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/B6KKELEY

LIBRARY

UNIVERSITY OF
V CALIFORNIA

EARTH

SCIENCES
LIBRARY







THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

GEOLOGY LIBRARY
IN MEMORY OF

PROFESSOR

GEORGE D. LOUDERBACK
1874-1957



GLACIERS OF NORTH AMERICA.



PLATE 1




Sketch map showing the distribution of some of the better-known glaciers of North America.
Southern limit of Pleistocene ice sheet indicated by a heavy broken line.



GLACISES



OF



NOETH AMEEICA



A BEADING LESSON FOE STUDENTS OF
GEOGRAPHY AND GEOLOGY



BY



ISRAEL C. RUSSELL

PROFESSOR OF GEOLOGY, UNIVERSITY OF MICHIGAN, AUTHOR OF
"LAKES OF NORTH AMERICA," ETC.



BOSTON, U.S.A., AND LONDON

GINN & COMPANY, PUBLISHERS

C&e Sltfjenaettm }3rros

1897



GEOLOGICAL SCIENCES LIB*



COPYBIQHT, 1897

BY ISRAEL C. RUSSELL



ALL BIGHTS RESERVED



.



SCIENCES
LIBRARY



TO THE KEADEE.



UNTIL within the past few years, nearly all current knowledge of
glaciers was based on 'the study of those of the Alps. Practically all
theories of the origin, growth, motion, etc., of glaciers were inspired from
the same source. An enlargement of the field of study, however, has
shown not only that glaciers of the same type as those of Switzerland exist
in many other lands, but in numerous instances are larger and present
greater diversity ; and besides, additional types or " genera " have been
discovered that are not represented in Europe or in fact on any of the
three continents of the Eastern Hemisphere.

As geological and geographical explorations have been extended, it
has been found that North America is not only a favorable field for the
growth of these twin sciences, but in many ways furnishes the best
example of continental development that has as yet been studied. Strange
as it may appear in the face of the overshadowing popular interest that
centers in the glaciers of the Alps, North America offers more favorable
conditions for the study of existing glaciers and of the records of ancient
ice sheets than any other continent. Of each of the three leading types
of glaciers thus far reorganized, namely, the alpine, piedmont, and conti-
nental, North America furnishes magnificent examples. In fact there is
no other continent, except the little known region about the South Pole,
in which other than the alpine type of glaciers exist. Of alpine glaciers
representatives occur in North America in abundance and in great variety,
ranging from the " pocket editions " about the summits of the High Sierra,
California, to the magnificent Seward glacier, Alaska, the largest river of
ice flowing from a mountain group that has yet been discovered. Of
piedmont glaciers, the type specimen, so to speak, and the only one of
the class yet explored, is the great ice sheet that intervenes between

006



IV TO THE READER.

Mount St. Elias and the Pacific, known as the Malaspina glacier. The
still larger continental glaciers of the nature of the ice sheet that
formerly covered the northern half of North America, and the smaller
sheet beneath which northwestern Europe was once buried are repre-
sented in the Northern Hemisphere at the present time by a single
example in Greenland.

The magnificence of the field for glacial study in North America has
only been appreciated within recent years, and is still unrecognized out-
side of a limited circle of special students. By gathering in the book
before you the information now available concerning North American
glaciers, it has been my aim not only to report the present condition in
this country of an important branch of geological and geographical enquiry,
but to make you familiar with glacial phenomena in general and stimu-
late a thirst for fresh explorations and renewed study along an almost
untrodden path.

From what I have seen personally of the glaciers of the United States
and Canada, and from glimpses obtained in previous years of those of
Switzerland and New Zealand, as well as from all that I have read con-
cerning the ice fields of other lands, I think I can affirm, without fear of
contradiction, that southern Alaska and adjacent portions of Canada offer
one of the most promising fields for glacial study that can be found. I
shall be more than repaid for the labor expended in writing this little
book if it leads even indirectly to a renewal of the explorations now barely
begun in that instructive, highly picturesque, and most attractive region.

ISRAEL C. RUSSELL.



CONTENTS.



CHAPTER I.

PAGE

INTRODUCTION. . . . . , . . ...... . . . . . r ,

A typical glacier. Variations from the type. The term " glacier " indefinite.

LEADING CHARACTERISTICS OF GLACIERS . . . . ' . . . 2
Mode of accumulation. Rate of flow. Three types of glaciers : alpine, piedmont, and
continental. Divisions of the surface of a glacier, neve and glacier proper. Banded
structure. Glacier grain. Moraines : lateral, medial, terminal, and frontal. Crevasses.

The starting of crevasses. Bergschrunds. Ice falls. Marginal crevasses. Surface
features: glacier tables, sand cones, debris pyramids. Melting and drainage; super-
glacial and subglacial streams. Characteristics of streams flowing from glaciers.

WHAT is A GLACIER ? . . . . . . . . . .16

GLACIAL ABRASION . . ..... . . . . . . 18

Worn and striated rock surfaces.
SMOOTHED AND STRIATED SURFACES NOT PRODUCED BY GLACIERS . - . 19

Scorings made by river and lake ice and by ice floes.
SPECIAL FEATURES OF GLACIATED SURFACES . . . . . .20

Semilunar cracks, chatter marks, disrupted gouges, etc.
GLACIAL DEPOSITS '. . ....:.. 22

Lateral moraines. Perched blocks. Terminal moraines. Morainal embankments.

Frontal moraines. Interlobate moraines. Till. Boulder clay. Drumlins.

GLACIAL SEDIMENTS . . . ... . . . . . . 28

Osars. Kames. Sand and gravel plains.
CHANGES IN TOPOGRAPHY PRODUCED BY GLACIERS . . . . . . 30



CHAPTER II.

GENERAL DISTRIBUTION OF THE GLACIERS OF NORTH AMERICA . . . . . 32
Cordilleran region. Greenland region.

CHAPTER III.

GLACIERS OF THE SIERRA NEVADA . . * . , * .. .' ; , . . 37
THE HIGH SIERRA . ,' . . . ~ . , . . . . ./ . . . 37
Southern limit of glaciers in the United States.

MOUNT DANA GLACIER . . ".;*;.. . . . ... . . . 39

MOUNT LYELL GLACIER . . - . . . . ..... .- . 40

PARKER CREEK GLACIER . . . . . , "i . . . . 41



yi CONTENTS.

PAGE

CHARACTERISTICS OF THE GLACIERS OF THE HIGH SIERRA 41

Nave's. Crevasses. Lamination or ribboned structure. Dirt bands. Glacier tables.
Ice pyramids. Moraines. Glaciated surfaces and scratched stones. Glacier move-
ments. Glacier mud. Ice tongues or devil's slides. Red snow. Surface melting.

PIONEER EXPLORATIONS IN THE HIGH SIERRA 4&

John Muir. Joseph Le Conte. Geological Survey of California. J. D. Whitney.
Clarence King. Conditions favoring observations.

ANCIENT GLACIERS . . . . .... . . . . . 52



CHAPTER IV.

GLACIERS OF NORTHERN CALIFORNIA AND THE CASCADE MOUNTAINS .... 55
Volcanoes of the Pacific coast.

MOUNT SHASTA . . . . . . . . > . .... . 55

Observations by Clarence King. Observations by Gilbert Thompson.

MOUNT RAINIER (TACOMA) . . . . . . . ... .62

Glaciers in the United States first reported by A. V. Kautz. Observations by S. F.
Emmons. Recent ascents.

MOUNT HOOD 67

Observations by A. Wood. Observations by Arnold Hague.

MOUNT BAKER 69

Observations by E. T. Colman, J. S. Diller, and J. S. Newberry.

CHAPTER V.

GLACIERS OF CANADA 71

Subdivision of the Cordilleras. Glaciers of the Selkirk mountains. Observations by
W. S. Green. Illecellewaet glacier. Glacier of the Stikine River region. Glaciers of
Northwestern Canada described in connection with those of Alaska.



CHAPTER VI.

GLACIERS OF ALASKA .74

Topographic and climatic conditions favoring glaciation. Height of Mount Logan and
of Mount St. Elias. Narratives of early voyages. Belcher, Vancouver, and others.
Observations by W. P. Blake, G. W. Lamplugh, W. H. Dall. Recent explorations.
Observations by C. W. Hayes.

TIDE-WATER GLACIERS . . . . . . .... . 77

Hutli glacier. Norris glacier.
TAKU GLACIER . . . . ... .... . . . . 78

MUIR GLACIER . . . . . : - '. . .. . . . ' . . 80

Indian names. Muir's exploration. Observations by Professors Wright and Reid.
Visit by the present writer. Glacier bay. Thickness of the ice. Icebergs, two
hypotheses concerning. An ancient forest beneath the ice. Characteristics of the
glacier's surface. Dying glacier. Recent recession. Vancouver's observation on the
former extent of glacial ice in Glacier bay.

GLACIERS ON THE WEST SIDE OF GLACIER BAT . . ' . . . . 91
Pacific glacier. Glacier of Dundas bay.



CONTENTS. Vll

PAGE

GLACIERS OF DISENCHANTMENT BAY . . . . . . . . . 92

Turner, Hubbard, and Nunatak glaciers. View from Haenke island. View from
Osier island. Cape Enchantment.

ICY CAPE - . . . . . , ""'' . ... . . .95

ALPINE GLACIERS . . . , . . . . . . . . 96

Vast ne>e region about Mounts Fairweather, Logan, and St. Elias. View northward
from Mount St. Elias. Seward glacier. Ice falls and rapids. Agassiz glacier.
Guyot glacier.

GLACIERS OF LYNN CANAL . . ... . . . . . 101

Taya inlet. Chilkat inlet. Davidson glacier.
GLACIERS OF THE INTERIOR . ... . ... . . . 104

Glaciers of Chilkoot and Chilkat passes. Observations by E. T. Glave. Glaciers be-
tween Yukon and Copper rivers. Observation of C. W. Hayes. Fredrick Schwatka.
H. T. Allen.

ABSENCE OF GLACIERS IN CENTRAL AND NORTHERN ALASKA . . . . 107
GLACIERS OF THE ALASKAN PENINSULA AND THE ALEUTIAN ISLANDS . . . 108

Mt. Makushin.

PIEDMONT GLACIERS ^ . . . . . . .","..' . . 109

Characteristics. Bering glacier.

MALASPINA GLACIER .... . . .__.'..,.". . . 109

Area. Lobes. Characteristics of the non-moraine-covered surface. Moraines. Sur-
face of the fringing moraines. Forests on the moraines. Character of the outer margin.

Icy cape. Sitkagi bluffs. Marginal lakes. Crater lake. Lake Castani. Lakes
about the Chaix hills. Drainage. Fountain stream. Yahtse. Osar, Kame, and Kiwik
streams. Sub- and englacial deposits. Osars. Alluvial cones. Glacial and ocean
records. Recent advance of the ice. Fossil shells of living marine species at high
elevations.

SUBSOIL ICE . . . . . . .... . . . . 127

Frozen subsoil along the Yukon. Lieut. Cartwell's explorations on Kowak river. Ice
cliffs of Eschscholtz bay. Remains of the mammoth. Character and origin of the
tundra. Depth of frozen subsoil in Siberia. Explanations of the origin of subsoil ice.

Computations of Prof. R. S. Woodward. A possible origin of frozen subsoil.



CHAPTER VII.

GLACIERS IN THE GREENLAND REGION . . . . . . . . . . 131

GRINNELL LAND . . . . . . . . . . . . . 131

Observations by members of the Lady Franklin Bay expedition. Report by Gen. A. W.
Greely. Henrietta Nesmith glacier. Reports by Lieutenant Lockwood and Sergeant
Brainard. Mer de Glace Agassiz. " Chinese Wall."

GREENLAND . . . ..... . . ",. . . . . 133

Extent of continental glacier. Character of the interior. Elevation of central part of
the ice sheet. Characteristics of the margins of the inland ice. Observations of Lieu-
tenant Peary near Disco island. Humboldt glacier. Observations by Dr. Kane on the
west coast. Observations by Dr. Nansen on the east coast. Reports of Lieutenant
Lockwood and Sergeant Brainard concerning glaciers in the north of Greenland. Cape
Britannia. Explorations of the interior. Baron Nordenskiold. Lieutenant Peary.
Christian Maigaara. Dr. Nansen. Importance of the study of Arctic glaciers.
Observations by Chamberlin.



viii CONTENTS.



CHAPTER VIII.

PAGE

CLIMATIC CHANGES INDICATED BY THE GLACIERS OP NORTH AMERICA . . . 146

Character of the evidence. Records of recent recession in the glaciers of California,
Oregon, and Washington. British Columbia. Alaska. Greenland. Weight of the
evidence. Climatic changes indicated by the glaciers of the Northern Hemisphere.

THEORETICAL CONSIDERATIONS 156

Influence of debris on the advance and retreat of glaciers.



CHAPTER IX.

How AND WHY GLACIERS MOVE ... . . . . . . . 160

The nature of glacial flow. Observations by Koch and Klocke.
HYPOTHESES OF GLACIAL MOTION 163

The sliding hypothesis. " De Saussure's theory." The hypothesis of dilatation. The
hypothesis of plasticity. The hypothesis of regelation. The hypothesis of expansion
and contraction. The hypothesis of liquefaction under pressure. The hypothesis of
molecular change. The hypothesis of granular change. Observations by T. C. Cham-
berlin.

AN ECLECTIC HYPOTHESIS . . . . , . ... . . 186

Summary of the properties of ice. Summary of glacial phenomena. Authors of the
eclectic hypothesis.



CHAPTER X.

THE LIFE HISTORY OF A GLACIER .......... 190

Periods of growth and decline. The snow line. Spheroid of 32. Birth of a glacier.
Development. Moraines. Marginal lakes. Ice cascades. Widening and flattening of
moraines. Buried forests. Forest-covered moraines. Debris pyramids. Stranded
lateral moraines. Polished and striated surfaces. Terminal moraines. Moraine-
dammed lakes. Rock-basin lakes. Death of a glacier. Climatic cycles. Pleistocene
ice sheets.

CONCLUDING NOTE . ..... V 206

INDEX 207



ILLUSTEATIONS.



PAGE

PLATE 1. SKETCH MAP OF NORTH AMERICA V . . . . . Frontispiece

(FiG. A. MOUNT DANA GLACIER, CALIFORNIA )
' (FiG. B. MOUNT LYELL GLACIER, CALIFORNIA )
" 3. MOUNT LYELL, CALIFORNIA . . . . . . . . . .42

" 4. MORAINAL EMBANKMENTS, BLOODY CANON, CALIFORNIA . . . . 52

" 5. SKETCH MAP OF MOUNT SHASTA, CALIFORNIA . . . ' , , . 56

(FiG. A. WHITNEY GLACIER, MOUNT SHASTA, CALIFORNIA
" (FiG. B. SUMMIT OF MOUNT RAINIER, WASHINGTON
" 7. SKETCH MAP OF MOUNT RAINIER ......... 64

(FiG. A. SURFACE OF COWLITZ GLACIER, MOUNT RAINIER
' (FiG. B. ICE CAVE AT THE END OF NISQUALLY GLACIER, MOUNT RAINIER)

(FiG. A. SUMMIT OF MOUNT BAKER, WASHINGTON )

' (FiG. B. CREVASSES, ILLECELLEWAET GLACIER, CANADA)

(FiG. A. ILLECELLEWAET GLACIER, SELKIRK MOUNTAINS, CANADA)
" 10 \ 72

' (FiG. B. SIDE VIEW OF ILLECELLEWAET GLACIER )

" 11. NORRIS GLACIER, TAKU INLET, ALASKA . . . . ... 78

" 12. MAP OF MUIR GLACIER, ALASKA . . . . . . . . 80

(FiG. A. ICE CLIFF AT THE END OF MUIR GLACIER )
' ( FIG. B. ICE CLIFF OF MUIR GLACIER AT Low TIDE )

f FIG. A. SURFACE OF MUIR GLACIER, WITH WHITE GLACIER, A TRIBUTARY)
' (FiG. B. BURIED FOREST AT THE END OF MUIR GLACIER )

(FiG. A. HUBBARD GLACIER, DISENCHANTMENT BAY, ALASKA) .

' ( FIG. B. GLACIATED ROCKS, HAENKE ISLAND, ALASKA j

(FiG. A. SURFACE OF SEWARD GLACIER, ALASKA )
' (FiG. B. DAVIDSON GLACIER, LYNN CANAL, ALASKA)

" 17. SKETCH MAP OF MOUNT ST. ELIAS REGION, ALASKA . . . 108

" 18. FRONT OF MALASPINA GLACIER, ALASKA . . .- . . * .110
" 19. CENTRAL PORTION OF MALASPINA GLACIER, ALASKA . ; . ., . 112
" 20. MALASPINA GLACIER, FROM THE CHAIX HILLS . . .; " . , . 118
4l (FiG. A. MORAINE-COVERED BORDER OF MALASPINA GLACIER) .

' ( FIG. B. ENTRANCE TO TUNNEL IN MALASPINA GLACIER )

" 22 ( FlG< A> BRYANT GLACIER, GREENLAND) .

' (FiG. B. TIIKTOO GLACIER, GREENLAND)



X ILLUSTRATIONS.

PAGE

FIGURE 1. IDEAL SKETCH MAP OF AN ALPINE GLACIER , , 7

" 2. DRUMLIN 25

u 3. GLACIER TABLES, PARKER CREEK GLACIER, CALIFORNIA ... 44

" 4. ICE PYRAMIDS, MOUNT LYELL GLACIER, CALIFORNIA . . . . .45

" 5. ICEBERG, MUIR INLET, ALASKA . ... . ..... 83

u 6. SECTION OF THE END OF A TIDE -WATER GLACIER. (AFTER REID.) . . 85

u 7. SECTION OF THE END OF A TIDE -WATER GLACIER. (AFTER RUSSELL.) . 86

" 8. SIDE VIEW OF A MEDIAL MORAINE ON MUIR GLACIER, ALASKA . . 88

" 9. LAKELET ON MALASPINA GLACIER, ALASKA ... . . 116

" 10. GRAIN OF GLACIAL ICE . . 175



I am especially indebted to the Director of the U.S. Geological Survey for the electro-
types used in reproducing the illustrations forming Plates 3, 4, 5, 17, 18, 19, and 20. Other

acknowledgments for similar favors will be made hi advance.

I. C. R.



GLACIERS OF NORTH AMERICA.



CHAPTER I.

INTRODUCTION.

IT may be said of glaciers in general that they are bodies of ice formed
by the accumulation and consolidation of snow in regions where the
snowfall for a series of years is in excess of the amount melted and that
they flow to regions where waste exceeds supply.

While a typical glacier is easily recognized, and there is no dissent
from what is commonly understood by the name applied to bodies of flow-
ing ice, yet the limitations of the term are indefinite. A type may be
chosen, as the well-known Mer de Glace, Switzerland, for example, in
which most of the characteristics of glaciers are exhibited. Other ice
bodies are known, however, equally deserving to be classed as glaciers,
that are markedly different from such a type. The vast ice sheet of
Greenland exhibits a great departure from the ice streams of Switzerland
in certain features ; while the small ice bodies in the Sierra Nevada,
California, present minor variations in other characteristics. In both of
these illustrations, and in many others equally at variance with the type
chosen, the term glacier is as appropriate as in the case of the ice stream
on the border of the Vale of Chamounix.

The difficulties in determining the limitations of the term glacier may
be illustrated by the use of the word river. When does a stream cease to
be a brook, or a creek, or even a lake, since many lakes are but expan-
sions of streams, and reach the dignity of a river? In. a similar way, it
is difficult to decide when an accumulation of snow acquires sufficient of
the characteristics of a typical glacier to be included in the same class ;
or again, when a glacier loses motion and becomes a stagnant ice body,
when it shall cease to be known by the title it earned when it was an
avenue of ice drainage.



GLACIERS OF NORTH AMERICA.



In instances where the conditions are indefinite or peculiar, only an
arbitrary decision can, perhaps, be reached ; but usually the presence or
absence of a number of the commonly recognized characteristics of typi-
cal glaciers is sufficiently pronounced to exclude controversy.



LEADING CHARACTERISTICS OF GLACIERS.

Mode of Accumulation. The formation of glaciers in any region
depends primarily on climatic conditions. When the climate is such that
the amount of snow falling for a term of years is in excess of the amount
melted, evaporated, or blown away, perennial snow banks are formed, the
more deeply buried portions of which become compacted into ice. The
change from snow to ice is known to result from pressure and from par-
tial melting and refreezing. Many observations have been made which
show that normal glaciers have a characteristic flowing motion. The
material of which they are composed is drained from regions of
accumulation in much the same manner as rivers drain areas where
the rainfall exceeds evaporation. This process of ice drainage relieves
areas of heavy snowfall from their burdens, and prevents indefinite
accumulation.

Three Types of Glaciers. For convenience of reference the glaciers
now known may be arranged in three classes, namely, alpine, piedmont,
and continental. These three classes are not always distinct and clearly
separable, but typical examples of each may be selected that are well
characterized, and differ in essential features from typical examples of each
of the other classes. In each group there are conspicuous variations
which suggest minor or more specific subdivisions.

Of the three great classes referred to above, the most widely known is
the alpine type, which derives its name from the mountains of central
Europe, where it was first studied. Alpine glaciers occur about high
peaks and on the summits and flanks of mountain ranges in many parts
of the world, but reach their most perfect development in temperate
regions. The Himalayas, the Alps, the mountains of Scandinavia, the
Southern Alps of New Zealand, the Cordilleras, etc., furnish well-known
examples. Glaciers of this type originate as a rule in amphitheatres and
cirques, partially surrounded by lofty peaks and overshadowing preci-
pices, and flow through rugged valleys leading from them as winding
ice rivers which carry the excess of snow falling on the mountains to



INTRODUCTION. 3

lower regions, where a higher mean annual temperature causes it to melt.
They are essentially streams of ice, formed usually by the union of many
branches, and end abruptly when the drainage changes from a solid to a
liquid form.

Glaciers of the piedmont type are formed where alpine glaciers leave
the rugged denies through which they flow and expand and unite on an
adjacent plain. They may be considered as analogous to lakes, for the
reason that they are fed by tributary ice streams. The influx of ice is
counterbalanced by melting, especially from the surface and borders, of
the partially stagnant mass. The characteristics of glaciers of this type
are foreshadowed when individual alpine glaciers leave a high-grade gorge
and expand in a lateral valley or on a plain. The expanded terminus of
Davidson glacier, on the border of Lynn canal, Alaska, illustrates what
may be taken as the first step toward the formation of a piedmont glacier.
The semicircular or delta-like ice foot of the Rhone glacier, Switzerland,
where it spreads out at the head of the Rhone valley, is a more widely
known, although a comparatively diminutive example of the same char-
acter. If one fancies a score or more glaciers of the Davidson and Rhone
type, uniting on a plain and forming a single confluent plateau of ice
many square miles in area, he will appreciate the leading characteristics
of the ice sheets termed piedmont glaciers.

A type of the piedmont glacier, and the only one of the class thus far
described, is Malaspina glacier, Alaska, situated at the southern base of
Mount St. Elias and neighboring mountains, from which it is nourished
by many ice streams. This magnificent ice sheet covers an area of 1500
square miles, and is from 1000 to 1500 feet thick. West of Malaspina
glacier, and occupying a plain intervening between high mountains
and the sea, is another piedmont glacier, known as Bering glacier,
which is of the same general character as its companion, but has not
been explored.

Ice bodies of the third class, as their name implies, are of vast extent
and may even cover entire continents. Existing examples are confined
to Greenland and to Antarctic regions. Others that have now vanished,
left unmistakable records over large portions of northeastern North
America and northwestern Europe. The principal characteristics of con-
tinental glaciers are their vast extent, their comparatively level surfaces,
and the prolongation of portions of their borders into lobes and even
into well-defined streams, where the topographic and other conditions are
favorable.



4 GLACIERS OF NORTH AMERICA.

On comparing the three classes of glaciers just enumerated, one find)-
that alpine glaciers, when well developed, appear as trunk streams formec
by the union of many branches. They usually flow through narrow
valleys from higher to lower regions, and end abruptly in precipitous
walls of ice or expand at their extremities and terminate with low frontal
slopes, according to local conditions. In many ways they are analogous
to rivers. Piedmont glaciers receive many tributaries of the alpine
type, are not confined by rocky walls, and do not have the well-defmet'
stream-like flow exhibited by glaciers descending narrow valleys. The}
are only moderately lobed, do not send out well-defined branches, and an
in part stagnant ice masses. Their nearest counterparts in ordinary wate 1 '
drainage, as already mentioned, are found in lakes fed by mountair
streams. Continental glaciers are without tributaries, their broad surface.'
forming the necessary gathering-ground for snow accumulation. Thei
margins may be strongly lobed, or even send out well-defined tongues o
ice, but the area of ice extending beyond the margins of the central snow
field is in existing examples comparatively small.

Each of the three types of glaciers here enumerated is represented ir
North America, and their characteristics and distribution will be describee t
in the following chapters.

Neve and Glacier Proper. Glaciers of the alpine type, and in ^.
less marked way those of the continental type, have their surface ,
divided into two portions, a neve* or snow region above, and an ice portio:
below. The lower portion has no specific name, but is frequently desig
nated as the " glacier proper. " The line of demarcation is the snow lint
i.e. the lowest limit of perennial snow. As compacted ice occurs als
directly beneath the neVe* from which it is formed, this division of i
glacier into two portions applies only to the surface. Moreover, t' 3
position of the dividing line is subject to secular variations. At time/.,



Online LibraryIsrael C. (Israel Cook) RussellGlaciers of North America; a reading lesson for students of geography and geology → online text (page 1 of 24)