Williams, Emlyn - "Night Must Fall"

Amelia Edith Barr - "The Hallam Succession"

A. H. Leahy - "Heroic Romances of Ireland Volume 2"

Willa Cather - "O Pioneers!"

New Philadelphia Book Publisher Highlights Local Talent
Book and Publishing News from Publishers Newswire(tm)

Looking for Child to be on Cover of a New Book, 'The Model Child'
PHILADELPHIA, Pa. -- The Philadelphia literary world will celebrate the launch of two new players today, April 10th: Kay Square Press, a new publishing company focused on Philadelphia-area artists, their stories, and their art; and Kay Square's first release, 'With the Rich and Mighty: Emlen Etting of Philadelphia' (ISBN: 978-0-9815129-0-7), a critical biography by Kenneth C. Kaleta.

FlatSigned Press Alleges Don Imus Remarks Damage Legacy of President Gerald R. Ford
NEW YORK, N.Y. -- Nathan Yungerberg, an accomplished model scout and professional child photographer is launching a nation-wide casting call to find the cover model for his highly anticipated book release, 'The Model Child: A Parents Guide to the Child Modeling Industry' (ISBN: 978-0-9817018-0-6).

Books: The Elements of Geology

W >> William Harmon Norton >> The Elements of Geology




BASIN DEPOSITS

DEPOSITS IN DRY BASINS. On desert areas without outlet to the sea,
as on the Great Basin of the United States and the deserts of
central Asia, stream-swept waste accumulates indefinitely. The
rivers of the surrounding mountains, fed by the rains and melting
snows of these comparatively moist elevations, dry and soak away
as they come down upon the arid plains. They are compelled to lay
aside their entire load of waste eroded from the mountain valleys,
in fans which grow to enormous size, reaching in some instances
thousands of feet in thickness.

The monotonous levels of Turkestan include vast alluvial tracts
now in process of building by the floods of the frequently
shifting channels of the Oxus and other rivers of the region. For
about seven hundred miles from its mouth in Aral Lake the Oxus
receives no tributaries, since even the larger branches of its
system are lost in a network of distributaries and choked with
desert sands before they reach their master stream. These
aggrading rivers, which have channels but no valleys, spread their
muddy floods--which in the case of the Oxus sometimes equal the
average volume of the Mississippi--far and wide over the plain,
washing the bases of the desert dunes.

PLAYAS. In arid interior basins the central depressions may be
occupied by playas,--plains of fine mud washed forward from the
margins. In the wet season the playa is covered with a thin sheet
of muddy water, a playa lake, supplied usually by some stream at
flood. In the dry season the lake evaporates, the river which fed
it retreats, and there is left to view a hard, smooth, level floor
of sun-baked and sun-cracked yellow clay utterly devoid of
vegetation.

In the Black Rock desert of Nevada a playa lake spreads over an
area fifty miles long and twenty miles wide. In summer it
disappears; the Quinn River, which feeds it, shrinks back one
hundred miles toward its source, leaving an absolutely barren
floor of clay, level as the sea.

LAKE DEPOSITS. Regarding lakes as parts of river systems, we may
now notice the characteristic features of the deposits in lake
basins. Soundings in lakes of considerable size and depth show
that their bottoms are being covered with tine clays. Sand and
gravel are found along; their margins, being brought in by streams
and worn by waves from the shore, but there are no tidal or other
strong currents to sweep coarse waste out from shore to any
considerable distance. Where fine clays are now found on the land
in even, horizontal layers containing the remains of fresh-water
animals and plants, uncut by channels tilled with cross-bedded
gravels and sands and bordered by beach deposits of coarse waste,
we may safely infer the existence of ancient lakes.

MARL. Marl is a soft, whitish deposit of carbonate of lime,
mingled often with more or less of clay, accumulated in small
lakes whose feeding springs are charged with carbonate of lime and
into which little waste is washed from the land. Such lakelets are
not infrequent on the surface of the younger drift sheets of
Michigan and northern Indiana, where their beds of marl--sometimes
as much as forty feet thick--are utilized in the manufacture of
Portland cement. The deposit results from the decay of certain
aquatic plants which secrete lime carbonate from the water, from
the decomposition of the calcareous shells of tiny mollusks which
live in countless numbers on the lake floor, and in some cases
apparently from chemical precipitation.

PEAT. We have seen how lakelets are extinguished by the decaying
remains of the vegetation which they support. A section of such a
fossil lake shows that below the growing mosses and other plants
of the surface of the bog lies a spongy mass composed of dead
vegetable tissue, which passes downward gradually into PEAT,--a
dense, dark brown carbonaceous deposit in which, to the unaided
eye, little or no trace of vegetable structure remains. When
dried, peat forms a fuel of some value and is used either cut into
slabs and dried or pressed into bricks by machinery.

When vegetation decays in open air the carbon of its tissues,
taken from the atmosphere by the leaves, is oxidized and returned
to it in its original form of carbon dioxide. But decomposing in
the presence of water, as in a bog, where the oxygen of the air is
excluded, the carbonaceous matter of plants accumulates in
deposits of peat.

Peat bogs are numerous in regions lately abandoned by glacier ice,
where river systems are so immature that the initial depressions
left in the sheet of drift spread over the country have not yet
been drained. One tenth of the surface of Ireland is said to be
covered with peat, and small bogs abound in the drift-covered area
of New England and the states lying as far west as the Missouri
River. In Massachusetts alone it has been reckoned that there are
fifteen billion cubic feet of peat, the largest bog occupying
several thousand acres.

Much larger swamps occur on the young coastal plain of the
Atlantic from New Jersey to Florida. The Dismal Swamp, for
example, in Virginia and North Carolina is forty miles across. It
is covered with a dense growth of water-loving trees such as the
cypress and black gum. The center of the swamp is occupied by Lake
Drummond, a shallow lake seven miles in diameter, with banks of
pure-peat, and still narrowing from the encroachment of vegetation
along its borders.

SALT LAKES. In arid climates a lake rarely receives sufficient
inflow to enable it to rise to the basin rim and find an outlet.
Before this height is reached its surface becomes large enough to
discharge by evaporation into the dry air the amount of water that
is supplied by streams. As such a lake has no outlet, the minerals
in solution brought into it by its streams cannot escape from the
basin. The lake water becomes more and more heavily charged with
such substances as common salt and the sulphates and carbonates of
lime, of soda, and of potash, and these are thrown down from
solution one after another as the point of saturation for each
mineral is reached. Carbonate of lime, the least soluble and often
the most abundant mineral brought in, is the first to be
precipitated. As concentration goes on, gypsum, which is insoluble
in a strong brine, is deposited, and afterwards common salt. As
the saltness of the lake varies with the seasons and with climatic
changes, gypsum and salt are laid in alternate beds and are
interleaved with sedimentary clays spread from the waste brought
in by streams at times of flood. Few forms of life can live in
bodies of salt water so concentrated that chemical deposits take
place, and hence the beds of salt, gypsum, and silt of such lakes
are quite barren of the remains of life. Similar deposits are
precipitated by the concentration of sea water in lagoons and arms
of the sea cut off from the ocean.

LAKES BONNEVILLE AND LAHONTAN. These names are given to extinct
lakes which once occupied large areas in the Great Basin, the
former in Utah, the latter in northwestern Nevada. Their records
remain in old horizontal beach lines which they drew along their
mountainous shores at the different levels at which they stood,
and in the deposits of their beds. At its highest stage Lake
Bonneville, then one thousand feet deep, overflowed to the north
and was a fresh-water lake. As it shrank below the outlet it
became more and more salty, and the Great Salt Lake, its withered
residue, is now depositing salt along its shores. In its strong
brine lime carbonate is insoluble, and that brought in by streams
is thrown down at once in the form of travertine.

Lake Lahontan never had an outlet. The first chemical deposits to
be made along its shores were deposits of travertine, in places
eighty feet thick. Its floor is spread with fine clays, which must
have been laid in deep, still water, and which are charged with
the salts absorbed by them as the briny water of the lake dried
away. These sedimentary clays are in two divisions, the upper and
lower, each being about one hundred feet thick. They are separated
by heavy deposits of well-rounded, cross-bedded gravels and sands,
similar to those spread at the present time by the intermittent
streams of arid regions. A similar record is shown in the old
floors of Lake Bonneville. What conclusions do you draw from these
facts as to the history of these ancient lakes?

DELTAS

In the river deposits which are left above sea level particles of
waste are allowed to linger only for a time. From alluvial fans
and flood plains they are constantly being taken up and swept
farther on downstream. Although these land forms may long persist,
the particles which compose them are ever changing. We may
therefore think of the alluvial deposits of a valley as a stream
of waste fed by the waste mantle as it creeps and washes down the
valley sides, and slowly moving onwards to the sea.

In basins waste finds a longer rest, but sooner or later lakes and
dry basins are drained or filled, and their deposits, if above sea
level, resume their journey to their final goal. It is only when
carried below the level of the sea that they are indefinitely
preserved.

On reaching this terminus, rivers deliver their load to the ocean.
In some cases the ocean is able to take it up by means of strong
tidal and other currents, and to dispose of it in ways which we
shall study later. But often the load is so large, or the tides
are so weak, that much of the waste which the river brings in
settles at its mouth, there building up a deposit called the
DELTA, from the Greek letter of that name, whose shape it
sometimes resembles.

Deltas and alluvial fans have many common characteristics. Both
owe their origin to a sudden check in the velocity of the river,
compelling a deposit of the load; both are triangular in outline,
the apex pointing upstream; and both are traversed by
distributaries which build up all parts in turn.

In a delta we may distinguish deposits of two distinct kinds,--
the submarine and the subaerial. In part a delta is built of waste
brought down by the river and redistributed and spread by waves
and tides over the sea bottom adjacent to the river's mouth. The
origin of these deposits is recorded in the remains of marine
animals and plants which they contain.

As the submarine delta grows near to the level of the sea the
distributaries of the river cover it with subaerial deposits
altogether similar to those of the flood plain, of which indeed
the subaerial delta is the prolongation. Here extended deposits of
peat may accumulate in swamps, and the remains of land and fresh-
water animals and plants swept down by the stream are imbedded in
the silts laid at times of flood.

Borings made in the deltas of great rivers such as the
Mississippi, the Ganges, and the Nile, show that the subaerial
portion often reaches a surprising thickness. Layers of peat, old
soils, and forest grounds with the stumps of trees are discovered
hundreds of feet below sea level. In the Nile delta some eight
layers of coarse gravel were found interbedded with river silts,
and in the Ganges delta at Calcutta a boring nearly five hundred
feet in depth stopped in such a layer.

The Mississippi has built a delta of twelve thousand three hundred
square miles, and is pushing the natural embankments of its chief
distributaries into the Gulf at a maximum rate of a mile in
sixteen years. Muddy shoals surround its front, shallow lakes,
e.g. lakes Pontchartrain and Borgne, are formed between the
growing delta and the old shore line, and elongate lakes and
swamps are inclosed between the natural embankments of the
distributaries.

The delta of the Indus River, India, lies so low along shore that
a broad tract of country is overflowed by the highest tides. The
submarine portion of the delta has been built to near sea level
over so wide a belt offshore that in many places large vessels
cannot come even within sight of land because of the shallow
water.

A former arm of the sea, the Rann of Cutch, adjoining the delta on
the east has been silted up and is now an immense barren flat of
sandy mud two hundred miles in length and one hundred miles in
greatest breadth. Each summer it is flooded with salt water when
the sea is brought in by strong southwesterly monsoon winds, and
the climate during the remainder of the year is hot and dry. By
the evaporation of sea water the soil is thus left so salty that
no vegetation can grow upon it, and in places beds of salt several
feet in thickness have accumulated. Under like conditions salt
beds of great thickness have been formed in the past and are now
found buried among the deposits of ancient deltas.

SUBSIDENCE OF GREAT DELTAS. As a rule great deltas are slowly
sinking. In some instances upbuilding by river deposits has gone
on as rapidly as the region has subsided. The entire thickness of
the Ganges delta, for example, so far as it has been sounded,
consists of deposits laid in open air. In other cases interbedded
limestones and other sedimentary rocks containing marine fossils
prove that at times subsidence has gained on the upbuilding and
the delta has been covered with the sea.

It is by gradual depression that delta deposits attain enormous
thickness, and, being lowered beneath the level of the sea, are
safely preserved from erosion until a movement of the earth's
crust in the opposite direction lifts them to form part of the
land. We shall read later in the hard rocks of our continent the
records of such ancient deltas, and we shall not be surprised to
find them as thick as are those now building at the mouths of
great rivers.

LAKE DELTAS. Deltas are also formed where streams lose their
velocity on entering the still waters of lakes. The shore lines of
extinct lakes, such as Lake Agassiz and Lakes Bonneville and
Lahontan, may be traced by the heavy deposits at the mouths of
their tributary streams.

We have seen that the work of streams is to drain the lands of the
water poured upon them by the rainfall, to wear them down, and to
carry their waste away to the sea, there to be rebuilt by other
agents into sedimentary rocks. The ancient strata of which the
continents are largely made are composed chiefly of material thus
worn from still more ancient lands--lands with their hills and
valleys like those of to-day--and carried by their rivers to the
ocean. In all geological times, as at the present, the work of
streams has been to destroy the lands, and in so doing to furnish
to the ocean the materials from which the lands of future ages
were to be made. Before we consider how the waste of the land
brought in by streams is rebuilt upon the ocean floor, we must
proceed to study the work of two agents, glacier ice and the wind,
which cooperate with rivers in the denudation of the land.





CHAPTER V

THE WORK OF GLACIERS


THE DRIFT. The surface of northeastern North America, as far south
as the Ohio and Missouri rivers, is generally covered by the
drift,--a formation which is quite unlike any which we have so far
studied. A section of it, such as that illustrated in Figure 87,
shows that for the most part it is unstratified, consisting of
clay, sand, pebbles, and even large bowlders, all mingled pell-
mell together. The agent which laid the drift is one which can
carry a load of material of all sizes, from the largest bowlder to
the finest clay, and deposit it without sorting.

The stones of the drift are of many kinds. The region from which
it was gathered may well have been large in order to supply these
many different varieties of rocks. Pebbles and bowlders have been
left far from their original homes, as may be seen in southern
Iowa, where the drift contains nuggets of copper brought from the
region about Lake Superior. The agent which laid the drift is one
able to gather its load over a large area and carry it a long way.

The pebbles of the drift are unlike those rounded by running water
or by waves. They are marked with scratches. Some are angular,
many have had their edges blunted, while others have been ground
flat and smooth on one or more sides, like gems which have been
faceted by being held firmly against the lapidary's wheel. In many
places the upper surface of the country rock beneath the drift has
been swept clean of residual clays and other waste. All rock
rotten has been planed away, and the ledges of sound rock to which
the surface has been cut down have been rubbed smooth and
scratched with long, straight, parallel lines. The agent which
laid the drift can hold sand and pebbles firmly in its grasp and
can grind them against the rock beneath, thus planing it down and
scoring it, while faceting the pebbles also.

Neither water nor wind can do these things. Indeed, nothing like
the drift is being formed by any process now at work anywhere in
the eastern United States. To find the agent which has laid this
extensive formation we must go to a region of different climatic
conditions.

THE INLAND ICE OF GREENLAND. Greenland is about fifteen hundred
miles long and nearly seven hundred miles in greatest width. With
the exception of a narrow fringe of mountainous coast land, it is
completely buried beneath a sheet of ice, in shape like a vast
white shield, whose convex surface rises to a height of nine
thousand feet above the sea. The few explorers who have crossed
the ice cap found it a trackless desert destitute of all life save
such lowly forms as the microscopic plant which produces the so-
called "red snow." On the smooth plain of the interior no rock
waste relieves the snow's dazzling whiteness; no streams of
running water are seen; the silence is broken only by howling
storm winds and the rustle of the surface snow which they drive
before them. Sounding with long poles, explorers find that below
the powdery snow of the latest snowfall lie successive layers of
earlier snows, which grow more and more compact downward, and at
last have altered to impenetrable ice. The ice cap formed by the
accumulated snows of uncounted centuries may well be more than a
mile in depth. Ice thus formed by the compacting of snow is
distinguished when in motion as GLACIER ICE.

The inland ice of Greenland moves. It flows with imperceptible
slowness under its own weight, like, a mass of some viscous or
plastic substance, such as pitch or molasses candy, in all
directions outward toward the sea. Near the edge it has so thinned
that mountain peaks are laid bare, these islands in the sea of ice
being known as NUNATAKS. Down the valleys of the coastal belt it
drains in separate streams of ice, or GLACIERS. The largest of
these reach the sea at the head of inlets, and are therefore
called TIDE GLACIERS. Their fronts stand so deep in sea water that
there is visible seldom more than three hundred feet of the wall
of ice, which in many glaciers must be two thousand and more feet
high. From the sea walls of tide glaciers great fragments break
off and float away as icebergs. Thus snows which fell in the
interior of this northern land, perhaps many thousands of years
ago, are carried in the form of icebergs to melt at last in the
North Atlantic.

Greenland, then, is being modeled over the vast extent of its
interior not by streams of running water, as are regions in warm
and humid climates, nor by currents of air, as are deserts to a
large extent, but by a sheet of flowing ice. What the ice sheet is
doing in the interior we may infer from a study of the separate
glaciers into which it breaks at its edge.

THE SMALLER GREENLAND GLACIERS. Many of the smaller glaciers of
Greenland do not reach the sea, but deploy on plains of sand and
gravel. The edges of these ice tongues are often as abrupt as if
sliced away with a knife (Fig. 92), and their structure is thus
readily seen. They are stratified, their layers representing in
part the successive snowfalls of the interior of the country. The
upper layers are commonly white and free from stones; but the
lower layers, to the height of a hundred feet or more, are dark
with debris which is being slowly carried on. So thickly studded
with stones is the base of the ice that it is sometimes difficult
to distinguish it from the rock waste which has been slowly
dragged beneath the glacier or left about its edges. The waste
beneath and about the glacier is unsorted. The stones are of many
kinds, and numbers of them have been ground to flat faces. Where
the front of the ice has retreated the rock surface is seen to be
planed and scored in places by the stones frozen fast in the sole
of the glacier.

We have now found in glacier ice an agent able to produce the
drift of North America. The ice sheet of Greenland is now doing
what we have seen was done in the recent past in our own land. It
is carrying for long distances rocks of many kinds gathered, we
may infer, over a large extent of country. It is laying down its
load without assortment in unstratified deposits. It grinds down
and scores the rock over which it moves, and in the process many
of the pebbles of its load are themselves also ground smooth and
scratched. Since this work can be done by no other agent, we must
conclude that the northeastern part of our own continent was
covered in the recent past by glacier ice, as Greenland is to-day.

VALLEY GLACIERS

The work of glacier ice can be most conveniently studied in the
separate ice streams which creep down mountain valleys in many
regions such as Alaska, the western mountains of the United States
and Canada, the Himalayas, and the Alps. As the glaciers of the
Alps have been studied longer and more thoroughly than any others,
we shall describe them in some detail as examples of valley
glaciers in all parts of the world.

CONDITIONS OF GLACIER FORMATION. The condition of the great
accumulation of snow to which glaciers are due--that more or less
of each winter's snow should be left over unmelted and
unevaporated to the next--is fully met in the Alps. There is
abundant moisture brought by the winds from neighboring seas. The
currents of moist air driven up the mountain slopes are cooled by
their own expansion as they rise, and the moisture which they
contain is condensed at a temperature at or below 32 degrees F.,
and therefore is precipitated in the form of snow. The summers are
cool and their heat does not suffice to completely melt the heavy
snow of the preceding winter. On the Alps the SNOW LINE--the lower
limit of permanent snow--is drawn at about eight thousand five
hundred feet above sea level. Above the snow line on the slopes
and crests, where these are not too steep, the snow lies the year
round and gathers in valley heads to a depth of hundreds of feet.

This is but a small fraction of the thickness to which snow would
be piled on the Alps were it not constantly being drained away.
Below the snow fields which mantle the heights the mountain
valleys are occupied by glaciers which extend as much as a
vertical mile below the snow line. The presence in the midst of
forests and meadows and cultivated fields of these tongues of ice,
ever melting and yet from year to year losing none of their bulk,
proves that their loss is made good in the only possible way. They
are fed by snow fields above, whose surplus of snow they drain
away in the form of ice. The presence of glaciers below the snow
line is a clear proof that, rigid and motionless as they appear,
glaciers really are in constant motion down valley.

THE NEVE FIELD. The head of an Alpine valley occupied by a glacier
is commonly a broad amphitheater deeply filled with snow. Great
peaks tower above it, and snowy slopes rise on either side on the
flanks of mountain spurs. From these heights fierce winds drift
the snows into the amphitheater, and avalanches pour in their
torrents of snow and waste. The snow of the amphitheater is like
that of drifts in late winter after many successive thaws and
freezings. It is made of hard grains and pellets and is called
NEVE. Beneath the surface of the neve field and at its outlet the
granular neve has been compacted to a mass of porous crystalline
ice. Snow has been changed to neve, and neve to glacial ice, both
by pressure, which drives the air from the interspaces of the
snowflakes, and also by successive meltings and freezings, much as
a snowball is packed in the warm hand and becomes frozen to a ball
of ice.

THE BERGSCHRUND. The neve is in slow motion. It breaks itself
loose from the thinner snows about it, too shallow to share its
motion, and from the rock rim which surrounds it, forming a deep
fissure called the bergschrund, sometimes a score and more feet
wide.

SIZE OF GLACIERS. The ice streams of the Alps vary in size
according to the amount of precipitation and the area of the neve
fields which they drain. The largest of Alpine glaciers, the
Aletsch, is nearly ten miles long and has an average width of
about a mile. The thickness of some of the glaciers of the Alps is
as much as a thousand feet. Giant glaciers more than twice the
length of the longest in the Alps occur on the south slope of the
Himalaya Mountains, which receive frequent precipitations of snow
from moist winds from the Indian Ocean. The best known of the many
immense glaciers of Alaska, the Muir, has an area of about eight
hundred square miles (Fig. 95).