IRLF
LIBRARY
UNIVERSITY OF J
CALIFORNIA^/
EARTH
SCIENCES
LIBRARY
GBOOIlAPiBY
EARTH
SCIENCES
LIBRARY
ILLINOIS
STATE GEOLOGICAL SURVEY.
BULLETIN No. 7.
Physical Geography of the Evanston-
Waukegan Region
BY
Wallace W. Atwood and James Walter Goldthwait
Urbana
Univetsity of Illinois
1908
EARTH
SPRINGFIELD ILL.:
Phillips Bros., State Printers.
1908.
STATE GEOLOGICAL COMMISSION.
GOVERNOR C. S. DENEEN, Chairman.
PROFESSOR T. C. CHAM BERLIN, V ice-Chairman.
PRESIDENT EDMUND J. JAMES, Secretary.
H. FOSTER BAIN, Director.
R. D. SALISBURY, Consulting Geologist, in charge of the preparation
of Educational Bulletins.
990909
CONTENTS.
PAGE.
List of Illustrations. , . , ...../, VII
Letter of Transmittal IX
General Geographic Features, by W. W. Atwood 1
Location and extent of area 1
Upland area 2
Shore line 3
Lake plain 3
Drainage 3
Geological Formations, by W. W. Atwood 4
General characteristics 4
Nature of materials 4
Bedrock surface beneath the drift .._, 4
Structure 5
Sources of materials 5
Origin and work of continental glaciers 6
Formation of an ice sheet 6
The North American ice sheet , . 9
Work of glacier ice. 10
Erosive work. 10
Deposition by ice 13
Direction of movement 16
Effect of topography on movement 17
Glacial deposits . . . . ... 17
General characteristics. ..... i 17
Ground moraine 20
Distribution < 20
Constitution . 21
Topography 23
Terminal moraines. '2*3
Formation 23
Topography 24
Stratified drift 24
Contrast between glaciated and unglaciated areas 26
Present Shore Line, by J. W. Goldthwait. '. 28
Evolution seen in shore line topography 28
Geological agents at work along shore lines 29
Waves 29
Undertow 31
Shore current •••••• • • • 32
Development of coastal topography 32
Changes in profile 32
The sea cliff 33
The beach ridge ,;. < . , 35
The barrier 36
Changes in horizontal configuration 38
VI
Contents — Concluded.
PAGE.
Spits, bars and hooks 38
Dunes 44
The shore cycle 45
The north -shore 47
General aspects 47
The ten-fathom terrace 48
The coastal topography — Rogers Park to Winnetka 50
Winnetka to Waukegan 51
Waukegan to the State line 52
Mature condition of the shore line 53
Records of the Extinct Lakes, by J. W. Goldthwait 54
Introduction 54
Lake Chicago 55
Glenwood stage 55
Glenwood shores in the Bvanston district 56
Glenwood beaches in the Waukegan district 58
Change from the Glenwood to the Calumet stage 60
Calumet stage 61
Calumet shores in the Evanston district 61
Calumet beach in the Waukegan district 63
Interval between the Calumet and Toleston stages 63
Lake Algonquin, the low water stage and the Nipissing great lakes 64
The Toleston beaches 65
Lower Toleston bluff and shore terrace in the Waukegan district 68
Effects of recent fluctuations in lake level 68
The Development of the Ravines, by W. W. Atwood 69
Morainic surface as left by the ice 69
Origin of a gully 69
The course of a valley 70
Tributary valleys 70
How a valley gets a stream 71
Limits of a valley 72
A cycle of erosion 73
Base-level plains and peneplains 75
Characteristics of valleys at various stages of development 76
Transportation and deposition 79
Topographic forms resulting from stream deposition 79
Rejuvenation of streams 80
The influence of the changes in the level of Lake Michigan on valley develop-
ment 81
Underground water, by W. W. Atwood 85
Shallow ground water 85
Artesian wells 85
Geographic Conditions and Settlement, by W. W. Atwood 89
History 89
Location of roads ! 89
Towns and villages 90
Soil and sub-soil 91
Farms 91
Suburban and summer homes 92
Former village of St. Johns 92
Economic uses of the glacial material 92
Rainfall 93
APPENDIX.
A. Bibliography 94
B. Field Trips 95
VII
LIST OF ILLUSTRATIONS.
PLATES.
PAGB.
PLATE I. Fig. A. Glaciated stones showing both form and striae 17
B. Limestone boulder in Pettibone Creek, North Chicago
C. Igneous boulder at Northwestern Railway station, Waukegan
II. Fig. A. Abandoned clay pit near Fort Sheridan 23
B. Sketch of ground moraine topography
C. Sketch of terminal moraine topography
III. Fig. A. Receding cliff at Grosse Point 33
B. Sand dunes at Rogers Park
IV. Fig. A. Lake cliff and beach near Fort Sheridan 34
B. Lake cliff at Racine, Wisconsin
V. Fig. A. Pier and beach near county line 38
B. Bar at mouth of ravine near county line :
VI. . Map of old shore lines of the Evanston district 56
VII. Fig. A. Lower Toleston bluff and beach ridge 65
B. Ancient beach ridge in Evanston
VIII. Fig. A. Morainic upland descending to lake shore 69
B. Young valleys
IX. Fig. A. Same valleys as shown in Plate VIII 74
B. A later stage of development
X. Fig. A. North Fork Pettibone Creek, North Chicago 77
B. A broad, open valley north of Kenosha
•
XI. Erosion features near Highwood 79
XII. Mouth of Pettibone Creek, North Chicago 82
XIII. Fig. A. Little Fort Creek in the western portio n of Waukegan 84
B. Glacial boulders used in building
XIV. Fig. A. A truck farm near Rogers Park 90
B. The site of the town of St. Johns . . .
FIGURES IN TEXT.
FIGURE * PAGE.
1. Index map ............................................................ 2
2. Diagrammatic cross-section of a field of ice and snow ..................... 7
3. Map of area covered by the North American ice sheet at its maximum exten-
sion
VIII
List of Illustrations — Concluded.
FIGURE PAGE.
4. A hill before the ice passes over it 12
5. The same hill after it has been eroded by the ice 12
6. Diagram showing the effect on a valley of ice moving transversely across it 12
7. Diagram showing ice moving across a valley 13
8. Diagram showing the relation of the drift to the underlying rock where the
drift is thick 15
9. The same where the drift is relatively thin 15
10. Stratified drift at Wlnthrop Harbor. 25
11. Drainage in the -driftless area,. . . . . .- : .' 26
12. Drainage in a glaciated area 26
13. Diagram showing the relation of residual soil to the underlying rock 27
14. Diagram showing the movement of particles in a wave 29
15. Series of particles in their orbits. Diff. of phase 45° 30
16. Same as Fig. 15, but with the diff. of phase 90° 30
17. Same as Pig. 15, but with the amplitude doubled 30
18. Condition for breakers — wave shortened and raised 30
19. Section of a cliff and wave-cut terrace. 33
20. Section of a cut and built terrace .....-.- 34
21. Section of a beach 35
22. Sections of a retreating barrier '. 37
23. Map of New Jersey .....' '. 38
24. Map of a part of Long Island .;........ : 39
25. Sketch map of a bay, enclosed by overlapping bars 40
26. Sketch map of a hooked spit 41
27. Map of Rockaway beach 42
28. Map of Sandy Hook ...'.... 43
29. Section showing how a deeply submerged terrace may develop 50
30. Map of the Great Lake region in the late Wisconsin stage of glaciation 55
31. Map of the ice front lakes at the time of the Pt. Huron moraine 56
32. Map of the old shore lines between Waukegan and State line 59
33. Diagram to explain "stoping" 61
34. Map of Lake Algonquin 64
35. Map of the Great Lakes at the low water stage . '. 67
36. Map of the Nipissing Great Lakes 67
37. Diagram illustrating the relation of ground water to streams 71
38. Diagram illustrating the shifting of divides. 73
39. Diagram showing topography at the various stages of an erosion cycle 76
40. Diagrammatic cross-section of a young valley. 77
41. Diagrammatic profile of a young valley. . . . . 77
42. Diagrammatic cross-section of a valley in a later stage of development 77
43. The same at a still later stage . . . 77
44. Topographic map of a part of the North Shore near Ravinia, showing several
young valleys — . 78
45. Diagram illustrating the topographic effect of rejuvenation of a stream by
uplift ; .' 80
46. Normal profile of a valley bottom ... 81
47. Profile of a stream rejuvenated by uplift. 81
48. Topographic map of the lower portion of Pettlbone Creek 82
49. Topographic sketch map of one of the head waters of Dead River between
Waukegan and Beach 83
50. Well section in South Evanston 86
51. Main absorbing areas for Potsdam and St. Peters formations 87
52. Map of southern portion of Zion City 90
IX
LETTER OF TRANSMITTAL.
STATE GEOLOGICAL SURVEY, UNIVERSITY OF
URBANA, ILL., OCT. 25, 1907.
Governor C. S. Deneen, Chairman and. Members of the Geological
Commission:
GENTLEMEN — I submit herewith a report upon the physical geo-
graphy of the Evanston-Waukegan region, with the recommendation
that it be published as Bulletin 7 of the survey. This report has been
prepared under the direction of Professor R. D. Salisbury of the Uni-
versity of Chicago, consulting geologist of this survey. It forms the
first of a series now in preparation of "Educational Bulletins." These
have been called educational because their purpose is to put useful
information concerning the geology and geography of the State, or
some parts of it, before those who are not special students of these
sciences. More particularly, their purpose is to put into available
form such knowledge as will help those who are not geologists in
understanding the common phenomena of their own regions. The
bulletins are therefore intended to serve the citizens at large, rather
than special students of geology, or special industries of the State
which depend, directly or .indirectly upon the mineral resources.
Other and more technical publications serve this latter purpose.
Two classes of people are kept especially in mind in the prepara-
tion of these bulletins. These are: (i) Intelligent citizens whose
attention, for one reason or another, has never been directed to geo-
logy. Among such citizens there are always some who are interested
in understanding their home regions; and through the understanding
of one region the general principles of geology may be grasped, much
more easily. The knowledge thus acquired may be a source of
much satisfaction to those who possess it. Furthermore, there is al-
ways the possibility that occasion may arise in the future when the
information can be turned to account in economic ways. (2)
Teachers of physical geography and geology. These sciences are now
taught somewhat generally in high schools, and might be pursued
with great advantage much more widely than now in the country
schools. According to the improved methods of study at the present'
time, it is essential that the subjects studied be so illustrated and ap-
plied that the knowledge acquired becomes a part of the student's per-
manent equipment. His study of physical geography fails of its full
purpose unless it puts him into possession of the ability to interpret
-H G
the surface of the land as he travels to and fro in after life. The
best way to. acquire this ability appears to be to make application of
principles studied in -the school to the phenomena of the region in
which the school is located. Many of the principles of physical geo-
graphy and geology are illustrated within easy reach of most of the
schools in the State.
The second purpose of those bulletins, therefore, is to put the
schools of the various parts of the State into possession of a general
account of the principal geographic and geological features of their re-
gions, which may be used as a sort of field book. This field study in
physical geography serves the same purpose as laboratory work in
physics and chejnistry, in connection with those subjects.
It will be long before all the important regions of the State can be
Covered; in" this way. In the choice of areas selected for early treat-
merit, three -considerations have controlled. These are the following:
(i). Areas of great inherent interest have taken precedence over
those not so favored. (2). Areas of which topographic maps have
been made take precedence over those not so mapped; and (3) areas
where the bulletins are likely to be used, again have precedence. Topo-
graphic maps have as yet been made over but a relatively small por-
tion of the State. Fortunately the lake shore from Chicago north-
ward has now been mapped, the Waukegan quadrangle, immediately
north of the Highwood and extending to the State line having just
been completed.
This area, one of exceptional and varied interest from the point of
view of physical geography, was chosen as the first to be reported on.
I)r. Wallace W. Atwood of the University of Chicago, and Dr. James
Walter Goldthwait of Northwestern University, already thoroughly
familiar with the region, collaborated in the preparation of the accom-
panying report. It is hoped that the material here brought together
will stimulate the interest not only of the citizens and students of the
area, but that it may also enrich the teaching of physical geography
throughout the State. The clear description of the action of the
continental ice sheet which once covered the region, the fascinating
history of Lake Michigan, and finally the analyses of the development
of stream courses in the area should be of general interest. Inci-
dentally the discussion of the water resources of the area is of practi-
cal importance to all residents of this thickly copulated ?rea.
The survey is under great obligations to Professor Salisbury and
the authors of this report for its preparation. Acknowledgments
should also be made to the U. S. Geological Survev for the rse of
figures 3 and 13, and to Director E. A. Birge of the Wisconsin Geolo-
gical and Natural History Survey for the use of figures i^ and 12;
fig. A, plate I : fig. B, plate VIII and fig. A and B, plate IX.
Others similar educational bulletins are being prepared and will be
offered for publication as rapidly as circumstances will permit.
"R.espectfullv,
H. FOSTER, BAIN,
Director.
IX
LETTER OF TRANSMITTAL.
STATE GEOLOGICAL SURVEY, UNIVERSITY OF ILLINOIS.
URBANA, ILL., OCT. 25, 1907.
Governor C. S. Deneen, Chairman and Members of the Geological
Commission:
GENTLEMEN — I submit herewith a report upon the physical geo-
graphy of the Evanston-Waukegan region, with the recommendation
that it be published as Bulletin 7 of the survey. This report has been
prepared under the direction of Professor R. D. Salisbury of the Uni-
versity of Chicago, consulting geologist of this survey. It forms the
first of a series now in preparation of "Educational Bulletins." These
have been called educational because their purpose is to put useful
information concerning the geology and geography of the State, or
some parts of it, before those who are not special students of these
sciences. More particularly, their purpose is to put into available
form such knowledge as will help those who are not geologists in
understanding the common phenomena of their own regions. The
bulletins are therefore intended to serve the citizens at large, rather
than special students of geology, or special industries of the State
which depend, directly or indirectly upon the mineral resources.
Other and more technical publications serve this latter purpose.
Two classes of people are kept especially in mind in the prepara-
tion of these bulletins. These are: (i) Intelligent citizens whose,
attention, for one reason or another, has never been directed to geo-
logy. Among such citizens there are always some who are interested
in understanding their home regions ; and through the understanding
of one region the general principles of geology may be grasped, much
more easily. The knowledge thus acquired may be a source of
much satisfaction to those who possess it. Furthermore, there is al-
ways the possibility that occasion may arise in the future when the
information can be turned to account in economic ways. (2)
Teachers of physical geography and geology. These sciences are now
taught somewhat generally in high schools, and might be pursued
with great advantage much more widely than now in the country
schools. According to the improved methods of study at the present
time, it i-s essential that the subjects studied be so illustrated and ap-
plied that the knowledge acquired becomes a part of the student's per-
manent equipment. His study of physical geography fails of its full
purpose unless it puts him into possession of the ability to interpret
-]>, G
X
the surface of the land as he travels to and fro in after life. The
best way to acquire this ability appears to be to make application of
principles studied in the school to the phenomena of the region in
which the school is located. Many of the principles of physical geo-
graphy and geology are illustrated within easy reach of most of the
schools in the State.
The second purpose of those bulletins, therefore, is to put the
schools of the various parts of the State into possession of a general
account of the principal geographic and geological features of their re-
gions, which may be used as a sort of field book. This field study in
physical geography serves the same purpose as laboratory work in
physics and chemistry, in connection with those subjects.
It will be long before all the important regions of the State can be
covered in this way. In the choice of areas selected for early treat-
ment, three considerations have controlled. These are the following:
( I ) . Areas of great inherent interest have taken precedence over
those not so favored. (2). Areas of which topographic maps have
been made take precedence over those not so mapped; and (3) areas
where the bulletins are likely to be used, again have precedence. Topo-
graphic maps have as yet been made over but a relatively small por-
tion of the State. Fortunately the lake shore from Chicago north-
ward, has now been mapped, the Waukegan quadrangle, immediately
north of the Highwood and extending to the State line having just
been completed.
This area, one of exceptional and varied interest from the point of
view of physical geography, was chosen as the first to be reported on.
Dr. Wallace W. Atwood of the University of Chicago, and Dr. James
Walter Goldthwait of Northwestern University, already thoroughly
familiar with the region, collaborated in the preparation of the accom-
panying report. It is hoped that the material here brought together
will stimulate the interest not only of the citizens and students of the
area, but that it may also enrich the teaching of physical geographv
throughout the State. The clear description of the action of the
continental ice sheet which once covered the region, the fascinating
history of Lake Michigan, and finally the analyses of the development
of stream courses in the area should be of .general interest. Inci-
dentally the discussion of the water resources of the area is of practi-
cal importance to all residents of this thickly populated ?rea.
The survey is under great obligations to Professor Salisbury and
the authors of this report for its preparation. Acknowledgments
should also be made to the U. S. Geological Survev for the iise of
figures 3 and 13, and to Director E. A. Birge of the Wisconsin Geolo-
gical and Natural History Survey for the use of figures 11 and 12;
fig. A, plate I : fig. B, plate VIII and fig. A and B, plate IX.
Others similar educational bulletins are being prepared and will be
offered for publication as rapidly as circumstances will permit.
Respectfully,
H. FOSTER BAIN,
Director.
PHYSICAL GEOGRAPHY OF THE EVANSTON-
WAUKEGAN REGION.
BY WALLACE W. ATWOOD AND JAMES WALTER GOLDTHWAIT.
GENERAL GEOGRAPHIC FEATURES.
(BY w. w. ATWOOD.)
Location and Extent of Area — The area with which this report is
concerned lies north of Chicago, and extends northward to the Illi-
nois-Wisconsin line. Its eastern boundary is the shore line of Lake
Michigan, and its western margin, the DesPlaines river (Fig. i). It
is a little over 30 miles long and varies in width from 5 to 10 miles.
Its area is about 250 square miles. Of this area, the portion immed-
iately adjoining Lake Michigan has attracted most attention. It is a
beautiful suburban-home district and a region of considerable scien-
tific and educational interest. Each year hundreds, if not thousands
of students visit points of special interest along this shore. It is not
uncommon for special trains to be chartered and entire schools to be
taken on educational excursions to this "North Shore" region. The
portion near the lake may be regarded as a great physiographic labor-
atory.
The "Chicago region" is interpreted as the area mapped in the
Chicago folio of the United States Geological Survey, and includes
the area covered by the Calumet, Des Plaines, Riverside and Chicago
sheets, of the U. S. Geological Survey. The north boundary of the
Riverside and Chicago quadrangles,* latitude 42 degrees, is the south-
ern boundary of the area here under discussion. The Evanston and
Highwood quadrangles are located just north of the Chicago region
and included within the region here concerned (Fig. i).
The quadrangle adjoining the Highwood on the north, includes
the Waukegan region and is known as the Waukegan quadrangle.
This map will soon be ready for distribution.
* A quadrangle is the area represented on one sheet of the U. S. Geological Survey topo-
graphic map. Topographic maps of the quadrangles included in the Chicago folio and of the
Evanston, Waukegan and Highwood regions may be purchased of the director of the U. S.
Geological Survey, Washington, D. C., at 5 cents per copy or $3.00 per hundred. The Evanston,
Waukegan and Highland sheets should be used in connection with this report, and the Chicago
folio, also to be had of the U. S. Geological Survey, will also be instructive.
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
WINTHROP HRRBOR
CANP LOGON
ZION CITY
BEACH
E.VANSTON- WAUKE.GON
REGION
WAUKE.6AN
N. CHICAGO
SHERIDAN
3HWOOD
3HLOND PARKr7
IVINIO
6LENCOE
LAKESIDE -£.
WIIMNETKA
WILMtTTF
FIG. 1. General map showing location and extent of the Evanston-Waukegan region, the
quadrangles for which topographic maps are available, and the chief points mentioned in the
report.
The general geographic features of the region are: (i) the mor-
aine plain or rolling upland, (2) the present shore, (3) the lake plain
with associated beach ridges,' and (4) the ravines.
"Upland Area — The larger part of the area consists of rolling up-
land more than 60 feet above the level of the lake. Going northward
from Chicago the Northwestern railroad bed becomes noticeably
higher a few rods south of the station at Winnetka, and before the
station is reached the road bed has passed from the lower, flatter plain
to the south, to the rolling upland farther north. Northward from
Winnetka the railroad remains on the upland to Waukegan, where it
descends again to the lake plain. West of the railroad, the undulating
ATWOOD.] GENERAL GEOGRAPHIC FEATURES. 6
surface of the upland contains many swamps, ponds and other de-
pressions without outlets. The topography is such as is common to
glacial drift and it will be fully discussed later in the report.
Shore Line — The modern lake cliff extends from the southern mar-
gin of Waukegan southward a little beyond Evanston. It varies in
height up to 80 feet, and at places is almost vertical. At the base of
the cliff, is the modern beach. Over the beach zone, the waves and
undertow work the .sands and gravels back and forth. When strong
winds blow from the east or northeast, the waves reach, at certain
places, to the base of the cliff and thus submerge the entire beach.
As the winds die down or set in from the west, the lake waters fall
or are blown eastward, uncovering a wide beach. Normally there is
a belt 50 to 100 feet wide bordering the water, and rising a few feet
.above the level of the lake.
Lake Plain — This appears in the southeast and northeast corners of
the area. Evanston, Wilmette, Kenilworth and a portion of Win-
netka are located on the plain at the southeast. The lower or manu-
facturing portion of Waukegan, most of Zion City, and all of Beach,
Camp Logan and Winthrop Harbor are on the lake plain at the
northeast corner of the area. The beaches associated with the plain
are low, even-crested ridges of sand and gravel built upon the plain
and running approximately parallel to the present shore line of the
lake. At the landward margin of the lake plain there is usually a
distinct rise of 10 to 60 feet to the upland. This is well shown at
Winnetka and at Waukegan. In the southern portion of the area,
in the vicinity of the Chicago river, the change from the plain to the
upland is not abrupt, and the margin of the plain is not easily recog-
nized.
East of the Northwestern railroad the upland belt has been dis-
sected by numerous intermittent or wet-weather streams. The gullies
and ravines which have resulted from the work of such streams add
much to the roughness of the topography, and much to the scenic at-
tractiveness of the region.
Drainage — The drainage of the western portion of the area joins
the Des Plaines river, and thence by way of the Illinois and Missis-
sippi enters the Gulf of Mexico. The central portion is drained by the
north branch of the Chicago river. The waters following this route
are now diverted up the south branch of the Chicago river into the
Chicago drainage canal, and thence into the Des Plaines. The eastern
border of the area is drained by numerous short streams into Lake
Michigan. From the lake these waters may go in part southward
through the Chicago outlet, and in part northward to the Atlantic
ocean by way of the great lakes and the St. Lawrence river.
THE EVANSTON-WAUKEGAN REGION. [BULL. 7
THE GEOLOGICAL FORMATIONS.
(BY w. w. AT WOOD.)
Nature of Materials — General Characteristics — All of the rock
material within the Evanston-Waukegan region is glacial drift, com-
posed of clay, sand, gravel and bowlders. A part of this material has
been re-worked by rivers, winds, or waves since the ice retreated.
Such material is stratified, and is sometimes called modified drift, and
will receive special attention later. The portion that may be consid-
ered as unmodified, or but slightly modified glacial drift, underlies the
lake plain and the entire upland. It is well exposed in the lake cliff,
in many of the ravines, and in most all excavations. Road cuttings,
sewer or water-pipe excavations, and all deep basements or cellars,
when being excavated, afford excellent opportunities for studying
this formation. The material grades from fine silt, to huge bowlders
10 or 12 feet in diameter. Between these extremes there are various
grades of sand, gravel and cobble-stones. The great mass of the ma-
terial is firmer than sand, and may be classed as clay, or better as
stony clay.
In addition to the variation in size, there is variation in the kinds
of rocks found in the drift. Almost any exposure in the region will
yield four or five varieties, while on the beach it is easy to find 20 or
more different kinds of stones.
The shapes of the pebbles and bowlders in the unstratified drift are
not like those of stream or shore pebbles. Instead of having smoothly
rounded forms, the stones of the drift are commonly sub-angular,
with numerous flat faces, or facets. The facets usually show polish-
ing, parallel grooving, and scratching, as though smoothed and
striated while being held firmly in one position, and moved over a
hard surface (Plate I, Fig. A).
Bed-rock Surface Beneath the Drift — Nowhere within the Evans-
ton-Waukegan region, so far as the authors are aware, does the bed-
rock underlying the glacial drift appear at the surface. The nearest
exposures of the rock that underlies this area are within the Chicago
region. When these exposures are examined they are usually found
to be smoothed and polished, and marked by gooves and scratches
similar to those upon the pebbles and bowlders in the drift. The
scratches on the bed-rock are usually parallel at any one locality,
but when examined at widely separated localities within the Chicago
region, they are found to vary in direction from 20 degrees to 45
degrees south of west.
ATWOOD.] THE GEOLOGICAL FORMATIONS. &
Structure — Any good section of the glacial drift along the north
shore shows 'that most of the material is unstratified. In other words,
the sand, clay, gravel and bowlders are at most places intimately in-
termingled, and show no signs of assortment. At a few places, most
noticeably in the lake cliff just south of Pettibone creek, at North
Chicago, the glacial material is assorted. Here sands and gravels of
a given size are arranged in distinct lavers. Such material was evi-
dently deposited by water, and presumably by water associated with
the melting of the glacial ice which once covered the region.
The unassorted or unstratified glacial drift was deposited by the
ice itself, and it now lies as the ice left it. As the ice melted or for
any reason gave up the rock material it was carrying, such material
was left on the surface beneath. In this process, there was no possi-
bility of getting the sands or pebbles of a common size together.
The material, large or small, which was left at one time, took its
place on that which had been last deposited in the same place. Un-
stratified glacial drift is known as till.
The various phenomena of the drift of the region give unmistakable
evidence of that agent that brought that material. The physical and
structural features of the material are identical with those of the
material carried or but recently deposited by the glaciers of today.
The markings of the bed-rock surface, exposed in neighboring re-
gions to the north and south, and underlying the same great sheet or
drift that occupied the Evanston-Waukegan region, are identical
with the markings of the bed-rock surfaces under living glaciers,
and of rock surfaces from which glaciers have but recently retreated.
Furthermore, the shapes and markings of the stones in the drift are
identical with the shapes and markings of stones underneath and in
the base of the glaciers of today. The drift is, therefore, of glacial
origin.
Sources of the Drift Materials — The clay matrix of the drift is
highly calcareous, and was derived largely from limestone and cal-
careous shale by grinding and crushing. The limestone was pre-
sumably the underlying Niagara formation which appears at several
places in Chicago, and is reached in the deep wells of the Evanston-
Waukegan region. This formation extends far to the northeast.
Of the stones of the drift in this region, about 90 per cent are from
the Niagara limestone, while the remaining 10 per cent are of sand-
stone, shales and crystalline rock, foreign to Illinois. From the di-
rection of glacial striae on bed-rock in Chicago and in southern Wis-
consin, it is known that the glacier that brought the drift material
to this region, moved southward in the basin of Lake Michigan and
spread southward over the area bordering the lake on the west. If
the course of the ice be retraced, it is found that the sandstones and
crystalline rocks in the drift of this region must have come at least
500 miles, and" may have traveled much farther. Such rocks occur,
in place, about the eastern part of Lake Superior, northern Lake
Huron, and further northward. The glacier that reached this area
was therefore not local. Furthermore, drift similar to that in the
Evanston-Waukegan region covers most of Illinois, and extends over
6 THE EVANSTON-WAUKEGAN EEGION. [BULL. 7
most of the northern United States and Canada. The drift of this
region is therefore a part of a great sheet of drift deposited by a glacier
of continental dimensions.
ORIGIN AND WORK OF CONTINENTAL GLACIERS.*
THE FORMATION OF AN ICE SHEET.
To clearly understand the origin of the drift, and the methods by
which it attained its present widespread distribution, it is necessary to
consider some elementary facts and principles concerning the forma-
tion and work of a continental glacier, even at the risk of repeating
what is already familiar.
The temperature and the snow fall of a region may stand in such a
relation to each other that the summers' heat may barely suffice to
melt the winters' snow. If under these circumstances the annual tem-
perature were to be reduced, or the fall of snow increased, the sum-
mer's heat would fail to melt all the winter's snow, and some portion
of it would endure through the summer, and through successive sum-
mers, constituting a perennial snow field. Were this process once in-
augurated, the depth of the snow would increase from year to year.
The area of the snow field would be extended at the same time, since
the snow field would so far reduce the surrounding temperature as to
increase the proportion of the annual precipitation which fell as snow.
In the course of time, and under favorable conditions, the area of the
snow field would attain great dimensions, and the depth of the snow
would become very great.
As in the case of existing snow fields, the lower part of the snow
would eventually be converted into ice. Several factors would con-
spire to this end. i. The pressure of the overlying snow would tend
to, compress the lower portion, and snow rendered sufficiently com-
pact by compression would be regarded as ice. 2. Water arising
from the melting of the surface snow by the summer's heat would
percolate through the superficial layers of snow, and, freezing below,
take the form of ice. 3. On standing, even without pressure or par-
tial melting, snow appears to undergo changes of crystallization
which render it more compact. In these and perhaps other ways, a
snow field becomes an ice field, the snow being restricted to its
surface.
Eventually the increase in the depth of the snow and ice in a snow
field will give rise to new phenomena. Let a snow and ice field be
assumed in which the depth of snow and ice is greatest at the center,
with diminution toward its edges. The field of snow, if resting on a
level base, would have some such cross-section as that represented in
the diagram, Fig. 2.
* In the preparation of the text bearing on the principles of glaciation, free use has been
made of material in Bull. V, Wisconsin Geological and Natural History Survey, Salisbury and
Atwood.
ATWOOD.J THE GEOLOGICAL FORMATIONS.
FIG. 2. Diagrammatic cross-section of a field of ice and snow (c) resting
on a level base (a— b)
When the thickness of the ice has become considerable, it is evident
that the pressure upon its lower and marginal parts will be great.
We are wont to think of ice as a brittle solid. If in its place there
were some plastic substances which would yield to pressure, the
weight of the ice would cause the maginal parts to extend themselves
in all directions by a sort of flowing motion.
Under great pressure, many substances which otherwise appear to
be solid, exhibit the characteristics of plastic bodies. Among the sub-
stances exhibiting this property, ice is perhaps best known. Brittle
and resistent as it seems, it may yet be molded into almost any de-
sirable form is subjected to sufficient pressure, steadily applied through
long intervals of time. The changes of form thus produced in ice are
brought about without visible fracture. Concerning the exact nature
of the movement, physicists are not agreed, but the result appears to
be essentially such as would be brought about if the ice were capable
of flowing, with extreme slowness, under great pressure continuously
applied.
In the assumed ice field, there are the conditions for great pressure
and for its continuous application. If the ice be capable of moving
as a plastic body, the weight of the ice would induce gradual movement
outward from the center of the field, so that the area surrounding the
region where the snow accumulated would gradually be encroached
upon by the spreadirig of the ice. Observation shows that this is what
takes place in every snow field of sufficient depth. Motion thus brought
about is glacier motion, and ice thus moving is glacier ice.
Once in motion, two factors would determine the limit to which the
ice would extend itself: (i) the rate at which it advances; (2) the
rate at which the advancing edge is wasted. The rate of advance
would depend upon several conditions, one of which in all cases, would
be the pressure of the ice which started and which perpetuates the
motion. If the pressure be increased the ice will advance more rapidly,
and if it advances more rapidly, it will advance farther before it is
melted. Other things remaining constant, therefore, increase of pres-
sure will cause the ice sheet to extend itself farther from the center
of motion. Increase of snowfall will increase the pressure of the snow
and ice field by increasing its mass. If, therefore, the precipitation
over a given snow field be increased for a period of years, the ice
sheet's marginal motion will be accelerated, and its area enlarged. A
decrease of precipitation, taken in connection -with unchanged wastage
would decrease the pressure of the ice and retard its movement. If,
while the rate of advance diminished, the rate of wastage remained
constant, the edge of the ice would recede and the snow and ice field
be contracted.
THE EVANSTON-WAUKEGAN REGION. [BULL. 7
The rate at which the edge of the advancing ice is wasted depends
largely on the climate. If, while the rate of advance remains con-
stant, the climate become warmer, melting will be more rapid, and
the ratio between melting and advance will be increased. The edge of
the ice will therefore recede. The same result will follow if, while
temperature remains constant, the atmosphere becomes drier, since
this will increase wastage by evaporation. Were the climate to be-
come warmer and drier at the same time, the rate of recession of the
ice would be greater than if but one of these changes occurred.
If, on the other hand, the temperature over and about the ice-field
be lowered, melting will be diminished, and if the rate of movement
be constant, the edge of the ice will advance farther than under the
earlier conditions of temperature, since it has more time to advance
before it is melted. An increase in the humidity of the atmosphere,
while the temperature remains constant, will produce the same result,
since increased humidity of the atmosphere diminishes evaporation.
A decrease of temperature, decreasing the melting, and an increase of
humidity, decreasing the evaporation, would cause the ice to advance
farther than either change alone, ^ince both changes decrease the
wastage. If, at the same time that conditions so change as to increase
the rate of movement of the ice, climatic conditions so change as to
reduce the rate of waste, the advance of the ice before it is melted will
be greater than where only one set of conditions is altered. If, instead
of favoring advance, the two series of conditions conspire to cause the
ice to recede, the recession will likewise be greater than when but one
set of conditions is favorable thereto.
Greenland affords an example of the conditions here described. The
large part of the half million or more square miles which this body of
land is estimated to contain, is covered by a vast sheet of snow and ice,
thousands of feet in thickness. In this field of snow and ice, there is
continuous though slow movement. The ice creeps slowly toward the
borders of the island, advancing until it reaches a position where the
climate is such as to waste (melt and evaporate) it as it advances.
The edge of the ice does not remain fixed in position. There is rea-
son to believe that it alternately advances and retreats as the ratio
between movement and waste increases or decreases. These oscilla-
tions in position are doubtless connected with climatic changes. When
the ice edge retreats, it may be because the waste is increased, or be-
cause the snowfall is decreased, or both. In any case, when the ice
edge recedes from the coast, it tends to recede until its edge reaches
a position where the melting is less rapid than in its former position,
and where the advance is counterbalanced by the waste. This repre-
sents a condition of equilibrium so far as the edge of the ice is con-
cerned, and here the edge of the ice would remain so long as the con-
ditions were unchanged.
When for a period of years the rate of melting of the ice is dimin-
ished, or the snowfall increased, or both, the ice edge advances to a new
line where melting is more rapid than at its former edge. The edge
of the ice would tend to reach a position where waste and advance
balance. Here its advance would cease, and here its edge would re-
main so long as climatic conditions were unchanged.
ATWOOD.]
THE GEOLOGICAL FORMATIONS.
If the conditions determining melting and movement be continually
changing, the ice edge will not find a position of equilibrium, but will
advance when the conditions are favorable for advance, and retreat
when the conditions are reversed.
Not only the edge of the ice in Greenland, but the ends of existing
mountain glaciers as well, are subject to fluctuation, and are delicate
indices of variations in the climate of the regions where they occur.
The North American Ice Sheet — In the area north of the eastern
part of the United States and in another west of Hudson Bay it is
believed that ice sheets similar to that which now covers Greenland
began to accumulate at the beginning of the glacial period. From these
areas as centers, the ice spread in all directions, partly as the result
of accumulation, and partly as the result of movement induced by the
weight of the ice itself.
FIG. 3. Map of area covered by the North American ice sheet of the glacial epoch at its
maximum extension, showing the approximate southern limit of glaciation, the three main
centers of ice accumulation, and the driftless area within the border of the glaciated region.
(Courtesy of U. S. Geological Survey.)
10 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
The ice sheets spreading from these centers came together south of
Hudson's bay, and invaded the territory of the United States as a
single sheet, which, at the time of its greatest development, covered a
large part of our country (Fig. 3), its area being known by the extent
of the drift which it left behind when it was melted. In the- east, it
buried the whole of New England, most of New York, and the north-
ern part of New Jersey and Pennsylvania. Farther west, the southern
margin of the ice crossed the Ohio river in the vicinity of Cincinnati,
and pushed out over the uplands a few miles south of the river. In In-
diana, except at the extreme east, its margin fell considerably short of
the Ohio ; in Illinois it reached well toward that river, attaining here its
most southerly latitude. West of the Mississippi, the line which marks
the limit of its advance curves to the northward, and follows, in a
general way, the course of the Missouri river. The total area of the
North America ice sheet, at the time of its maximum development, has
been estimated to have been about 4,000,000 square miles> or about ten
times the estimated area of the present ice-field of Greenland.
Within the general area covered by the ice, there is an area of sev-
eral thousand square miles, mainly in south-western Wisconsin, where
there is no drift. The ice, for some reason, failed to cover this drift-
less area though it overwhelmed the territory on all sides.
The Evanston-Waukegan region was affected by the ice of more
than one glacial epoch, but the chief results now observable were ef-
fected during the last, and the others need not be considered. Figure
30 shows the maximum portion of ice in this region during the last
glacial epoch.
WORK OF GLACIER ICE.
As the edge of an ice sheet, or as the end of a glacier, retreats, the
land which it has previously covered is laid bare, and the effects which
the passage of the ice produced may be seen. In some cases one may
actually go back a short distance beneath the ice now in motion, and
see its mode of work and the results it is effecting. The beds of living
flaciers, and the beds which glaciers have recently abandoned are
Dund to present identical features. Because of their greater accessi-
bility, the latter offer the better facilities for determining the effects of
glaciation.
The conspicuous phenomena of abandoned glacier beds fall into two
classes, (i) those which pertain to the bed rock over which the ice
moved, and (2) those which pertain to the drift left by the ice.
Erosive Work of the Ice— Effect on Topography — The leading fea-
tures of the rock bed over which glacier ice has moved, are easily rec-
ognized. Its surface is generally smoothed and polished, and fre-
quently marked by lines (striae) or groves, parallel to one another.
An examination of the bottom of an active glacier discloses the method
by which the polishing and scoring are accomplished.
The lower surface of the ice is thickly set with a quantity of clay,
sand, and stony material of various grades of coarseness. These earthy
and stony materials in the base of the ice are the tools with which it
ATWOOD.] THE GEOLOGICAL FORMATIONS*. 11
works. Thus armed, the glacier ice moved slowly forward, resting
clown upon the surfaces over which it passes with the whole weight of
its mass, and the grinding action between the stony layer at the base of
the ice and the rock bed over which it moves, is effective. If the mater-
ial in the bottom of the ice be fine, like clay, the rock bed is polished.
If coarser materials, harder than the bed-rock, be mingled with the fine,
the rock bed of the glacier will be scratched as well as polished. If
there are bowlders in the bottom of the ice they may cut grooves or
gorges in the underlying rock. The grooves may subsequently be
polished by the passage over and through them of ice carrying clay or
other fine, earthy matter.
All these phases of rock wear may be seen about the termini of re-
ceding glaciers, on territory which they have but recently abandoned.
There can thus be no possible doubt as to the origin of the polishing,
planing and scoring.
There are other peculiarities, less easily defined, which characterize
the surface of glacier beds. The wear effected is not confined to the
mere marking of the surface over which it passes. If prominences of
rock exist in its path, as is often the case, they oppose the movement of
the ice, and receive a corresponding measure of abrasion from it. If
they be sufficiently resistant they may force the ice to yield by passing
over or around them, but if they be weak, they are likely to be des-
troyed.
As the ice of the North American ice sheet advanced, seemingly more
rigid when it encountered yielding bodies, and more yielding when it
encountered resistant ones, it denuded the surface of its loose and mov-
able materials, and carried them forward. This accumulation of earthy
and stony debris in the bottom of the ice, gave it a rough and grind-
ing lower surface, which enabled it to abrade the land over which it
passed much more effectively than ice alone could have done. Every
hill and every mound which the ice encountered contested its advance.
Every sufficiently resistant elevation compelled the ice to pass around
or over it ; but even in these cases the ice left its' marks upon the sur-
face to which it yielded. The powerful pressure of pure ice, which is
relatively soft, upon firm hills of rock, which are relatively hard, would
effect little. The hills would wear the ice, but the effect of the ice on
the hills would be slight. But where the ice is supplied with earthy
and stony material derived from the rock itself, the case is different.
Under these conditions, the ice, yielding only under great pressure and
as little as may be, rubs its rock-shod base over every opposing surface,
and with greatest severity where it meets with greatest resistance. Its
action may be compared to that of a huge "flexible-rasp" fitting down
snugiy over hills and valleys alike, and working under enormous pres-
sure.
The abrasion effected by a moving body of ice under such conditions
would be great. Every inch of ice advance would be likely to be at-
tended by loss to the surface of any obstacle over or around which it
is compelled to move. The sharp summits of the hills, and all the an-
gular rugosities of their surfaces would be filed off, and the hills
smoothed down to such forms as will offer progressively less and less
12
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
resistance. If the process of abrasion be continued long enough, the
forms, even of the large hills, may be greatly altered, and their dimen-
sions greatly reduced. (Figs. 4 and 5.) Among the results of ice
wear, therefore, will be a lowering of the hills, and a smoothing and
softening of their contours, while their surfaces will bear the marks
of the tools which fashioned them, and will be polished, striated or
grooved, according to the nature of the material which the ice pressed
down upon them during its passage.
PIG. 4. A hill before the ice passes over it.
FIG. 5. The same hill after it has been eroded by the ice. A, the
stoss side; S, the lee side.
It was not the hills alone which the moving ice affected. Where it
encountered valleys in its course, they likewise suffered modification.
Where the course of a valley was parallel to the direction of the ice
movement, the ice moved through it. The depth of moving ice is one
of the determinants of its velocity, and because of the greater depth
of ice in valleys, its motion here was more rapid than on the uplands
above, and its abrading action more powerful. Under these conditions
the valleys were deepened and widened.
Where the courses of the valleys were transverse to the direction of
ice movement, the case was different. The ice was too viscous to span
the valleys, and therefore filled them. In this case it is evident that
the greater depth of the ice in the valley did not accelerate its motion,
since the ice in the valley-trough and that above it were in a measure
opposed. If left to itself, the ice in the valley would tend to flow in the
PIG. 6. Diagram showing effect on a valley of ice moving traversely across it.
direction of the axis of the valley. Shallow valleys crossed by the ice
suffered most wear on the side opposing ice movements. (Fig. 6.)
When deep, narrow valleys were transverse to the direction of ice ad-
ATWOOD.] THE GEOLOGICAL FORMATIONS. 13
vance, the ice that first entered them may have become stationary,
forming a bridge over which the main mass of ice moved. (Fig. 7).
In such cases the valley did not suffer much wear.
ICE
fffi S5&&52
d
PIG. 1. Diagram to illustrate case where ice fills a valley (c) and the upper
ice then moves on over the filling.
In general, the effort was to cut down prominences, thus tending to
level the surface. But when it encountered valleys parallel to its move-
ment they were deepened, thus locally increasing relief. Whether the
reduction of the hills exceeded the deepening of the valleys, or whether
the reverse was true, so far as corrasion alone is concerned, is uncer-
tain. But whatever the effect of the erosive work of ice action upon
the total amount of relief, the effect upon the contours was to make
them more gentle. Not only were the sharp hills rounded off, but even
the valleys which were deepened were widened as well, and in the pro-
cess their slopes became more gentle. A river-erosion topography,
modified by the wearing (not the depositing) action of the ice, would
be notably, different from the original, by reason of its gentler slopes
and softer contours. (Figs. 4 and 5.) The great lobe of ice that
moved southward in the Lake Michigan trough undoubtedly deepened
that depression. The present bed of Lake Michigan is at places about
300 feet below sea level and much of the deepening below sea-level
may be due to glacial erosion.
Deposition by the Ice — Effect on Topography — On melting, glacier
ice leaves its bed covered with the debris which it gathered during its
movement. Had this debris been equally distributed on and in and
beneath the ice during its movement, and had the conditions of de-
position been everywhere the same, the drift would constitute a mantle
of uniform thickness over the underlying rock. Such a mantle of drift
would not greatly alter the topography; it would simply raise the
surface by an amount equal to the thickness of the drift, leaving
elevations and depressions of the same magnitude as before, and sus-
taining the same relations to one another. But the drift carried by the
ice, in what ever position, was not equally distributed during trans-
portation, and the conditions under which it was deposited were not
uniform, so that it produced more or less notable changes in the topo-
graphy of the surface on which it was deposited.
The unequal distribution of the drift is readily understood. The
larger part of the drift transported by the ice was carried in its basal
portion ; but since the surface over which the ice passed was variable,
it yielded a variable amount of debris to the ice. Where it was hilly,
the friction between it and the ice was greater than where it was plain,
and the ice carried away more load. From areas where the surface
14 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
was overspread by a great depth of loose material favorably disposed
for removal, more debris was taken than from areas where material in
a condition to be readily transported was meager. Because of the topo-
graphic diversity and lithological heterogeneity of the surface of the
country over which it passed, some portions of the ice carried much
more drift than others, and when the ice finally melted, greater depths
of drift were left in some places than in others. Not all of the material
transported by the ice was carried forward until the ice melted. Some
of it was probably carried but a short distance from its original posi-
tion before it lodged. Drift was thus accumulating at some points
beneath the ice during its onward motion. At such points the surface
was being built up; at other points, abrasion was taking place, and the
surface was being cut down. The drift mantle of any region does not,
therefore, represent simply the material which was on and in and
beneath the ice of that place at the time of its melting, but it repre-
sents, in addition, all that lodged beneath the ice during its move-
ment.
The constant tendency was for the ice to carry a considerable part
of its load, forward toward its thinned edge, and there to leave it. It
follows that if the edge of the ice remained constant in position for
any considerable period of time, large quantities of drift would have
accumulated under its marginal portion, giving rise to a belt of rela-
tively thick drift. Other things being equal, the longer the time dur-
ing which the position of the edge was stationary, the greater
the accumulation of drift. Certain ridge-like belts where the drift is
thicker than on either hand, are confidently believed to mark the posi-
tion where the edge of the ice-sheet stood for considerable periods of
time.
The morainic belt of this type that is nearest the region under con-
sideration is known as the Valparaiso moraine. This moraine bor-
ders Lake Michigan at a distance of about 20 miles from the shore-
line. It marks the maximum position of the Lake Michigan lobe during
the later phase of the Wisconsin or last glacial epoch. West of Wau-
kegan this moraine crosses the main line of the Chicago and North-
western railroad between the towns of Cary and Harrington. Farther
south, Glen Elyn, Hinsdale and Lemont are located in this hilly belt
and in Indiana the city of Valparaiso, from which the moraine received
its name, is located within the belt. "
Because of the unequal amounts of material carried by different
parts of the ice, and because of the unequal and inconstant conditions
of deposition under the body of the ice and its edge, the mantle of drift
has a very variable thickness; and a mantle of drift of variable thick-
ness cannot fail to modify the topography of the region it covers. The
extent of the modification will depend on the extent of the variation.
This amounts in the aggregate to hundreds of feet. The continental
ice sheet, therefore, modified the topography of the region it covered,
not only by the wear it effected, but also by the deposits it made.
In some places it chanced that the greater thicknesses of drift were
left in the position formerly marked by valleys. Locally the body of
drift was so great that valleys were completely filled, and therefore
completely obliterated as surface features. Less frequently, drift not
ATWOOD.]
THE GEOLOGICAL FORMATIONS.
15
FIG. 8. Diagrammatic section showing relation of drift to underlying rook, where the
drift is thick, relative to the relief of the rock. A and B represent the location of post-glacial
valleys.
only filled the valleys but rose even higher over their former positions
than on either side. In other places the greater depths of drift, in-
stead of being deposited in the valleys, were left on pre-glacial eleva-
tions, building them up to still greater heights. In short, the mantle of
drift of unequal thickness was laid down upon the rock surface in such
a manner that the thicker parts sometimes rest on hills and ridges,
sometimes on slopes, sometimes on plains, and sometimes in valleys.
These relations are suggested by (Fig. 8 and 9). From them it will
be seen that in regions where the thickness of the drift is great, rela-
tive to the relief of the underlying work, the topography may be com-
pletely changed. Not only may some of the valleys be obliterated by
being filled, but some of the hills may be obliterated by having the
lower land between them built up to their level. In regions where the
thickness of the drift is slight, relative to the relief of the rock beneath,
the hills cannot be buried, and the valleys cannot be completely filled,
so that the relative positions of the principal topographic features will
remain much the same after the deposition of the drift, as before
(Fig. B).
FIG. 9. Diagrammatic section showing relation of drift to underlying rock where the drift
is thin relative to the relief ol the underlying rock.
In case the pre-glacial valleys were filled and the hills buried, the
new valleys which the surface waters will in time cut in the drift sur-
face will have but little correspondence in position with those which
existed before the ice incursion. A new system of valleys, and there-
fore a new system of ridges and hills, will be developed, in some meas-
ure independent of the old. These relations are illustrated by Fig. 8.
Inequalities in the thickness of drift lead to a still further modifica-
tion of the surface. It frequently happened that in a plane or nearly
plane region, a slight thickness of drift was deposited at one point,
while all about it much greater thicknesses were left. The area of thin
drift would then constitute a depression, surrounded by a higher sur-
face built up by the thicker deposits. Such depressions would at first
have no outlets, and are therefore unlike the depressions shaped by rain
and river erosion. The presence of depressions without outlets is one
16 THE EVANSTON-WAUKEGAN KEGION. (BULL. 7
of the marks of a drift-covered (glaciated) country. In these depres-
sions water may collect, forming lakes or ponds, or in some cases only
marshes and bogs.
The thickness of drift in the Evanston-Waukegan region is so great
that the underlying rock topography is obliterated, and the rolling sur-
face of the upland is due entirely to the distribution of the drift. There
are numerous undrained depressions in the upland surface, and many
of them contain ponds or marshes, especially during the spring.
In the farming district about Waukegan there are numerous wells
75 to 100 feet deep in which bed-rock was not reached. Southwest of
Lake Forest, on L. F. Swift's farm, there is a well 280 feet deep in drift
and one mile farther west another well down 180 feet, without strik-
ing bed-rock.
In the following cases rock was reached, and therefore the thickness
of drift determined :
1. At Mrs. M. J. Durkin's, three miles north of Waukegan, bed-rock was
reached at 150 feet. The well is 175 feet deep.
2. At H. W. Ferry's, four and one-half miles north of Waukegan, bed-rock
was reached at 128 feet.
3. Three miles west of Waukegan on a farm owned by Mrs. Durkin, bed-
rock was reached at 90 feet.
4. At L. F. Swift's artesian well, Lake Forest, bed-rock was reached at
212 feet. The well is 989 feet deep.
5. At Mr. Booth's well, a quarter of a mile southwest of Mr. Swift's,
bed-rock was reached at about 280 feet.
6. At C. B. Farwell's artesian well, Lake Forest, rock was struck at 160
feet*
7. In Highland Park rock was struck at 160 to 175 feet.f
8. At Mr. Lloyds' artesian well, in the north part of Winnetka, rock was
struck at 150 feet.*
9. In Ravina a well reaches bed-rock at 164 feet*
10. At Dr. Oliver Marcy's, South Evanston, bed-rock was found 72 feet
below the surface.f
The average thickness of drift in the upland region is probably about 150
feet, and in the lake plain areas from 50 to 75 feet. In most places the sur-
face of the rock is well. below the surface of the lake.
Direction of Ice Movement — The direction in which glacier ice
moved may be determined in various ways, even after the ice has dis-
appeared. The shapes of the rock hills over which the ice passed
(p. 12), the direction from which the materials of the drift came,
the striations on bed-rock, and the course of the margin of the drift,
are all used in making such determinations. From the course of the
drift margin, the general direction of movement may be inferred when
it is remembered that the tendency of glacier ice on a plane surface is
to move at right angles to its margin.
For the exact determination of the direction of ice movement, re-
course must be had to the striae on the bed-rock. Were the striated
rock surface perfectly plane, and were the strise even lines, they would
only tell that the ice was moving in one of two directions. But the
rock surface is not usually perfectly plane, nor the strise even lines,
* From the Pleistocene Features and Deposits of the Chicago Area; Frank Leverett. Bull.
2, Geol. and Nat. Hist. Surv., Chicago Acad. of Sci.
t Frank Leverett, in 17th Ann. Kept. U. S. Geol. Surv.. Ft. II, P. 800.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 1.
Fig. A. Glaciated stones showing both form and striae (Matz.)
[Courtesy of Wisconsin GeoJ. Nat. Hist. Surv.]
Pig. B. Limestone bowlder in north fork of Fig. C. Igneous bowlder at Northwestern
Pettibone Creek, North Chicago. Railway station, Waukegan.
ATWOOD.] THE GEOLOGICAL FORMATIONS. 17
and between the two directions which lines alone might suggest, it is
usually possible to decide. The minor prominences and depressions in
the rock surface were shaped according to the same principles that
govern the shaping of hills (Fig, 5) and valleys (Fig. 6) ; that is, the
proximal or stoss (struck) sides of the minor prominences, and the
distal sides of small depressions suffered the more wear. With a good
compass, the direction of the striae may be measured to within a frac-
tion of a degree, and thus the direction of ice movement in a particu-
lar place be definitely determined.
In the Evanston-Waukegan area the source of the material in the
drift is the only guide in determining the direction from which the ice
came, but from the study of a larger area it is known that the ice which
invaded this region moved southward through the Lake Michigan
trough, spreading westward over the bordering lands on the west side
of the lake.
Effect of Topography on Movement — The effect of glaciation on to-
pography has been outlined, but the topography in turn exerted an im-
portant influence on the direction of ice movement. The extreme de-
gree of topographic influence is seen in mountain regions like the Alps,
where most of the glaciers are confined strictly to the valleys.
As an ice sheet invades a region, it advances first and farthest along
the lines of least resistance. In a rough country with great relief,
tongues or lobes of ice push forward in the valleys, while the hills or
other prominences tend to hold back or divide the onward moving
mass. The edge of an ice sheet in such a region would be irregular.
The marginal lobes of ice occupying the valleys would be separated
by re-entrant angles marking the sites of hills and ridges.
As the ice advanced southwestward from the Laborador center of
accumulation (Fig. 3) one lobe followed the Lake Superior trough
and another lobe moved through the Lake Michigan trough. There
was, therefore, relatively less ice to move directly southwestward over
the Wisconsin region. These conditions help to account for the drift-
less or unglaciated region in the southwestern portion of Wisconsin.
The Green Bay lobe (Fig. 30) developed on the west flank of the Lake
Michigan lobe, and was led off by the depression in that direction.
GLACIAL DEPOSITS.
General Characteristics — When the ice of the continental glacier be-
gan its motion, it carried none of the stony and earthy debris which
constitutes the drift. These materials were derived from the surface
over which the ice moved.
From the method by which it was -gathered, it is evident that the
drift of any locality may contain fragments of rock of every variety
which occurs along the route followed by the ice which reached that
locality. When the ice had moved far, and when there were frequent
changes in the character of the rock constituting its bed, the variety of
materials in the drift is great. The heterogeneity of the drift arising
from the diverse nature of the rocks which contributed to it is litho-
-2 G.
18 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
logical heterogeneity — a term which implies the commingling of mater-
ials derived from different rock formations. Thus it is common to find
pieces of sandstone, limestone, quartzite, granite, gneiss, schist, etc.,
intimately commingled in the drift, wherever the ice which produced
it passed over formations of these several sorts of rock. Lithological
heterogeneity is one of the notable characteristics of glacial formations.
In the Evanston-Waukegan region the glacial sands commonly con-
tain particles of quartz, feldspar, hornblende, augite, pyrite, and mag-
netite. When the sand is dry, the magnetite may be easily withdrawn
from the other grains by a magnet. The pebbles and large stones of
the drift include the following :
1. Red sandstone, compact and fine grained.
2. Yellow sandstone, coarse grained and friable.
3. Mottled sandstone, red and yellow.
4. Brown sandstone, rich in iron oxides.
5. Red quartzite, compact and hard but with sand grains noticeable.
6. Conglomerate, composed of sand and gravel and due to local cementa-
tion. ; ,
7. White limestone, compact and hard.
8. Fossiliferous limestone, composed largely of shells.
9. Marble, finely crystalline.
10. Shale, soft, with layers that part easily.
11. Slate, hard, with layers that part easily.
12. Red granite, pink and red feldspar crystals predominating.
13. Gray granite, white feldspar crystals predominating.
14. Syenite, like granites but with little or no quartz.
15. Diorite, quartz and feldspar present but black hornblende crystals
predominating.
16. Gabbro, quartz and feldspar present but black pyroxene crystals pre-
dominating.
17. Porphyry, quartz phenocrysts most common.
18. Basalt, dark green or black and very finely crystalline.
19. Gneiss, banded.
20. Schist, more closely banded than gneiss, and often appears to be in
layers.
21. Quartz, white, glassy and very hard.
22. Jaspar, red, fine textured and very hard.
23. Flint, gray or black, brittle, glassy and very hard.
24. Chert, white, brittle, and very hard.
25. Pyrite, light yellow and heavy.
Collections of these sorts of rock may easily be made almost any-
where on the beach, but stony material is most accessible near North
Chicago, and southward to Lake Bluff, and near Glencoe and Lake-
side.
Another characteristic of the drift is its physical heterogeneity. As
first gathered from the bed of moving ice, some of the material of the
drift was fine and some coarse. The tendency of the ice in all cases
was to reduce its load to a still finer condition. Some of the softer
materials, such as soft shale, were crushed or ground to powder,
forming what is commonly known as clay. Clayey (fine) material. is
likewise produced by the grinding action of ice-carried bowlders upon
the rock-bed, and upon one another. Other sorts of rock, such as soft
sandstone,' were reduced to the physical condition of sand, instead of
clay, and from sand to bowlders all grades of coarseness and fineness
are represented in the glacial drift.
ATWOOD.] THE GEOLOGICAL FORMATIONS. 19
The two largest bowlders known to the writer, in this region, are:
1. A gray magnesian limestone fully 8 feet in length and located on the
beach near Glencoe. This bowlder is near the base of the cliff and a few
rods north of the east-west road nearest the Northwestern railroad station.
The upper surface is beautifully striated.
2. A gray magnesian limestone bowlder in the North Branch of Petti-
bone creek. This rock is 15 feet in length and may be found by following
the creek down stream from North Chicago. It is on the left side and about
20 feet above the water (Fig. B, Plate I). The surfaces of this bowlder are
also striated.
The limestone bowlders are of relatively local origin and may
have been carried but a few miles. The igneous rock at Waukegan
has come at least 300 miles, and may have come much farther.
Since the ice does not assort the material which it carries, as water
does, the clay, sand, gravel and bowlders will not, by the action of the
ice, be separated from one another. They are therefore not stratified.
As left by the ice, these phyically heterogeneous materials are confus-
sedly commingled. The finer parts constitute a matrix in which the
coarser are embedded.
Physical heterogeneity (Plate II), therefore, is another characteristic
of glacial drift. It is not to be understood that the proportions of these
various physical elements, clay, sand, gravel and bowlders, are con-
stant. Locally any one of them may predominate over any or all the
others to any extent.
Since lithological and physical heterogeneity are characteristics of
glacial drift, they together afford a criterion which is often of service
in distinguishing glacial drift from other surface formations. It fol-
lows that this double heterogeneity constitutes a feature which can be
utilized in determining the former extension of existing glaciers, as
well as the former existence of glaciers where glaciers do not now
exist.
Another characteristic of glacial drift, and one which clearly dis-
tinguishes it from all other formations with which it might be con-
founded, is easily understood from its method of formation. If the
ice in its motion holds down rock debris upon the rock surface over
which it passes with such pressure as to polish and striate the bed-rock,
the material carried will itself suffer wear comparable to that which
it inflicts. Thus the stones, large and small, of glacial drift, will be
smoothed and striated. This sort of wear on the transported blocks
of rock, is effected both by the bed-rock reacting on the bowlders
transported over it. and by bowlders acting on one another in and un-
der the ice. The wear of bowlders by bowlders is effected wherever
adjacent ones are carried along at different rates. Since the rate of
motion of the ice is different in different parts of the glacier, the mu-
tual abrasion of transported materials is a process constantly in opera-
tion. A large proportion of the transported stone and blocks of rock
may thus eventually become striated.
From the nature of the wear to which the stones are subjected when
carried in the base of the ice, it is easy to understand that their shapes
must be different from those of water- worn materials. The latter are
rolled over and over, and thus lose all their angles and assume a more
20 THE EVANSTON-WAUKEGAN KEGION. [BULL. 7
or less rounded form. The former, --held more or less firmly in the ice,
and pressed against the underlying rock or rock debris as they are
carried slowly forward, have their faces planed and striated. The plan-
ation and striation of a stone need not be confined to its under surface.
On either side or above it other stones, moving at different rates, are
made to abrade it, so that its top and sides may be planed and scored.
If the ice-carried stones shift their positions, as they may under var-
ious circumstances, new faces will be worn. The new face thus
planed off may meet those developed at an earlier time at sharp angles,
altogether unlike anything which water-wear is capable of producing.
The stone thus acted upon shows a surface bounded by planes and
more or less beveled, instead of a rounded surface such as water-wear
produces. We find, then, in the shape of the bowlders and smaller
stones of the drift, and in the markings upon their surfaces, additional
criteria for the identification of glacier drift (Plate I, Fig. A).
The characteristics of glacial drift, so far as concerns its constitution,
may then be enumerated as, (i) its lithological, and (2) physical heter-
ogeneity, (3) the shapes, and (4) the markings of the stones of the
drift. In structure, the drift which is strictly glacial, is unstratified.
In the broadest sense of the term, all deposits made by glacier ice
are moraines. Those made beneath the ice and back from its edge
constitute the ground moraine, and are distinguished from the consid-
erable marginal accumulations which, under certain conditions, are ac-
cumulated at or near the margin. These marginal accumulations are
terminal moraines. Associated with the moraines which are the de-
posits of the ice directly, there are considerable bodies of stratified
gravel and sand, the structure of which shows that they were laid down
by water. This is to be especially noted, since lack of stratification is
popularly supposed to be the especial mark of the formations to which
the ice gave rise.
These deposits of stratified drift lie partly beyond the terminal mor-
aine, and partly within it. They often sustain very complicated rela-
tions both in the ground and terminal moraines. The drift as a whole
is therefore partly stratified and partly unstratified. Structurally the
two types and thoroughly distinct, but their relations are often most
complex, both horizontally and vertically.
GROUND MORAINE.
- Distribution — The ground moraine constitutes the great body of the
glacial drift. Bowlder clay, a term descriptive of its constitution in
some places, and till, are other terms often applied to the ground mor-
aine. The ground moraine consists of all the drift which lodged
beneath the ice during its advance, all that was deposited back from its
edge while its margin was farthest south, and most of that which was
deposited while the ice was retreating. From this mode of origin it is
readily seen that the ground moraine should be essentially as wide-
spread as the ice itself. Locally, however, it failed of deposition. Since
it constitutes the larger part of the drift, the characteristics already
ATWOOD.] THE GEOLOGICAL FORMATIONS. 21
enumerated as belonging to .drift in general are the character-
istics of the till. Wherever obstacles to the progress of the ice lay
in its path, there was a chance that these obstacles, rising somewhat
into the lower part of the ice, would constitute barriers against which
debris in the lower part of the ice would lodge. It might happen also
that the ice, under a given set of conditions favoring erosion, would
gather a greater load of rock-debris than could be transported under
the changed conditions into which its advance brought it. In this case,
some part of the load would be dropped and over-ridden. Especially
near the margin of the ice where its thickness was slight and diminish-
ing, the ice must have found itself unable to carry forward the loads
of debris which it had gathered farther back where its action was more
vigorous. It will be readily seen that if not earlier deposited, all mater-
ial gathered by the under surface of the ice would ultimately find itself
at the edge of the glacier, for given time enough, ablation will waste
all that part of the ice occupying the space between the original posi-
tion of the debris, and the margin of the ice. Under the thinned margin
of the ice, however, considerable accumulations of drift must have been
taking place while the ice was advancing. While the edge of the ice
sheet was advancing into territory before uninvaded, the material ac-
cumulated beneath its edge at one time, found itself much farther from
the margin at another and later time. Under the more forcible ice
action back from the margin, the earlier accumulations, made under the
thin edge, were partially or wholly removed by the thicker ice of a
later time, and carried down to or toward the new and more advanced
margin. Here they were deposited, to be in turn distributed and trans-
ported still farther by the farther advance of the ice.
Since in its final retreat the margin of the ice must have stood at
all points once covered by it, these submarginal accumulations of drift
must have been made over the whole country once covered by the ice.
The deposits of drift made beneath the marginal part of the ice during
its retreat, would either cover the deposits made under the body of the
ice at an earlier time, or be left alongside them. The constitution of
the two phases of till, that deposited during the advance of the ice,
and that deposited during1 its retreat, is essenti?n" the same, and there
is nothing in their relative positions, to sharply differentiate them.
They are classed together as subglacial till.
Subglacial till was under the pressure of the overlying ice. In keep-
ing with these conditions of accumulation, the till often possesses a
firmness suggestive of great compression. Where its constitution is
clayey it is often remarkably tough. Wrhere this is the case, the qual-
ity here referred to has given rise to the suggestive name "hard pan."
Where the constitution of the till is sandy, rather than clayey, this firm-
ness and toughness are less developed, or may be altogether wanting,
since sand cannot be compressed into coherent masses like clay.
Constitution — The till is composed of the more or less comminuted
materials derived from the land across which the ice passed. The soil
and all the loose materials which covered the rock entered into its
composition. Where the ice was thick and its action vigorous, it not
22 THE EVANSTON-WAUKEGAN REGION. [BULL 7
only carried away the loose material which it found in its path, but,
armed with this material, it abraded the underlying rock, wearing down
its surface and detaching large and small blocks of rock from it. It
follows that the constitution of the till at any noint is dependent upon
the nature of the soil and rock from which it was derived.
If sandstone be the formation which has contributed most largely to
the till, the matrix of the till will be sandy. Where limestone instead
of sandstone made the leading contribution to it, the till has a more
earthy or clayey matrix. Any sort of rock which may be very generally
reduced to a fine state of division under the mechanical action of the
ice, will give rise to clayey till.
The nature and the number of the bowlders in the till, no less than
the finer parts, depend on the character of the rock overridden. A hard
and resistant rock, such as quartzite, will give rise to more bowlders
in proportion to the total amount of material furnished to the ice, than
will softer rock. Shale or soft sandstone, possessing relatively slight
resistance, will be much more completely crushed. They will, there-
fore, yield proportionately fewer bowlders than harder formations, and
more of the finer constituents of till.
The bowlders taken up by the ice as it advanced over one sort of rock
and another, possessed different degre.es of resistance. The softer ones
were worn to smaller dimensions or crushed with relative ease and
speed. Bowlders of soft rock, are therefore, not commonly found in
any abundance at great distances from their sources. The harder ones
yielded less readily to abrasion, and were carried much farther before
being destroyed, though even such must have suffered constant re-
duction in size during their subglacial journey. In general it is true
that boulders in the till, near their parent formations, are larger and
less worn than those which have been transported great distances.
The ice which covered this region had come a great distance and had
passed over rock formations of many kinds. The till therefore con-
tains elements derived from various formations ; that is, it is litho-
logically heterogeneous. This heterogeneity can not fail to attract
the attention of one examining any of the many exposures of drift
along the lake shore or the stones lodged on the beach.
In general the till of any locality is made up largely of material de-
rived from the formations close at hand. This fact seems to afford
sufficient warrant for the conclusion that a considerable amount of
deposition must have gone on beneath the ice during its movement,
even back from its margin. To take a concrete illustration, it would
seem that the drift of the Evanston-Waukegan region should have had
a larger contribution than it has of material derived from Canadian
territory, if material once taken up by the ice was all or chiefly carried
down to its thinned edge before deposition. The fact that so 'little of
the drift came from these distant sources would seem to prove that a
large part of the material moved by the ice, is moved a relatively short
distance only. The ice must be conceived of as continually depositing
parts of its load, and parts which it has carried but a short distance, as
it takes up new material from the territory newly invaded. In keep-
ing with the character of till in general, that of this region was de-
rived largely from limestone.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 2.
. A. Abandoned clay pit near Fort Sheridan. [Courtesy of the C. & N. W. Ry.]
Fig. B. Sketch of ground moraine topography.
Fig. C. Sketch of terminal moraine topography.
ATWOOD.] THE GEOLOGICAL FORMATIONS. 28
Topography — The topography of the ground moraine is in general
the topography already described (pp. 13-15) in considering the modi-
fication of preglacial topography effected by ice deposition. As left by
the ice, its surface was undulating. (Plate II, Fig. B.) The undula-
tions did not take the form of hills and ridges with intervening valleys,
but of swells and depressions standing in no orderly relationship to
one another. Undrained depressions are found in the ground moraine,
but they are, as a rule, broader and shallower than the "kettles" com-
mon to terminal moraines (Plate II, Fig. C.) It is in the broad, shallow
depressions that many of the lakes and more of the marshes of south-
eastern Wisconsin are located.
The rolling, undulating topography characteristic of ground mo-
raines is well shown just west of the Chicago and Northwestern road
between Glencoe and Waukegan. North of Waukegan, the upland
is typical ground moraine, but the lowland is an ancient lake flat.
When the entire morainic area from the shore of Lake Michigan to
the Des Plaines river is considered, it is found to consist of three
somewhat distinct north-south ridges* separated by lowlands of gently
rolling topography. The west ridge decreases in height to the south,
and dies out in a plain near Mont Clare in the southwestern part of
Jefferson township. The southern terminus of the middle ridge is near
the head of the Chicago river, and at the border of the former extension
of the lake. The eastern ridge is the one with which we are chiefly
concerned in the north shore region. This ridge extends from the
northern boundary of the State southward to Winnetka, where it is
intersected by the present lake shore. The most easterly of these
ridges rises about 100 feet above the lake, a mile back from the shore.
Its crest is followed by the C. & N. W. railway for some miles. These
ridges still remain much as the ice left them. The time which has
elapsed since the ice disappeared from the region has been too short
for them to have been greatly changed. A bowlder train on the lake
bottom was reported by Lyman Cooley, of the Chicago Drainage
Commission as running southeastward for several miles from the ter-
minus of this ridge, and Mr. Leverett thinks this may be the residue
from the till ridge which has been cut away by the lake.* Aside from
the ravines the upland of the Evanston- Waukegan region has a ground
moraine topography. If the ravines were filled and the rolling upland
extended eastward, descending gradually to the lake level, the surface
as left by the ice would be essentially reproduced.
TERMINAL MORAINES.
Formation — The marginal portion of the ice sheet was more heavily
loaded — certainly more heavily loaded relative to its thickness — than
any other. Toward its margin, the thinned ice was constantly losing
its transportive power, and at its edge this power was altogether gone.
Since the ice was continually bringing drift down to this position and
* These ridges have been fully described by Leverett in "The Pleistocene Features and
Deposits of the Chicago Area. " Bull. 2, p. 42, Geol. and Nat. Hist. Surv., Chicago Acad. of
Sci.
t For fuller discussion see Chicago Folio U. S. Geol. Surv., p. 6, by Wm. C. Alden.
24 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
leaving it there, the rate of drift accumulation must have been greater,
on the average, beneath the edge of the ice than elsewhere.
Whenever, at any stage of its history, the edge of the ice remained
essentially constant in position for a long period, the corresponding
submarginal accumulation of drift was great, and when the ice melted,
the former site of the stationary edge would be marked by a broad
ridge or belt of drift, thicker than that on either side. Such thickened
belts or drift are terminal moraines. It will be seen that a terminal mo-
raine does not necessarily mark the terminus of the ice at the time of
its greatest advance, but rath,er its terminus at any time when its edge
was stationary or nearly so.
These submarginal moraines are often made of materials identical
with those which constitute the ground moraine. Such materials as
were carried on the ice were dropped at its edge when the ice which
bore them melted from beneath. If the surface of the ice carried
many bowlders, many would be dropped along the line of its edge
wherever it remained stationary for any considerable period of time.
A terminal moraine, therefore, embraces (i) the thick belt of drift
accumulated beneath the edge of the ice while it was stationary' or
nearly so; and (2) such debris as was carried on the surface of the
ice and dumped at its margin. In general the latter is relatively
unimportant.
Topography of terminal moraines — The most distinctive feature of
a terminal moraine is not its ridge-like character, but its peculiar
topography. In general, it is marked by depressions without outlets,
associated with hillocks and short ridges comparable in dimensions
to the depressions (Plate II, Fig. C). Both elevations and depres-
sions are, as a rule, more abrupt than in the ground moraine. In the
depressions there are many marshes, bogs, ponds and small lakes.
The shapes and the abundance of round and roundish hills have locally
given rise to such names as "The Knobs," "Short Hills," etc. Else-
where the moraine has been named the "Kettle Range," from the
number of kettle-like depressions in its surface. It is to be kept in
mind that it is the association of the "knobs" and "kettles," rather
than either feature alone, which is the distinctive mark of terminal
moraine topography. Terminal moraines have no distinct develop-
ment within the area here described, and are mentioned here only
for general contrast with the ground moraine.
STRATIFIED DRIFT.
While it is true that glacier ice does not distinctly stratify the de-
posits which it makes, it is still true that a very large part of the drift
for which the ice of the glacial period was directly or indirectly re-
sponsible is stratified. That this should be so is not strange when it is
remembered that most of the ice was ultimately converted into running
water, just as the glaciers of today are. The relatively small portion
which disappeared by evaporation was probably more than counter-
blanced, at least near the margin of the ice, by the rain which fell
upon it. It can not be considered an exaggeration, therefore, to say
THE GEOLOGICAL FOEMATIONS.
25
that the total amount of water which operated on the drift, first and
last, was hardly less than the total amount of the ice itself. The drift
deposited by the marginal part of the ice was affected during its depo-
sition, not only by the water which arose from the melting of the ice
which did the depositing, but by much water which arose from the
melting of the ice far back from the margin. The general mobility of
the water, as contrasted with the ice, allowed it to concentrate its activi-
ties along those lines which favored its motion, so that different por-
tions of the drift were not affected equally by the water of the melting
ice.
All in all, it will be seen that the water must have been a very im-
portant factor in the deposition of the drift, especially near the margin
of the ice. But the ice sheet had 'a marginal belt throughout its whole
history, and water must have been active and effective along this belt,
not only during the decadence of the ice sheet, but during its growth
as well. It is further to be noted that any region of drift stood good
chance of being operated upon by the water after the ice had departed
from it, so that in regions over which topography directed drainage
after the withdrawal of the ice,, the water had the last chance at the
drift, and modified it in such a way and to such an extent as circum-
stances permitted.
FIG. 10. Section showing relations of stratified drift (a), till (b), and beach sands and
gravels (c), as exposed at Winthrop Harbor.
There are no clearly defined areas of stratified drift in the upland
part of the Evanston-Waukegan region, but within the drift ex-
posures along the lake cliff, lenses or patches of stratified drift may
be seen frequently.
At Winthrop Harbor the section represented in Fig. 10 is exposed
along the main north-south road. The stratified drift at the base
was deposited beyond the ice edge during its advance, or during some
temporary period of recession. After the assorted material was laid
down, the ice advanced over this particular area, and deposited a
layer of till. The sands and gravels above the unstratified drift of
the section are beach formations of the Glenwood stage of Lake
Chicago.
26
THE EVANSTON-WAUKEGAN KEGION.
BULL. 7
FIG. 11. Drainage in the driltless area. The absence of ponds and marshes
is to be noted. (Courtesy of Wisconsin Geol. Nat. Hist. Surv.)
FIG. 12. Drainage in a glaciated region, Walworth and Waukesha counties, Wis., showing
abundance of marshes and lakes. (Courtesy Wis. Geol. Nat. Hist. Surv.)
ATWOOD.J THE GEOLOGICAL FORMATIONS. 27
Stratified drift covers much of the surface below an altitude of
640 feet. (See topographic maps.)
To appreciate the changes which glaciation effected in this region,
it may be pointed out that both the topography and the surface ma-
terial of unglaciated regions are very different from those of this re-
gion. The driftless or unglaciated area in the northwestern part of
the State already referred to, has a surface shaped almost wholly by
running water. All depressions are valleys and have outlets. The
region is therefore well-drained, and so without the ponds, marshes,
etc., which often characterize recently glaciated areas (Figs, n and
12).
Unglaciated surfaces are generally overspread by a mantle of soil
and earth which has resulted from the decomposition of the underlying
rock. This earthy material sometimes contains fragments and even
large masses of rock like that beneath. These fragments and masses
escaped disintegration because of their greater resistance, while the
surrounding rock was destroyed. This mantle rock grades from fine
material at the surface down through coarser, until the solid rock is
reached, tne upper surface of the rock being often ill-defined (Fig.
13). The thickness of the mantle is approximately constant in- like
topographic situations where the underlying rock is uniform. The
residual soils are made up chiefly of the insoluble parts of the rock
from which they are derived, the soluble parts having been removed
in the process of disintegration.
FIG. 13. Diagram showing the relation of residual soil to the underlying rock from
which it is derived. (Courtesy of U. S. Geol. Surv.)
With these residuary soils of the driftless area, the mantle rock of
glaciated tracts is in sharp contrast. Here, as already pointed out,
the material is diverse, having come from various formations and
from widely separated sources. It contains the soluble as well as the
insoluble parts of the rock from which it was derived. In it there is
no suggestion of uniformity in thickness, no regular gradation from
fine to coarse from the surface downward. The average thickness of
the drift is also much greater than that of the residual earths. Further,
the contact between the drift and the underlying rock surface is
usually a definite surface. (Compare Figs. 8 and 13.)
28 THE EVANSTON-WAUKEGAN REGION. [BULT,. 7
THE PRESENT SHORE LINE.
(BY J. W. GOLDTHWAIT.)
EVOLUTION SEEN IN SHORE LINE TOPOGRAPHY.
The land forms peculiar to shore lines depend for their existence
upon those movements of the waters which are initiated by the winds.
If there were no winds, such a lake as Lake Michigan would be prac-
tically without waves and currents, a dead, inert sheet of water; and
its shores would be without strength and character. Shore forms,
like all other forms, are changing, living objects in so far as solar
energy is expended upon them through the so-called geological
agents — in this case waves and currents. On sea shores the tides are
also of importance in determining and constantly modifying the shore
topography.
On a day when the air is calm or when a light off-shore breeze is
blowing and the lake is smooth, the agents just mentioned are tempo-
rarily inactive. On such a day one may stand on the bluff overlooking
Lake Michigan at any point on the north shore, and as far out as can
be seen the lake water is unclouded by sediment. At the base of the
bluff is a bare beach of sand or gravel, against the border of which
the small waves are lapping in a weak, desultory way. It is scene
of inactivity. At such a time the evolution of shore forms would not
be evident. But when a strong east wind has roused the waves to
violence, whitecaps dot its roughened surface, and a strong surf is
breaking near the shore and sweeping back and forth in rhythmic
fashion at the base of the cliff, nearly or quite concealing the beach
platform below. The waves are gnawing into the base of the bluff,
exposing the fresh, blue clay, where formerly may have been a turf-
covered slope. From the face of the bluff, thus steepened, great masses
of clay may be seen slipping down to the water's edge, where they are
further broken up by the waves and thoroughly separated into the
constituent boulders, gravel, sand and mud. Trees toppling from
the brink of the bluff emphasize the rapidity of the process (Plate
III, Fig. A). The waters of the lake for a long way out are muddy
with suspended sediment. By oblique advances and retreats of the
waves upon the shore, gravel is being washed up and down the
beach in zig zag fashion along the shore. It is an easy inference that
in the shallow water just beyond, sand is being drifted steadily lee-
ward. The lake is now in action, and the shore form in process of
development. One returns from such a view with a ready belief in
doctrine of change or evolution as applied to shore forms.
GOLDTHWAIT!
THE PRESENT SHORE LINE.
29
AGENTS AT WORK ALONG SHORE LINES.*
The Waves — When a strong wind sweeps across the surface of a
body of water, it communicates energy which sets every water particle
oscillating in an approximately circular orbit — the basis of the phen-
omenon which we call a wave. In the normal off-shore wave, or
in any normal wave away from the shore, there is very little forward
advance of the water; each particle returns nearly or quite to its
original position, so that the wave has well been called "a traveling
shape of water." In the form of wave known as the swell, which
moves in deep water, outside the area1 which is under the direct influ-
ence of the wind, the orbits of the particles of water are closed.
There is no permanent advance of the water. But in the wind wave,
the forward movement of the particle is always slightly in excess of
the return movement, so that each particle describes a spiral rather
than an ellipse, and there is generated a slow current which moves for-
ward following the waves. Figure 14 shows how the particles move
FIG. 14. Diagram showing the movement of particles in a wave. The waves
are moving from left to right.
in different parts of a wave, forward in the crest, backward in the
trough, upward in front of the crest and downward behind it. The
orbital motion of the particle is less rapid than the wind ; the advance
of the wave is even slower, and that of the wind driven current is
still slower. By transmission downward, these motions are extended
into deep water, but with rapidly diminishing effect. The deeper
the water, the less are the movements embarrassed by friction on the
bottom, the larger will be the waves and the stronger the currents.
On the open ocean, wind waves are sometimes fifty feet high and
1,500 feet long, measured from crest to crest; but these are excep-
tional. On Lake Michigan the waves exceptionally attain a height
of twenty feet.
The crest of a wave is always sharper than the trough, for the wave
assumes the form of a trochoid curve, such as is described by a point
within a circle which rolls on a horizontal line. (See Figure 15 H.)
The sharpness of the crest is exaggerated when the wave length is
shortened or its height increased. Compare, for instance, Figures
15, 16, 17 and 18.
* In the preparation of what follows regarding waves and their work the writer has drawn
freely from Gilbert's paper on ' 'The Topographic Features of Lake Shores, " U. S. Qeol. Sunr.,
5th Ann. Kept., pp. 69-123, 1885; and chapter 2 in Fenneman's "Lakes of Southeastern Wiscon-
sin, " Wis. Geol. and Nat. Hist. Surv. Bull. 8, 1902.
30
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
FIG. 15. Series of particles in their orbits. The circles represent the orbits of the particles
which revolve from left to right. At any given moment each particle is advanced in its orbit
54 degrees more than its neighbor on the right. The curved line connecting these simultaneous
positions of the particles represents the form of the wave. (After Penneman.)
FIG. 16. The phasal difference of the particles has been increased from 45° to 90°. The
crests of the waves thus become sharper. (After Fenneman.)
FIG. 17. The orbits have been increased to twice their former size; but the phasal
difference is the same as in flg. 15. (After Fenneman.)
Fig. 18. By an increase both in the phasal difference of the particles and in the size of
the orbits, a curve is developed, suitable for breakers. (After Fenneman.)
In Figure 15 various positions of a series of neighboring particles
in the waves in their respective orbits are shown, the phasal differ-
ence of the particles being 45°. The surface of the wave which
passes through these particles forms a low trochoid curve. In Figure
1 6 the wave has been shortened by increasing the difference in phase
of the particles to 90° ; and the trochoid is more pronounced in form
than before, with sharper crest and flatter troughs. In Figure 17 the
waves' length is like that of the first, but the amplitude of the orbital
motion has been increased, and as a consequence the contrast between
the crest and trough exaggerated. In Figure 18 the shortening and
increase of amplitude has gone so far as to develop a trochoid curve
that has loops in place of cusps — the condition for breaking waves.
White caps are an expression of such a curve as the last, developed
when the amplitude of the wave is increased more rapidly than its
length by a wind of fast increasing strength.
When a wave approaches a shelving shore, reaching shallower and
shallower water, its form is very considerably changed: (i). The
wave becomes higher; for the transmission of energy to a smaller
amount of water gives to each particle an increased orbital movement ;
(2). The wave is shortened, for increased friction diminishes the
velocity of orbital motion of every particle, and this means a greater
differential movement between the neighboring particles (compare
GOLDTHWAIT] . THE PRESENT SHORE LINE. 31
Figures 15 and 16; (3). The crest becomes stepper and sharper, the
result of shortening the wave ; and (4) the crest becomes a symmetri-
cal, steeper in front than behind, because the forward motion in the
crest, where the water is deeper, is more rapid than the backward mo-
tion in the trough, where water is shallower.
These changes of form become more and more marked, finally re-
sulting in the breaking of the wave. The crest is thrown forward
with a curling front, and the water foams and tosses with the con-
fusion of oscillatory and translatory movements, for the sudden
plunge of the broken crest starts new waves of translation or "soli-
tary waves/' which are quite different in nature from waves of oscil-
lation. In the wave of translation each particle is carried forward in
a semi-ellipse, those at the bottom moving as far as those at the sur-
face.
Waves of translation are very efficient in sweeping material ashore.
Since breakers usually form close to the water's edge, translatory
waves are usually of short range and consist merely of a forward dash
or "swash" of the wave to the crest of the beach. If, however, the in-
coming wind-waves break far off shore, as on a very shallow bottom,
the diminution of height may permit them to re-form in conjunction
with the translatory waves, and to run ashore until finally they break
again. Translatory waves, where uncombined with oscillatory waves,
are easily distinguished by their extremely broad and flat troughs, and
narrow, sharp crests. The on-shore dash of the broken wave is fol-
lowed by a return wash of the water down the beach slope to the point
where it meets the next incoming wave of translation. Thus there is
between the breakers and the water's edge a zone where material is
shifted ba'ck and forth by opposed rhythmic movements. Under dif-
ferent conditions of shore profile, wave force, etc., .either the inward
or the outward action may be favored, and the erosion or deposition
determined.
Undertow — The return flow of the broken wave gives rise to a per-
manent outgoing movement known as the "undertow." In a more
comprehensive way, the undertow may be thought of as the means
by which all water moved ashore by the wind-driven currents and by
the waves of translation finds its way back to deep water. Instead of
being a steady movement, it is a pulsating one, markedly so just out-
side the breaker line, because of the continual passage of oscillatory
waves above it, and the alternate cooperation and opposition of those
oscillations. Close to the breaker line, indeed, the on-shore transla-
tory motion may counter-balance the undertow, and these conditions
are favorable for deposition of material from both the off-shore and
the on-shore forces. The pulsating nature of the undertow greatly
increases its ability to transport waste seaward, for by hundreds of re-
peated jerks, a pebble which would be immovable under a steady cur-
rent of the average velocity of the undertow, may be carried out inch
by inch to a considerable depth. Thus it is that while the average
velocity of currents along the Lake Michigan shore would permit
them to carry sand no farther out than to a depth of about 36 feet,
gravel, which may be suspected to have been carried out by the lake
32 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
currents, is found much farther off shore. It is also to be expected,
of course, that irregularity of the lake shore will lead to local con-
centrations of the outgoing current.
The office of the undertow is primarily to dispose of material eroded
by the waves ; but it also scours the submerged platform across which
the waves are sawing back into the land. Without it, of course, there
could be no inland recession of a shore.
Shore Current — Usually the storm wind does not blow straight on-
shore, but at an angle to it. Consequently the waves far off shore are
advancing with fronts oblique to the shore line. That part of the
incoming wave which first reaches shallow water will be retarded,
the wave front being bent or refracted until, by the time the wave
breaks, it is nearly parallel to the beach. So efficient is this refraction
that with winds from very diverse quarters the obliquity of the surf
to the shore line is always a small angle. It is usually enough, how-
ever, to determine a marked drift along the shore, called the "shore
current." This is the great agent of transportation of sand and
gravel along shore, though it is aided in this work by the waves
themselves in the zigzag swash and return flow along the beach.
Although on some coasts it is true that storm winds from different
quarters frequently reverse the direction of the shore current, it
nearly always happens that on account of the prevailingly greater
strength of wind from one direction, one of the opposed currents
is the dominant one.
DEVELOPMENT OF COASTAL TOPOGRAPHY.
When a lake is first formed in an enclosed basin, or when a con-
siderable change in level brings a lake into a new position against
the land, the waves and currents find a coast which is not adjusted to
their erosive and constructive activity.
The coast may be very irregular in outline and ill adapted to an
organized system of waves and currents. This is particularly the case
with a newly formed lake, or with a shore which has been produced
by the submergence of a river-sculptured land surface (as by a sink-
ing of the land with reference to the sea). On the other hand, if the
shore line be determined by a rise of the submerged sea floor to form
a shelving coastal plain, or if the lowering of the level of a lake lays
bare a smooth lake plain, the shore may have a simple outline, but its
profile may not be adjusted to the waves. Whatever be the. nature
of the initial shore line, whether it be an irregular shore of depres-
sions or a straight shore of elevation, changes in profile, and to a
greater or lesser degree in horizontal configuration are sure to be
wrought out by the waves.
CHANGES IN PROFILE.
In profile, the new shore may be steep, and the undertow may thus
be favored, so that more loose material will be swept off-shore by the
waves than can be brought in by on-shore action. Or the slope of
the new shore may be gentle, in which case incoming waves will be
stronger than the undertow, and more material brought in than
is swept out. In either case, the opposed forces will tend to con-
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 3.
m
Fig. A. Receding cliff at Gross Point.
Fig. B. Sand dunes at Rogers Park.
GOL.DTHWAIT.J
THE PRESENT SHORE LINE. 33
struct a profile on which the incoming and the outgoing of beach
gravel and sand is balanced — an ideal adjusted curve known as the
"profile of equilibrium." Once gained, this profile is in a general way
stable. Yet it is subject to a gradual change because the beach ma-
terial is constantly being worn out and scattered far off shore, and
because, with progressive change in horizontal outline of the shore,
the amount of waste material along shore is continually changing.
The latter element of change, the variation in direction and rate
of "long-shore drift" (beach gravel and sand), is a consequence of
the initial irregularity of the shore, both in plan and in profile. Not
only will the shore agents seek to establish a balanced profile, but
the shore currents especially will so distribute the beach waste as to
reduce the iivegularities of the shore by cutting back the headlands
and filling in the bays. A closer inspection of this development of
shore topography may now be made. It will be convenient to con-
sider first the changes wrought in profile and then the changes in
horizontal configuration, although these must always go on at the
same time.
The Sea Cliff — If the initial slope is sleeper than the profile of equil-
ibrium, the waves strike the shore forcibly and cut away the material
at the waters' edge, while, together with the shore currents and the
undertow, they separate and carry away the debris — the coarser part
being drifted along shore and the finer being carried in suspension
far off shore, until it settles in deep water. The debris thus gathered
is used by the waves as a tool by which to cut away the base of the
cliffs. The process is essentially a horizontal sawing at the water's
edge, whereby a submerged terrace, flatter than the initial slope, is
cut backward into the land, and the coast above lake level is steepened
to a line of cliffs.
^^ffEiS^ ¥ -^
FIG. 19. Section showing how a cliff and wave-cut terrace is developed.
(Salisbury and Alden.)
The initial profile D B A is thus gradually changed to a profile D
D ' A ' . The wave cut D ' A ' , instead of being horizontal, will slope
gently off shore, because its outer border began to be eroded first
and because the wave action is stronger there. The width and the
slope of the cut terrace, the depth of its submerged outer border, and
the height of its upper border above lake level, vary according to the
-3G.
34 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
strength of the wave action, the time during which the waves and
currents have been at work, and the strength of material. The
longer the process goes on, the broader and deeper will be the outer
border of the terrace. The greater the "fetch" of the waves, the
farther up the slope can erosion extend, and the higher the upper
border of the terrace will be. On abrupt rocky shores the terraces are
usually narrow and steeply inclined. In the north shore district, be-
tween Evanston and Waukegan, the platform at the base of the clay
bluffs has a gentle slope and rises usually three or four feet above
lake level. (See Plate III, Fig. A, and Plate IV, Fig. A.)
The recession of these clay bluffs is accompanied by land slips of
considerable size, particularly in the spring, when the thawing of the
frozen clays and the percolation of water supplied by spring rains
lubricates the structure, so that great blocks of the ov,er-steepened
cliff part and slide downward toward the lake. Fresh land slides
of this kind often form a sod-covered terrace or group of step-like
terraces along the bluffs, the bare clay surface above the terrace fre-
quently showing grooves where stones or roots of the loosened block
scraped against the opposite side of the slipping plane during the dis-
placement. Frequently, also, the loosened and lubricated clay slides
down the cliff face in a plastic condition, forming steep cones of
sticky mud; but wave action soon trims them away, steepening the
lower part of the cliff, eating back into the more solid landslide block,
and thus favoring a renewal of the slipping. Successive blocks are
thus pulled down by gravity as the waves cut inland. Much material
also creeps down the steep cliff face in small amounts, and very much
is washed down by rain, developing innumerable gullies from which
the waste is spread out on the beach in fan-like deposits. ( See Plate
XI.)
It must not be thought, however, that ^ie shore terrace is wholly
a wave-cut form. It is commonly covered with a sheet of gravel and
sand called the beach, and if it borders deep water, its outer margin
is usually extended by deposits of waste carried out by the undertow.
FIG. 20. Cross section of a sea cliff with a cut-and-built terrace.
So long as the shore line is advancing into an upland which slopes
toward the lake, as is quite generally the case along the north shore,
the shore cliffs will of necessity be increasing in height. In other
words, the cliff face, from which waste is being swept to the lake by
land slides, creeping, and rain-wash, is constantly increasing in area,
and thus the rate of supply of waste is increasing. A critical point
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 4.
Fig. A. Cliff and beach near Fort Sheridan. [Courtesy of C. & N. W. Ry.]
Fig. B. Lake cliff at Racine, Wis.. near Racine College. The waves have continued to
encroach upon the land in spite of the piers. [Courtesy of C. & N. W. Ry.]
GOLDTHWAiT.f THE PRESENT SHORE LINE. 35
may thus be reached when the supply of waste begins to exceed the
capacity of the waves and currents to transport it. The waves and
currents then become overloaded, the beach on the terrace is broadened
and thickened by deposition of waste, and the cliffs retreat with less
and less rapidity. Meanwhile, the terrace has been broadened and
deepened until its outer edge may be as low as the level of effective
erosion by waves and currents, a limit known as "wave base."
Farther retreat of the cliffs will go on only so fast as the material
of the beach is worn out by the slow grinding process, and the terrace
will become flatter as more and more of it is reduced to the wave
base. So it comes about that the most rapid retreat of the lake cliff
is usually in the early stages of its development. It may then possess
a simple wave-cut platform from which the material is carried as fast
as it is fed down the cliffs. Such bare clay platforms may be seen
occasionally along the north shore where cliff recession is most active,
but usually the platform is covered with at least a thin veneer of sand
and gravel. At those points where the till includes more bowlders and
pebbles than usual, the beach is more gravelly than where the till con-
sists almost entirely of clay. The beach reflects somewhat imperfectly
the composition ^ of the associated cliffs.
The Beach Ridge — When the coastal slope is flatter than the profile
of equilibrium, the undertow is weaker than the on-shore movement of
translatory waves; hence material is shifted shoreward and cast up
at or near the water's edge in such a way as to steepen the slope. The
profile of typical beach has a gentle sigmoid curve, the back-slope of
PIG. 21. Cross section of a beach.
the ridge being short, steep and convex upward, while the front slope
(below the convex curve of the ridge) is long, gentle and concave —
the concavity expressing an equilibrium between the opposed forces.
Because the on-shore wave action increases rapidly toward the water's
edge to the detriment of the undertow, the deposition becomes rapidly
greater near that line and the resulting slope is increasingly steeper —
that is, concave. But the crest of the ridge and its back-slope are de-
termined chiefly by the angle at which the beach material comes to rest
when cast up out of reach of the waves.
It must not be thought, however, that slope is the only factor which
determines whether waves and currents of a griven strength will build a
beach or cut a terrace and cliff. Load (amount of sand, gravel, etc.
handled by the waves) is quite important. And, as will be brought out
later, the amount of load depends largely upon the strength of shore
currents. Much more waste may be brought to a given place by drift
of material along the shore than by the on-shore sweep of translatory
36 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
waves. Beach ridges may therefore accumulate, even on moderately
steep slopes, if the supply of shore drift is too great for the undertow to
sweep away.
Beach ridges are common along the abandoned shorelines of the
Evanston-Waukegan district, to be described in pages 54-68. Some of
them were doubteless true beaches, built by on-shore transportation in
shallow water; but the more conspicuous ridges seem to have been
great barriers or bars of the sort presently to be described and to be
attributed mainly to long shore transportation. Occasional secondary
ridges often with faint crests, which lie on the lakeward slope of the
main ridges (e. g. the lower ridges on the campus at Northwestern
University) seem to have been normal shallow water beaches.
The Barrier — When the initial slope is excessively flat the incoming
waves break some distance off-shore and there grows up along the
breaker line a reef or "barrier." The material accumulated in it is
brought partly from off-shore by the incoming surf and partly from the
land by the outgoing undertow. The barrier, then, like the ordinary
beach ridge may be looked upon as the result of the effort of the pre-
dominant on-shore movement to steepen the slope to the curve of
equilibrium, it being necessary in this case that the beach ridge be
built off-shore instead of at the water's edge, if a curve of sufficient
steepness is to be constructed within the range of the waves. Again,
however, the long-shore supply of waste must be considered, as well as
on and off-shore movements of beach material. It is believed that
shore drift currents are often of great importance in the accumulation
of barriers, for the breaker line is a line of greatest agitation of the
water, sand and gravel is constantly being danced up and down below
the breakers, and the shore currents, which would be powerless to
move such coarse material if it were at rest on the lake bottom, can shift
it very considerably by repeated jerks while it is temporarily in suspen-
sion. In the protected water lagoon behind the barrier, sediment
swept from the land by storms or from the lake by currents may be
deposited. Vegetation is likely to gain possession of this lagoon and
slowly to convert it into a marsh or peat bog (Fig. 22).
So long as the supply of material to a beach or a barrier is constant,
its form will be maintained in spite of the loss of material by attrition
and by off-shore transportation. It may be that the supply by shore
drift on the outer side will exceed the loss, in which case the reef will
build slowly forward into the lake. More frequently, however, the
supply fails to keep pace with the loss, especially where sand is blown
inland from the beach by strong on-shore winds, forming a line of
marching dunes, which are followed consistently by the beach or
barrier itself. So it happens, sooner or later, that a barrier is beaten
back across its lagoon, in which it is likely that considerable swamp
deposits have already been formed (see Pig. 22). The line of reefs,
reaching the main land shore is then replaced by the beach ridge, and
finally, if erosion continues to predominate, by a line of receding
cliffs.
GOLDTHWAIT.] THE PRESENT SHORE LINE. 37
FIG. 22. Cross sections of a barrier. In the lower figure the barrier has moved inland, part
way across a marshy lagoon, (b) barrier; (1) lagoon; (m) marsh; (p) peat; (d) dune.
The life history of a barrier beach is finely illustrated on the New
Jersey coast. (See Figure 23.) The heavy surf of the Atlantic
ocean running ashore on the low shelving coast has cast up a long line
of barrier breaches a few miles off shore. At Atlantic City the barrier
is a mile broad and constantly growing on its seaward side, under the
excessive supply of shore drift. Hotels along the beach have been
moved forward at times in order to keep near the ocean front. Farther
north, near Barnegat Bay, the barrier has retreated. Here the supply
of shore drift is not sufficient to counterbalance the waste lost by
attrition, by off-shore scattering and by the construction and mainten-
ance of dunes, which are marching inland across the salt marshes of the
broad lagoon. On the outer side of the beach each storm exposes and
gnaws back the edge of a stratum of tide-marsh deposit, a compact mass
of mud and eel-grass — the former lagoon deposits across which the
beach is being pushed. The lagoon narrows northward, toward Point
Pleasant, where the barrier joins the low mainland. Thence northward
for about 15 miles to Long Branch, the barrier is replaced by a line of
low sea-cliffs which are receding so rapidly during storms as to ser-
iously endanger property along the shore. Erosion here is in excess
of deposition ; the barrier has been beaten inland, worn out and replaced
with bluffs.
The ultimate form of any shoreline, therefore, is normally the cliff
and terrace. If the water is deep, cliffs develop at once, and are main-
tained so long as no abnormal supply of load is brought by shore-drift
currents. If the water is shallow, a beach or a barrier is first thrown up
to establish the profile of equilibrium; but if no excessive load is
brought by 'long-shore currents, the barrier is gradually beaten inland
and replaced by the sea-cliff.
Among the abandoned shore lines of the Evanston district, the
great ridges of the Glenwood, Calumet and Toleston stages, described
in pages 54-66, may be regarded as barriers, built far off-shore, partly
by the on-shore sweeping of waste and partly by 'long-shore currents.
The great Ridge avenue bar in Evanston is as good an illustration as
any. (See pp. 61-63 and the map, Plate VI.) The absence of barrier
38
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
FIG. 23. Outline map of New Jersey showing the shore line with its retreating barriers.
beaches along the present shore of Lake Michigan may be attributed
to the mature condition reached by the lake in the long interval since
its higher stages. The present lake cliffs are comparable in their devel-
opment to those of the Long Branch district.
CHANGES IN HORIZONTAL CONFIGURATION.
Spits, Bars and Hooks — The changes wrought in the horizontal con-
figuration of the shore are closely associated with the activity of 'long-
shore currents, but they cannot be separated from the work of waves
and undertow. It is usually true that along an initially irregular shore
the headlands present steeper slopes than the re-entrants. Moreover,
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PL 5.
Fig. A. Pier and beach near county line showing effect of southward drift.
Fig. B. Bar at mouth°of>avine near'county'line.
OLDTHWAIT.J
THE PBESENT SHORE LINE.
the exposure to wave action is greater on the headlands; hence the
usual development of the eroded sea-cliff on the salients, and of the
beach ridge or the barrier in the re-entrants of the coast.
The wasting headlands supply beach material for the shore currents
to drift into the re-entrants, where it may be cast up as a "pocket- or
bay-head beach," similar to the beach formerly accounted for by
excessive on-shore action. With a constant excess of supply of shore-
drift, such a beach will grow continually on its outer border. If it is
built up across the mouth of a stream, it may form either a continuous
bar, which, except during floods, is increased by the waves (a condition
illustrated by Plate V, Fig. B) or a discontinuous bar, through which
a channel is maintained by the stream, is formed (the case of Petti-
bone Creek and others of its size, Plate XII). The outlet beach is
always at the farther end of the bar as viewed in the direction of the
shore-drift current, because the stream is diverted to leeward by the
drift. If the beach grows outward by continual deposition on its sea-
ward side, the stream is correspondingly extended, not straight out
to the lake, but obliquely, indicating a constant response to the deflec-
tive force of the shore-current. Thus in the map (Fig, 24) streams
of the Long Island shore have been extended across the growing
sand beaches in deflected courses (e. g. the stream behind West
Meadow beach).
CraneJteck
"ft'
^ ^4*. ^ I"**8**1
V^wftr
^r V»S^ »
,4%^W
^//I^
FIG. 24.
Map of apart of the north shore of Long Island (sketched from the Islip,
N. Y.. sheet of the IT. S. Geol. Surv.)
40 THE BVANSTON-WAUKEGAN REGION. [BULL. 7
Sooner or later the deflected stream, especially if it be a small one,
is likely to be blocked at its mouth by thegrowthof the terroce. Its
water then reaches sea or the lake by percolation through the terrace
gravels.
North of Waukegan many streams follow deflected courses behind
the beach ridges of the extinct lake stages. As the lake has fallen in
level, from stage to stage, these streams have incised themselves along
the deflected courses, excavating valleys which run parallel to the
shorelines for long distances. Deflected courses are rare and fragment-
ary along the present shore, however, because of the absence of spits
and bars of any considerable length ; but the position of the mouths of
such streams as Pettibone Creek and Little Dead River, near the south
end of the obstructing bars, indicates the deflecting tendency of the
southerly drift currents.
It is obvious that shore currents collecting waste from the eroded
headlands and moving along in a wind-driven course will fail to con-
form in detail to any considerable irregularity of the shore, but will
extend off in a gentle curve, thus directing the shoredrift out into
deeper water, where it comes to rest as a submerged reef.
The greatest deposition is of course nearest the source of supply,
much of the coarser material being dropped close to the headland,
while the finer is swept farther on before it comes to rest at the end of
the reef. As the train of waste is built outward, it is also built up by
the overloaded waves (along the line of storm breakers as already
described for the barrier) and thus becomes a "spit," whose profile is
like that of the barrier beach, described on pages 36-37. By continued
growth, the spit becomes a "bar," reaching so far across the bay as
nearly or wholly to enclose it (e. g. Stony Brook Harbor, in Fig. 24).
No hard and fast distinction can be made between a spit and a bar;
they are different stages of development of a single form. Nor can a
bar be distinguished wholly from a barrier, for in neither of these
forms is the constructive agent a single and independent one. It is
convenient, however, to think of the barrier as constructed chiefly Hy
FIG. 25. Sketch map showing a bay enclosed by a pair of overlapping bars. The
arrows indicate the direction of wind driven currents.
on-shore action and the bar by 'long-shore drift. Since headlands split
the wind-driven currents so that on the two sides of the bay the shore-
drift moves in converging or even in opposed directions, it commonly
GOLDTHWAIT.]
THE PRESENT SHORE LINE.
41
happens that spits are built out toward each other, and the bay is
finally inclosed by the union of them, or, more frequently, the overlap-
ping of one by the other. Since the strongest surf and shore currents
come with wind in one quarter, and the currents on the two sides of a
bay are unequal, one spit commonly experiences more rapid growth
than the other. From the greater exposure of the spit on the windward
shore of the bay, it tends to hug the shore more closely than its neigh-
bor; consequently when the two overlap the windward spit or bar is
always the outer one.
The free end of a growing spit is always subject to deflection during
storms when the wind comes from a quarter other than the prevailing
one.
FIG. 26. Sketch map showing the development of a hooked spit.
Suppose, for instance, that tKe strong winds come prevailingly from
the northeast ; a spit will be built toward the southwest from the head-
land in Fig. 26 by the prevailing shore currents. If, after the spit has
grown out a certain distance, it comes under the influence of a strong
southeast wind (B) the shore current will be deflected in such a way
that the point of the spit will be turned inward, forming a hook. With
the return of ordinary conditions, the northerly shore current will be
destroyed, construction of the spit will go on as at first until another
change in quarter of a storm wind repeats the deflection and a new
hook is formed beyond the first. A long series of hooks may thus be
constructed along the growing end of the spit. This is remarkably
illustrated by Rockaway Beach, near New York City (see Fig. 27).
42
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
FIG. 27. Outline map of Rockaway Beach, Long Island.
Sandy Hook, outside New York Harbor, is another good example
of a hooked spit, built by heavily laden shore currents,
which- run northward from the cliffs near Long Branch,
New Jersey (Fig. 28). By continued growth on its outer
side and by the shifting of dunes, it has gained a breadth
of over half a mile near its northern end. Two branch spits on its
western or bay side, point significantly toward the south, indicating
that the shore drift on that side is a southward one, exactly opposite
to the northward drift of the ocean side. This is a normal feature, to
be expected on any well developd hook, as is obvious when the position
of the main hook relative to the bay and the consequent fetch of the
bay waves from different quarters is considered. The main spit in the
case of Sandy Hook incloses a bay at its southeast corner. While a
southeast storm would favor active drifting of beach material north-
ward along the Atlantic border of the hook, it would not stir the water
on the bay side except so far as the ocean waves rounded the promon-
tory and were refracted through a large arc as they ran southward up
the bay. To the extent that this occurs, the drift of material along
the bay side of Sandy Hook would be southward. A southwest wind
likewise would be quite as inefficient in determining the drift along the
bay side, because there would be almost no fetch for the waves, and the
shore under consideration would be protected from the wind by the
highlands of Navesink. A west or northwest wind, on the other hand,
would have the advantage of blowing the length of the bay and would
clearly produce the dominant short drift — one toward the south. From
the very conditions under which great hooked spits are constructed,
therefore, minor branches on their protected side, if developed at all,
extend in opposite direction to the main spit.
Thus it came about in one of the extinct stages of Lake Michigan,
when the lake stood about 35 feet higher than now, and the great Ridge
Avenue barrier in the Evanston district enclosed a broad bay (called
the "Wilmette embankment" on the map, Plate VI), that two or three
branch hooks were built out on the bay side of the barrier by currents
running northward — just opposite to the southward flowing currents
GOLDTHWAIT.]
THE PRESENT SHORE LINE.
43
S A. f</ D y HOOK BAY
FIG. 28. Sketch map of Sandy Hook, N. J.
of the dpen lake. The largest of these secondary hooks lies west of
Rogers' Park. Another diverges from the main ridge near the Evan-
ston golf club grounds. These repeat, in miniature, the type of spit
illustrated at Spermaceti Cave on the inner side of Sandy Hook (see
Fig. 28). A comparison ' of Fig. 28 and Plate VI, in this detail, will
be found instructive.
44 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
In the early high-level stages of Lake Michigan, described on pages
54-68, beach ridges, barriers, bars and spits were extensively devel-
oped; for the original shore of the lake, determined by glacial topo-
graphy was very irregular, both in plan and in outline, and ill-adapted
to wave work. Whenever the slope was deficient or the supply of 'long-
shore drift excessive, beach, ridges, bars and similar forms were built.
But as time went on, the shores were smoothed and straightened by the
waves, so as to correct the deficiencies in contour and profile, beach
ridges were superseded by shore cliffs as the lake began a steady ad-
vance on the land. The present shore, therefore, exhibits no beach
ridges, bars or barriers. The lake has outgrown the tendency to con-
struct them, in its successful development of a line of mature cliffs.
DUNES.
Sand dunes, while commonly associated with shore lines, are very
frequently developed independently of them. The conditions for their
growth are wind, a constant supply of sand, which is sometimes dry,
and the absence of a cover of vegetation. On deserts, like the Sahara,
the third condition is made possible by an arid climate, while the sand
is supplied by shrunken rivers and crumbling sandstone. But even in
a humid climate like that of the Great Lake region, dunes may accum-
ulate near shores where the supply of sand by shore currents is very
rapid and the exposure to wind is great. In such places the wind is
able to sweep the sand up from the beach faster than vegetation can
establish a protective cover.
Sand is the chief constituent of beaches, for clay is extracted by
waves and currents and swept far off shore in suspension, while peb-
bles are rapidly ground down in process of transportation along shore.
The well-rounded forms of beach pebbles testify to this. Sand itself
is relatively indestructible because each grain in the beach is surrounded
by a thin film of water held to it by capillary attraction. When struck
a blow by a breaking wave, therefore, each grain is shielded from its
neighbors by a minute but efficient cushion. Without capillary at-
traction, sand would be far more easily worn out, beaches would be
relatively rare, and the great strata of sandstone which mark long
periods of earth history would be wanting. It is only when the sand on
the beach dries that the wind is effective in lifting and transporting it.
Periodic drying is possible along the sea border, where the ebb of the
tide lays bare the beach twice every day. It is less favored on lake
shores, because of relative stability of lake waters. But of course the
beach cast up by a great storm becomes in part a dry sand ridge during
tfie succeeding period of less active surf and it may then supply the
sand necessary for dunes. The fact that dunes may accumulate about
tideless bodies of water like the Great Lakes was expressed as an un-
expected discovery by Edward Desor in his report of the surface
deposits about the Upper Peninsula of Michigan in 1850.*
* Report of Edward Desor to Messrs. Poster and Whitney, "Report on the Geolosry of the
Lake Superior Land District," Part II. chapter XVI.; Senate Exec. Doc. No. 4. 1851. The
writings of Desor and Whittelsey in this report are of great interest and show a remarkably
clear appreciation of shore line topography.
GOLDTHWAIT.J THE PRESENT SHORE LINE. 45
With a strong off-shore wind, beach sand may be blown into the
lake, to be again handled by the waves and currents. But with an on-
shore wind the sand is swept in beyond the reach of the waves, accum-
ulating in low mounds about any obstructions such as stones, bushes,
or clumps of juniper. Thus started, the dune is sufficient cause for its
own growth, for the passing sand is accumulated in the still air on its
leeward side as fast as it is eroded from the windward side. It is a
significant fact that dunes are much larger and much more extensively
distributed on the east side of Lake Michigan than on the west, be-
cause the prevailing winds here are west winds, and the strong east
winds on which the dunes of the west shore must depend for growth
are prevailingly storm winds, accompanied by rain, which wets the
beach and keeps the sand in place. On the east side of Lake Michigan,
especially near its southern end, to which sand is eventually swept from
the whole of the shore, the dry west winds have heaped up great num-
bers of dunes, ranging in height up to 200 feet. In Dune Park, Indi-
ana, the dunes may be seen moving inland across a forested area, bury-
ing and killing trees, and also moving off from previously buried for-
ests, leaving the dead trunks as mere skeletons. A famous instance
of dune migration is that of the Kurische Nehrung, a long sandbar
off the north coatst of Germany, where a dune ridge within historic
times marched over a church, burying it for 30 years, at the end of
which time it was gradually uncovered.
Dunes are limited in height by the great velocity of upper air cur-
rents, to about 200 feet. Their on-shore march is also limited by the
fact that it is attended by the attrition of the sand and the scattering
over a wider area.
Dunes occur in the north shore district along the beach between Wau-
kegan and the State line, and in less notable form at other points, as
will presently be described (see pp. 51-52 and Plate III, Fig. B).
They are also found in association with some of the old beach ridges
of Lake Chicago, notably near the "Glenwood" beaches west of Grosse
Point (see Plate VI and p. 57).
THE SHORE CYCLE.
Assuming all that has been said regarding the work of shore pro-
cesses under different conditions and during successive stages of con-
tinuous activity, one may best appreciate the shore lines to be studied
if the changes in their form are stated^in terms of an imaginary "cycle"
of shore action, such as might express the history of any shore, initially
irregular, which is acted upon by the waves for an unlimited period of
time. It may be said at the outset that few shore lines, if any, live to
see the cycle completed, for the relation of land to sea or level of the
lake is never constant for so long a time.
The shore cycle begins when the body of water comes into a new
position with respect to the land. This may be brought about by a
rising of the land (or a lowering of the waters, the movement being
a relative one, with the same result in either case) such as is now in
progress about Hudson's Bay and in many other parts of the world.
46 THE EVANSTON-WAUKEGAN EEGION. I BULL. 7
The resulting shore line is known as a "shoreline of elevation," and is
characterized by long gentle curves, because it is determined by the
smooth floor of the formerly submerged area. The coast of New Jer-
sey, briefly described on pages 37-38, may be taken as a type.
The new shore line may be formed, on the other hand, by a sinking
of the land with respect to the sea. In this case the waters encroach
on the coast and the rough stream-carved topography is partly sub-
merged, producing an irregular "shoreline of depression," of which
the Chesapeake Bay region is a conspicuous example.
In the case of Lake Michigan, the shore cycle began when the great
ice-sheet melted off from the region, leaving a lake surrounded by
irregular glacial topography. Its irregular border was comparable to
a shore line of depression in so far as it was undeveloped and unad-
justed to the shore agent.
At the outset, the salients and re-entrants of the irregular coast,
with their different exposures to wave action, experience unlike alter-
ation. On the steeply sloping exposed headlands, the waves cut back
cliffs and terraces, while the shore currents shift much debris along
to the nearby re-entrants. In the more gently sloping and less ex-
posed bays, the waves steepen the slope by casting up beaches or bar-
riers, while the material swept in from the headlands considerably
augments the load and the tendency to deposition. In the less pro-
nounced bays, pocket beaches may result, while the sharper re-entrants
v\ ill gradually be cut off by spits, bars and hooks. So long as the
cliff ed headlands continue to project from the shore and to supply
beach material, the re-entrants will continue to fill up and build out-
ward. Thus with receding head-lands and advancing bay shores there
is a two-fold tendency to straighten the shore from one of irregular
outline to one of gentle curves. In the development of these curves,
the waves and currents will be guided chiefly by the initial contour of
the coast and the variability of its profile, as well as by the dominant
winds. The higher headlands will usually recede much less rapidly
than the lower; the broader and deeper re-entrants will usually be the
last to be closed by bars ; the smaller headlands and re-entrants are the
first to be replaced by the curve of the mature shore, but gradually
the shore line becomes an organized whole, in which all parts show
well balanced adjustment to the forces at work, and straight lines and
gentle curves are the rule. With continued progress of the shore
cycle, a mature shore may be imagined slowly to retreat as the material
along its border is lost by attrition, scattering, and dune action. The
barriers and bars beaten inland are succeeded by cliffs, so that the
entire straightened shore consists of wave-cut bluffs.
The same progression of changes in shore line topography can be
traced in a shoreline of elevation, like that of New Jersey, the chief
difference being that the elevated shore line begins with a straightness
comparable to the sub-mature or mature stage of a shore line of de-
pression.
The great barrier ridges and brooks of the extinct Lake Chicago
(the ancestor of Lake Michigan) mark a considerable progress of the
shore cycle ; for by them the initially irregular shore line was greatly
GOLDTHWAIT.I THE PRESENT SHORE LINE. 47
straightened. In the first, highest stage (called the "Glenwood")
as shown on the map (Plate VI). Skokie Bay was nearly shut off
from the main lake by the growth of a great hooked bar from Grosse
Point village southward to Morton Grove. Before the shore line of
this Glenwood stage had become thoroughly mature, however, the
lake fell twenty feet to the level of the second or Calumet stage, and
a new cycle was begun. By the drawing down of the waters across
the smoothed Glenwood lake floor to the lower level, a "shore line
of elevation" was produced, the straightness of the final Glenwood
beach being in part inherited by its successor. Thus after each fall
of lake level the process of straightening of the shore line was re-
sumed, and each shore line of elevation was more nearly mature than
its predecessor.
In a general way, the present cliffs of the north shore express the
continually renewed progress of the shore cycle, in successive steps,
to a stage somewhat beyond maturity. But in reality the cycle has
been interrupted in other ways than by repeated lowerings of lake
level. As will be told further on, there was a stage in the latter
part of the lake history when the level of the waters was much lower
than now, and this was succeeded by a rising of the lake upon its
shores to a height of about 15 feet above the present level.
During this period of rising waters came the greatest advance in
cliff development. The constant deepening of the water favored shore
erosion, and the lake rapidly advanced into the land, cutting back a
long line of cliffs, which are still well preserved north of Waukegan.
Since this time the lowering of lake level has been resumed, and the
attendant shallowing of the water on the shore has been unfavorable
to the maintenance of the cliffs. North of Waukegan a broad sand
terrace has been built out, but south of Waukegan the lake has
succeeded better in trimming back the shore and the cliffs have not
only been maintained but constantly freshened by encroachment.
Inasmuch as erosion by stream action is normally going on all the
while that the shore cycle is progression there will always be gaps in
the cliffs where a stream valley issues on the shore ; and there a bar
will be maintained by the shore drift. An exception to this rule of in-
teraction of the shore cycle and the river cycle is found on the coast
of Normandy, where the recession of the cliffs is so fast that streams
by erosion can not at their mouths come to sea level, but are left well
up or "hanging" on the face of the cliffs. It is rare that the shore
cycle proceeds so much more rapidly than the river cycle. All the
streams entering Lake Michigan within our area have lowered their
valleys as fast as the shore bluffs have receded.
THE NORTH SHORE.
General Aspects — The present shore line of this region may, for con-
venience, be divided into three parts according to its position with ref-
erence to the old shore lines of the lake ; ( I ) the section from Rogers'
Park to Winnetka; (2) that from Winnetka to Waukegan; (3) and
that from Waukegan to the State line. Along the second or middle
stretch of coast line, the lake has cut back beyond its earlier shores.
48 THE EVANSTON-WAUKEGAN REGION. [BULL.
North and south of it the ancient beach ridges, terraces and dunes lie
inland from the present lake, but are steadily being approached and de-
stroyed by the waves. Along the whole coast, except possibly for a few
miles north of Waukegan, the present shore line is being cut back, and
in most places so rapidly as to call for vigorous measures for pro-
tection of property by break-waters, piers,etc. Data collected before
1870, by Dr. Edmund Andrews, include a record of the erosion at nine
points along the shore within our area:
At Evanston the erosion was 16.95 feet a year; at the old pier, two miles
farther north, 0.00 feet a year; at the State line, 16.50 feet a year.
Winnetka, 4.05 feet a year; one mile farther north, 6.05 feet a year; at
Lake Forest, 1.65 feet a year; at Waukegan, 0.00 feet a year; two miles
farther north, 0.00 feet a year; at the State line, 16.50 feet a year.
Since that time the building of piers along the whole shore as far
north as Waukegan has greatly retarded, though it has not stopped
the recession of the shore. From Evanston to Waukegan there is a
continuous line of clay bluffs. South of Evanston and north of Wau-
kegan, where the low sand terrace of the former lake shore remains,
the present beach is low, and the indications of its recession are less
conspicuous. South of Hyde Park, Illinois, and in Indiana, the shore
is being built out by an excessive supply of shore drift.
Lake Survey chart No. 4 (Lake Michigan) shows that the lake
floor within the five fathom line, usually half a mile to a mile off shore,
is either sandy or stony, sand being more common between the State
line and Lake Bluff, and a stony bottom more common farther south
as far as Rogers' Park. At one place only do soundings reveal a rock
bottom — a mile off Grosse Point, north of Evanston, where a pro-
tective ledge, in four to five fathoms of water, and within a mile of
shore, seems to determine the most prominent salient of the shore line.
Beyond the five-fathom line, the lake shore is commonly of clay in
the southern part of the area and of sand in the northern part.
The Ten-Fathom Terrace — The slope of the lake floor between
Rogers' Park and Waukegan is moderately uniform, though somewhat
steeper outside the ten-fathom line than within it. Off Waukegan
this change of slope begins to be more pronounced, and a few miles
farther north, off Zion City, it becomes so abrupt as to mark a distinct
terrace, whose outer border descends rapidly from the ten-fathom
line, while within that line the terrace rises gently up to the shore line,
with a breadth of about two miles.
In his early paper, of 1870,* Dr. Andrews called particular attention
to submerged terraces shown by soundings about the borders of Lake
Superior, Michigan and Huron. These were said to extend out to a
depth of ten fathoms. He considered the terrace to be the "terrace
of erosion" formed during the advance of the present lake into the
land, it being remarked that "the waves of our great lakes ceased to
have any erosive power upon the bottom at the depth of about 60
feet; hence, when the shores are worn back there is left under water
a sort of shelf or terrace, the surface of which slopes gently outward
* ' 'The North American lakes considered as chronometers of post-glacial time." Chi. Acad .
Sci., Trans., Vol. II, pp. 1-23.
GCLDTHWAIT.] THE PRESENT SHORE LINE. 49
to the depth of about 60 feet. ****** Where the shores
are of drift clay the terrace generally has a breadth of from two to
six miles, and occasionally more. But where it is of rock the width
is much less. On some of the hard rocks of Lake Superior the terrace
is scarcely 200 feet wide. Softer rocks frequently show a breadth of
1,500 feet. It is a curious and unexpected fact that the depth of the
erosion is much less affected than the breadth of it by the hardness
of the material. Even rock shores often show the edge of the terrace
to be 60 feet down."
Andrews' explanation of the terrace finds another contradiction in
his statement that "the waves cease to have power to move sand at
the depth of twenty-four to thirty-six feet. * * * Beyond thirty-
six feet depth the bottom [of the southern part of Lake Michigan] is
always of a smooth impalpable clay."
When it is realized that a considerable part of the material in the
receding cliffs of bowder clay is pebbles and sand, it is hard to see
how a terrace could be cut in this material to a depth of 60 feet by
waves which fail to move sand in water deeper than 36 feet. More-
over, we might well expect to find the terrace strongly developed off-
shore from the present clay bluffs of the Evanston-Waukegan district
if anywhere ; whereas there is only a long or rather gradual slope.
All these inconsistencies suggest that the terrace may be better
explained in some other way than by the activity of Lake Michigan at
its present level. It will be stated in succeeding pages that during the
latter part of the early stages of the lake, the waters in the Michigan,
Superior and Huron basins were all drawn down, at least 50 or 75
feet below their present level, by the opening of a new
and lower outlet beneath the retreating ice sheet near North
Bay, Ontario. (See Fig. 35.) The borders of the lake
basin were then laid bare even more extensively than now.
By a differential uplift of the northeastern part of the Great Lake
region, which did not directly affect the southern part, this North Bay
outlet was raised higher and higher, while the lakes everywhere in
the southern parts of the basins responded by rising upon their shores,
submerging them to a greater and greater extent, until they finally
overflowed at Port Huron (the southern end of Lake Huron), and
further drowning of shores was rendered impossible by the southern
outlet. It seems probable that this ten- fathom terrace marks the
erosion of the lake border, while the waters were rising from the low
North Bay plane, to essentially their present level, — a time peculiarly
favorable to the cutting back of a long line of cliffs and a broad ter-
race; for constant deepening of the water means constant steepening
of the submerged slope and increase in the capacity of the waves and
currents to erode and transport material.
So as the waters rose and the lake cliff was cut back, a broad,
gently sloping terrace of erosion might be worked out, the outer border
of which would be much too deep for the present waves and currents
to erode, but at the depth appropriate to a terrace cut during the North
Bay stage. According to this explanation we would be led to suppose
that the North Bay plane of the lake was about 60 feet lower than the
-4G.
50 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
4-s."-. Jr'aJU e. -J
FIG. 29. Diagram showing how a deeply submerged terrace may have been developed by
cliff recession during a rising of the water level from the low water stage to the "Nipissing"
stage. (a b c) cliff and terrace cut during low water stage; (d e c) cliff and terrace after the
rise and encroachment of waters.
present. It may be said, however, that detailed study of the lake
charts prepared since Dr. Andrews' time shows that if a ten-fathom
terrace does exist over a wide area it is often discontinuous and not of
uniform height. Not too much emphasis should be placed upon it*
THE COASTAL TOPOGRAPHY.
Rogers Park to Winnetka. — Near Rogers Park, the beach lies on
the outer side of a broad terrace of sand ridges, beaches, and dunes
which were built while the lake was falling from an old level to its
present mark. The crest of the present beach rises 3 or 4 feet above
the lake, and is usually well covered with "shingle," i. e., well rounded
discoidal pebbles, whose shape bears witness to a long journey along
the shore. The waves break moderately close to shore, showing that
the profile of equilibrium is fairly well established by the beach. The
conditions are in some measure artificial, however, for piers and break-
waters have been built at frequent intervals to catch the shore-drift
and thus to accumulate a beach deposit more rapidly than it can be
worn out and transported by the shore agents. These piers act sub-
stantially like rock headlands, affording re-entrants or artificial coves
in which pocket beaches are built out in an endeavor to straighten the
shore line. From the end of each a submerged sand spit runs south-
ward parallel to the shore, in the path of the deflected shore current
just as a drift-built spit tails out from a headland across a bay. It is
very noticeable that the beach accumulates more rapidy on the north
side of each pier than on the south side, because the dominant drift by
both waves and currents is toward the south.
In spite of the piers and artificial beaches, the lake is advancing on
the land at a rather rapid rate. The cutting is obvious
at several places in Rogers Park where streams run out
to the lake shore and the cement sidewalks or the ma-
cadam road structures end brokenly at the border of the storm
beach. Recession is just as truly indicated, however, by the natural
cliffs cut by the waves in the old beaches 10 to 15 feet high and in the
* Mr. Leverett states in a letter to the present writer, May 26, 1906, that after examining
the charts with this matter in mind he finds frequent terrace-like stretches which s uggest that
a submerged shore line rises slowly from twelve fathoms near Chicago to ten fathoms at
Milwaukee and eight fathoms or less in the northern part of Lake Michigan, as if f rom tilting,
But he does not regard the evidence as of much weight.
GOLDTHWAIT.J THE PRESENT SHOEE LINE. 51
dune ridges. These dunes are forested, and have been established in
position for a very long time, but are now being slowly destroyed as
the waves cut inland. The recession of the shore is accomplished, of
course, only during heavy storms when the waves rise across the
beach and attack the sand deposits along its inner border. After such
a storm, when the water has subsided to a lower position on the beach
slope, the waves build up a secondary beach profile, relatively low and
weak in expression, at the water's edge.
Near the southeast corner of Calvary cemetery, in South Evanston,
at the turn in Sheridan Road, is a small belt of sand dunes, which are
not "established" like .those of Rogers Park, but actively moving in-
land. They are only 15 feet high, and almost bare of vegetation,
clothed with almost nothing but beach grass. The dense network of
rootlets is well shown on the eroded outer side of the dunes. The con-
trast between the bare lake-ward slopes and the grass-covered inland
slopes comes out well as one looks along the line of sand hills. (Plate
III, Fig. B). A lone tree, withered and lifeless, with its trunk and
spreading roots half resurrected from a cover of drift sand on one of
the dunes tells the story of dune migration, like the church at Kurishe
Nehrung, or the resurrected forests at Dune Park.
From Calvary northward through Evanston to the Life Saving sta-
tion, beakwaters, piers and made land interfere with the normal shore
line topography. On the campus of Northwestern University, the
lower of the old shore lines run obliquely out to the lake, and the
low-cut bluff is 20 feet high, and capped by the beach deposits of the
Toleston, or 20- foot, stage of Lake Chicago (see pp. 65-66). A
long pier at the Evanston waterworks has induced the accumulation
of a broad protective beach at the north end of the University campus,
and the bluff there is consequently established. At Grosse Point, the
bluff consists of the characteristic till or bowlder clay, with hardly a
foot of old lake-floor sediments above it. Where the Calumet beach
ridge is cut off by the lake at Grosse Point, the bluff is 40 feet high,
and shows a very good section of the till and over-lying beach de-
posits. The cliffs are rapidly receding at this point, and new land-
slides are often seen after a storm. The salient Grosse Point seems
to be due in part to the protective off-shore ledges and in part to the
Calumet beach ridge.
From Grosse Point to Winnetka the freshly cut bluffs maintain a
height of 25 to 50 feet, running obliquely across the till plain which
formed the floor of the Wilmette embayment, during the Calumet
stage (see Plate VI).
Winnetka to Waukegan. — In the northern part of Winnetka the
bluff (which marks the highest of the extinct lake stages) is cut off
by the present shore, and farther north, for about 20 miles, the lake lies
against the Highland Park morainic ridge, with steep cliffs from 50
to 100 feet high. These cliffs are actively receding, although in most
places the recession is very considerably retarded by the protective
piers, which obstruct the shore-drift and maintain a narrow beach.
The southward drift of shore currents is clearly seen here, as elsewhere
by a greater accumulation on the north side of each pier. One excep-
tionally long pier, which shows this well, is just north of the Cook
52 THE EVANSTON-WAUKEGAN EEGION. [BULL. 7
county line (Plate V, Fig. A.) Landslides on the cliff face, gullies,
and fans, as described on pages 33 and 34, are all exhibited here. Lo-
cally, however, protection is so efficient as to allow the cliffs to become
established in position and covered with young vegetation.
Across the mouth of each large ravine the waves maintain a bar of
shingle and sand, usually a complete barrier to the little stream. The
streams are so small and so intermittent in their activity that in ordin-
ary times they offer no resistance to the obstructing waves. A stag-
nant pool of water behind the bar filters slowly through the gravels
and sand as fast as it is brought down the ravine. A heavy shingle
bar blocks the mouth of a creek at the Cook county line (see Plate V,
Fig. B). During exceptionally heavy rains and spring thaws,
however, the stream may be so swollen as to over-top the bar
and to cut a channel across it in spite of the opposed wave action. The
largest streams, of course, most often open a channel. Pettibone
Creek is one of these, which usually carries enough water to maintain
at least a small breach through the south end of its bar (see Plate
XII).
Waukegan to the State Line. — At Waukegan a coastal terrace makes
its appearance, and, rapidly broadening, runs northward with a width
of a mile or more, across the State line. This is a fragment of the
same low terrace which borders the shore south of Evanston, — a broad
stretch of beach sediments corrugated by ridges which have developed
along the whole shore during the recession and subsidence of the lake ;
but it has been destroyed by cliff recession between Waukegan and
Evanston. At its southern end, in the yards of the American Steel
and Wire Company, at Waukegan, this terrace has been considerably
extended by artificial filling, or erosion on its borders would doubtless
be as apparent as on the face of the clay bluffs immediately to the
south. North of the city there is reason to believe that the shore is
stationary or even building out, as suggested by Dr. Andrews' figures.
The sandy beach is bordered by active dunes, which show no sign of
loss on the outer side by wave erosion nor of rapid landward migration.
They support a scant growth of beach grass, juniper, and scrub pine,
which only imperfectly prevents the shifting of the sand. Occasionally
a clump of juniper acts as a nucleus for a growing young dune, but
more frequently the relation between the hills and the juniper seems
to be very irregular. About the clumps of beach grass there are fre-
quently circular markings on the sand made by the whisking about
of the grass by the wind. Gravel appears not only along the beach
but beneath the dunes on their outer side and about 10 feet above the
lake, marking beach deposits of an extinct stage. In the dune district
between Waukegan and Zion City it is not apparent whether the dunes
are moving inland or not. Since the winds, especially the dry winds,
are prevaimgly off-shore, the dunes must lose much material by scat-
tering into the lake. If the beach were advancing lakeward, the dune
belt would probably be broader than it is, for it is only 100 yards broad
at most, and toward Waukegan much narrower. Behind the dimes
the broad tract of marsh, interrupted by low flattish ridges of sand
and occasionally sloughs or lagoons of stagnant water, reaches inland
to the sharply cut bluff of an extinct 14- foot stage. Dead River is
OOLDTHWAIT.] THE PRESENT SHORE LINE. 53
one of the largest of these sloughs. At Zion City, Shiloh boulevard
leads eastward from the railroad station to the lake, affording a good
opportunity to study the corrugated sand and marsh terrace and the
beach and low dunes of the present shore. Andrews' figures show that
the beach near the State line is retreating at a very rapid rate, and an
inspection of the terrace ridges and sloughs (as shown on the Coast
Survey chart) confirms this fact. The ridges run obliquely out to the
lake, where they are successively cut off by the advancing beach.
Mature Condition of the Shore Line. — The present shore line is one
of long sweeping curves, well established profile of equilibrium, and
landward encroachment, having all the characteristics of maturity.
That this advanced stage is due not simply to the work of the lake at
its present level, but in a large measure to the smooth floor and even
border which Lake Michigan inherited from its ancestors, has already
been mentioned, but will be more strongly appreciated when the history
of the lakes is reviewed.
54 THE EVANSTON-WAUKEGAN REGION. I BULL. 7
THE RECORDS OF THE EXTINCT LAKES.
BY J. W. GOLDTHWAIT.
INTRODUCTION.
Lake Michigan is the lineal descendant of a series of extinct lakes
whose history is recorded in raised beaches and terraces, abandoned
outlets, and lake floor deposits higher than the present lake. The an-
cestral lakes owed their high level to the great ice sheet, which acted
as a dam across the northern side of the basins, holding the water up
to the level of the lowest notch in the inclosing land basins. The
cutting down of outlets, the uncovering of new outlets at lower levels
as the ice sheet melted northward, and differential uplifts or tiltings
of the land combined to complicate the series of changes in level and
outline of the lake during its early history.
The Evanston-Waukegan district contains stretches of the aban-
doned lake shores, in which one may read somewhat imperfectly the
record of successive events of lake history. Between Winnetka and
Waukegan the old shores have been totally destroyed by the advance
of the lake upon the land; but north and south of this section, shore
forms of considerable variety and of great instructiveness are to be
seen well above the present shore.
In the Evanston district, the old lake shore is much smoother than
the higher upland back of it, and forms the northern corner of the
cresentiform Chicago plain. While this is a lake plain in the sense that
it is the floor of an extinct lake, the plain does not owe its flatness
wholly to submergence. The greater part of it is covered with bowlder
clay, thinly veneered, if at all, by lake floor sediments. Had the orig-
inal floor been as irregular as the upland and then been smoothed off
by wave action, there would hardly be such broad stretches of the lake
plain left bare of lacustrine sediment. The plain seems therefore to
be a glacier-made till plain, whose surface was given a finishing touch
by the lake water which once covered it. In this respect it is to be
contrasted with the broad, flat plains of the Red River valley in Dakota
and in Minnesota, which was once beneath a similar ice-front lake,
but is flat because of the accumulation of fine sediment to a depth of
40 or 50 feet on the lake floor.
In the Waukegan district, the area once covered by the lake is by
no means a plain. It includes not only a broad flat terrace along the
present lake shore, but a steep, high bluff, and a sloping upland with
several parallel beach ridges.
GOLDTHWAIT.]
RECORDS OF EXTINCT LAKES.
55
It is the purpose of the present chapter to point out and explain
these records of the former higher levels of the lake. The history of
Lake Michigan is closely connected with the history of the other Great
Lakes. This history has been worked out chiefly by Mr. F. B. Taylor,
Mr. Frank Leverett, and Dr. W. C. Alden, of the United States Geo-
logical Survey.*
LAKE CHICAGO.
Glenwood Stage. — At the time of its last great advance, the North
American ice sheet reached southward as far as the lobate border
indicated in Fig. 30. As its front withdrew by melting from the term-
inal moraine, and began to uncover the south end of the Lake Michigan
basin, a body of water appeared between the ice front and the inclosing
moraine, — a lake which has been appropriately named "Lake Chicago."
FIG. 30. Map showing the ice sheet of the late Wisconsin stage, at the time of its
greatest extent.
Its outlet was through the lowset notch or "col" in the morainic
divide near Chicago, along the line of the present drainage canal into
the Desplaines and Illinois rivers.
When the lake first formed along the margin of the Michigan ice lobe,
the outlet col seems to have been high enough to hold the waters up to
about 60 feet above the present lake level ; but, by rapid cutting, it
* For the correlation of the lower stages of Lake Chicago with Lake Algonquin and the
Nipissing great lakes, the present writer accepts all due responsibility. This part of the lake
history must not be considered as completely demonstrated.
56 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
was soon lowered a few feet, becoming stationary at about 55 feet
above Lake Michigan. Possibly the halt at the 55-foot, or Glenwood,
level was determined by the discovery of a sill of bed rock beneath the
loose drift of the outlet valley.*
FIG. 31. Map showing the ice front lakes and the ice sheet at the time of the re-advance to the
Port Huron-Manistee moraine, ( Leverett and Taylor. )
At one time before the close of the Glenwood stage, the ice seems to
have halted in its retreat and to have even re-advanced to the vicinity
of Milwaukee, over-riding the Glenwood beach deposits there, and
burying them beneath a thick deposit of ice-laid and water-laid red
clay, f
Glenwood Shores in the Evanston District — '•In the northern part of
Winnetka, a short distance south of the pumping station, the cliff and
terrace of the Glenwood stage appear half way up the lake cliff, and
extend inland with pronounced form for three-quarters of a mile. The
terrace is about 55 feet above Lake Michigan, and is composed of
stratified sand and gravel ; and behind it the bluff rises to a height of 20
* Investigations by the writer in the Chicago outlet, since this report was written, make it
probable that the level of Lake Chicago in the Glenwood stage was controlled not by a sill of
rock, but rather by the surface of a gravel deposit (a "valley train") which occupied the valley
below Lemont, when first the ice withdrew from the district. It may have taken the outlet
river a long time to sink its channel through this gravel deposit, for it reached 15 miles or
more down the valley.
t These are described by Alden in the Milwaukee folio, U. S. Geol. Surv. That the lake
was still at the Glenwood level after this advance seems to be shown by the occurrence of beach
ridges at the Glenwood level, and superposed upon the red clay in Sheboygan county, Wiscon-
sin, 35 miles north of Milwaukee.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 6.
MAP OF THC
/ \ OLD SHORE LINE6
GCLDTHWAIT.] RECORDS OF EXTINCT LAKES. 57
to 30 feet, with a very steep slope, affording a fine outlook for residences
facing this lake. A short distance out from the base of the bluff is a low
sand ridge, which seems either to be an off-shore reef, or a beach
thrown up when the lake fell slightly from the level at which it had cut
the bluff. A second sand ridge lies about a block east of the first, run-
ning out to the brink of the lake cliff, as shown on the map (Plate VI).
The old cliff runs southward on the west side of Maple street, becom-
ing less distinct as it approaches the railroad, where artificial grading
has destroyed its true form. On the west side of the railroad, south of
Cherry street, it appears indistinctly. Close to the east side of t!he
Grosse Point road is a belt of gravel behind which the rolling upland
of the Highland Park ground moraine ridge, which here tails out, is
covered with a sheet of wind-blown sand, two to eight feet thick. Be-
yond the end of the moraine west of Kenilworth, the beach
assumes the form of a distinct ridge, followed by the road to Grosse
Point. A half mile north of Grosse Point it sends out its first hook to
the southwest, a narrow ridge of gravel three-quarters of a mile long.
In the southern part of the village several smaller hooks curve sharply
around to the west, the outermost forming a quarter circle, followed
by a curving road and connecting with the most northerly hook at the
road corner northwest of the village. This outer hook is much broader
than the others and is made irregular by a line of sand dunes, which
are 25 feet high, but greatly subdued by plowing and rain-wash. A
branch ridge runs nearly straight west from this for over half a mile.
The largest hook of all, however, runs west-southwest from Grosse
Point, and is followed by the Glen View road. This is a mile and a half
long, and banked up with a line of subdued dunes.
About a mile south of Grosse Point the main or outer beach ridge
divides, the inner ridge taking a course a few hundred feet west of the
ridge road which follows the outer one. Half a mile farther on, the
outer forks again, so that there are three distinct ridges, all parallel and
all of approximately the same height. The outer one is bordered by a
terrace which seems to be the shore line of the next lower of the stages
of Lake Chicago. It is followed for a mile or two by a branch of the
ridge road, and gradually spreads and flattens out at Niles Center.
The middle of the ridge determines the course of the main road nearly
as far as Niles Center, flattening, like the first, into a low sand deposit.
The inner ridge, which is the best developed of all and a few feet higher,
sends off about twelve hooks on its west side, and finally terminates east
of Morton Grove, in a spreading gravel deposit.
West of the Chicago river and southwest of Morton Grove, the road
to Niles and Norwood Park follows a beach ridge which marks the con-
tinuation of the Glenwood shore. In section 19 (Niles), the ridge shows
only imperfectly the effects of shore action, being covered with only a
thin deposit of gravel and sand ; but approaching Niles it becomes a
very marked ridge, with characteristic sigmoid profile and gravelly
structure. Through the village of Edison the shore line is a little
58 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
obscure, forming a graver slope against a moderately steep till bluff;
but at Norwood Park (just south of the map, plate VI), it again be-
comes a strong- feathered ridge, whose crest, by railroad levels, is 59
feet above Lake Michigan.
The form of the complex set of hooked bars and their relation to the
cut bluff and gravel beach at Winnetka. indicate that thev were built
by strong southward shore currents which swept around the end of the
eastern moraine ridge and across the Skokie marsh, which was then
a bay (Plate VI). North of Grosse Point the water was too shallow
to permit the formation of any considerable hooks, the shore currents
running straight southward ; but south of that place, where the currents
ran out into deeper water, they were subject to frequent deflection, and
well marked hooks were built one after another as the bar grew, like the
hooks on Rockaway Beach, Long Island (Fig. 27). So far was the
hooked bar extended, that it nearly shut in the Skokie embayment,
leaving a gap at Morton Grove only a mile wide. The building of the
middle and outer ridges may have been initiated by a very slight fall
of lake level, toward the close of the Glenwood stage. The northward
weakening of the Glenwood beach from Niles toward Glenview, shows
the effect of the Grosse Point bar in protecting the shores of the Skokie
re-entrant.
There was doubtless an embayment also in Glenwood time in the
Desplaines valley, running northward at least as far as Desplaines, but
no distinct shore topography was developed in so shallow and so pro-
tected a re-entrant. It was shut off from the open lake by a great
hooked split, at Oak Park.*
Glenwood Beaches in the Waukegan District — In the city of Wau-
kegan the Glenwood beach ridge may be found just east of Genesee
street, running northward on the west side of Sheridan road not far
back from the top of a steep bluff that marks a much lower stage
(Fig. 32). Although usually much obscured by grading, the beach
ridge is in some places quite distinct and has an altitude of 50 to 55 feet
above the lake. In the southern part of the town it seems to have been
cut off by the advance of the lake on the land at a later time. When
followed northward it is seen to cross the Kenosha highway in section
1 6, and to follow close to the brink of the Toleston bluff where the
road runs eastward (between sections 16 and 9) to the lake. The
Glenwood ridee is closelv associated with rolling morainic mounds,
which in places are quite sandy and may in part be covered with dune
sand. In section Q (Waukegan) the 55-foot ridge is broken in several
places by transverse streams. Behind the bar a small creek, following
a deflected course for a mile or more, has cut a deep, terraced valley.
Curious topography produced by the encroachments of the lake on the
one hand and the terracing of the deflected stream on the other, will be
described in a later chapter (pages 83-84).
* See Salisbury and Alden, ' 'The Geography of Chicago and Its Environs, " Geog. Soc. Chi.
Bull. 1. pp. 35 to 37.
fefi? TILL AND6RAVEL fflOGL AHM 6L[NUOOD3[aGH
— GLENWOOD BEACH RIDGE
--C/\LUMET BEACH RIDGE
IIIHHTOIISTON BLUFF
;^:.: TERRACE Of SAND RIDGES AND MARSH
60 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
In section 4 (Waukegan) the beach ridge continues northward with
characteristic strength, and thence for over six miles is followed by
Sheridan road. Near Beach station it has three closely set crests. At
Zion City it is double, the two ridges having the same height, 53 feet
above the lake, and crossing Shiloh boulevard near Dowie's residence.
In places it is raised a few feet by blown sand. Near Withrop Harbor
it is again double and not so well defined. Behind it, on the outer slope
of the till ridge, a low cliff has developed. The beach ridge crosses the
State line with a crest which rises and falls several feet because of
dune action.
West of this 50 to 55-foot Glen wood beach ridge is another long
ridge, from 5 to 15 feet higher, usually much broader, and commonly
so till-like in structure as to suggest an ice-front deposit rather than
a beach ridge. Locally, however, (as at the gravel pit at the southeast
corner of section 9, near Winthrop Harbor), it is seen to be built of
well stratified gravels. As is shown by the map, this till and gravel
ridge can be followed continuously from the State line nearly to
Waukegan, where it blends with the rolling morainic topography.
This outermost ridge, 60 to 70 feet above Lake Michigan, might
be regarded as a deposit formed near and in part against the ice front
when Lake Chicago was first opening and before the erosion of the
Chicago outlet had established a 50 to 55-foot mark. The lake at that
time was probably only a narrow belt of water against the ice (some-
what broader, however, north of Zion City), and wave action was weal*:
.and embarrassed .by ice-front accumulations.
THE CHANGE FROM THE GLENWOOD TO THE CALUMET STAGE.
While the ice front receded and Lake Chicago expanded northward,
the erosion of the outlet floor seems to have been suddenly checked,
and to have ceased temporarily ; so as to hold the lake for a consider-
able time at a level about 35 feet above the present. It seems as if
the drop from 55 to 35 feet was a rather sudden one, for the Glen-
wood and Calumet beaches are usually quite distinct, with no beaches
to mark intermediate stages. Accordingly, a process of sudden deep-
ening of an outlet, known as "stoping," has been suggested. In brief,
it is as follows :*
The outlet of a lake may flow across a region of hori-
zontally bedded rocks in which certain layers are weak and
others resistant (see Fig. 33, upper diagram). Under- such
conditions rapids or even falls are likely to be developed where
a river runs off from the hard stratum on to the weak one. While in
the upper portion of the outlet, the hard layer suffers very little erosion,
the rapids farther down quickly work up stream, by sapping or stoping.
Thus, while the lake is held to the level of the sill at the head of the
outlet, the rapids work up stream nearer and nearer the lake, and
finally cut through the sill with a rush, and the lake level falls suddenly
into adjustment with the flat "stope." It is not even necessary to
* This explanation is merely an abstract of Professor Chamberlin's original presentation of
the view of stoping, in Monograph XXV, of the U. S. Geol. Surv., ' 'Lake Agassiz, " pp. 250-251.
GOLDTHWAIT.]
RECORDS OF EXTINCT LAKES.
61
postulate a bed rock structure, for, if the outlet is across a morainic
ridge whose outer border is moderately steep and whose structure is
locally very resistant, stoping may take place. Suppose, for instance,
that in Figure 33 (lower diagram) an outlet for the lake is found
across the moraine in a line of cross-section, and that at b-c there is
an exceptionally resistant belt of drift, more bowldery and compact
than the surrounding drift. Profiles of erosion would develop in suc-
cession somewhat as indicated in the figure, rapids forming first on the
outer side of the resistant band and working up stream until' they cut
through the obstruction, whereat the weaker material, no longer pro-
tected, would quickly yield to erosion and the lake would fall to fit
the new channel floor.
PIG. 33. Diagrams showing in profile how the level of a lake may suddenly fall by
' 'stoping." In the upper figure the stoping is through horizontal bed rook. In the lower one it
is through a resistant portion of the moraine, a, b, e, d are successive positions of the top of
the rapids developed by stoping; e is the final position of the head of the outlet.
THE CALUMET STAGE.5"
The lake remained at the new level, 35 feet above the present lake,
for another long interval, while the ice withdrew toward the northern
part of the Great Lake region. Strong beaches and terraces were
formed in the Chicago district, and northward at least as far as Lud-
ington, Michigan, and Manitowoc, Wisconsin. How much farther
north they extended is not known. The Calumet stage seems to have
closed with the lowering of the Chicago outlet of the lake 10 to 15
feet.f
Calumet Shores in the Evanston District. — During the Calumet
stage, nearly the entire till plain east of the Glenwood beach was
submerged, for it all lies below the 35-foot mark. The border of the
* It has long been supposed (following Dr. Andrews) that the Glenwood and Calumet stages
were separated by a stage of low water when the lake fell to a level at least as low as the
present and probably much lower. The evidence cited is a peat bed which lies beneath the
Calumet ridge at Grosse Point. But recent study of this locality strongly suggests the ' 'peat"
is merely a lacustrine deposit, formed in quiet water behind the barrier during the Calumet
stage, and buried by shoreward advance of the reef. Other evidences of a low lake stage, once
correlated with the pre-Calumet stage, seem now to belong to much later periods, described on
pages 63 and 66.
t Recently evidence has been found at Lockport which seems to indicate that this second
drop in level of Lake Chicago was accomplished by stoping of the old outlet through a sill of
bed rock at that place.
62 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
lake was near the outer Glenwood bar. Between Niles Center and
Grosse Point, it is marked by a pretty distinct terrace of gravel, sand,
and black soil, such as might be expected to form along the shore of
an embayment. About three miles east of this, a great off-shore barrier
was built at this stage, the Rose Hill barrier, which is followed for
six miles by Ridge avenue, through Evanston and Rogers Park, and
terminates near Rose Hill cemetery. This barrier, like the Glenwood
bars, was doubtless constructed in part by southward shore currents,
which brought gravels and sand from the cliffs east of Winnetka. But
all of the ridge north of Grosse Point, and the associated cliffs, have
been cut away by Lake Michigan, the Ridge avenue bar then protected
a long lagoon/ which we may call for convenience the Wilmette em-
bayment, since Wilmette is near the head of the bay and on its floor.
The Ridge is a conspicuous feature, and is widely known for its well-
built boulevard and its fine residences. It rises about 20 feet above
the flat till plain, with a steeper slope usually on the western side than
on the east or front. While the whole barrier deposit shows a width
of a quarter to a half of a mile, the beach ridge on its outer side is
very narrow (see Plate VI).
At the termination of the ridge, near Grosse Point, a freshly exposed
cross-section may usually be seen in the lake cliff, in which the brown
cross-bedded beach gravels overlie horizontally bedded sand and the
glacial bowlder clay. Close to the base of the stratified portion is a
band of peaty clay, very thinly laminated, and composed in part of
bits of wood and decayed plant stems. This was thought by Dr.
Andrews to indicate a condition of low water between the Glenwood
and Calumet stages; but it may with equal reason be regarded as a
layer of lagoon muds and plant remains buried by the on-shore migra-
tion of the barrier. The crest of the ridge, where it is gravelly to the
surface (and thus evidently an outer beach ridge unmodified by dunes)
is usually about 38 feet above Lake Michigan. But locally the beach
ridge is coated with wind-blown sand, which raises it several feet
higher.
On the west side of the barrier are minor beach ridges and distinct
hooks, which show that wave and current action in the Wilmette em-
bayment was vigorous, and independent of the waves upon the lake.
The best of these hooks diverges from the main ridge southwest of
Rogers Park, running out a mile into the open bay, with a graceful
curve, and ending near the center of section 25, just south
of the Chicago city line (Plate VI). On it can be
traced a gravelly beach ridge, built by the bay waves,
and a higher dunve ridge. Two small but very distinct
branch hooks, with crests nearly as high as the Ridge avenue
beach, occur in Rogers Park. A good place to see one of these is a
field near the corner of Lunt avenue and Pine street. The low ground,
protected by the long hook, is covered with fine lake sediments, — a
stretch of true "lake plain," on which there are large truck farms.
These hooked spits indicate clearly that there was pretty strong wave
action in the Wilmette bay, inducing a northward shore current just
opposite in direction to the shore current on the outer side of the Ridge
avenue bar. The case is analogous, to that of Sandy Hook and its
branch spits (described on page 43) ;. and a comparison of the two is
GOLDTHWAIT.] BECORDS OF EXTINCT LAKES. 63
interesting and instructive. The dominant waves in the Wilmette bay
came with a south or southwest wind, for they had the greatest "fetch."
A short branch spit, which crosses Hill street just north of the Evans-
ton golf links, at Ridge avenue, shows again the northward drift of
beach material on the bay side of the great barrier.
Calumet Beach in the Waukegan District. — In the northern part of
Waukegan, two miles north of the city (in section 9) scraps of terraces
at altitudes appropriate to the Calumet stage appear on the face of the
Toleston bluff; but some of these at least seem to be old ravine ter-
races, preserved in a curiously exposed position.
Near Beach Station (Fig. 32) the Calumet ridge ap-
pears on the brink of the Toleston bluff, and runs north-
ward with short interruptions to the State line, never far
from the bluff of th,e lower stage. Through Zion City
it is followed by Elizabeth avenue. Near Winthrop Harbor it
was cut away, during the Toleston stage, for half a mile. Although
usually a low, faint feature, and subdued by plowing, it is broad and
strong between Zion City and the Camp Logan road. Here a peaty
deposit, lying between the Glenwood and the Calumet beach ridges,
contains a great abundance of fresh water shells.*
Since these shells are all of living species and none have been found
either here or elsewhere within the stratified deposits of the Calumet
beach, they seem not to belong to Calumet time, but rather to the
present. There are no certain traces of life in the lake during the
Glenwood and Calumet stages.
INTERVAL BETWEEN THE CALUMET AND TOLESTON STAGES.
It is not known how far north the ice had receded during the Calu-
met stage before the Chicago outlet was lowered and Lake Chicago
fell to 10 or 15 feet. There is reason to believe that soon after the fall
occurred the ice uncovered a still lower outlet to the northeast and
for a time the lakes experienced a low-water stage.
The chief evidences of this low-water stage are, (i) peat deposits
buried by Toleston gravels in Evanston and elsewhere, and ( 2)
drowned valleys on the east side of Lake Michigan, described by Lever-
ett as a record of deep channeling in adjustment to a lake level at
least 50 feet lower than the present, a channeling which took place after
the Glenwood stage and before the Toleston. f
* Identified by Mr. Bryant Walker of, Detroit: Lynnaea reflexa (Say.), Planorbis trivalvis
(Say.), Planorbis bicannatis (Say.), Planorbis parvus (Say.).'Physa elliptica (Lea.), Pisidium
t It is perhaps possible that these valleys were both deepened and drowned at a time
subsequent to a 25-foot stage, for there is good evidence of a later low water stage.
64 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
LAKE ALGONQUIN, THE LOW-WATER STAGE, AND THE NIPISSING
GREAT LAKES.
The name Toleston has been given to a group of shore lines in the
Chicago district which lie from 10 to 25 feet above Lake Michigan.
The Toleston beaches fall pretty definitely into two divisions, a higher
group, from 20 to 25 feet above the lake, and a lower group, from 12
to 15 feet. The higher area always marked by beach ridges; the lower
frequently by a distinct wave cut cliff.
Recent studies have strengthened the belief that the 1 5-foot mem-
ber of the Toleston group of beaches does not mark the shore of a
local Lake Chicago, but of two of its larger successors, Lake Algon-
quin and the Nipissing great lakes.*
While this is not yet fully demonstrated, it will be seen to explain
certain features of the Toleston beaches in the Evanston-Waukegan
district in a way which other interpretations fail to do, especially the
strong development of the lower Toleston bluff.
FIG. 34. Map showing the supposed ^outline of Lake Algonquin and its contemporaries.
The position of the ice border is hypothetical. The outline of the lakes is known chiefly
through the work of Taylor and Leverett.
Lake Algonquin occupied the whole of the Michigan and Huron
basins and part or all of the Superior basin. It came into the Michi-
gan basin when the ice had uncovered the Straits of Mackinac and
Lake Chicago coalesced with its contemporary in the Huron
*See "Abandoned Shore Lines of Eastern Wisconsin, " by J. W. Goldthwait. Wis. Geol.
and Nat. Hist. Surv., Bull. XVII, 1907.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 7.
Fig. A. Lower Toleston cliff and beach ridge.
Toleston beach ridge at Evanston.
GOLDTHWAIT.] RECOKDS OF EXTINCT LAKES. 65
basin. At that time the discharge of Lake Algonquin seems to have
been eastward across Ontario, through the Trent valley, a region
which at that time stood much lower than now ; but it was later shifted
to Port Huron, by uplifts of the more northerly region. The Chicago
outlet may have shared to a slight decree in draining Lake Algon-
quin, but the outlet at Port Huron finally obtained the whole dis-
charge by being cut down more rapidly than the outlet at Chicago.
During the long Algonquin stage, the northern part of the great lake
suffered tiltings or differential warpings, which brought the shores up
out of water and left them in deformed attitudes, rising and diverg-
ing vertically toward the north. The Lake Michigan basin south of
Manistee, however, and the Huron basin south of Point Au Barques
seems to have been unaffected by the movements, so that the 1 5-foot
beach in that southern portion of the Great Lake region is still hori-
zontal.*
The Toleston Beaches — The main Toleston beach ridge makes its
appearance not far north of the campus at Northwestern Univer-
sity, in Evanston. From the waterworks southward beyond the obser-
vatory, the inner half only of the beach ridge is preserved, on the brink
of the present lake bluff. But at the north gate of the campus, the com-
plete ridge runs inland from the lake, beneath Heck Hall and Univer-
sity Hall. (See Plate VII, Fig. B.) Thence its course through the
city is on the east side of Chicago avenue to South Evanston, where
it is followed pretty closely by Clark street to the southern borders of
the map. (Plate VI.)
Its crest on the University campus is 24 feet above the lake, the upper
4 feet being sandy, though perhaps not from dune action. A recent
cross-section in the bluff, where the ridge runs out to the lake, showed
one foot of peat about 5 feet above the lake, beneath the Toleston
gravels. Below the peat is a compact deposit of very fine gray sand, of
unknown depth. A single shell was found in the sand close to the peaty
layer. A section studied by Leverett in 1888 showed similar peat layers,
with associated shell-bearing clays nine feet above the lake. Dr. Oliver
Marcy, in 1864, made a record of an exceptionally good exposure in the
cliffs, which were then unprotected by the piers and artificial beach.
The peat, a clay bed containing molluskan shells of nine genera (all
existing species) was found ten feet above the lake. Farther down,
on the contorted glacial clays, was found a "humus soil, with stumps and
logs (coniferous)," six inches thick and buried by three feet of gravel.
A cellar excavation on Davis street, Evanston, recently showed a peat
bed between the blue bowlder clay and the over-lying Toleston
gravels and sands. Minute fibrous rootlets could be seen pene-
trating the till at the base of the peat, indicating that the deposit is in
* Leverett and Taylor have found no beach extending up to the region of coalescence, in
either of the basins, above the Algonquin plane. In eastern Wisconsin, likewise, no beaches
above the Algonquin seem to extend north of the Manistee moraine.
—5 G
66 THE EVANSTON-WAUKEGAN BEGION. • [BULL. 7
situ, presumably a land surface deposit. If so, it registers a stage of
low water preceding the Toleston. A marl bed near the base of the
Toleston gravels here, contains an abundance of shells.
South of Cavalry cemetery, through Rogers Park, the Toleston ridge
is associated with a higher ridge of dunes, which lies between Clark
street and the Northwestern railroad, and has an altitude of 25 to 30
feet above the lake. A measurement in a borrow pit near Calvary,
where the gravel ridge is covered with five feet of sand, places the top-
most gravel layer 22 feet above Lake Michigan. This seems, then, to
be about the height of the outer Toleston beach.
Below this highest ridge of the Toleston group are always several
lower beach ridges.*
In the Waukegan district no beaches occur at the 20 to 25-foot level.
Beaches of this stage were destroyed by the recession of the bluffs
when the lake stood about 15 feet above its present level (lower Toles-
ton or Nipissing stage).
Lake Algonquin was extinguished by the recession of the ice front,
uncovering a low pass between Lake Nipissing and the Mattawa
river (east of North Bay, Ontario.) The waters fell considerably in
adjustment to the new outlet and the Port Huron pass was left high and
dry. It is not known just how far the lake fell to the new outlet. If
the ten-fathom terrace already described on pages 48-50, is of signifi-
cance in this connection, the drop as registered in the Michigan basin
was about 60 feet. But this terrace is a . questionable one. With a fall
of 60 feet, the lake would have assumed some such outline as that shown
in Figure 35. f
The low water stage was not to endure, however, for continued
upwarping of the northern part of the lake region raised the North
Bay pass up to, and at last above, the level of the recentlv abandoned
Port Huron pass. Everywhere south of the rising outlet the lakes
responded by rising on their shores until the waters overflowed again
at Port Huron. (Fig. 36.) This transition stage, mark-
ing the climax of the rising of the lakes, when both the
Nipissing and the Port Huron outlets were in use, has
been called the stage of the Nipissing great lakes, and
its shore line the Nipissing shore line. In the southern part of the
Michigan and Huron basins the shore line of this stage seems to be
10 or 15 feet above the present lakes, and in a horizontal position; but
toward the north the old shore line rises gradually and very uniformly
as a result of the tilting. The shore lines of the Nipissing stage are
characterized by an exceptionally strong development of cut bluffs
and terraces, rather than by beach ridges. In this manner they express
the vigorous encroachment of a lake which was rising upon its snores
(see Fig. 29).
* On the University campus the Toleston ridges occur at heights of 24, 23, 19, 16 and 14
feet. At Chase avenue, Rogers Park, they are 30 feet (a dune covered ridge on the west side of
Clark street), 23 feet (east side of Clark street), 23 feet, 16 feet (one block east of Clark street)
and many others from 10 to 15 feet above the lake. There is reason for including those below 16
feet in the second or lower division of the Toleston.
t Recent studies strongly suggest that the low-water stage was very much lower than this—
perhaps at about sea level.
GOLDTHWAIT.]
EECORDS OF EXTINCT LAKES.
67
PIG. 35. Map showing a possible outline of the Great Lakes at the low water stage
just preceding the Nipissing stage.
FIG. 36. Map of the Nipissing Grea Lakes. (After Taylor.)
68 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
At the close of the Nipissing stage, uplifts brought the North Bay
outlet above water, and the discharge through the Saint Clair river
was fully restored. From that time to the present, the only permanent
changes in level have been a lowering of the lake, in response to the
continued deepening and widening of the outlet. It is this lowering,
without doubt, causing the lake to slowly withdraw from its Nipissing
shore line, which resulted in the accumulation of the broad sand ter-
race of beach and dune ridges bordering the lake in the Waukegan
district, and near Rogers Park.
Lower Toleston Bluff and Shore Terrace in the Waukegan District.
— The rising of the waters from the low water stage to the Nipissing
level was attended by vigorous cliff cutting in the Waukegan district.
This is clearly shown by the conspicuous bluff which lies just west of
the Chicago & Northwestern railroad all the way between Waukegan
and the State line. (Plate VII, Fig. A.) In height,
this bluff varies from 15 to 40 feet, according to the
distance it receded into the upland. It is higher between
Waukegan and Beach Station than north of that place. It
is usually very steep except where long cultivation has favored the
reduction of its steep slope. The base of the bluff, sometimes bordered
by a cut and built terrace, is usually 13 or 14 feet above Lake Michigan ;
but near Waukegan it seems to be only 5 or 10 feet above the lake,
probably because it was trimmed away during the subsequent fall of
the waters to their present level. In general, however, the lowering
of level has resulted in the over-shallowing of the shore, and the con-
struction of a broad terrace of low sand ridges, described on page 52.
Between Zion station and the lake, 24 of these sand ridges cross Shiloh
boulevard. Farther south, the number becomes much less until near
Waukegan there is only a broad marsh with sloughs between the Toles-
ton bluff and the present beach. North of Zion the terrace becomes
higher and drier and more extensively wooded.
EFFECTS OF RECENT FLUCTUATIONS IN LAKE LEVEL.
Since the settlement of the Great Lake region the level of Lake
Michigan and Lake Huron has fluctuated noticeably. Not only is there
a regular seasonal fluctuation of about one and one-half feet (high
water coming in June or July, and low water in midwinter) , but there
are greater changes through periods of several years. In 1886 the
lake was about two feet higher and in 1896 nearly three feet lower
than in 1906. At high water in 1838 the lake stood nearly six feet
higher than at low water in 1896. When these secular changes of level
are plotted next to a rainfall curve* the connection between periods of
unusual rainfall or drought and periods of high or low water is evi-
dent. With such considerable fluctuations, known by actual gauge
measurements, it seems likely that a good part of the low coast near
Waukegan has been built up within historic times.
* This has recently been done in "Geologry of Huron County, Michgan," by A. C. Lane,
Gepl. Surv. of Mich., Vol. VII, Part 2, plate 5.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 8.
Fig. A.. Moraine upland descending to lake shore.
Fig. B. Young valleys. [Courtesy of Wisconsin Geol. Nat. Hist. Surv.]
ATWOOD.] DEVELOPMENT OF RAVINES.
THE DEVELOPMENT OF THE RAVINES.*
BY W. W. ATWOOD.
Morainic Surface— The surface of the drift, when exposed by the
retreat of the ice, was probably somewhat rougher than much of the
upland of today. The drift deposits bordering modern glaciers re-
semble the heaps of debris as they were left in this region. But the
minor inequalities have been reduced in the process of soil making,
or by the work of rain and running water. The larger features such as
the hills or mounds and the larger depressions remain.
The broad open valley west of the lake ridge is not the result of
erosion since the drift was deposited, but is a great depression left in
the surface of the drift when the ice retreated. All of the ravines and
valleys leading directly to the lake have been developed since the drift
was deposited and are the result of rain water running off over the
slope.
Origin of a Gully — When the ice melted, the upland extended far-
ther to the east and presumably descended gradually to the level of the
lake (Plate VIII, Fig. A.) As the rain fell upon this new land, a part
of the water sank in, a part was evaporated, some collected in hollows
or undrained depressions on the surface and the remainder ran off
over the surface. The land, it is fair to assume, did not have an equal
or uniform slope to the lake at all places, nor was the material over any
considerable area perfectly homogeneous. The surface water tended to
gather in the depressions of the surface, however slight they were.
This tendency is shown on almost every hillside during and after any
considerable shower. The water concentrated in the depressions is in
excess of that flowing over other parts of the surface and therefore
flows faster. Flowing faster, it erodes the surface over which it flows
more rapidly, and as a result the initial depressions are deepened, and
washes or gullies are started. (See PI. VIII, Fig. A, and PI. XI.)
Should the run-off not find irregularities of slope, it would, at the
outset, fail of concentration ; but should it find the material more easily
eroded along certain lines than along others, the lines of easier wear
would become the sites of greater erosion. This would lead to the de-
velopment of gullies, that is to irregularities of slope. Either inequality
of slope or material may therefore determine the location of a gully,
and one of these conditions is indispensable.
* In the preparation of this portion of the text free use has been made of similar matter in
Bull. V, Wisconsin Geol. and Nat. Hist. Surv., by Salisbury and Atwood.
70 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
Once started, each wash or gully becomes the cause of its own growth,
for the gully developed by the water of one shower, determines greater
concentration of water during the next. Greater concentration means
faster flow, faster flow means more rapid wear, and this means corres-
ponding enlargement of tne depression through which the flow takes
place. The enlargement effected by successive showers affects a gully
in all dimensions. The water coming in at its "head carries the head
back into the land (head erosion), thus lengthening the gully; the
water coming in at its sides wears back the lateral slopes, thus widening
it; and the water flowing along its bottom deepens it. Thus gullies
grow to be ravines and farther enlargement by the same processes con-
verts ravines into valleys. A river valley therefore is often but a gully
grown big.
The Course of a Valley. — In the lengthening of a gully or valley
headward, the growth will be in the direction of greatest wear. Thus,
in Plate VIII, Fig. A, if the water coming in at the head of the gully
effects most wear in the direction A, the head of the gully will advance
in that direction; if there be most wear in the direction B or C, the
head will advance toward one of these points. The direction of greatest
wear will be determined either by the slope of the surface, or by the
nature of the surface material. The slope may lead to the concentra-
.tion of the entering waters along one line, and the surface material
may be less resistant in one direction than in another. If these factors
favor the same direction of head-growth, the lengthening will be more
rapid than if but one is favorable. If there be more rapid growth
along two lines, as B and C, than between them, two gullies may de-
velop. The frequent and tortuous windings common to ravines and
valleys are therefore to be explained by the inequalities of slope or
material which affected the surface while the valley was developing.
Tributary Valleys. — Following out this simple conception of valley
growth, we have to inquire how a valley system (a main valley and
its tributaries) is developed. The conditions which determine the loca-
tion and development of gullies on a new land surface, determine the
location and development of tributary gullies. In flowing over the side
slopes of a gully or ravine, the water finds either slope or surface
material failing of uniformity. Both conditions lead to the concen-
tration of the water along certain lines, and concentration of flow on
the slope of an erosion depression, be it valley or gully, leads to the
development of a tributary depression. In its growth, the tributary
repeats, in all essential respects, the history of its main. It is length-
ened headward by water coming in at its upper end, is widened by
side wash, and deepened by the downward cutting of the water which
flows along its axis. The factors controlling its development are the
same as those which controlled the valley to which it is tributary.
There is one peculiarity of the courses of tributaries which deserves
mention. Tributaries, as a rule, join their mains with an acute angle
up-stream. In general, new land surfaces, such as are now under con-
sideration, slope toward the sea or some large body of water. If a
tributary gully were to start back from its main at right angles, more
ATWOOD.] DEVELOPMENT OF RAVINES. 71
water would come; in on the side away from the shore, on account of
the seaward, or, as in the North Shore region, the lakeward slope of
the land. This would be true of the head of the gully as well as of
other portions, and the effect would be to turn the head more and more
toward parallelism with the main valley. Local irregularities of sur-
face may, and frequently do, interfere with these normal relations, so
that the general course of a tributary is occasionally at right angles to
its main. Still more rarely does the general course of a tributary make
an acute angle with its main on the downstream side. Local irregulari-
ties of surface determine the windings of a tributary, so that their
courses for longer or shorter distances may be in violation of the
general rule. This case is well illustrated by the first tributary, from
the lake, on the south side of Pettibone creek, near North Chicago (Fig-
48). This tributary leads toward the lake joining the main at an
acute angle down stream. The encroachment by the waves has carried
away the head of the gully and left a V-shaped notch in the cliff from
which the drainage is inland.
On the whole, the valleys of a system, whose history has not been
interrupted, in a region where the surface material is not notably
heterogeneous, follow the course indicated above. This more general
case is illustrated by nearly every drainage system along the shore
from Winnetka to the Illinois-Wisconsin line.
How a Valley Gets a Stream. — Valleys may become somewhat deep
and long and wide without possessing permanent streams, though from
their inception they have temporary streams, the water for which is
furnished by showers or melting snows. Yet sooner or later, valleys
come to have permanent streams. How are they acquired? Does the
valley find the stream or does the stream find the valley? For the
answer to these questions, a brief digression will be helpful.
In cultivated regions, wells are of frequent occurrence. In a flat
region of uniform structure, the depth at which well water may be
obtained is essentially constant at all points. If holes (i and 2, Fig.
FIG. 37. Diagram illustrating the relations of ground water in streams.
37) be excavated below this level, water seeps into them, and in a
series of wells the water stands at a nearly common level. This means
that the sub-structure is full of water up to that level. These relations
are illustrated by Fig. 37. The diagram represents a vertical section
through a flat region from the surface (s. s.) down below the bottom
of wells. The water stands at the same level in the two wells and the
plane through them, at the surface of the water, is the ground water
level. If in such a surface a valley were to be cut until its bottom was
below the ground water level, the water would seep into it, as it does
into the wells; and if the amount were sufficient, a permanent stream
would be established. This is illustrated in Fig. 37. The line AA
72 THE EVANSTON-WAUKEttAN EEGION. [BULL. 7
represents the ground water level, and the level at which the water
stands in the wells, under ordinary circumstances. The bottom of the
valley is below the level of the ground water, and the water seeps into
is from either side. Its tendency is to fill the valley to the level AA.
But instead of accumulating in the open valley as it does in the en-
closed wells, it flows away, and the ground water level on either hand
is drawn down.
The level of the ground water fluctuates. It is depressed when the sea-
son is dry (A' A') and raised when precipitation is abundant (A" A").
When it is raised, the water in the wells rises, and the stream in the
valley is swollen. When it falls, the ground water surface is de-
pressed, and the water in the wells becomes lower. If the water surface
sinks below the bottom of the wells, the wells "go dry;" if below the
bottom of the valley, the valley becomes, for the time being, a "dry
run." When a well is below the lowest ground-water level its supply
of water never fails, and when the valley is sufficiently below the same
level, its stream does not cease to flow, even in periods of drought.
On account of the free evaporation in the open valley, the valley de-
pression must be somewhat below the level necessary for a well, in
order that the flow may be constant.
It will be seen that intermittent streams, that is, streams which flow
in wet seasons and fail in dry, are intermediate between streams which
flow after showers only, and those which flow without interruption.
In the figure the stream would become dry if the ground water level
sank to A' A'.
It is to be noted that a permanent stream does not normally precede
its valley, but that the valley, developed through gully-hood and
ravine-hood to valley-hood by means of the temporary streams sup-
plied by the run-off of occasional showers, finds a stream, just as dig-
gers of wells find water. The case is not altered if the stream be fed
by springs,, for the valley finds the spring, as truly as the well-digger
finds a "vein" of water. Most of the North Shore gullies have but
intermittent streams. A few are deep enough or have found a suffi-
cient number of springs to have a permanent supply of water.
Limits of a Valley. — So soon as a valley acquires a permanent
stream, its development goes on without the interruption to which it
was subject while the stream was intermittent. The permanent stream,
like the temporary one which preceded it, tends to deepen and widen
its valley, and, under certain conditions, to lengthen it as well. The
means by which these enlargements are affected are the same as be-
fore. There are limits, however, in length, depth and width, beyond
which a valley may not go. No stream can cut much below the level
of the water into which it flows, and it can cut to that level only at
its outlet. Up stream from that point a gentle gradient will be estab-
lished over which the water will flow without cutting. In this condi-
tion the stream is at grade. Its channel has reached base level; that
is, the level to which the stream can wear its bed. This grade is,
however, not necessarily permanent, for what was base level for a
small stream in an early stage of its development is not necessarily
base level for the larger stream which succeeds it at a later time.
ATWOOD.] DEVELOPMENT OF RAVINES. 73
FIG. 38. Diagram showing the shifting of a divide. The slopes 1A and IB are unequal. The
steeper slope is worn more rapidly and the divide is shifted from 1 to 4, where the two slopes
become equal and the migrating of the divide ceases.
Weathering, wash and lateral corrasion of the stream coninue to
widen the valley after it has reached base level. The bluffs of valleys
are thus forced to recede, and the valley is widened at the expense
of the upland. Two valleys, widening on opposite sides of a divide,
narrow the divide between them and may ultimately wear it out.
When this is accomplished, the two valleys become one. The limit
to which a valley may widen on either side is therefore its neighbor-
ing valley, and since, after two valleys have become one by the elimin-
ation of the ridge between them, there are still valleys on either hand,
the final result of the widening of all valleys must be to reduce all
the area which they drain to base level. As this process goes for-
ward, the upper flat into which the valleys were cut is being restricted
in area, while the lower flats developed by the streams in the valley
bottoms are being enlarged. Thus the lower flats grow at the expense
of the higher.
There are also .limits in length which a valley may not exceed. The
head of any valley may recede until some other valley is reached.
The recession may not stop even there; for if, on opposite sides of a
divide, erosion is unequal, as between lA and iB, Fig. 38, the divide
will be moved toward the .side of less rapid erosion, and it will cease
to recede only when erosion on the two sides becomes equal (4A and
46). In homogeneous material this will be when the slopes on the
two sides are equal.
It should be noted that the lengthening of a valley headward is not
normally the work of the permanent stream, for the permanent stream
begins some distance below the head of the valley. At the head, there-
fore, erosion goes on as at the beginning, even after a permanent
stream is acquired.
Under certain circumstances, the valley may be lengthened at its
debouchure. If the detritus carried by it is deposited at its mouth, or
if the sea bottom beyond that point rise, the land may be extended
seaward, and over this extension the stream will find its way. Thus at
their lower, as well as at their upper ends, both the stream and its
valley may be lengthened.
A cycle of erosion. — If, along the borders of a new-born land area, a
series of valleys were developed, essentialy parallel to one another,
they would constitute depressions separated by elevations, represent-
ing the original surface not yet notably affected by erosion (see Plate
VIII, Fig. B). These inter- valley areas might at first be wide or
narrow, but in process of time they would necessarily become narrow,
for once a valley is started, all the water which enters it from either
side helps to wear back its slopes, and the wearing back of the slopes
74 THE EVANSTON-WAUKEGAN REGION. [BULL 7
means the widening of the valleys on the one hand and the narrowing
of the inter-valley ridges on the other. Not only would the water
running over the slopes of a valley wear back its walls, but many other
processes conspire to the same end. The wetting and drying, the freez-
ing and the thawing, the roots of plants and the boring of animals, all
tend to loosen the material on the slopes or walls of the valleys, and
gravity helps the loosened material to descend. Once in the valley
bottom, the running water is likely to carry it off, landing it finally in
the sea. Thus the growth of the valley is not the result of running
water alone, though this is the most important single factor in the
process.
Even if valleys developed no tributaries they would, in the course
of time, widen to such an extent as to nearly obliterate the intervening
ridges. The surface, however, would not easily be reduced to perfect
flatness. For a long time at least there would remain something of
slope from the central axis of the former inter-stream ridge toward
the streams on either hand ; but if the process of erosion went on for a
sufficiently long period of time, the inter-stream ridge would be brought
very low, and the result would be an essentially flat surface between
the streams, much below the level of the old one.
The first valleys which started on the land surface (see Plate VIII,
Fig. B) would be almost sure to develop numerous tributaries. Into
tributary valleys water would flow from their sides and from their
heads, and as a result they would widen and deepen and lengthen just
as their mains had done before them. By lengthening headward they
would work back from their mains some part, or even all the way
across the divides separating the main valleys. By this process the
tributaries cut the divides between the main streams into shorter cross
ridges. With the development of tributary valleys there would be many
lines of drainage instead of two, working at the area between two
main streams. The result would be that the surface would be brought
low much more rapidly, for it is clear that many valleys within the
area between the main streams, widening at the same time, would
diminish the aggregate area of the upland much more rapidly than
two alone could do.
The same thing is made clear in another way. It will be seen (Plate
IX, Figs. A and B) that the tributaries would presently dissect an
area of uniform surface, tending to cut it into a series of short ridges
or hills. In this way the amount of sloping surface is greatly in-
creased, and as a result every shower would have much more effect
in washing loose materials down to lower levels, whence the streams
could carry them to the sea.
The successive stages in the process of lowering a surface are sug-
gested by Fig. 39, which represents a series of cross sections of a land
mass in process of degradation. The uppermost section represents a
level surface crossed by young valleys. The next lower represents the
same surface at a later stage, when the valleys have grown larger,
while the third and succeeding sections represent still later stages in the
process of degradation. Plate VIII, Fig. B, and Plate IX, Figs. A
and B, represent in another way the successive stages of stream work
in the general process of degradation.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PL 9.
Fig. A. The same valleys as shown in plate 8, fig. B, in a later stage of development.
[Courtesy of Wisconsin Geol. Nat. Hist. Surv.]
Fig. B. Same valleys as shown in fig. A in a still later stage of development.
[Courtesy of Wisconsin Geol. Nat. Hist. Surv.]
ATWOOD.] DEVELOPMENT OF RAVINES. 75
In this manner a series of rivers, operating for a sufficiently long
period of time, might reduce even a high land mass to a low level,
scarcely above the sea. The new level would be developed soonest
near the sea, and the areas farthest from it would be the last — other
things being equal — to be brought low. The time necessary for the*
development of such a surface is known as a cycle of erosion and the,
resulting surface is a base level plain; that is, a plain as near sea level
as river erosion can bring it. At a stage shortly preceding the base
level sage the surface would be a peneplain. A peneplain, therefore, is
a surface which has been brought toward, but not to base level. Land
surfaces are often spoken of as young or old in their erosion history,
according to the stage of advancement which has been made toward
base leveling. Thus the Colorado canyon, deep and impressive as it
is, is, in terms of erosion, a young valley, for the river has done but a
small part of the work which must be done in order to bring its basin
to base level.
Base level plains and peneplains. — It is important to notice that a
plane surface (base level) developed by streams could only be devel-
oped at elevations but slightly above the sea ; that is, at levels at which
running water ceases to be an effective agent of erosion; for so long
as a stream is actively deepening its valley its tendency is to roughen
the area which it drains, not to make it smooth. The Colorado river,
flowing through high land, makes a deep gorge. All the streams of the
western plateaus have deep valleys, and the manifest result of their
action is to roughen the surface. The ravines of the North Shore
region have notably roughened the topography of that region. Given
time enough, and the streams of any region will have cut their beds
to low gradients. Then, though deepening of the valleys will cease,
widening will not; and inch by inch, and shower by shower, the ele-
vated lands between the valleys will be reduced in area, and ultimately
the whole will be brought down nearly to the level of the stream beds.
This is illustrated by Fig. 39.
It is important to notice further that if the original surface on
which erosion began is level, there is no stage intermediate between
the beginning and the end of an erosion cycle, when the surface is
again level, or nearly so, though in the stage of a cycle next preceding
the last — the peneplain stage (fourth profile, Fig. 39) — the surface-
approaches flatness. It is also important to notice that when streams
have cut a land surface down to the level at which they cease to erode
that surface will still possess some slight slope, and that to seaward.
In the Evanston-Waukegan region the streams flowing into Lake Mich-
igan can cut no lower than the level of the lake and the base level
plain to which they are tending to reduce this region slopes gently
lakeward.
No definite degree of slope can be fixed upon as marking a base
level. The angle of slope which would practically stop erosion in a
region of slight rainfall would be great enough to allow of erosion if
the precipitation were greater. All that can be said, therefore, is that
the angle of slope must be low. The Mississippi has a fall of less
76
THE EVANSTON-WAUKEGAN REGION.
LBULL. 7
FIG. 39. Cross sections showing various stages of erosion in one cycle.
than a foot per mile for some hundreds of miles above the gulf. A
small stream in a similar situation would have ceased to lower its chan-
nel before so low a gradient was reached.
Characteristics of Valleys at Various Stages of Development. — In the
early stages of its development a depression made by erosion has steep
lateral slopes, the exact character of which is determined by many con-
siderations. Its normal cross section is usually described as V-shaped
(Plate XI and Fig. 40). In the early stages of its development, espe-
cially if in unconsolidated material, the slopes are normally convex in-
ward. If cut in solid rock, the cross section may be the same, though
many variations are likely to appear, due especially to the structure of
the rock and to inequalities of hardness. If a stream be swift enough
to carry off not only all the detritus descending from its slopes, but
to abrade its bed effectively besides, a steep sided gorge develops. If
it becomes deep, it is a canyon. For the development of a canyon, the
material of the walls must be such as is capable of standing at a high
angle. A canyon always indicates that the down cutting of a stream
keeps well ahead of the widening.
The profile of a valley at the stage of its development corresponding
to the above section is represented diagrammatically by the curve A B
in Fig. 41. The sketch (PI. VIII, Fig. A) represents a bird's eye view
of valleys in the same stage of development.
At a stage of development later than that represented by the
V-shaped cross section the corresponding section is U-shaped, as shown
in Fig. 42. The same form is shown in Plate X, Fig. A. This repre-
sents a stage of development where detritus descending the slopes is
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 10
Fig. A. North fork of Fettibone creek, North Chicago.
Fig. B. A broad open valley north of Kenosha, Wis. [Courtesy of C. & N. W. Ry. ]
ATWOOD.]
DEVELOPMENT OF RAVINES.
77
not all carried away by the stream, and where the valley is being
widened faster than it is deepened. Its slopes are therefore becoming
gentler. The profile of the valley at this stage would be much the
same as that in the preceding, except that the gradient in the^ower por-
tion would be lower. ;",,
FIG. 40. Diagrammatic cross section of a young valley corresponding with in
shown in Plate XI.
FIG. 41. Diagrammatic profile of a young valley.
PIG. 42.
Diagrammatic cross section of a valley at a stage corresponding with that
shown in plate X, fig. A.
FIG. 43. Diagrammatic cross section of a valley at a stage I later than that shown in fig. 42,
and corresponding with the view shown in plate X. fig. B.
Still later the valley assumes the shape shown in Plate X, Fig. B, and
the cross section shown in Fig. 43. This transformation is effected
partly by erosion and partly by deposition in the valley. When a
stream has cut its valley as low as conditions allow, it becomes sluggish.
A sluggish stream is easily turned from side to side; and directed
against its banks, it may undercut them, causing them to recede at the
point of undercutting. In its meanderings it undercuts at various points
at various times, and the aggregate result is the widening of the valley.
By this process alone the stream would develop a flat at grade. At the
same time all the drainage which comes in at the sides tends to carry
the walls of the valley farther from its axis.
A sluggish stream is also generally a depositing stream. Its deposits
tend to aggrade (build up) the flat which its meanderings develop.
When a valley bottom is built up it becomes wider at the same time,
for the valley is, as a rule, wider at any given level than at any lower
78
THE EVANSTON-WAUKEGAN KEGION.
one. Thus the U-shaped valley is finally converted into a valley with
a flat bottom, the flat being due in large part to erosion and in smaller
part to deposition. Under exceptional circumstances the relative im-
portance^of these two factors may be reversed.
Contour interval /O feet
FIG. 44. Topographic 'map of a part of the North Shore near Ravinia, showing several
young vaileys.
It will be seen that the cross section of a valley affords a clue to its
age. A valley without a flat is young, and increasing age is indicated
by increasing width. Valleys illustrating many stages of development
are to be found in the Evanston-Waukegan region. The gullies and
ravines represent extreme youth (Fig. 44). An intermediate stage
of development is shown in the valley of Pettibone creek (Plate X,
Fig. A), North Chicago, and in the valley of Dead river west of
Camp Logan. Old age is not illustrated in the region, for there has not
been sufficient time since the ice melted for valleys to have reached
that stage in a region where there is so much material to be removed.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 11.
II
II
-So
d $-*
ATWOOD.] DEVELOPMENT OF RAVINES. 79
Transportation and Deposition. — Sediment is carried by streams in
two ways: (i) By being rolled along the bottom, and (2) by being
held in suspension. Dissolved mineral matter (which is not sediment)
is also carried in the water. By means of that rolled along the bottom
and carried in suspension, especially the former, the stream, as already
stated, abrades its bed.
The transporting power of a stream of given size varies with its
velocity. Increase in the declivity or the volume of a stream increases
its velocity and therefore its transportive power. The transportation
effected by a stream is influenced (i) by its transporting power and
(2) by the size and amount of material available for carriage. Fine
material is carried with a less expenditure of energy than an equal
amount of coarse. With the same expenditure of energy, therefore, a
stream can carry a greater amount of the former than of the latter.
Since the transportation effected by a stream is dependent on its
gradient, its size and the size and amount of material available, it fol-
lows that when these conditions change so as to decrease the carrying
power of the river, deposition will follow if the stream was previously
fully loaded. In other words, a stream will deposit when it becomes
overloaded.
Overloading may come about in the following ways: (i) By de-
crease in gradient, checking velocity and therefore carrying . power ;
(2) by decrease in amount of water, which may result from evapora-
tion, absorption, etc.; (3) by change in the shape of the channel, so
that the friction of flow is increased, and therefore the force available
for transportation lessened ; (4) by lateral drainage bringing in more
sediment than the main stream can carry; (5) by change in the char-
acter of the material to which the stream has access, for if it becomes
finer, the coarse material previously carried will be dropped and the
fine taken; and (6) by the checking of velocity when a stream flows
into a body of standing water.
Topographic forms resulting from stream deposition. — The topo-
graphic forms resulting from stream deposition are various. At the
bottoms of steep slopes, temporary streams build alluinal fans. These
are commonly developed at the base of the lake cliff (Plate XI).
Along its flood plain portion a stream deposits more or less sediment
on its flats. The part played by deposition in building a river flat has
already been alluded to. A depositing stream often wanders about in
an apparently aimless way across its flood plain. At the bends in its
course cutting is often taking place on the outside of a curve while
deposition is going on in the inside. The valleys of Pettibone creek
near North Chicago, and of Dead river near Camp Logan, illustrate
this process of cutting and building in the flood plain.
Besides depositing on its flood plain, a stream often deposits in its
channel. Any obstruction of a channel which checks the current of a
loaded stream occasions deposition. In this way "bars" are formed.
Once started the bar increases in size, for it becomes an obstacle to
flow, and so the cause of its own growth. It may be built up nearly
to the surface of the stream and in low water it may become an island
by the depression of the surface water.
80 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
At their debouchures streams give up their loads of sediment.
Under favorable conditions deltas are built. The material carried to
the lake in the region under consideration is distributed along the
shore by the waves and currents and therefore no deltas of notable
size are developed.
Rejuvenation of Streams. — After the development of a base level
plain its surface would suffer little change (except that effected by
underground water) so long as it maintained its position. But if, after
its development, a base level plain were elevated relative to sea level,
the old surface in a new position would be subject to a new series of
changes identical in kind with those which had gone before. The ele-
vation would 'give the established streams greater fall and they would
re-assume the characteristics of youth. The greater fall would acceler-
ate their velocities, the increased velocities would entail increased ero-
sion, increased erosion would result in the deepening of the valleys, and
the deepening of the valleys would lead to the roughening of the
surface. But in the course of time the rejuvenated streams would cut
their valleys as low as the new altitude of the land permitted ; that is,
to a new base level. The process of deepening would then stop and the
limit of vertical relief which the streams were capable of developing
would be attained. But the valleys would not stop widening when they
stopped deepening, and as they widened the intervening divides would
become narrower and ultimately lower. In the course of time they
would be destroyed, giving rise to a new level surface much below the
old one, but developed in the same position which the old one occupied
when it originated ; that is, a position but little above sea level.
FIG. 45. Diagrammatic cross-section illustrating the topographic effect of rejuvenation
by uplift. Compare with Fig. A, Plate XIII.
If at some intermediate stage in the development of a second base-
level plain, say at a time when the streams had half completed their
work, rejuvenation by uplift were to occur, the half completed cycle
would be brought to an end and a new one begun. The streams would
again be quickened, and as a result they would promptly cut new and
deeper channels in the bottoms of the great valleys which had already
been developed. The topography which would result is suggested by
the above diagram (Fig. 45), which illustrates the cross section which
would be found after the following sequence of events : ( I ) The de-
velopment of a base level, A A; (2) uplift, rejuvenation of the streams
and a new cycle of erosion half completed, the new base level being at
B B; (3) a second uplift, bringing the second (incomplete) cycle of
erosion to a close, and by rejuvenating the streams inaugurating the
third cycle. As represented in the diagram, the third cycle has not
progressed far, being represented only by the narrow valley, C. The
base level is now 2-2, and the valley represented in the diagram has
not yet reached it. (Compare with Fig. A, Plate XIII.)
ATWOOD.] DEVELOPMENT OF RAVINES. 81
The rejuvenation of a stream shows itself in another way. The nor-
mal profile of a valley bottom in a non-mountainous region is a gentle
curve, concave upward with gradient increasing from debouchure to
source. Such a profile is shown in Fig. 46. Fig. 47, on the other hand,
is the profile of a rejuvenated stream. The valley once had a profile
FIG. 46. Normal profile of a valley bottom in a non-mountainous region.
FIG. 47. Profile of a stream rejuvenated by uplift.
similar to that shown in Fig. 46. Below B its former continuation is
marked by the dotted lines, B C. Since rejuvenation the stream has
deepened the lower part of its valley and established there a profile in
harmony with the new conditions. The upper end of the new curve
has not yet reached beyond B.
The Influence of the Changes in the Level of Lake Michigan in Val-
ley Development. — In this region certain of the older streams have
been rejuvenated, not by an uplift of the land, but by the lowering of
Lake Michigan. The lowering of the lake level depressed the base to
which the streams could work, and therefore quickened the downward
cutting in the valleys. All valleys that were developed before the
subsidence of the lake waters must have been affected by this change.
The narrow, V-shaped gullies continued to grow deeper, but did not
essentially change in form. In valleys which had broad, flat bottoms
at the time of the lowering of the lake, the deepening of the channel
left the former bottom lands as terraces. These terraces grew smaller
as the rejuvenated streams developed their new or inner valleys, and
unless broad to begin with could not be expected to remain until today.
In a few of the larger valleys such terraces have been identified. In
Pettibone creek terrace remnants occur at several places in the valley
(Fig. 48). The best preserved remnant is in the lower portion of the
valley on the north side of the stream. This terrace is forty feet above
the present lake level (C-T, Fig. 48). Following up stream, several
remnants of the forty-foot terrace occur.. They vary in width up to
300 feet and their surfaces retain the characteristic abandoned chan-
nels of old flood plains. This terrace corresponds in elevation to the
Calumet stage of Lake Chicago.
Twenty feet above the stream, and about twenty-five feet above the
present lake level, there are several distinct terrace remnants. These
correspond with the Upper Toleston stage. In the area shown on Fig.
48 one such remnant (T-T) is brought out by the ten-foot contour
map. Several other small remnants at the Upper Toleston level may
—6 G
THE EVANSTON-WAUKEGAN REGION.
[BULL.. 7
be recognized in the valley. At about eight feet above the stream and
thirteen feet above the lake there are several benches or terrace-like
remnants (L-T) that correspond to the Lower Toleston, or Nipissing
stage.
FIG. 48. Topographic map of the lower portion of Pettibone Creek valley near North
Chicago, by Fred Kay and F. D. Mabrey. A broad terrace (C-T) corresponding to the Calumet
stage of Lake Chicago is shown on the North side of the valley. In the bottom of the valley
small remnants (T-T) correspond to the upper Toleston, and (L-T) to the lower Toleston
stages of Lake Chicago.
The mouth of Pettibone creek is one of the most interesting physio-
graphic laboratories of the North Shore region. The view shown in
Plate XII reproduces the conditions as they existed at one time, and
may be taken as an illustration of the educational value of a visit to
such a place. In the foreground there is a sand and gravel pit, which is
being developed by a shore current set up by a southeasterly wind.
The growth of the spit is diverting the stream northward. The stream
channel across the beach indicates by its structure that the beach mate-
rial formerly (probably but a few days preceding the date of the
photograph) blocked the outlet. Strong east or northeast winds may
account for such an accumulation. The sands and gravels blocked the
\
' V 2
F .-::-'•
ATWOOD. ]
DEVELOPMENT OF RAVINES.
outlet of the stream. The ponded waters rose, formed a considerable
'lake and overflowed. When the outlet of the valley lake was estab-
lished, the waters of Lake Michigan were two to three feet higher on
this side of the lake than when the picture was taken, for the outlet
stream failed at that time to cut as low as at present. This is shown
in the small terrace in the channel across the beach. The terrace
corresponds to and is continuous with the miniature wave-cut terrace
at the base of the small cliff in the sand and gravel on the beach. When
the lake subsided from the sand and gravel cliff the stream was able
to cut lower and entrenched its course to the depth shown in the view.
Each time that the level of Lake Michigan changed* the streams in
the bordering lands were affected. When the lake level fell the streams
were quickened and valley deepening was augmented (Fig. A, Plate
XIII). When the lake level rose the lower portions of the valleys
must have been drowned by the advancing lake waters. The streams
lost velocity and began to fill or silt up their valleys. Examples of such
filling are known in the larger valleys leading to Lake Michigan in
Wisconsin. No good case is known in the Evanston-Waukegan area.
but the valley of Dead river west of Camp Logan may have had such a
history. There are at least eight feet of alluvium in the lower portion
of the valley, just west of the station. Furthermore, the broad flat-bot-
tomed form of the valley suggests that it has been partially filled with
silts. The valley is larger than those developed by similar streams
since the re-advance of the lake waters in Calumet times, and there-
fore would seem to have had a longer history. When the excavations
are made at the mouth of Pettibone creek, in constructing a harbor for
the United States naval training station, some interesting exposures
are likely to be made.
FIG. 49. Topographic sketch map of one of the head waters of Dead River between
Waukegan and Beach. A. the present outlet; B, a possible former outlet; near C' the original
outlet.
One of the tributaries of Dead river between Waukegan and Beach
has had a curious and interesting history. This valley trends south-
ward on the west side of the Glenwood beach for some distance, and
then turns sharply to the east, crossing the ancient shore lines and
opening into the lake flat. The topographic sketch map (Fig. 49)
* The changes of lake-level are given in pp. 54-68.
84 THE EVANSTON-WAUKEGAN REGION. [BULL. 7
shows the general form of the valley, the present outlet of the stream
A, the ancient outlet near C', and a possible former outlet at B. The
location of the Glenwood and lower Toleston shore lines are also shown
in the figure. Up stream from A the valley has a sharp inner gorge or
trench cut below well marked Calumet and Toleston terraces. It is
evident, therefore, that this portion of the valley was well developed
during the Calumet stage of Lake Chicago ; that when the lake waters
fell to the Toleston level the valley bottom was appropriately lowered,
and when the outlet at A was established the stream began cutting the
inner trench.
Down the main valley from outlet A the higher Toleston level, about
twenty-five feet above Lake Michigan, is well developed. It is evident
that this valley bottom was reduced about as far as was possible during
that time, and that a considerable flood plain was developed. In this
portion of the valley there are also remnants of the lower Toleston flood
plain. This means that the stream occupied this portion during a
part at least of the lower Toleston time. Therefore, the diversion of the
head waters through outlet A did not occur until late in Toleston time.
Between C and C' there are terrace remnants that appear to be por-
tions of old flood plains. This indicates that the valley extended south-
ward from outlet C and that the east side of the valley has since been
removed by wave cutting.
The sharp cliff shown in Fig. 49, west of the railroad, was developed
by the waters of Lake Nipissing rising to the lower Toleston level.
These waters cut away the east side of the valley between C and C'
and norrowed the morainic belt north of C and east of the valley. At
A and B the valley swung to the east, and at these places the east
wall became very narrow. Possibly the waves succeeded in cutting
through to the valley at A and B somewhat as they are now doing at
a point north of Kenosha, Wis.* There the flood plain is essentially at
the level of the lake, but in the case shown in Fig. 49 the flood plain
where the capture took place was about fifteen feet above the lake
waters at that time. Possibly the actual capture of the stream was
accomplished by a small stream working head ward from the Nipissing
cliff. When, by one or the other of these ways, the outlet A was
established, the stream began entrenching its course above that point.
If outlet B was ever occupied by much of a stream, it was not occupied
by such a stream very long. The amount of cutting at that point is
very slight. Since most of the waters are diverted at A, there is little
outflow now at C.
* Described in ' 'Intercision, a peculiar kind of modification of drainage. " by J. W. Goldtlr
wait. School Sci. and Math., Vol. VIII, pp. 129-139, February, 1908.
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 13.
Fig. A. Little Fort creek in the western portion of Waukegan. These terraces probably
espond to the Calumet stage of Lake Chicago as shown in the valley development.
Fig. LJ. Glacial bowlders used in a building.
ATWOOD.] UNDERGROUND WATER. 85
UNDERGROUND WATER.
(BY w. w. AT WOOD.)
Shallow Ground Waters. — In what has preceded, reference has been
made only to the results accomplished by the water which runs off
over the surface. The water which sinks beneath it is, however, of no
small importance in reducing a land surface. The enormous amount
of mineral matter in solution in spring water bears witness to the effi-
ciency of the ground water in dissolving rock, for since the water did
not contain the mineral matter when it entered the soil, it must have
acquired it below the surface. By this means alone, areas of more
soluble rock are lowered below those of less solubility. Furthermore,
the water is still active as a solvent agent after a surface has been
reduced to so low a gradient that the run-off ceases to erode mechani-
cally.
The seepage of ground water on steep valley slopes and on the lake
cliff sometimes saturates the glacial clays and causes them to flow.
These mud streams may often be seen near Fort Sheridan, Highwood
and at other places where the cliff is not clothed with vegetation. At
places the addition of ground water to the clay in a steep bank or bluff
so increases the weight of the mass as to cause landslides. Such land-
slides are well known in the southeast portion of the Fort Sheridan
grounds on the modern lake bluff. Sometimes the saturation of the
clay in the lake and valley bluffs causes the clay to become so slippery
that the overlying mass, which may be relatively dry, slides oft and
moves for some distance down the slope.
In the farming districts, within the Evanston-Waukegan area, ground
water is reached in the common wells at depths varying from five to
loo feet. At some places the glacial drift contains very little water
and the farmers have found it necessary to drill into the bed-rock for-
mation to secure a good water supply.
Artesian Wells. — The village of Highland Park, the city of Wauke-
gan, the Northwestern Railway and the Corn Products Refining Com-
pany at Waukegan, and numerous private citizens in the North Shore
region, have artesian wells.
At Highland Park the public well is 1,590 feet deep. At L. E.
Swift's, Lake Forest, the artesian well is 989 feet deep. At Mr. Booth's,
Lake Forest, the artesian well is about 800 feet deep. At Miss Cul-
ver's, Lake Forest, there is an artesian well 2,062 feet deep. In South
Evanston there is an artesian well 1,748 feet deep. (Fig. 50.)
86
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
There are two horizons from which the artesian water supply is
obtained. One is reached at about 800 feet and continues downward
for about 400. The lower horizon is reached between 1,300 and 1,500
feet and continues several hundred feet. The lower limit of this horizon
has not been reached in the region.
ia.o'
/to'
NI»G ft HA
LIKICSTONC.
CINCINNATI
L IMC 57"0/VfS
ST. PETERS
SANDSTONE.
POTSO/IW
SANDSTONE:
FIG. 50. Artesian well section in South Evanston showing the formations that underlie
the entire Evanston-Waukegan region.
The waters in the artesian wells are supplied by the rainfall of cen-
tral Wisconsin. The formations shown in Fig. 50 reach the surface
in that region and descend gradually southward and southeastward
under the Evanston-Waukegan area and much farther. The limestones
overlying the St. Peters and Potsdam sandstones are relatively imper-
vious, and the waters are retained in the porous sandstone layers until
the overlying beds are punctured. The outcropping area of the St.
Peters sandstone in Wisconsin is much less than that of the Potsdam
(Fig. 51) and the thickness of the formation is also less. The lower
water bearing horizon therefore contains a much larger supply than
the upper.
Mr. Leverett has made the following report on wells within this
region: "At Waukegan the public water supply was formerly obtained
from artesian wells, but since 1895 it has been obtained by pumping-
from Lake Michigan. Three wells were sunk to depths of 1,135, 1,600
and 2,005, respectively. The first well is reported by Major DeWolf
to have obtained water of fair quality, though rather heavily charged
With iron. The second well obtained an unpleasant water with bad
odor, thought to be sulphurous. The wells were discontinued because
ATWOOD.]
UNDERGROUND WATER.
87
.(POTSDAM SANDSTONE.
lEE]] OUTCROPPING OR WITHIN REACH OF
— ' [SURFACE WATERS.
__(ST. PETERS SANDSTONE
^wlj OUTCROPPING OR WITHIN REACH OF
**** I SURFACE. WATEf?S.
SCALFi
foo MILtS
FIG. 51, Main absorbing areas for the Potsdam and St. Peters formations. From the
17th Ann. Rep. U. S. Gfeol. Surv., Part II. pi. CXI, by Frank Leverett.
of the hardness of the water, it being unfit for boiler use. The water
also was found unsuitable for sprinkling lawns, it being destructive
to grass. The Lake Michigan water is not too hard for boiler use and
in other ways is more satisfactory than the artesian water. The present
intake is at a distance of 1,700 feet from the shore, but it is proposed
to extend the tunnel to a distance of about a mile.
"At Lake Forest, wells which yield thirty barrels per day are
usually obtained at a depth of forty feet or less. An artesian well at
the residence of Hon. C. P. Farwell reached a depth of 960 feet and
obtained a flow of water whose head was originally fifty feet above
the surface, or about 125 feet above Lake Michigan. The drift at this
well has a thickness of 160 feet.
88
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
"At Highland Park there are four artesian wells with depths of
1, 800 to 2,200 feet. Mr. P. T. Dooley, a well driller, residing at this
village, reports that wells five inches in diameter yield about 150 gal-
lons per minute. A strong flow of water is obtained at about 900 feet
and also at about 1,300 feet, as well as at lower horizons. The wells
all flowed when first made, but at present scarcely reach the surface.
The elevation of the well mouths is no to 115 feet above Lake Michi-
gan, or 690 to 695 feet above the sea. The thickness of drift is about
175 feet."
Tabulated Artesian Well Data. T
(Compiled from Leverett's Report.*)
i ! , , • " / '•• _ ... „
( Locality and Owner.
i • ' . ':
Altitude.
Depth.
Capacity
per
minute.
Water bed and veins .
... ^ feet..
612
Feet.
1 602
Gallons.
Limestone, 5C2-832 ft.
Highland Park— city well .......
Lake Forest— C. C. Parwell . . . '. .
685
650+
600
2,200
960
( 1,135 |
I 1 600 >
150
60
Galena, 900 ft.; Lower
Magnesian 1,300 ft.;
Potsdam 1700-2200 ft.
Probably St. Peters
sandstone
St Peters, Lwr. Magn.
Winnetka — Lloyd's well
658
1 2,005 1
1,570
150
and probably Potsd.
Probably Lwr. Magn.
•.?•;•'•' •••• '• i
, pp. 813-818.
Altitude of Top of St. Peters Sandstone in Chicago and Evanston-
Waukegan Region.
( Compiled from Leverett's Report.*)
Location.
Altitude
below tide.
Thickness
Chicago . .
Feet.
225+
200+
Evanston . . » .
222
420 V
Highland Park
320
200
Lake Bluff
258
167
Winnetka.
281
212
The surface of Lake Michigan is 581 feet above mean sea level.
* Loc. cit., p. 795.
ATWOOD.] GEOGRAPHIC CONDITIONS AND SETTLEMENT.
GEOGRAPHIC CONDITIONS AND SETTLEMENT.
(BY w. w. ATWOOD.)
History.^-When settlers came to northeastern ' ijliftpis in the early
part of the last century, many of them selected the North Shore region
in preference to the Chicago district. The old settlejrs wjio live in the
district recall the days when Chicago was spoken m;a? a "mud hole."
The site of Waukegan was 'selected for a city b^or|ei','-l^(at of Chicago,
and a small village and fort we^e established eairc of jliighwood near
the shore, when Chicago was lijttle more than ^a1, trying post. Tfie
region continues to be very attractive for 'suburfiia^: n;pmes, and large
industrial interests have been established at Watkk^g^.;
Location of Roads. — Before the railroad; was built ijtorth of Chicago
there was a government highway from Fort ; iDdar^pf ti! to Green Bay
known as the Green Bay road. The location pi tll,!^ road was con-
trolled by physiographic conditions. In the southern portion of the
district, just north of Chicago, it was located on a beach ridge. This
old shore line offered an even grade where the land was drier than on
either side, and where the road material was sand and gravel. The
road followed the ancient shore line through the present site of Evans-
ton to the southern margin of Wilmette, where the beach ridge comes
to the modern lake cliff. Ridge road, in Evanston, is a portion of the
old Green Bay road. It is conspicuously above the general level of the
lake plain and the homes now located there are favored by a good
outlook and by good drainage through the beach material away from
the basements and cellars.
Through Wilmette the government road was unfortunately near the
lake cliff and was frequently washed away by the waves. At the foot
of Lake avenue, Wilmette, as reported by C. P. Westerfield, a surveyor,
at Waukegan, 111., the present shore line is nearly 300 feet west of
where it was in 1857. The original location of the old government
road at this place is more than 200 feet east of the present shore line.
A short distance north of Winnetka the Green Bay road turned
westward to avoid crossing the numerous ravines, and thence northward
near the present line of the Chicago & Northwestern Railway. The old
road turned westward just far enough to reach the uneroded rolling
upland, and the modern steam and electric roads have taken advantage
of the same route just west of most of the ravines. The railroads have
built culverts where they cross the heads of some of the longer ravines.
The Grosse Point road, west of Evanston and Wilmette, is also an
old highway, and was located on a beach ridge because of the peculiar
90
THE EVANSTON-WAUKEGAN REGION.
[BULL. 7
advantages offered by the sand and gravel. In the Chicago region
there are several other illustrations of this same physiographic control
of the early highways.
The roads or streets in the most recently surveyed village in the
North Shore region show an interesting relationship to the topography
of the village site. In the southern portion of Zion City there are
several head-water ravines of one of the tributaries of Dead river,
and the influence of these ravines on the location of the streets is
clearly shown in Fig. 52. A similar topographic control of roads is
illustrated in Lake Forest and to some extent in Highland Park.
]DDD
3DDD
1DDD
]DDD
son
JUL
:naQQ5on
man
ODD
HDD
mo
ODDDC
DDDOC
FIG. 52. Road map of the southern portion of Zion City.
Towns and Villages, — The margin of the lake flat where the rolling
upland begins is a favorite site for villages. In the Chicago region
beginning at the south, Dyer, Ind., Flossmoor, Chicago Heights,
Homewood, Palos Springs, Palos Park, LaGrange, Galewood and Nor-
wood Park are at this margin. In the Evanston-Waukegan region
there are not many such sites, but Winnetka has such a location at
the south, and Waukegan at the north. The opportunity for a harbor,
the lake flat for wharfs and industrial plants, and the upland for the
home district, were important factors that influenced the selection of
the Waukegan site.
Soils and Sub-soils. — When the great ice sheet retreated the moraine
deposits were exposed to the processes of weathering and erosion.
The waters that went below the surface dissolved some of the mineral
matter in the drift. Most of the calcareous material in the upper three
to five feet of the drift has now been leached out. The clay in this
upper zone usually fails to respond to acid as less exposed clay in the
region will. Expansion and contraction due to changes in temperature
loosened the material and made it more porous. The freezing and
ILLINOIS GEOLOGICAL SURVEY.
Bull. No. 7, PI. 14.
Fig. A. Truck farm near Rogers Park.
Pig. B. Site of the town of St. John, showing two orchard trees that were in the
western portion of the town. LCourtesy of C. & N. W. Ry.]
ATWOOD.] GEOGRAPHIC CONDITIONS AND SETTLEMENT. 91
thawing of the ground water also left the land less compact. For two
or three decades after the retreat of the ice, judging from the present
condition of the drift heaps along the Chicago Drainage Canal, this
region was essentially barren. As plant life began to appear, the
growth of roots assisted in loosening the ground, and the decay of
vegetable matter contributed to the surface loam or soil. The decayed
vegetable matter is dark brown or black, and today affects the color
of the uppermost one or two feet in every exposure in the drift of this
region. The oxidation of the iron-bearing elements in the drift has
given to the five to ten feet underlying the soil a light yellow or buff
color.
These various soil making processes are operative on the lake plain
and on the upland, but they have affected the drift of the upland to
slightly greater depths than that of the plain. Usually the uppermost
zone of one or two feet, colored by decayed vegetable matter and much
oxidized mineral matter, is defined as the soil. The somewhat oxidized,
leached and loosened zone below the soil and above the unmodified
drift is known as the sub-soil.
Unfortunately there is no exposure known in this region, that goes
down to bed rock, showing the relation of the unmodified drift to
the underlying rock formation. Judging from well data within the
region and from exposures in the surrounding territory, we may, how-
ever, infer that if such exposure were made, the conditions would
be as shown in Fig. 8. The drift would be sharply defined from the
bed rock. The surface of the rock would undoubtedly show signs of
glacial action such as striations, grooving and polishing. In regions
not invaded by ice the relations are very different. In such regions
the soil is derived directly from the disintegration of the rock at the
surface and is known as residual soil. There is a gradual gradation
from the soil into the sub-soil and downward through the less and
less decomposed material to the unmodified bed rock, as shown in
Fig. 13-
Most rock is more or less variable in composition and texture and
therefore some parts yield more readily than others to the agents of
weathering. The result is differential weathering, with the soil thicker
at some places than at others. The sandy and gravelly soils found at
some places in the southeast and northeast portions of the area are
beach formations and were described in connection with the lake plain.
Farms. — In the southern portion of the region, the lowlands between
the ancient beaches are largely used as truck farms. These areas
were lagoons during certain stages in the retreat of the lake waters
and from the abundance of decaying vegetable matter in such places
came to have rich soils. The tendency of late has been to cover large
portions of these lagoons with hot-houses (Plate XIV) and to raise
vegetables for the Chicago and North Shore markets at all seasons of
the year.
The rolling upland is excellent farm land. Over most of the moraine
belt there is a loamy deposit several inches thick that is easily tilled
and is very productive. Between Waukegan and Beach and extending
92 THE EVANSTON-WAUEEGAN REGION, [stru,. 7
somewhat farther north there is a narrow four-foot bed of peaty ma-
terial that is exceedingly rich soil and might be used for lawn or field
dressing. The deposit is just west of the bluff which borders the rail-
road. Associated with the peat there is some bog iron ore but not in
sufficient quantity to be of commercial value.
Suburban and Summer Homes. — The ravine country east of the
railroad between Winnetka and North Chicago is largely devoted to
suburban and summer homes. Its eastern margin borders the lake,
and has lost much by the encroachment of the waves. In 1897 Mr.
Leverett published the following statement.* "The rate at which the
lake bluff is being encroached upon by wave action has become a matter
of much concern to the residents. It is estimated by old settlers that
from Waukegan to Evanston there has been, during the thirty years
from 1860 to 1890, a strip about 150 feet in width, undermined and
carried into the lake. This amounts to about 500 acres, representing
a,t present valuation nearly one million dollars' worth of property."
The Former Village of St. Johns. — In 1845 and for about ten years
following there was a village located in the southeast corner of what
is now the Fort Sheridan grounds. This village was known as St.
Johns. The chief industry was brick making, the yards employing as
many as eighty men. A portion of the brick yard (Plates II, Fig. A,
and XI) may now be seen and the boundaries of the kilns may be
identified. In 1858 the railroad built a spur to the brick yards and
the old railroad grade may be easily followed northeastward through
the village of Highwood into the Fort Sheridan grounds. North of
the clay pit remnants of a foundation and of an orchard are at the
very margin of the lake cliff. Reports differ as to the amount of land
that has been cut away at this point, 'but all agree that it was more
than 100 feet. Some old settlers insist that 300 to 400 feet have been
removed, and that the wearing away of the land caused the site to be
abandoned. The orchard trees (Plate XIV, Fig. B) at the edge of
the cliff and even overhanging are reported by some to have been in
the yard to the west of the westermost house in the village. If this is
true, the entire site of the village of St. Johns is east of the present
shore line.
The Economic Uses of the Glacial Material. — The clay brought to
this region by the glacier has been used in the manufacture of brick
at several places. The manufacture of brick at St. Johns has been
referred to. A few years ago brick was made at Spauldings, three
miles west of Waukegan, and at North Chicago. The beach gravels
are used in concrete work, for roofing and as road material. Large
quantities oT a fine grade of gravel, torpedo gravel, are used in concrete
and at Waukegan in the manufacture of ready roofing material. The
glacial bowlders are sometimes used very artistically in foundations
or in chimneys, fences or gate posts (Plate XIII, Fig. B).
* Pleistocene features and deposits of the Chicago Area, Bull. II, Geol. and Nat. Hist. Sur.
of the Chicago Academy of Sciences.
ATWQOD.] GEOGRAPHIC CONDITIONS AND SETTLEEENT. 93
Rainfall* — Illinois is one of the most favored, of the west-central
states in the matter of rainfall. A deficiency of rainfall has never
been so serious as to cause a complete failure of any crop over a great
part of the State, such as the less humid states of the West and North-
west have experienced. Its greatest danger lies in a deficiency between
June and September, there being many years when the corn and other
crops which ripen in autumn are shortened by drought at that season.
Often heavy rains and low temperature from April to June keep the
ground cold and damp; then a reversal of conditions suddenly occurs
and the ground becomes baked by the hot, dry atmosphere and blazing
sun.
The average rainfall for Illinois is distributed as follows: Spring,
10.2 inches; summer, 11.2 inches; autumn, 9 inches; winter, 7.7 inches;
giving an annual precipitation of 38.1 inches. The range in the rain-
fall at Chicago for the years 1867 to 1895, inclusive, was 23.4 inches,
the lowest annual rainfall being 22.4 inches in 1867 and the highest
45.8 inches in 1883. In general, an annual precipitation of less than
25 inches results unfavorably to crops in Illinois, but this depends very
largely upon its seasonal distribution. A year of 30 inches or more of
rainfall at a given station may have a more prolonged and serious
drought in the growing season, than one with but 24 inches.
* Quoted from Alden in the Chicago Polio, U. S. Geol. Survey. For additional information
relative to the rainfall in Illinois see Mr. Leverett's paper on the ' 'Water Resources of Illinois"
in the 17th Ann. Rep. U. S. Qeol. Surv. Part II. Also "The Illinois Glacial Lobe," Mongr.
XXXVIII, U. S. Geol. Surv.. Chapters XII, XIII, XIV.
94 THE EVANSTON-WAUKEGAN KEGION. [BULL. 7
APPENDIXES.
A.
BlBLIOGBAPHY.
1868. Geology of Cook County, by H. M. Bannister; Geol. Surv. Illinois,
Vol. Ill, Geology and Palaeontology, pp. 239-256, Springfield, 1868.
1868. Report on the Survey of the Illinois River, by James A. Wilson and
William Gooding; Rept. Chief Eng., U. S. A., 1868, p. 438.
1878. The North American Lakes Considered as Chronometers of Post-
Glacial Time, by Dr. Edmund Andrews; Trans. Chicago Acad. Sci., Vol. II,
Article 1, pp. 1-24,
1877. Geology of Eastern Wisconsin, by T. C. Chamberlin; Geol. Surv. of
Wis., Vol. II, 1873-77, pp. 219-233.
1884. Microscopic Organisms in the Bowlder Clays of Chicago and Vicin-
ity, by H. A. Johnson and B. Thomas; Bull. Chicago Acad. Sci., Vol. I, No. 4.
3886. Chicago Artesian Wells, on Their Structure and Sources of Supply,
by Leander Stone: Bull. Chicago Acad. Sci., Vol. I, No. 8.
1888. Raised Beaches at the Head of Lake Michigan, by Frank Leverett:
Trans. Wisconsin Acad. Sci., Vol. VII, 1883-87, pp. 177-192.
1889. Water Supplies of Illinois in Relation to Health, by L. E. Cooley:
Rept. State Board of Health, Springfield, 1889.
1890. Lake and Gulf Waterway, by L. E. Cooley. Private publication.
1890. Survey of Waterway from Lake Michigan to the Illinois River at
LaSalle, 111., by Capt. W. L. Marshall, U. S. Eng.: Ann. Rept. Chief of En-
gineers to the Secretary of War, 1889, Part 3, Appendix JJ, pp. 2399-2574.
1894. The Ancient Outlet of Michigan, by W. M. Davis: Pop. Sci.
Monthly, Vol. XLVI, 1894, pp. 218-229.
1894. Currents of the Great Lakes as Deducted from the Movements of
Bottle Papers During the Seasons 1892 and 1893, by Mark W. Harrington:
Weather Bureau Bulletin B, U. S. Dept. Agriculture, 1894.
1894. The Geological Survey of the Great Lakes, by Dr. J. W. Spencer:
Proc. Am. Assoc. Adv. Sci., Brooklyn Meeting, 1894, pp. 242-243.
1896. The Water Resources of Illinois, by Frank Leverett: Seventeenth
Ann. Rept. U. S. Geol. Survey, Pt. II, 1896, pp. 695-849.
1897. The Pleistocene Features and Deposits , of the Chicago Area, by
Frank Leverett: Chicago Acad. Sci., Bull. II, Geol. and Nat. Hist. Surv.,
1897.
1897. A Short History of the Great Lakes, by Frank B. Taylor: Studies
in Indiana Geography, Terre Haute, 1897.
1897. Modification of the Great Lakes by Earth Movement, by G. K. Gil-
bert: Nat. Geog. Mag., Vol. VIII, 1897, pp. 233-247.
1897. The Age of the Great Lakes of North America — A Partial Biblio-
graphy, by Alex. N. Winchell: Am. Geologist, Vol. XIX, 1897, pp. 336-338.
1899. The Geography of Chicago and Its Environs, by Rollin D. Salisbury
and William C. Alden: Bull. No. 1, Geog. Soc. Chicago, 1899.
1899. The Illinois Glacial Lobe, by Frank Leverett: Mon. U. S. Geol.
Survey, Vol. XXXVIII, 1899, pp. 339-459.
1901. Plant Societies of Chicago and Vicinity, by H. C. Cowles: Bull. No.
2, Geog. Soc. of Chicago.
1906. Correlation of the raised beaches on the west side of Lake Michigan,
by J. W. Goldthwait: Jour. Geol., Vol. 14, pp. 411-424.
1907. Abandoned shore-lines of eastern Wisconsin, by J. W. Goldthwait:
Wis. Geol. and Nat. Hist. Surv. Bull., No. XVII.
AT WOOD-G OLDTHW AIT. ] APPENDIX. 95
B.
FIELD TRIPS.
For the Study of Ravines and Valleys —
1. Dead river between Waukegan and Beach.
2. Little Port river, Waukegan.
3. Pettibone creek, North Chicago.
4. Near Glencoe.
5. Near Ravinia.
6. Near County Line station on the Chicago & Milwaukee Electric railway.
7. At Beck's crossing, north of Glencoe.
For the Study of Shore Features —
1. Winnetka.
2. Ft. Sheridan.
3. South of Pettibone creek.
For Study of Old Beaches —
1. From Evanston Lighthouse west on Central street.
2. At Winnetka.
3. From Waukegan north to State line.
For Study of Dunes —
1. Rogers Park near Calvary cemetery.
2. North of Waukegan on lowland.
3. On beach between Lake Bluff and North Chicago.
96 INDEX. [BULL. 7
INDEX.
PAGE.
Abandoned lake shore lines * 37
Absorbing areas of aquifers 87
Agents at work on shore lines • • 29
Aggradation 77
Alden, W. C., cited 23, 55, 56, 58, 93
Alden, W. C., Salisbury, R. D., and, cited 33
Algonquin stage • • 64
Altitude of St. Peters sandstone 88
Andrews, Dr. Edmund, cited 48, 62
Artesian wells • • 16, 85
Atwood, W. W., cited 69
Development of the Ravines 69
General Geographic Features
Geographic Conditions and Settlement 89
The Geological Formations • • 4
Underground Water 85
Atwood, W, W., and J. W. Goldthwait,. Physical Geography of the Evanston-Wau-
kegan Region 1
B.
Barriers 36
Barrington, Moraine near ' • 14
Bars 38
Basalt in drift • • 18
Base level in streams 72
Plains • • 75
Beach ridges s 35
Beach Station, beach ridges at 68
Beach Station, Calumet beach at 63
Bpd rock • • 16
In outlet of Glenwood lake 56
Of region • • 4, 5
Bibliography 94
Booth's well • • - 16, 85
Bowlder clay , 20
Definition • • 4
Bowlders, largest in drift 19
Uses of • • 92
Brick clays 92
C.
Calumet atlas sheet 1
Stage • • 37, 47, 60
Terrace 81, 82
Calvary, gravel pit at • • 66
Camp Logan, lake plain at
Streams near • • 79, 83
Canada, drift from 1 6
Cary, near moraine • • 14
Chamberiin, T. C., cited 60
Changes in shore profile • • 32
Characteristics of valleys 76
Chert in drift • • \L 18
Chesapeake Bay, a depressed area 46
Chicago, atlas sheet
Academy of Science, acknowledgements to 16, 23, 48, 50, 92
INDEX. 97
Index — Continued.
PACHB.
Artesian wells • • 85
Rock exposures In 5
Chicago & Northwestern Railroad 2, 3 23
"Chicago" region defined 1
Chicago river 3
Topgraphy near head 23
Cincinnati shale in deep wells 86
Clay of region 4
Clays 92
Coastal topography 32, 50
Colorado canyon 75
Conglomerate in drift • • 18
Constitution of drift in area 18
Till . . • • 20
Continental glaciers 6
Cooley, Lyman, acknowledgements to 23
Corn Products Refining Company, artesian well 85
Course of a valley 70
Cross-section of ice sheet 7
Culver's well 85
Currents along shore 32
Cycles of erosion 73
Cycle of shore processes • • 45
D.
Dead river, flood plain of 79, 83
Deflected streams near Waukegan 40
Deposition hy ice 13
Streams • • 79
Deposits of glaciers 17
Desor, Edward, cited 44
DesPlaines atlas sheet 1
River 3
Valley at Gflenwood stage 58
Development of coastal topography 32
Development of the Ravines (by W. W. Atvvood) 69
Direction of glacial movement- • 5
Glacial striae 4
Ice movement • • 16
Distribution of drift 20
Drainage of area • « 3
Drift covered area 26
Driftless area • • , 26
Drift 20
Material, sources of • • 5
Of region 4
Driftless areas 10, 17
Drainage of • • 26
Topography of 27
Drowned valleys 63
Dunes 44, 51
Durkin's wall- • L 16
E.
Effect on topography of ice 10
Movement • • 17
Erosion cycles 73
Erosion of lake shore . . 28, 48, 92
Erosive work of ice - 10
Evanston, atlas sheet 1
Beach ridges in •• 37
City well 88
Coastal topography 50
Peat at 65
Shore erosion at • • 48
Shore line at 3
Evolution of shore line 28
Extent of area • • 1
Extinct lakes 54
—7 G
98 INDEX. [BULL. 7
Index — Continued.
F.
PAGE.
Farms in region 91
Farwell's well 16, 87
Fenneman, N. M., acknowledgements to . . . . 29'
Ferry's well • • 16
Field trips, suggestions for 95
Flint in drift 18
'Fluctuations in lake level 68
Formation of an ice sheet • • 6
Terminal moraines 23
Former village of St. Johns 92
Foster - and Whitney quoted 44
Fresh water shells • • 63
G.
Gabbro in drift 18
Galena-Trenton in deep wells 86, 88
Geographic Conditions and Settlement (by W. W. Atwood) 89
Features of the Region (by W. W. Atwood) 1
Geological Formations (by W. W. Atwood) 4
Gilbert, G. K.. acknowledgements to 29
Glacial deposits 17
Drift, constitution of 4
Drift in deep wells 86
Material, uses of 92
Glencoe, drift near 18
Ground moraine near 23
Large bowlders near ....•« 19
Glen Elyn, on moraine 14
Glenwood stage 37, 45, 47, 55
Beach formation 25
Goldthwait, J. W., cited 64, 84
Records of the Extinct Lakes 54
The Present Shore Line 28
Goldthwait, J. W., W. W. Atwood, and, Physical Geography of the Evanston-Wau-
kegan Region 1
Government road 89
Grade of streams '.'.' 72
Granite in drift. . • • 18
Gravels 92
Green Bay glacial lobe 17
Road ". 89
Greenland ice sheets • • 8
Grosse Point, beach ridges at 57
Coastal topography 50
Dunes near 45
Exposures near 62
Hooked bar near 47
Road • 89
Rock shore at 48
Ground moraine . . • « 20
Waters 71, 85
Gullies, origin of 69
H.
Hanging valleys of Normandy 47
Height of waves 29
Highland Park artesian wells 85
Moraine . . • - 51
Roads 90
Well 16
Highwood, atlas sheet 1
Hin^dale, on moraine . . « • 14
History of settlement 89
Hodked spit 41
H o 3k s . . . . . . 39
Horizontal configuration of shore lines. . • • 38
Hudson Bay, an elevated area 46
,. Center of glaciation 9( IQ
Hyde Park, deposition at '.'.'. .' 49
INDEX. 99
Index — Continued,
i.
PACK.
Ice sheet, formation of 6
Influence of changes in lake level on streams 81
Intermittent streams 71, 72
J.
Jaspar in drift 18
K.
Kay, Fred, acknowledgements to • ' 82
Kenilworth, lake plain at * 3
Kettle holes • • L 23, 24
Knobs and kettles 24
L.
Labrador center of dispersion 17
Lagoons along shores • • 36
Lake Algonquin 64
Correlation of • • 55
Lake Bluff, drift near 18
Lake Chicago- • 46, 54
Glenwood stage 25
Lake Forest artesian wells • • 85
Deep wells 87
Roads • • 90
Shore erosion at . •„ 48
Wells at • • 16
Lake Michigan, deepened by glaciers 13
Glacial lobe • • 13, 17
Shore line 28
Waters, quality of • • 87
Lake plain in area 3
Lake side, drift near • • 18
Lake Superior, glacial lobe 17
Lake survey charts 48
Lane, A. C., cited 68
Lemont, on moraine 14
Length of waves 29
Leverett, Frank, acknowledgements to
16, 23, 50, 55, 63, 64, 65, 86, 87, 88, 92, 93
Limestone in drift 18
Limit of glaciation • • 10
Limits of a valley 72
Lithologic hetereogeneity of drift • • 17 •
Little Dead river, bar at 40
Lloyd's well • • 16
Location of region 1
Roads • • 89
Long Island, bar on 39
Lower Magnesian limestone in deep wells • • 86. 88
Lynnaea, reflexa 63
M.
Mabrey, F. D., acknowledgements to 82
"Marcey, D. Oliver, quoted • • 65
Marcy's well 16
Marshes • • _, 24, 26, 36, 58, 68
Mature conditions of shore line 53
Modified drift • • 24
Definition 4
Mont Clare, plain near 23
Moraine at Highland Park 51
Surface • » 69
Moraines 14, 20
Morton Grove, gravel ridge at 57
Hooked bar near • • 47
Motion of ice chest 7
Movement of ice • • 16
100 INDEX. (BULL. 7
Index — Continued.
N.
PAGE.
Nature of materials in geological formations 4
New England, glaciation In • • 10
New Jersey coast 37
New York harbor • • 42
Niagara limestone in deep wells 86
Of region 5
Niles center and plain • • • 57
Nipissing great lakes 55
Shore lines 66
Terraces : 50, 82
Normandy, hanging valleys of 47
North American ice sheet • • 9, 10, 11
North Chicago, assorted drift near 5
North Shore • • 1
"North Shore" region defined 1
Northwestern University Campus, beach ridges on 36, 51, 65, 66
Norwood Park, shore lines • • 58
O.
Oak Park, hooked spit at 58
Origin of continental glaciers • • 6
Origin of a gully 69
P.
Peat 63, 65, 92
Peat bogs • • 36
Peneplains 75
Pettibone Creek 82
Assorted drift near 5
Bar at • • 30. 40
Flood plain of 79
Intermediate age of • ' ,78
Large bowlders near ,r 19
Physa elliptica • • 63
Physical Geography of the Evanston-Waukegan Region (by W. W. Atwood and
J. W. Goldthwait) 1
Physical heterogeneity of drift 18
Pisidium, sp • • , 63
Planorbis Mcannatus 63
Parvus • • 63
Trivalvus 63
Porphyry in drift • • 18
Potdam sandstone in deep wells 86. 88
Present shore line of area • • 28
• Price of topographic maps 1
Profile of equilibrium • • 33
Shore, changes in 32
Pyrite in drift • • 18
Q.
Quality of waters 87
Quartz in drift •• 18
Quartsite In drift 18
R.
Rainfall in area 93
Rate of erosion along lake 48
Ravines, development of 69
Ravinia, shore near • • 78
Wells at 16
Records of the Extinct Lakes (by J. W. Goldthwait) • • 54
Red clays of Glenwood stage . . * 56
Region discussed • • 1
Rejuvenation of streams 80
Residual soils, formation of • • L 27
Ridge Avenue, Evanston 37, 39, 62
Ridge Road • • 89
Riverside, atlas sheet 1
INDEX. 101
Index — Continued.
PAGE.
Road location In region :..,'./.'' -&&,
Roads at Highland Park •.-,.. ;-.'. .-,.,.'. < . . >.-.'. *'.'. -9C
Lake Forest 90
Zlon City , . . . 90
Rock exposures in Chicago 4
In lake bottom 48
Rockaway Beach 41
Rogers Park, coastal toopography • 50
Hooked spit near 43, 62
Lake bottom at 48
Rose Hill barrier 62
Run off • • 69
S.
St. Johns 92
St. Peter sandstone, altitude of • • 88
In deep wells 86
Salisbury, R. D., cited • • 59, 69
And Alden, W. C., cited 33
Sands • • 92
Sandstone in drift 18
Sandy Hook 42
Schist in drift • • 18
Scratched 'pebbles 4
Sea cliff • • 33
Seepage 85
Settlement of region 89
Shells in Calumet beach sands 63
Shore current 32
Cycle • • 45
Shore line of area 28
Elevation • • 46
Through area 3
Shore terrace • • 34
Shores of (ilenwood stage 56
Skokie marsh 58
Slope of lake shore 48
Soils of region - 90
South Evanston artesian well 85
Sources of drift material 5
Southern limit of drift , 10
Spermaceti cave 43
Spits 38
Stages of valley development 76
Stopping of shore line 60
Stony Brook harbor 40
Stratified drift 24
Striae on rock 7
Structure of region 5
Submerged terraces 48
Suburban homes. 92
Subglacial till 20
Suggested field trips 95
Summer homes 92
Swift's well 16, 85
Syenite in drift 18
T.
Taylor, F. B., acknowledgements to 55, 64. 67
Temporary streams 71, 72
Terminal moraines 20, 23
Terrace along shore 34
Of Calumet stage 81
Of erosion 48
Ten fathom 4«
Of Toleston stage 81, 82
Till 20
Definitiofi of 5
Toleston stage 37, 63
Terrace 81
Topographic forms of stream deposits 79
Topography of coast 32, 50
Drift covered areas 23
Terminal moraines 24
Towns of region 90
102 INDEX. [BULL.
Index — Concluded.
PAGE.
Transportation by streams 79
Trenton, in deep wells 86
Tributary valleys .. .. . 70
Truck farms on lowlands. 91
U.
Underground Water (by W. W. Atwood) 85
Undertow 31
Unglaciated areas, topography of 27
United States Geological Survey, acknowledgements to
9, 16, 23, 29, 39, 56, 60, 87, 93
Topographic maps of 1
Upland area 2
V.
Valleys, courses of 70
Valparaiso moraine 14
Villages of region 90
W.
Walker, Bryant, acknowledgements to 63
Wastage of ice sheet 8
"Washes" 69
Waukegan, artesian wells 85
Atlas sheet 1
Beach features at 68
Beach ridges at 60
Coastal topography 51. 52
Deflected streams near 40
Ground moraine near 23
Igneous rock near 19
Shore erosion at 48
Shore line at 3
Slope of shore at 48
Water supply 86
Wells at 16
Waves 29
Wells reaching bed rock 16
West Meadow Beach 39
Westerfleld, C. P., acknowledgements to 89
Wllmette, embayment 42. 62
Government road at 89
Lake plain at 3
Winnetka, coastal topography 50, 51
Highland near 2
Lake plain at 3
Ridge near 23
Shore erosion at 48
Wells at 16
Winthrop Harbor beach ridges 60
Exposure near 25
Lake plain at 3
Work of continental glaciers 6
Glacier ice 10
Wisconsin Geological and Natural History Survey, acknowledgements to
6, 26, 29, 64, 69
Y.
Yield of artesian wells : . . 87
Zion City, beach ridges at 60
Calumet beach at 63
Coastal topography 52
Lake plain at 5
Roads 89
Sand ridges at 68
Slope off shore at 48
LIBRARY CATALOGUE SLIPS.
[Mount each slip upon a separate card, placing the subject at the top oflthe second slip. The
name of the series should not be repeated on the series card, but the additional numbers
should be added, as received, to the first entry.]
AUTHOR.
Atwood, Wallace W., and James Walter Goldthwait
Physical Geography of the Evanston-Waukegan Re-
gion. Urbana, University of Illinois, 1908.
(102 pp. 48 fig. 14 pi.) State Geological Survey, Bulletin No. 7.
Goldthwait, James Walter, and Wallace W. Atwood
Physical Geography of the Evanston-Waukegan Re-
gion. Urbana, University of Illinois, 1908.
(1G2 pp. 48 fig. 14 pi.) State Geological Survey. Bulletin No. 7.
SUBJECT.
Wallace W. Atwood and James Walter Goldthwait
Physical Geography of the Evanston-Waukegan Re-
gion. Urbana, University of Illinois, 1908.
(102 pp. 48 fig. 14 pi.) State Geological Survey. Bulletin No. 7.
SERIES
State Geological Survey.
Bulletins. No. 7. W. W. Atwood and J. W.
Goldthwait. Physical Geography of the Evanstoii-Wau-
kegan Region,
NOTICE.
A portion of each edition of the Bulletins of the State Geological Survey is
set aside for gratuitous distribution. To meet the wants of libraries and in-
dividuals not reached in this first distribution, 500 copies are in each case
reserved for sale at cost, including postage. The reports may be obtained
upon application to the State Geological Survey, Urbana, Illinois, and checks
an money orders should be made payable to H. Foster Bain, Urbana.
The list of publications is as follows:
Bulletin 1. The Geological Map of Illinois: by Stuart Weller. Including a
folded, colored geological map of the State on the scale of 12 miles to the
inch, with descriptive text of 26 pages. Gratuitous edition exhausted. Sale
price 45 cents.
Bulletin 2. The Petroleum Industry of Southeastern Illinois; by W. S.
Blatchley. Preliminary report descriptive of condition up to May 10th, 1906.
109 pages. Gratuitous edition exhausted. Sale price 25 cents.
Bulletin 3. Composition and Character of Illinois Coals; by S. W. Parr;
with chapters on the Distribution of the Coal Beds of the State, by A. Bement,
and Tests of Illinois Coals under Steam Boilers, by L. P. Breckenridge. A
preliminary report of 86 pages. Gratuitous edition exhausted. Sale price
25 cents.
Bulletin 4. Year Book for 1906, by H. Foster Bain, director, and others. In-
cludes papers on the topographic survey, on Illinois fire clays, on limestones
for fertilizers, on silica deposits, on coal, and on regions near East St. Louif,
Springfield and in southern Calhoun county. 260 pages. Postage 9 cents.
Bulletin 5. Water Resources of the East St. Louis District; by Isaiah
Bowman, assisted by Chester Albert Reeds. Including a discussion of the
topographic, geologic and economic conditions controlling the supply of water
for municipal and industrial purposes, with map and numerous well records
and analyses. 128 pages, postage 6 cents.
Bulletin 6. The Geological Map of Illinois; by Stuart Weller. Second
edition. Including a folded colored geological map of the State on the scale
of 12 miles to the inch, showing the distribution of the formations and the
location of coal mines, oil pools, lead, zinc and fluorspar mines, with de-
scriptive text of 32 pages. Gratuitous edition exhausted Sale price 45 cents.
Bulletin 7. Physical Geography of the Evanston-WauJcegan Region; by
Wallace W. Atwood and James Walter Goldthwait. Forming the first of
the educational bulletins of the survey and designed especially to meet the
needs of teachers in the public schools. 102 pages. Postage 6 cents.
Circular No. 1. The Mineral Production of Illinois in 1905. Pamphlet, 14
pages, postage 2 cents.
Circular No. 2. The Mineral Production of Illinois in 1906. Pamphlet, 18
pages, postage 2 cents.
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