THE QUATERNARY
The last period of geological history, the Quaternary, may be said to
have begun when all, or nearly all, living species of mollusks and
most of the existing mammals had appeared.
It is divided into two great epochs. The first, the _Pleistocene_ or
_Glacial epoch_, is marked off from the Tertiary by the occupation of
the northern parts of North America and Europe by vast ice sheets; the
second, the _Recent epoch_, began with the disappearance of the ice
sheets from these continents, and merges into the present time.
The Pleistocene Epoch
We now come to an episode of unusual interest, so different was it
from most of the preceding epochs and from the present, and so largely
has it influenced the conditions of man's life.
The records of the Glacial epoch are so plain and full that
we are compelled to believe what otherwise would seem almost
incredible,--that following the mild climate of the Tertiary came a
succession of ages when ice fields, like that of Greenland, shrouded
the northern parts of North America and Europe and extended far into
temperate latitudes.
=The drift.= Our studies of glaciers have prepared us to decipher and
interpret the history of the Glacial epoch, as it is recorded in the
surface deposits known as the drift. Over most of Canada and the
northern states this familiar formation is exposed to view in nearly
all cuttings which pass below the surface soil. The drift includes two
distinct classes of deposits,--the unstratified drift laid down by
glacier ice, and the stratified drift spread by glacier waters.
The materials of the drift are in any given place in part unlike the
rock on which it rests. They cannot be derived from the underlying
rock by weathering, but have been brought from elsewhere. Thus where a
region is underlain by sedimentary rocks, as is the drift-covered area
from the Hudson River to the Missouri, the drift contains not only
fragments of limestone, sandstone, and shale of local derivation, but
also pebbles of many igneous and metamorphic rocks, such as granites,
gneisses, schists, dike rocks, quartzites, and the quartz of mineral
veins, whose nearest source is the Archean area of Canada and the
states of our northern border. The drift received its name when it was
supposed that the formation had been drifted by floods and icebergs
from outside sources,--a theory long since abandoned.
[Illustration: Fig. 352. Stratified Drift overlaying
Unstratified Drift, Massachusetts]
The distribution also of the drift points clearly to its peculiar
origin. Within the limits of the glaciated area it covers the country
without regard to the relief, mantling with its debris not only
lowlands and valleys but also highlands and mountain slopes.
The boundary of the drift is equally independent of the relief of
the land, crossing hills and plains impartially, unlike water-laid
deposits, whose margins, unless subsequently deformed, are horizontal.
The boundary of the drift is strikingly lobate also, bending outward
in broad, convex curves, where there are no natural barriers in the
topography of the country to set it such a limit. Under these
conditions such a lobate margin cannot belong to deposits of rivers,
lakes, or ocean, but is precisely that which would mark the edge of a
continental glacier which deployed in broad tongues of ice.
=The rock surface underlying the drift.= Over much of its area the
drift rests on firm, fresh rock, showing that both the preglacial
mantle of residual waste and the partially decomposed and broken rock
beneath it have been swept away. The underlying rock, especially if
massive, hard, and of a fine grain, has often been ground down to a
smooth surface and rubbed to a polish as perfect as that seen on the
rock beside an Alpine glacier where the ice has recently melted back.
Frequently it has been worn to the smooth, rounded hummocks known as
roches moutonnées, and even rocky hills have been thus smoothed to
flowing outlines like roches moutonnées on a gigantic scale. The rock
pavement beneath the drift is also marked by long, straight, parallel
scorings, varying in size from deep grooves to fine striae as delicate
as the hair lines cut by an engraver's needle. Where the rock is soft
or closely jointed it is often shattered to a depth of several feet
beneath the drift, while stony clay has been thrust in among the
fragments into which the rock is broken.
In the presence of these glaciated surfaces we cannot doubt that the
area of the drift has been overridden by vast sheets of ice which, in
their steady flow, rasped and scored the rock bed beneath by means of
the stones with which their basal layers were inset, and in places
plucked and shattered it.
=Till.= The unstratified portion of the drift consists chiefly of
sheets of dense, stony clay called till, which clearly are the ground
moraines of ancient continental glaciers. Till is an unsorted mixture
of materials of all sizes, from fine clay and sand, gravel, pebbles,
and cobblestones, to large bowlders. The stones of the till are of
many kinds, some having been plucked from the bed rock of the locality
where they are found, and others having been brought from outside and
often distant places. Land ice is the only agent known which can
spread unstratified material in such extensive sheets.
The _fine material_ of the till comes from two different sources. In
part it is derived from old residual clays, which in the making had
been leached of the lime and other soluble ingredients of the rock
from which they weathered. In part it consists of sound rock ground
fine; a drop of acid on fresh, clayey till often proves by brisk
effervescence that the till contains much undecayed limestone flour.
The ice sheet, therefore, both scraped up the mantle of long-weathered
waste which covered the country before its coming, and also ground
heavily upon the sound rock underneath, and crushed and wore to rock
flour the fragments which it carried.
The color of unweathered till depends on that of the materials of
which it is composed. Where red sandstones have contributed largely to
its making, as over the Triassic sandstones of the eastern states and
the Algonkian sandstones about Lake Superior, the drift is reddish.
When derived in part from coaly shales, as over many outcrops of the
Pennsylvanian, it may when moist be almost black. Fresh till is
normally a dull gray or bluish, so largely is it made up of the
grindings of unoxidized rocks of these common colors.
Except where composed chiefly of sand or coarser stuff, unweathered
till is often exceedingly dense. Can you suggest by what means it has
been thus compacted? Did the ice fields of the Glacial epoch bear
heavy surface moraines like the medial and lateral moraines of valley
glaciers? Where was the greater part of the load of these ice fields
carried, judging from what you know of the glaciers of Greenland?
=Bowlders of the drift.= The pebbles and bowlders of the drift are in
part stream gravels, bowlders of weathering, and other coarse rock
waste picked up from the surface of the country by the advancing ice,
and in part are fragments plucked from ledges of sound rock after the
mantle of waste had been removed. Many of the stones of the till are
dressed as only glacier ice can do; their sharp edges have been
blunted and their sides faceted and scored.
We may easily find all stages of this process represented among the
pebbles of the till. Some are little worn, even on their edges; some
are planed and scored on one side only; while some in their long
journey have been ground down to many facets and have lost much of
their original bulk. Evidently the ice played fast and loose with a
stone carried in its basal layers, now holding it fast and rubbing it
against the rock beneath, now loosening its grasp and allowing the
stone to turn.
Bowlders of the drift are sometimes found on higher ground than their
parent ledges. Thus bowlders have been left on the sides of Mount
Katahdin, Maine, which were plucked from limestone ledges twelve miles
distant and three thousand feet lower than their resting place. In
other cases stones have been carried over mountain ranges, as in
Vermont, where pebbles of Burlington red sandstone were dragged over
the Green Mountains, three thousand feet in height, and left in the
Connecticut valley sixty miles away. No other geological agent than
glacier ice could do this work.
The bowlders of the drift are often large. Bowlders ten and twenty
feet in diameter are not uncommon, and some are known whose diameter
exceeds fifty feet. As a rule the average size of bowlders decreases
with increasing distance from their sources. Why?
=Till plains.= The surface of the drift, where left in its initial
state, also displays clear proof of its glacial origin. Over large
areas it is spread in level plains of till, perhaps bowlder-dotted,
similar to the plains of stony clay left in Spitzbergen by the recent
retreat of some of the glaciers of that island. In places the
unstratified drift is heaped in hills of various kinds, which we will
now describe.
[Illustration: Fig. 354. Map of a portion of a Drumlin Area near
Oswego, New York]
=Drumlins.= Drumlins are smooth, rounded hills composed of till,
elliptical in base, and having their longer axes parallel to the
movement of the ice as shown by glacial scorings. They crowd certain
districts in central New York and in southern Wisconsin, where they
may be counted by the thousands. Among the numerous drumlins about
Boston is historic Bunker Hill.
Drumlins are made of ground moraine. They were accumulated and given
shape beneath the overriding ice, much as are sand bars in a river, or
in some instances were carved, like roches moutonnées, by an ice sheet
out of the till left by an earlier ice invasion.
=Terminal moraines.= The glaciated area is crossed by belts of
thickened drift, often a mile or two, and sometimes even ten miles
and more, in breadth, which lie transverse to the movement of the ice
and clearly are the terminal moraines of ancient ice sheets, marking
either the limit of their farthest advance or pauses in their general
retreat.
[Illustration: Fig. 355. Terminal Moraine, Staten Island]
The surface of these moraines is a jumble of elevations and
depressions, which vary from low, gentle swells and shallow sags to
sharp hills, a hundred feet or so in height, and deep, steep-sided
hollows. Such tumultuous hills and hummocks, set with depressions of
all shapes, which usually are without outlet and are often occupied by
marshes, ponds, and lakes, surely cannot be the work of running water.
The hills are heaps of drift, lodged beneath the ice edge or piled
along its front. The basins were left among the tangle of morainic
knolls and ridges (Fig. 105) as the margin of the ice moved back and
forth. Some bowl-shaped basins were made by the melting of a mass of
ice left behind by the retreating glacier and buried in its debris.
[Illustration: Fig. 356. Esker, New York]
=The stratified drift.= Like modern glaciers the ice sheets of the
Pleistocene were ever being converted into water about their margins.
Their limits on the land were the lines where their onward flow was
just balanced by melting and evaporation. On the surface of the ice
along the marginal zone, rivulets no doubt flowed in summer, and found
their way through crevasses to the interior of the glacier or to
the ground. Subglacial streams, like those of the Malaspina glacier,
issued from tunnels in the ice, and water ran along the melting ice
front as it is seen to do about the glacier tongues of Greenland. All
these glacier waters flowed away down the chief drainage channels in
swollen rivers loaded with glacial waste.
It is not unexpected therefore that there are found, over all the
country where the melting ice retreated, deposits made of the same
materials as the till, but sorted and stratified by running water.
Some of these were deposited behind the ice front in ice-walled
channels, some at the edge of the glaciers by issuing streams, and
others were spread to long distances in front of the ice edge by
glacial waters as they flowed away.
_Eskers_ are narrow, winding ridges of stratified sand and gravel
whose general course lies parallel with the movement of the glacier.
These ridges, though evidently laid by running water, do not follow
lines of continuous descent, but may be found to cross river valleys
and ascend their sides. Hence the streams by which eskers were laid
did not flow unconfined upon the surface of the ground. We may infer
that eskers were deposited in the tunnels and ice-walled gorges of
glacial streams before they issued from the ice front.
[Illustration: Fig. 357. Kames, New York]
_Kames_ are sand and gravel knolls, associated for the most part
with terminal moraines, and heaped by glacial waters along the
margin of the ice.
[Illustration: Fig. 358. Diagram Illustrating the Formation of
Kame Terraces
_i_, glacier ice; _t_, _t_, terraces]
_Kame terraces_ are hummocky embankments of stratified drift sometimes
found in rugged regions along the sides of valleys. In these valleys
long tongues of glacier ice lay slowly melting. Glacial waters took
their way between the edges of the glaciers and the hillside, and here
deposited sand and gravel in rude terraces.
_Outwash plains_ are plains of sand and gravel which frequently border
terminal moraines on their outward face, and were spread evidently by
outwash from the melting ice. Outwash plains are sometimes pitted by
bowl-shaped basins where ice blocks were left buried in the sand by
the retreating glacier.
_Valley trains_ are deposits of stratified drift with which river
valleys have been aggraded. Valleys leading outward from the ice front
were flooded by glacial waters and were filled often to great depths
with trains of stream-swept drift. Since the disappearance of the ice
these glacial flood plains have been dissected by the shrunken rivers
of recent times and left on either side the valley in high terraces.
Valley trains head in morainic plains, and their material grows finer
down valley and coarser toward their sources. Their gradient is
commonly greater than that of the present rivers.
=The extent of the drift.= The extent of the drift of North America
and its southern limits are best seen in Figure 359. Its area is
reckoned at about four million square miles. The ice fields which once
covered so much of our continent were all together ten times as large
as the inland ice of Greenland, and about equal to the enormous ice
cap which now covers the antartic regions.
The ice field of Europe was much smaller, measuring about seven
hundred and seventy thousand square miles.
=Centers of dispersion.= The direction of the movement of the ice is
recorded plainly in the scorings of the rock surface, in the shapes of
glaciated hills, in the axes of drumlins and eskers, and in trains of
bowlders, when the ledges from which they were plucked can be
discovered. In these ways it has been proved that in North America
there were three centers where ice gathered to the greatest depth,
and from which it flowed in all directions outward. There were thus
three vast ice fields,--one the _Cordilleran_, which lay upon the
Cordilleras of British America; one the _Keewatin_, which flowed
out from the province of Keewatin, west of Hudson Bay; and one the
_Labrador_ ice field, whose center of dispersion was on the highlands
of the peninsula of Labrador. As shown in Figure 359, the western ice
field extended but a short way beyond the eastern foothills of the
Rocky Mountains, where perhaps it met the far-traveled ice from the
great central field. The Keewatin and the Labrador ice fields flowed
farthest toward the south, and in the Mississippi valley the one
reached the mouth of the Missouri and the other nearly to the mouth of
the Ohio. In Minnesota and Wisconsin and northward they merged in one
vast field.
[Illustration: Fig. 359. Hypothetical Map of the Pleistocene Ice Sheets
of North America
From Salisbury's _Glacial Geology of New Jersey_]
The thickness of the ice was so great that it buried the highest
mountains of eastern North America, as is proved by the transported
bowlders which have been found upon their summits. If the land then
stood at its present height above sea level, and if the average slope
of the ice were no more than ten feet to the mile,--a slope so gentle
that the eye could not detect it and less than half the slope of the
interior of the inland ice of Greenland,--the ice plateaus about
Hudson Bay must have reached a thickness of at least ten thousand
feet.
In Europe the Scandinavian plateau was the chief center of dispersion.
At the time of greatest glaciation a continuous field of ice extended
from the Ural Mountains to the Atlantic, where, off the coasts of
Norway and the British Isles, it met the sea in an unbroken ice wall.
On the south it reached to southern England, Belgium, and central
Germany, and deployed on the eastern plains in wide lobes over Poland
and central Russia (Fig. 360).
[Illustration: Fig. 360. Hypothetical Map of the Pleistocene
Ice Sheet of Europe]
At the same time the Alps supported giant glaciers many times the size
of the surviving glaciers of to-day, and a piedmont glacier covered
the plains of northern Switzerland.
=The thickness of the drift.= The drift is far from uniform in
thickness. It is comparatively thin and scanty over the Laurentian
highlands and the rugged regions of New England, while from southern
New York and Ontario westward over the Mississippi valley, and on the
great western plains of Canada, it exceeds an average of one hundred
feet over wide areas, and in places has five and six times that
thickness. It was to this marginal belt that the ice sheets brought
their loads, while northwards, nearer the centers of dispersion,
erosion was excessive and deposition slight.
=Successive ice invasions and their drift sheets.= Recent studies of
the drift prove that it does not consist of one indivisible formation,
but includes a number of distinct drift sheets, each with its own
peculiar features. The Pleistocene epoch consisted, therefore, of
several glacial stages,--during each of which the ice advanced far
southward,--together with the intervening interglacial stages when,
under a milder climate, the ice melted back toward its sources or
wholly disappeared.
[Illustration: Fig. 361. Diagram illustrating Criteria by which
Different Drift Sheets are distinguished]
The evidences of such interglacial stages, and the means by which the
different drift sheets are told apart, are illustrated in Figure 361.
Here the country from N to S is wholly covered by drift, but the drift
from N to _m_ is so unlike that from _m_ to S that we may believe it
the product of a distinct ice invasion and deposited during another
and far later glacial stage. The former drift is very young, for its
drainage is as yet immature, and there are many lakes and marshes
upon its surface; the latter is far older, for its surface has been
thoroughly dissected by its streams. The former is but slightly
weathered, while the latter is so old that it is deeply reddened by
oxidation and is leached of its soluble ingredients such as lime.
The younger drift is bordered by a distinct terminal moraine, while
the margin of the older drift is not thus marked. Moreover, the two
drift sheets are somewhat unlike in composition, and the different
proportion of pebbles of the various kinds of rocks which they contain
shows that their respective glaciers followed different tracks and
gathered their loads from different regions. Again, in places beneath
the younger drift there is found the buried land surface of an older
drift with old soils, forest grounds, and vegetable deposits,
containing the remains of animals and plants, which tell of the
climate of the interglacial stage in which they lived.
By such differences as these the following drift sheets have been made
out in America, and similar subdivisions have been recognized in
Europe.
5 The Wisconsin formation
4 The Iowan formation
3 The Illinoian formation
2 The Kansan formation
1 The pre-Kansan or Jerseyan formation
In New Jersey and Pennsylvania the edge of a deeply weathered and
eroded drift sheet, the Jerseyan, extends beyond the limits of a much
younger overlying drift. It may be the equivalent of a deep-buried
basal drift sheet found in the Mississippi valley beneath the Kansan
and parted from it by peat, old soil, and gravel beds.
The two succeeding stages mark the greatest snowfall of the Glacial
epoch. In Kansan times the Keewatin ice field slowly grew southward
until it reached fifteen hundred miles from its center of dispersion
and extended from the Arctic Ocean to northeastern Kansas. In the
Illinoian stage the Labrador ice field stretched from Hudson Straits
nearly to the Ohio River in Illinois. In the Iowan and the Wisconsin,
the closing stages of the Glacial epoch, the readvancing ice fields
fell far short of their former limits in the Mississippi valley, but
in the eastern states the Labrador ice field during Wisconsin times
overrode for the most part all earlier deposits, and, covering New
England, probably met the ocean in a continuous wall of ice which set
its bergs afloat from Massachusetts to northern Labrador.
We select for detailed description the Kansan and the Wisconsin
formations as representatives, the one of the older and the other of
the younger drift sheets.
[Illustration: Fig. 362. Photograph of Relief Map of the United
States at the Time of the Wisconsin Ice Invasion
By the courtesy of E. E. Howell, Washington, D.C.]
=The Kansan formation.= The Kansan drift consists for the most part of
a sheet of clayey till carrying smaller bowlders than the later drift.
Few traces of drumlins, kames, or terminal moraines are found upon the
Kansan drift, and where thick enough to mask the preexisting surface,
it seems to have been spread originally in level plains of till.
The initial Kansan plain has been worn by running water until there
are now left only isolated patches and the narrow strips and crests of
the divides, which still rise to the ancient level. The valleys of the
larger streams have been opened wide. Their well-developed tributaries
have carved nearly the entire plain to valley slopes (Figs. 50 B, and
59). The lakes and marshes which once marked the infancy of the region
have long since been effaced. The drift is also deeply weathered. The
till, originally blue in color, has been yellowed by oxidation to
a depth of ten and twenty feet and even more, and its surface is
sometimes rusted to terra-cotta red. To a somewhat less depth it has
been leached of its lime and other soluble ingredients. In the
weathered zone its pebbles, especially where the till is loose in
texture, are sometimes so rotted that granites may be crumbled with
the fingers. The Kansan drift is therefore old.
[Illustration: Fig. 363. Plain of Wisconsin Drift, Iowa]
=The Wisconsin formation.= The Wisconsin drift sheet is but little
weathered and eroded, and therefore is extremely young. Oxidation has
effected it but slightly, and lime and other soluble plant foods
remain undissolved even at the grass roots. Its river systems are
still in their infancy (Fig. 50, A). Swamps and peat bogs are abundant
on its undrained surface, and to this drift sheet belong the lake
lands of our northern states and of the Laurentian peneplain of
Canada.
The lake basins of the Wisconsin drift are of several different
classes. Many are shallow sags in the ground moraine. Still more
numerous are the lakes set in hollows among the hills of the terminal
moraines; such as the thousands of lakelets of eastern Massachusetts.
Indeed, the terminal moraines of the Wisconsin drift may often be
roughly traced on maps by means of belts of lakes and ponds. Some
lakes are due to the blockade of ancient valleys by morainic débris,
and this class includes many of the lakes of the Adirondacks, the
mountain regions of New England, and the Laurentian area. Still other
lakes rest in rock basins scooped out by glaciers. In many cases lakes
are due to more than one cause, as where preglacial valleys have both
been basined by the ice and blockaded by its moraines. The Finger
lakes of New York, for example, occupy such glacial troughs.
Massive _terminal moraines_, which mark the farthest limits to which
the Wisconsin ice advanced, have been traced from Cape Cod and
the islands south of New England, across the Appalachians and the
Mississippi valley, through the Dakotas, and far to the north over the
plains of British America. Where the ice halted for a time in its
general retreat, it left _recessional moraines_, as this variety of
the terminal moraine is called. The moraines of the Wisconsin drift
lie upon the country like great festoons, each series of concentric
loops marking the utmost advance of broad lobes of the ice margin and
the various pauses in their recession.
Behind the terminal moraines lie wide till plains, in places studded
thickly with drumlins, or ridged with an occasional esker. Great
outwash plains of sand and gravel lie in front of the moraine belts,
and long valley trains of coarse gravels tell of the swift and
powerful rivers of the time.
=The loess of the Mississippi valley.= A yellow earth, quite like
the loess of China, is laid broadly as a surface deposit over
the Mississippi valley from eastern Nebraska to Ohio outside the
boundaries of the Iowan and the Wisconsin drift. Much of the loess was
deposited in Iowan times. It is younger than the earlier drift sheets,
for it overlies their weathered and eroded surfaces. It thickens to
the Iowan drift border, but is not found upon that drift. It is older
than the Wisconsin, for in many places it passes underneath the
Wisconsin terminal moraines. In part the loess seems to have been
washed from glacial waste and spread in sluggish glacial waters, and
in part to have been distributed by the wind from plains of aggrading
glacial streams.
[Illustration: Fig. 364. Bank of Loess, Iowa]
=The effects of the ice invasions on rivers.= The repeated ice
invasions of the Pleistocene profoundly disarranged the drainage
systems of our northern states. In some regions the ancient valleys
were completely filled with drift. On the withdrawal of the ice the
streams were compelled to find their way, as best they could, over a
fresh land surface, where we now find them flowing on the drift in
young, narrow channels. But hundreds of feet below the ground the
well driller and the prospector for coal and oil discover deep,
wide, buried valleys cut in rock,--the channels of preglacial and
interglacial streams. In places the ancient valleys were filled with
drift to a depth of a hundred feet, and sometimes even to a depth of
four hundred and five hundred feet. In such valleys, rivers now flow
high above their ancient beds of rock on floors of valley drift. Many
of the valleys of our present rivers are but patchworks of preglacial,
interglacial, and postglacial courses (Fig. 366). Here the river winds
along an ancient valley with gently sloping sides and a wide alluvial
floor perhaps a mile or so in width, and there it enters a young,
rock-walled gorge, whose rocky bed may be crossed by ledges over which
the river plunges in waterfalls and rapids.
[Illustration: Fig. 365. Preglacial Drainage, Upper Ohio Valley
After Chamberlain and Leverett]
[Illustration: Fig. 366. A Patchwork Valley
_a_ and _a´_, ancient courses still occupied by the river;
_b_, postglacial gorge; _c_, ancient course now filled with drift]
In such cases it is possible that the river was pushed to one side
of its former valley by a lobe of ice, and compelled to cut a new
channel in the adjacent uplands. A section of the valley may have been
blockaded with morainic waste, and the lake formed behind the barrier
may have found outlet over the country to one side of the ancient
drift-filled valley. In some instances it would seem that during the
waning of the ice sheets, glacial streams, while confined within walls
of stagnant ice, cut down through the ice and incised their channels
on the underlying country, in some cases being let down on old river
courses, and in other cases excavating gorges in adjacent uplands.
=Pleistocene lakes.= Temporary lakes were formed wherever the ice
front dammed the natural drainage of the region. Some, held in the
minor valleys crossed by ice lobes, were small, and no doubt many were
too short-lived to leave lasting records. Others, long held against
the northward sloping country by the retreating ice edge, left in
their beaches their clayey beds, and their outlet channels permanent
evidences of their area and depth. Some of these glacial lakes are
thus known to have been larger than any present lake.
Lake Agassiz, named in honor of the author of the theory of
continental glaciation, is supposed to have been held by the united
front of the Keewatin and the Labrador ice fields as they finally
retreated down the valley of the Red River of the North and the
drainage basin of Lake Winnipeg. From first to last Lake Agassiz
covered a hundred and ten thousand square miles in Manitoba and the
adjacent parts of Minnesota and North Dakota,--an area larger than all
the Great Lakes combined. It discharged its waters across the divide
which held it on the south, and thus excavated the valley of the
Minnesota River. The lake bed--a plain of till--was spread smooth and
level as a floor with lacustrine silts. Since Lake Agassiz vanished
with the melting back of the ice beyond the outlet by the Nelson River
into Hudson Bay, there has gathered on its floor a deep humus, rich in
the nitrogenous elements so needful for the growth of plants, and it
is to this soil that the region owes its well-known fertility.
=The Great Lakes.= The basins of the Great Lakes are broad preglacial
river valleys, warped by movements of the crust still in progress,
enlarged by the erosive action of lobes of the continental ice sheets,
and blockaded by their drift. The complicated glacial and postglacial
history of the lakes is recorded in old strand lines which have been
traced at various heights about them, showing their areas and the
levels at which their waters stood at different times.
With the retreat of the lobate Wisconsin ice sheet toward the north
and east, the southern and western ends of the basins of the Great
Lakes were uncovered first; and here, between the receding ice front
and the slopes of land which faced it, lakes gathered which increased
constantly in size.
The lake which thus came to occupy the western end of the Lake
Superior basin discharged over the divide at Duluth down the St. Croix
River, as an old outlet channel proves; that which held the southern
end of the basin of Lake Michigan sent its overflow across the divide
at Chicago via the Illinois River to the Mississippi; the lake which
covered the lowlands about the western end of Lake Erie discharged its
waters at Fort Wayne into the Wabash River.
The ice still blocked the Mohawk and St. Lawrence valleys on the east,
while on the west it had retreated far to the north. The lakes become
confluent in wide expanses of water, whose depths and margins, as
shown by their old lake beaches, varied at different times with the
position of the confining ice and with warpings of the land. These
vast water bodies, which at one or more periods were greater than all
the Great Lakes combined, discharged at various times across the
divide at Chicago, near Syracuse, New York, down the Mohawk valley,
and by a channel from Georgian Bay into the Ottawa River. Last of all
the present outlet by the St. Lawrence was established.
The beaches of the glacial lakes just mentioned are now far from
horizontal. That of the lake which occupied the Ontario basin has an
elevation of three hundred and sixty-two feet above tide at the west
and of six hundred and seventy-five feet at the northeast, proving
here a differential movement of the land since glacial times amounting
to more than three hundred feet. The beaches which mark the successive
heights of these glacial lakes are not parallel; hence the warping
began before the Glacial epoch closed. We have already seen that the
canting of the region is still in progress.
=The Champlain subsidence.= As the Glacial epoch approached its end,
and the Labrador ice field melted back for the last time to near its
source, the land on which the ice had lain in eastern North America
was so depressed that the sea now spread far and wide up the St.
Lawrence valley. It joined with Lake Ontario, and extending down the
Champlain and Hudson valleys, made an island of New England and the
maritime provinces of Canada.
The proofs of this subsidence are found in old sea beaches and
sea-laid clays resting on Wisconsin till. At Montreal such terraces
are found six hundred and twenty feet above sea level, and along Lake
Champlain--where the skeleton of a whale was once found among them--at
from five hundred to four hundred feet. The heavy delta which the
Mohawk River built at its mouth in this arm of the sea now stands
something more than three hundred feet above sea level. The clays of
the Champlain subsidence pass under water near the mouth of the
Hudson, and in northern New Jersey they occur two hundred feet below
tide. In these elevations we have measures of the warping of the
region since glacial times.
=The western United States in glacial times.= The western United
States was not covered during the Pleistocene by any general ice
sheet, but all the high ranges were capped with permanent snow and
nourished valley glaciers, often many times the size of the existing
glaciers of the Alps. In almost every valley of the Sierras and the
Rockies the records of these vanished ice streams may be found in
cirques, glacial troughs, roches moutonnées, and morainic deposits.
It was during the Glacial epoch that Lakes Bonneville and Lahontan
were established in the Great Basin, whose climate must then have been
much more moist than now.
[Illustration: Fig. 367. A Valley in the Driftless Area]
=The driftless area.= In the upper Mississippi valley there is an
area of about ten thousand square miles in southwestern Wisconsin
and the adjacent parts of Iowa and Minnesota, which escaped the ice
invasions. The rocks are covered with residual clays, the product of
long preglacial weathering. The region is an ancient peneplain,
uplifted and dissected in late Tertiary times, with mature valleys
whose gentle gradients are unbroken by waterfalls and rapids. Thus the
driftless area is in strong contrast with the immature drift topography
about it, where lakes and waterfalls are common. It is a bit of
preglacial landscape, showing the condition of the entire region before
the Glacial epoch.
The driftless area lay to one side of the main track of both the
Keewatin and the Labrador ice fields, and at the north it was
protected by the upland south of Lake Superior, which weakened and
retarded the movement of the ice.
South of the driftless area the Mississippi valley was invaded at
different times by ice sheets from the west,--the Kansan and the
Iowan,--and again by the Illinoian ice sheet from the east. Again and
again the Mississippi River was pushed to one side or the other of its
path. The ancient channel which it held along the Illinoian ice front
has been traced through southeastern Iowa for many miles.
[Illustration: Fig. 368. Cross Section of a Valley in Eastern Iowa
_a_, country rock; _b_, Kansan till; _c_, loess; _t_, terrace
of reddish sands and decayed pebbles above reach of present
stream; _s_, stream; _fp_, flood plain of _s_. What is the age
of rock-cut valley and of the alluvium which partially fills
it, compared with that of the Kansan till? with that of the
loess? Give the complete history recorded in the section.]
=Benefits of glaciation.= Like the driftless area, the preglacial
surface over which the ice advanced seems to have been well dissected
after the late Tertiary uplifts, and to have been carved in many
places to steep valley slopes and rugged hills. The retreating ice
sheets, which left smooth plains and gently rolling country over the
wide belt where glacial deposition exceeded glacial erosion, have made
travel and transportation easier than they otherwise would have been.
The preglacial subsoils were residual clays and sands, composed of the
insoluble elements of the country rock of the locality, with some
minglings of its soluble parts still undissolved. The glacial subsoils
are made of rocks of many kinds, still undecayed and largely ground to
powder. They thus contain an inexhaustible store of the mineral foods
of plants, and in a form made easily ready for plant use.
On the preglacial hillsides the humus layer must have been
comparatively thin, while the broad glacial plains have gathered deep
black soils, rich in carbon and nitrogen taken from the atmosphere.
To these soils and subsoils a large part of the wealth and prosperity
of the glaciated regions of our country must be attributed.
The ice invasions have also added very largely to the water power of
the country. The rivers which in preglacial times were flowing over
graded courses for the most part, were pushed from their old valleys
and set to flow on higher levels, where they have developed waterfalls
and rapids. This power will probably be fully utilized long before the
coal beds of the country are exhausted, and will become one of the
chief sources of the national wealth.
=The Recent epoch.= The deposits laid since glacial times graduate
into those now forming along the ocean shores, on lake beds, and in
river valleys. Slow and comparatively slight changes, such as the
warpings of the region of the Great Lakes, have brought about the
geographical conditions of the present. The physical history of the
Recent epoch needs here no special mention.
The Life of the Quaternary
During the entire Quaternary, invertebrates and plants suffered little
change in species,--so slowly are these ancient and comparatively
simple organisms modified. The Mammalia, on the other hand, have
changed much since the beginning of Quaternary time: the various
species of the present have been evolved, and some lines have become
extinct. These highly organized vertebrates are evidently less stable
than are lower types of animals, and respond more rapidly to changes
in the environment.
=Pleistocene mammals.= In the Pleistocene the Mammalia reached their
culmination both in size and in variety of forms, and were superior
in both these respects to the mammals of to-day. In Pleistocene times
in North America there were several species of bison,--one whose
widespreading horns were ten feet from tip to tip,--a gigantic moose
elk, a giant rodent (Castoroides) five feet long, several species of
musk oxen, several species of horses,--more akin, however, to zebras
than to the modern horse,--a huge lion, several saber-tooth tigers,
immense edentates of several genera, and largest of all the mastodon
and mammoth.
[Illustration: Fig. 369. Megatherium]
[Illustration: Fig. 370. Glyptodon]
The largest of the edentates was the Megatherium, a. clumsy ground
sloth bigger than a rhinoceros. The bones of the Megatherium are
extraordinarily massive,--the thigh bone being thrice as thick as
that of an elephant,--and the animal seems to have been well able to
get its living by overthrowing trees and stripping off their leaves.
The Glyptodon was a mailed edentate, eight feet long, resembling the
little armadillo. These edentates survived from Tertiary times, and in
the warmer stages of the Pleistocene ranged north as far as Ohio and
Oregon.
The great proboscidians of the Glacial epoch were about the size of
modern elephants, and somewhat smaller than their ancestral species in
the Pliocene. The _Mastodon_ ranged over all North America south of
Hudson Bay, but had become extinct in the Old World at the end of the
Tertiary. The elephants were represented by the _Mammoth_, which
roamed in immense herds from our middle states to Alaska, and from
Arctic Asia to the Mediterranean and Atlantic.
It is an oft-told story how about a century ago, near the Lena River
in Siberia, there was found the body of a mammoth which had been
safely preserved in ice for thousands of years, how the flesh was
eaten by dogs and bears, and how the eyes and hoofs and portions of
the hide were taken with the skeleton to St. Petersburg. Since then
several other carcasses of the mammoth, similarly preserved in ice,
have been found in the same region,--one as recently as 1901. We know
from these remains that the animal was clothed in a coat of long,
coarse hair, with thick brown fur beneath.
[Illustration: Fig. 371. Skull of Musk Ox, from Pleistocene
Deposits, Iowa]
=The distribution of animals and plants.= The distribution of species
in the Glacial epoch was far different from that of the present. In
the glacial stages arctic species ranged south into what are now
temperate latitudes. The walrus throve along the shores of Virginia
and the musk ox grazed in Iowa and Kentucky. In Europe the reindeer
and arctic fox reached the Pyrenees. During the Champlain depression
arctic shells lived along the shore of the arm of the sea which
covered the St. Lawrence valley. In interglacial times of milder
climate the arctic fauna-flora retreated, and their places were taken
by plants and animals from the south. Peccaries, now found in Texas,
ranged into Michigan and New York, while great sloths from South
America reached the middle states. Interglacial beds at Toronto,
Canada, contain remains of forests of maple, elm, and papaw, with
mollusks now living in the Mississippi basin.
What changes in the forests of your region would be brought about, and
in what way, if the climate should very gradually grow colder? What
changes if it should grow warmer?
On the Alps and the highest summits of the White Mountains of New
England are found colonies of arctic species of plants and insects.
How did they come to be thus separated from their home beyond the
arctic circle by a thousand miles and more of temperate climate
impossible to cross?
=Man.= Along with the remains of the characteristic animals of the
time which are now extinct there have been found in deposits of the
Glacial epoch in the Old World relics of Pleistocene _Man_, his bones,
and articles of his manufacture. In Europe, where they have best been
studied, human relics occur chiefly in peat bogs, in loess, in caverns
where man made his home, and in high river terraces sometimes eighty
and a hundred feet above the present flood plains of the streams.
In order to understand the development of early man, we should know
that prehistoric peoples are ranked according to the materials of
which their tools were made and the skill shown in their manufacture.
There are thus four well-marked stages of human culture preceding the
written annals of history:
4 The Iron stage.
3 The Bronze stage.
2 The Neolithic (recent stone) stage.
1 The Paleolithic (ancient stone) stage.
In the Neolithic stage the use of the metals had not yet been learned,
but tools of stone were carefully shaped and polished. To this stage
the North American Indian belonged at the time of the discovery of the
continent. In the Paleolithic stage, stone implements were chipped to
rude shapes and left unpolished. This, the lowest state of human
culture, has been outgrown by nearly every savage tribe now on earth.
A still earlier stage may once have existed, when man had not learned
so much as to shape his weapons to his needs, but used chance pebbles
and rock splinters in their natural forms; of such a stage, however,
we have no evidence.
[Illustration: Fig. 372. Paleolithic Implement from Great Britain]
=Paleolithic man in Europe.= It was to the Paleolithic stage that the
earliest men belonged whose relics are found in Europe. They had
learned to knock off two-edged flakes from flint pebbles, and to work
them into simple weapons. The great discovery had been made that fire
could be kindled and made use of, as the charcoal and the stones
discolored by heat of their ancient hearths attest. Caves and shelters
beneath overhanging cliffs were their homes or camping places.
Paleolithic man was a savage of the lowest type, who lived by hunting
the wild beasts of the time.
Skeletons found in certain caves in Belgium and France represent
perhaps the earliest race yet found in Europe. These short,
broad-shouldered men, muscular, with bent knees and stooping gait,
low-browed and small of brain, were of little intelligence and yet
truly human.
The remains of Pleistocene man are naturally found either in caverns,
where they escaped destruction by the ice sheets, or in deposits
outside the glaciated area. In both cases it is extremely difficult,
or quite impossible, to assign the remains to definite glacial or
interglacial times. Their relative age is best told by the fauna with
which they are associated. Thus the oldest relics of man are found
with the animals of the late Tertiary or early Quaternary, such as a
species of hippopotamus and an elephant more ancient than the mammoth.
Later in age are the remains found along with the mammoth, cave bear
and cave hyena, and other animals of glacial time which are now
extinct; while more recent still are those associated with the
reindeer, which in the last ice invasion roamed widely with the
mammoth over central Europe.
[Illustration: Fig. 373. Paleolithic Sketch on Ivory of the Mammoth]
=The caves of southern France.= These contain the fullest records of
the race, much like the Eskimos in bodily frame, which lived in
western Europe at the time of the mammoth and the reindeer. The floors
of these caves are covered with a layer of bone fragments, the remains
of many meals, and here are found also various articles of handicraft.
In this way we know that the savages who made these caves their homes
fished with harpoons of bone, and hunted with spears and darts tipped
with flint and horn. The larger bones are split for the extraction of
the marrow. Among such fragments no split human bones are found; this
people, therefore, were not cannibals. Bone needles imply the art of
sewing, and therefore the use of clothing, made no doubt of skins;
while various ornaments, such as necklaces of shells, show how ancient
is the love of personal adornment. Pottery was not yet invented. There
is no sign of agriculture. No animals had yet been domesticated; not
even man's earliest friend, the dog. Certain implements, perhaps used
as the insignia of office, suggest a rude tribal organization and the
beginnings of the state. The remains of funeral feasts in front of
caverns used as tombs point to a religion and the belief in a life
beyond the grave. In the caverns of southern France are found also the
beginnings of the arts of painting and of sculpture. With surprising
skill these Paleolithic men sketched on bits of ivory the mammoth with
his long hair and huge curved tusks, frescoed their cavern walls with
pictures of the bison and other animals, and carved reindeer on their
dagger heads.
[Illustration: Fig. 374. Restoration of Head of Pithecanthropus
erectus]
=Early man on other continents.= Paleolithic flints curiously like
those of western Europe are found also in many regions of the Old
World,--in India, Egypt, and Asia Minor,--beneath the earliest
vestiges of the civilization of those ancient seats, and sometimes
associated with the fauna of the Glacial epoch.
In Java there were found in 1891, in strata early Quaternary or late
Pliocene in age, parts of a skeleton of lower grade, if not of greater
antiquity, than any human remains now known. _Pithecanthropus erectus_,
as the creature has been named, walked erect, as its thigh bone shows,
but the skull and teeth indicate a close affinity with the ape.
In North America there have been reported many finds of human relics
in valley trains, loess, old river gravels buried beneath lava flows,
and other deposits of supposed glacial age; but in the opinion of some
geologists sufficient proof of the existence of man in America in
glacial times has not as yet been found.
These finds in North America have been discredited for various
reasons. Some were not made by scientific men accustomed to the
closest scrutiny of every detail. Some were reported after a number of
years, when the circumstances might not be accurately remembered;
while in a number of instances it seems possible that the relics might
have been worked into glacial deposits by natural causes from the
surface.
Man, we may believe, witnessed the great ice fields of Europe, if not
of America, and perhaps appeared on earth under the genial climate
of preglacial times. Nothing has yet been found of the line of man's
supposed descent from the primates of the early Tertiary, with the
possible exception of the Java remains just mentioned. The structures
of man's body show that he is not descended from any of the existing
genera of apes. And although he may not have been exempt from the law
of evolution,--that method of creation which has made all life on
earth akin,--yet his appearance was an event which in importance
ranks with the advent of life upon the planet, and marks a new
manifestation of creative energy upon a higher plane. There now
appeared intelligence, reason, a moral nature, and a capacity for
self-directed progress such as had never been before on earth.
=The Recent epoch.= The Glacial epoch ends with the melting of the
ice sheets of North America and Europe, and the replacement of the
Pleistocene mammalian fauna by present species. How gradually the one
epoch shades into the other is seen in the fact that the glaciers
which still linger in Norway and Alaska are the lineal descendants or
the renewed appearances of the ice fields of glacial times.
Our science cannot foretell whether all traces of the Great Ice Age
are to disappear, and the earth is to enjoy again the genial climate
of the Tertiary, or whether the present is an interglacial epoch and
the northern lands are comparatively soon again to be wrapped in ice.
=Neolithic man.= The wild Paleolithic men vanished from Europe with
the wild beasts which they hunted, and their place was taken by
tribes, perhaps from Asia, of a higher culture. The remains of
Neolithic man are found, much as are those of the North American
Indians, upon or near the surface, in burial mounds, in shell heaps
(the refuse heaps of their settlements), in peat bogs, caves, recent
flood-plain deposits, and in the beds of lakes near shore where they
sometimes built their dwellings upon piles.
The successive stages in European culture are well displayed in the
peat bogs of Denmark. The lowest layers contain the polished _stone_
implements of Neolithic man, along with remains of the _Scotch fir_.
Above are _oak_ trunks with implements of _bronze_, while the higher
layers hold _iron_ weapons and the remains of a _beech_ forest.
Neolithic man in Europe had learned to make pottery, to spin and weave
linen, to hew timbers and build boats, and to grow wheat and barley.
The dog, horse, ox, sheep, goat, and hog had been domesticated, and,
as these species are not known to have existed before in Europe, it is
a fair inference that they were brought by man from another continent
of the Old World. Neolithic man knew nothing of the art of extracting
the metals from their ores, nor had he a written language.
The Neolithic stage of culture passes by insensible gradations into
that of the age of bronze, and thus into the Recent epoch.
In the Recent epoch the progress of man in language, in social
organization, in the arts of life, in morals and religion, has left
ample records which are for other sciences than ours to read; here,
therefore, geology gives place to archæology and history.
Our brief study of the outlines of geology has given us, it is hoped,
some great and lasting good. To conceive a past so different from the
present has stimulated the imagination, and to follow the inferences
by which the conclusions of our science have been reached has
exercised one of the noblest faculties of the mind,--the reason. We
have learned to look on nature in new ways: every landscape, every
pebble now has a meaning and tells something of its origin and
history, while plants and animals have a closer interest since we have
traced the long lines of their descent. The narrow horizons of human
life have been broken through, and we have caught glimpses of that
immeasurable reach of time in which nebulae and suns and planets run
their courses. Moreover, we have learned something of that orderly and
world-embracing progress by which the once uninhabitable globe has
come to be man's well-appointed home, and life appearing in the
lowliest forms has steadily developed higher and still higher types.
Seeing this process enter human history and lift our race continually
to loftier levels, we find reason to believe that the onward, upward
movement of the geological past is the manifestation of the same wise
Power which makes for righteousness and good and that this unceasing
purpose will still lead on to nobler ends.
INDEX
Aa, lava, 241
Acadian coal field, 354
Accretion hypothesis, 304
Acidic rocks, 249
Adelsberg grotto, 47
Adirondacks, 309, 316
Africa, 357
Agassiz, Lake, 67, 111, 435
Agates, 251
Alabama, 317, 360
Alaska, 85, 138, 140, 378
Aletsch glacier, 121
Algæ, 51, 52
Algonkian era, 306, 310
Allegheny Mountains, 90, 224, 326, 403
Alluvial cones, 98
Alluvium, 62
Alps, 118, 121, 141, 210, 211, 212, 223, 229, 349, 427, 443
Amazon River, 175
Ammonites, 294, 367, 380, 382
Amphibians, 364, 383
Amphicyon, 413
Amygdules, 250
Andes, 236, 279
Angle of repose, 25
Antarctic continent, 294
Antecedent streams, 209
Antelope, 413
Anthracite, 281
Anticlinal folds, 203, 209
Ants, 20
Apennine Mountains, 399
Appalachia, 317, 351, 358
Appalachian coal field, 356
Appalachian deformation, 358
Appalachian Mountains, 211, 214, 218, 292
Aquifer, 44
Aragonite, 296
Archæopteryx, 393
Archean era, 305
Arenaceous rocks, 9
Argillaceous rocks, 9
Arizona, 32, 76, 140, 151, 164, 220, 229, 249, 257, 371, 390
Arkansas, 337, 356, 373
Arkose, 186, 282, 370
Artesian wells, 44
Arthropods, 322
Artiodactyls, 411
Assiniboine, Mount, 34
Atlas Mountains, 399
Atmosphere, 304, 305
Atolls, 191, 193
Augite, 274
Austin, Tex., 71
Australia, 190, 357
Avalanches, 26
Bad Lands, 397, 398
Baltic Sea, 170, 171, 199
Barite, 287
Barrier Reefs, 191, 192
Basal conglomerate, 173, 184
Basalt, 249
Baselevel, 80, 83
Basic rocks, 249
Basin deposits, 103
Bay bars, 164
Beaches, 162, 164
Bears, 413
Bedding planes, 5
Belemnites, 382
Belt Mountains, 309
Bergschrund, 121, 135, 137
Bermudas, 148
Birds, 392
Bison, 413
Bitter Root Mountains, 272
Black Hills, 309, 371
Blastoids, 339
Blastosphere, 311
Block mountains, 222, 226
Blowholes, 159
Blue Ridge, 309, 316
Bomb, volcanic, 256
Bonneville, Lake, 107, 488
Bosses, 270
Bowlders, erratic, 420
of weathering, 28
Brachiopods, 328, 383, 343, 364, 380
Brazil, 18, 286
Breccia, 218, 255, 264
British Columbia, 373, 378
Bronze stage, 443, 448
Bryozoans, 333
Bunker Hill, 422
Calamites, 361, 367
Calcareous rocks, 9
Calciferous series, 327
Calcite, 290
Caldera, 239
California, 24, 99, 186, 152, 158, 169, 170, 197, 224, 256, 262, 287,
357, 360, 371, 400
Great Valley of, 101, 199, 372, 396
Cambrian period, 315
glaciation in, 358
life of, 319
Camels, 412
Canada, 28, 86, 67, 69, 90, 182, 198, 200, 218, 218, 267, 307, 309,
316, 336, 364, 367, 482, 487
Cape Breton Island, 198
Cape Cod, 162
Carbonated springs, 261
Carbonates, formation of, 12
Carboniferous period, 350
life of, 301
Carnivores, 418
Cascade Mountains, 00, 400
Cats, 418
Catskill Mountains, 342
Caucasus Mountains, 399
Caverns, 46, 241
Cenozoic era, 394
Centipedes, 388
Cephalopods, 324, 388, 389, 344, 367, 380
Ceratites, 380
Ceratosaurus, 385
Chain coral, 389, 843
Chalcopyrite, 287
Chalk, 9, 374, 375
Chalybeate springs, 62
Champlain subsidence, 487
Charleston earthquake, 288
Chazy series, 327
Chelan, Lake, 141
Chemung series, 341, 342
Chesapeake Bay, 169, 170, 197
Chicago, 146, 198, 486
Chile, 286
China, 28, 161
Christmas Island, 194, 248
Cincinnati anticline, 329, 366
Cirques, 136
Clinton series, 336
Coal, 362, 370, 375
Coal Measures, 351
Coast Range, 101, 372, 399
Coastal plain, Atlantic, 188
Coelenterates, 320
Coke, 271
Colorado, 18, 29, 88, 87, 158, 288, 266, 271, 334
Colorado plateaus, 357, 403
Colorado River, 80, 76, 140, 154, 228, 307, 318, 317
Columbia lavas, 400
Columnar structure, 268
Concretions, 49
Cones, alluvial, 98
volcanic, 267
Conglomerate, 9, 178
Congo River, 175
Conifers, 377
Connecticut, 370
valley, 408
Contemporaneous lava sheets, 248, 268
Continental delta, 176, 183
Continental shelf, 183
Continents, 188
Contours, 60
Copper, 287, 310
Coquina, 177
Coral reefs, 188
Corals, ancient, 321, 332, 338, 379
Cordaites, 363
Cordilleran ice field, 426
Corniferous series, 341
Coves, 161
Crabs, 379
Crandall volcano, 268, 400
Crater Lake, 259
Creodonts, 418
Cretaceous period, 372
Crinoids, 382, 303, 379
Crocodiles, 384
Cross bedding, 65, 182
Crustacea, 322, 382, 368, 379
Crustal movements, 195
Cumberland plateau, 90
Cup corals, 388
Cycads, 377, 378
Cycle of erosion, 84, 185, 292
Cystoids, 321, 382, 367
Dalmatia, 170
Darwin's theory of coral reefs, 191
Dead Sea, 221, 279
Death Gulch, 264
Deep-sea deposits, 187
Deer, 413
Deflation, 152
Deformation, 279
Delaware River, 197, 403
Deltas, 108, 111, 197
of Ganges, 109
of Indus, 110
of Mississippi, 109, 197
Denudation, 57
Denver, 398
Desert, 15, 55
Devitrification, 257
Devonian period, 316, 341
Dicotyls, 377, 404
Digitigrade, 406
Dikes, 244, 265
Dinosaurs, 385
Dinothere, 410
Diorite, 274
Dip, 202
Dip fault, 225
Diplodocus, 286
Dipnoans, 346
Discina, 324
Dismal Swamp, 106
Dogs, 413
Dragon flies, 364
Drift, 18, 113, 416
bowlders of, 420
englacial, 125
extent of, 425
pebbles of, 114, 420
stratified, 423
thickness of, 429
Driftless area, 438
Drowned valleys, 197
Drumlins, 421
Duluth, 436
Dunes, 147
Dust falls, 145
Earth, age of, 292, 298, 302
interior of, 276
Earthquakes, 224, 233
causes of, 233, 237
Charleston, 233
distribution of, 236
geological effects of, 234
India, 236
Japan, 237
New Madrid, 236
Earthworms, 20, 21
Echinoderms, 321, 332, 333, 343, 363
Edentates, 441
Egypt, 98
Electric Peak, 269
Elephants, 410
Elevation, effects of, 85
movements of, 197
Eocene epoch, 395
Epicontinental seas, 318
Erratics, 133, 420
Eskers, 424
Etna, 248, 402
Europe, Pleistocene ice sheet of, 427
Eurypterids, 333, 339, 363, 367
Evolution, 300, 447
Faceted pebbles, 113, 114, 420
Falls of the Ohio, 343
Fan folds, 205
Fault scarps, 219
Faults, 217
Faunas, 299
Feldspar, 9, 10, 42
Ferns, 361
Finger lakes, 432
Fire clay, 353
Fishes, 334, 339, 345, 364, 405
Fissure eruptions, 242
Fissure springs, 44
Fjords, 139, 142
Flint, 18, 375
Flood plains, 85, 93
Floods, 54
Floras, 299
Florida, 46, 163, 177, 178, 188, 396
Flow lines, 252
Fluorite, 287
Folded mountains, 210
Folds, 201, 208
Foliation, 283
Foraminifera, 187, 374:
Forests, Carboniferous, 354, 361
Cretaceous, 377, 378
Devonian, 343
Tertiary, 404
Fort Wayne, 436
Fossils, 177, 296
Fractures, 215
Fragmental rocks, 8
France, 167, 171
cave men of, 445
Fringing reefs, 190
Frogs, 383
Frost, 15
Fundy, Bay of, 182
Gabbro, 274
Ganges, 58, 109, 197
Ganoids, 347
Garnet, 281
Gases, volcanic, 244
Gastropods, 324
Gastrula, 311
Geneva, Lake, 71
Geodes, 49
Geological time, divisions of, 295
Geology, definition of, 1, 3
departments of, 4
Georgia, 18, 373
Geysers, 52, 260
Glacial epoch, 142, 416
Glaciers, 113
abrasion by, 133
Alpine, 118
compared with rivers, 137, 142
crevasses of, 123
deposition by, 138
Greenland, 116
lower limit of, 129
melting of, 126
mode of formation, 118
moraines, 124
motion of, 120, 122, 134
piedmont, 131, 141
plucking by, 133
tables, 130
transportation by, 132
troughs, 137
wells, 129
young and mature, 129
Glauconite, 176
Globigerina ooze, 187
Glyptodon, 441
Gneiss, 283
Goats, 413
Gold, 287, 372
Goniatite, 344, 367
Graded slopes, 25
Granite, 9, 274
Graphite, 312
Graptolites, 320, 339
Gravitation, 22
Great Basin, 357, 360, 374, 376
Great Lakes, 198, 436
Great Plains, 82
Great Salt Lake, 107
Greenland, 115, 126, 378
Green Mountains, 309, 316, 420
Green sand, 176
Ground water, 39
Ground water surface, 40
Gryphæa, 379
Gymnosperms, 363, 377
Gypsum, 12, 335, 357, 371
Hade, 217
Hamilton series, 341
Hanging valley, 1389
Hanging wall, 217
Hartz Mountains, 214
Hawaiian volcanoes, 238, 248, 258, 279
Heat and cold, 13
Helderberg series, 341
Hematite, 310
Henry Mountains, 271, 376
High Plains, 100, 398
Hillers Mountain, 271
Himalaya Mountains, 122, 209, 210, 399
Historical geology, 4, 291
Honeycomb corals, 339
Hood, Mount, 260, 262
Hooks, 165
Hornblende, 274
Hornblende schist, 284
Hudson Bay, 90, 170
Hudson River, 197, 417
Hudson series, 327, 329
Humus acids, 10
Humus layer, 19
Huronian systems, 308
Hwang-ho River, 151
Hydrosphere, 22
Hydrozoa, 320
Icebergs, 116, 148
Iceland, 242, 258
Ichthyosaurus, 389
Idaho, 34, 400
Igneous rocks, 9, 249, 250, 251, 273
Illinoian formation, 429
Illinois, 54, 146, 356, 374
India, 28, 102, 147, 235, 357, 402
Indian Territory, 356
Indiana, 48, 104
Indo-Gangetic plain, 101
Indus River, 101, 110
Insects, 333, 364, 380
Interior of earth, 276
Internal geological agencies, 195
Intrusive masses, 270
Intrusive rocks, 273
Intrusive sheets, 268
Inverness earthquake, 236
Iowa, 29, 69, 73, 80, 86, 336, 356, 374, 431, 433, 439, 442
Iowan formation, 429
Iron ores, 13, 53, 279, 310
Islands, coral, 188
wave cut, 159, 161
Japan, 223, 224, 237
Joints, 5, 31, 216
Jordan valley, 279
Jura Mountains, 141, 212
Jurassic period, 369
Kame terraces, 424
Kames, 424
Kansan formation, 429
Kansas, 41, 50, 100, 336, 357, 373, 374, 429
Kaolin, 12
Karst, 47
Katahdin, Mount, 420
Keewatin ice field, 425
Kentucky, 45, 46, 343, 442
Keweenawan system, 308, 310
Kilauea, 239
Kings River Canyon, 403
Krakatoa, 245
Labrador, 198
Labrador ice field, 426
Laccolith, 271
Lagoon, 165, 167
Lahontan, Lake, 107, 438
Lake Chelan, 141
Lake dwellings, 448
Lake Geneva, 71
Lake Superior region, 284, 308, 310
Lakes, 70, 222, 432
basins, 97, 110, 127, 139, 141, 164, 165, 167, 191, 221, 222, 235,
259, 423, 432, 435
deposits, 104
glacial, 127, 139, 141, 423, 432, 435
Pleistocene, 435
salt, 106
Laminæ, 5
Landslides, 26, 234
Lapilli, 255
Laramie series, 375
Laurentian peneplain, 84, 308, 432
Lava, 238, 241
Lava domes, 243, 400
Lepidodendron, 362, 367
Lichens, 16
Lignite, 271
Limestone, 7, 177, 178, 190
Limonite, 13
Lingulella, 324
Lithosphere, 21
Lizards, 384
Llamas, 412
Loess, 150, 433
Long Island, 373
Louisiana, 336, 396
Lower Silurian period, 327
Luray Cavern, 48
Lycopods, 362
Magnetite, 279, 310
Maine, 169, 420
Malaspina glacier, 181
Maldive Archipelago, 198
Mammals, 393, 406, 440
Mammoth, 442
Mammoth Cave, 46
Mammoth Hot Springs, 52
Man, 414, 443
Mantle of waste, 17
Marble, 284, 329
Marengo Cavern, 48
Marl, 104
Marsupials, 393, 406
Martha's Vineyard, 161, 373, 395
Maryland, 56, 270
Massachusetts, 106, 162, 257, 309, 408, 417, 429
Mastodon, 410, 441, 442
Matterhorn, 34
Maturity of land forms, 80
Mauna Loa, 239
Meanders, 96
Medina series, 335, 403
Megatherium, 441
Mendota, Lake, 71
Mesa, 31, 32, 153
Mesozoic era, 369
Mesozoic peneplain, 376, 403
Metamorphism, 281
Mexico, 373, 375
Mica, 9
Mica schist, 284
Michigan, 104, 356, 443
Michigan, Lake, 149, 198
Mineral veins, 49, 286
Minnesota, 97, 426
Miocene series, 395
Mississippi, 337
Mississippi embayment, 373, 374, 395
Mississippi River, 56, 57, 82, 94, 96, 109
Mississippian series, 350
Missouri, 18, 236
Missouri River, 55, 97
Mobile Bay, 197
Mohawk valley, 436, 437
Molluscous shell deposits, 177
Mollusks, 324
Monadnock,83
Monkeys, 414
Monoclinal fold, 204
Monocotyls, 377, 404
Monotremes, 393, 406
Montana, 71, 309, 313, 373
Montreal, 268, 437
Monuments, 33
Moraines, 124
Mosasaurs, 390
Mountain sheep, 413
Mountains, age of, 229
life history of, 212, 215
origin of, 90, 210, 222
sculpture of, 33, 137
Movements of crust, 195
Muir glacier, 122, 129
Nantucket, 373
Naples, 201
Narragansett Bay, 197
Natural bridges, 46
Natural gas, 330
Natural levees, 93
Nautilus, 334
Nebraska, 50, 82, 100, 255, 356
Nebular hypothesis, 304
Neolithic man, 443, 448
Nevada, 104, 107, 222, 288, 289, 360, 400
Névé, 120
New Brunswick, 198
New England, 88, 373, 376, 378, 395, 403, 429, 432, 437
Newfoundland, 198
New Jersey, 148, 166, 168, 176, 196, 268, 269, 309, 310, 373, 437
New Madrid earthquake, 236
New Mexico, 31, 371, 399
New York, 60, 90, 309, 327, 329, 335, 336, 360, 421, 422, 423, 424,
432, 448
Niagara Falls, 60, 199
Niagara series, 335
Nile, 93, 109, 197
Normal fault, 217
North Carolina, 106
North Dakota, 67
North Sea, 170
Notochord, 347
Nova Scotia, 198
Nunatak, 116, 132
Ohio, 82, 198, 329, 335, 441
Ohio River, 55, 82
Oil, 330
Olenellus zone, 328
Olivine, 274
Oolitic limestone, 178
Ooze, deep-sea, 131
Ordovician period, 316, 327
life of, 331
Oregon, 222, 262, 400
Oreodon, 412
Ores, 287, 290
Organisms, work of, 16
Oriskany series, 341
Ornithostoma, 392
Orthoceras, 325, 367, 380
Oscillations, 196
a cause of, 273
effect on drainage, 85
Ostracoderms, 344
Ottawa River, 90
Outcrop, 2
Outliers, 31
Outwash plains, 425
Oxidation, 13
Oyster, 379, 380
Pahoehoe lava,241
Palæospondylus, 344
Paleolithic man, 444
Paleozoic era, 315
Palisades of Hudson, 268
Palms, 377
Pamir, 15
Peat, 94, 104
Peccaries, 412
Pelecypods, 324
Pelée, Mt., 246
Peneplain, 83
dissected, 86
Laurentian, 89, 308, 402
Mesozoic, 376, 403
Pennsylvania, 35, 211, 257, 357, 359, 403
Pennsylvanian series, 350, 351
Perissodactyl, 408
Perlitic structure, 252
Permian series, 350, 357, 360, 366
Petrifaction, 296
Petroleum, 330, 343
Phenacodus, 406
Phyllite, 283
Phyllopod, 323
Piedmont Belt, 87, 214, 309, 374
Piedmont plains, 99
Pikes Peak, 18
_Pithecanthropus erectus_, 446
Placers, 287
Plains of marine abrasion, 172
Planation, 81
Plantigrade, 406
Platte River, 82
Playa, 103
Playa lakes, 104
Pleistocene epoch, 416
Plesiosaurus, 389, 390
Pliocene epoch, 395
Plucking, 133
Po River, 58, 197
Pocono sandstone, 350, 404
Porosity of rocks, 40
Porphyritic structure, 252
Potholes, 59
Potomac River, 58, 66, 403
Predentata, 386
Pre-Kansan formation, 429
Primates, 414
Prince Edward Island, 198
Proboscidians, 410, 441, 442
Pteropods, 325
Pterosaurs, 391
Puget Sound, 396
Pumice, 250
Pyrite, 13
Quarry water, 15
Quartz, 6, 9
Quartz schist, 284
Quaternary period, 395, 416
Quebec, 28
Rain, erosion, 23
Rain prints, 181
Recent epoch, 416, 440, 447
Reconcentration of ores, 289
Record, the geological, 291
Red clay, 187
Red River of the North, 67
Red Sea, 221
Red snow, 115
Reefs, coral, 188
Regional intrusions, 272
Reptiles, 367, 383
Rhinoceros, 408
Rhizocarp, 343
Rhode Island, 356
Rhone glacier, 123
Rhyolite, 240
Richmond, Va., 370
Rift valleys, 221
Ripple marks, 180
Rivers, 54
bars, 65
braided channels, 94
deltas, 108
deposition, 62
discharge, 55
erosion, 59
estuaries, 85
flood plains, 93
floods, 54
graded, 74
gradients, 82
load of, 56
mature, 72, 80, 97, 98
meanders, 96
plains, 99
profile of, 73
revived, 85
run-off, 54
structure of deposits, 102
terraces, 96
transportation, 56, 64
waterfalls, 78
young, 67
Roches moutonnées, 134, 418
Rock bench, 156
Hock salt, 12, 357, 371
Rocky Mountains, 375, 399, 437
Ruminants, 412
Saber-tooth tiger, 413
Saguenay River, 90, 201
Sahara, 15, 146, 150
St. Elias Range, 399
St. Peter sandstone, 150
Salamanders, 383
Salina series, 335
Salt, common, 106, 335
Salt lakes, 106
San Francisco Bay, 197
Sand, beach, 163
of deserts, 149
reefs, 165, 167
storms, 145
Sandstone, 6, 7, 186
Sarcoui, 258
Sauropoda, 386
Schist, 283
Schladebach, 277
Scoria, 250, 255
Scorpions, 339, 340, 363
Scotland, 170, 220, 402
Sea, 155
erosion, 156
deposition, 174
transportation, 162
Sea arch, 159
Sea cave, 158
Sea cliff, 156, 157
Sea cucumber, 363
Seals, 414
Sea stacks, 169
Sea urchin, 332, 379
Seaweed, 176
Sedimentary rocks, 8, 9
Selkirk Mountains, 218
Septa, 338
Sequoia, 378
Shale, 8, 9
Sharks, 345, 405
Shasta, Mount, 262, 400
Sheep, 413
Shenandoah valley, 403
Shores of elevation, 167
Shores of depression, 169
Siderite, 63
Sierra Nevada Mountains, 24, 90, 99, 224, 229, 272, 287, 318, 357,
371, 372, 396, 398, 390, 402, 437
Sigillaria, 362, 367
Silica, 6, 178
Silurian period, 316, 334
life of, 338
Sink hole, 46
Slate, 207, 282
Slaty cleavage, 207
Slickensides, 217
Snake River lavas, 400, 401
Snakes, 384, 405
Soil, 19
Solfatara, 260
Solution, 11
Soufriére, 246
South America, 357
South Carolina, 233
South Dakota, 276, 374, 397
Spanish Peaks, 271, 376
Spherulites, 252
Spiders, 363
Spitzbergen, 378
Sponges, 320, 379
Springs, 41
thermal, 50
Stalactite, 48
Stalagmite, 48
Starfishes, 332
Staubbach, 140
Stegosaurus, 387
Stoss side, 134
Stratification, 5, 64, 180
Striæ, glacial, 114, 133, 418
Strike, 203
Strike fault, 225
Stromatopora, 331, 379
Stromboli, 244
Subsidence, 85, 183, 197
Sun cracks, 180
Superior, Lake, 257
Superposition, law of, 293
Susquehanna River, 403
Sutlej River, 209
Sweden, 199
Swine, 412
Switzerland, 28, 427
Syenite, 274
Synclinal fold, 204
Syracuse, N.Y., 436
Syringopora, 339
Tabulæ, 339
Taconic deformation, 329
Taconic Mountains, 376
Talc, 284
Talc schist, 284
Talus, 23
Tapir, 409
Teleost fishes, 349, 382, 405
Tennessee, 90, 373
Terminal moraines, 126, 422, 432
Terraces, 86, 96
Tertiary period, 395
Texas, 15, 69, 71, 166, 336, 356, 357, 371, 373, 374, 378
Theromorphs, 383
Throw, 217
Thrust faults, 217
Till, 418
Till plains, 420
Toronto, 443
Trachyte, 249, 258
Travertine, 52
Trenton series, 327
Triassic period, 369
Triceratops, 387
Trilobites, 322, 332, 339, 363, 367
Tuff, 255
Turkestan, 103
Turtles, 384
Unconformity, 227
Undertow, 174
Utah, 107, 271, 360, 371, 396, 399
Utica series, 327
V-Valleys, 74
Valley drift, 128
Valley trains, 425
Valleys, 66
Vermont, 309, 329, 420
Vernagt glacier, 129
Vertebrates, 334, 349
Vesuvius, 247, 259, 402
Virginia, 48, 84, 106, 370, 403, 442
Volcanic ashes, 244, 255
cones, 257
necks, 267
rocks, 249
Volcanoes, 238
causes of, 278
decadent, 260
submarine, 248
tertiary, 399
Walrus, 414
Warped valleys, 101
Warping, 198
Wasatch Mountains, 375
Washington, 18, 91, 150, 400
Waterfalls, 59, 78
Waves, 156
Weathering, 5
chemical, 10
differential, 29
mechanical, 13
Wells, 41
artesian, 44
West Virginia, 79, 357, 359
White Mountains, 443
Wind, 144
deposition, 147
erosion, 151
pebbles carved by, 152
transportation, 145
Wisconsin, 15, 18, 70, 71, 90, 94, 422, 426
Wisconsin formation, 429, 431
Wyoming, 50, 98, 371
Yahtse River, 131
Yellow Sea, 151, 170
Yellowstone canyon, 74
Yellowstone National Park, 50, 51, 52, 260, 261, 263, 269, 400
Yosemite, 403
Zeuglodon, 414
Zone of cementation, 49, 180
Zone of solution, 45
Zones of flow and of fracture, 207
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Transcriber's Notes
This transcription was derived from the 1905 publication obtained from
The Internet Archive. As the Index of the original 1905 book is missing
entries for U and V, the Index from the 1921 version was used to add the
missing sections.
One error was noted in preparing this revision (page 493 under Hudson
River should have been 417). Several hyphenated vs. unhyphenated forms
were standardized to the most prevalent. Minor corrections were made
where periods, commas, etc. were missing. A number of paragraphs which
were split by images were rejoined. In some cases, the text was moved to
the preceding or following page. As ALL CAPS was employed for the
Chapter Titles in the original book, the small caps subchapter headings
and Figure captions were not converted to all caps. The oe ligature in
Coelenterates was converted to "oe".
End of Project Gutenberg's The Elements of Geology, by William Harmon Norton