edition, con- 
taining same material securely bound in cloth, 55 cents. 

Contains nine sections, each descriptive of a national park and one larger section devoted to 
other national parks and monuments. 

Geological History of Yellowstone National Park, by Arnold Hague, 22 pages, 
including 10 illustrations, 10 cents. (This publication.) 

This pamphlet contains a general resume of the geologic forces that have been active in the 
Yellowstone National Park. 

Geysers, by Walter Harvey Weed, 32 pages, including 23 illustrations, 10 cents. 

In this pamphlet is a description of the forces which have produced the geysers, and the geysers 
of the Yellowstone are compared with those in Iceland and New Zealand. 

Fossil Forests of the Yellowstone National Park, by F. H. Knowlton, 32 pages, includ- 
ing 15 illustrations, 10 cents. 

This pamphlet contains descriptions of the fossil forests of the Yellowstone National Park and 
an account of their origin. 


A topographic map of the park may be purchased from the Director 
of the Geological Survey, Washington, D. C., at the price given. Remit- 
tances should be made by cash or money order. 

Map of Yellowstone National Park, size 28^ by 3 2 inches; scale, 2 miles to the 
inch. Price, 25 cents. 

The roads, trails, and names are put in black, the streams and lakes in blue, and the relief is 
indicated by brown contour lines.