While the generally level plateau surface about the Black Hills is

treeless, except for the scattered groves of wide-spreading cottonwoods

along the immediate banks of the larger streams, the central and higher

portions of the elevation itself is clothed with an open but abundant

forest, consisting principally of pines. The evergreen forests give to

the hills a nearly black colour when seen from a distance, and have

gained for them the name they bear.

The rocks which have been forced upward so as to form the Black Hills

dome were previously like those in the surrounding plain, quite

horizontal, and had a vertical thickness of at least 5,000 feet. The

uplift, if uneroded, would rise from the surrounding plain as a

flat-topped dome about 6,600 feet high, as is suggested by the highest

dotted line in the following diagram. In reality such a dome never

existed, for the reason that its growth was slow, and perhaps is

not completed even at the present day, and as soon as the rocks began to

rise, the rain, wind, streams, etc., commenced their task of

destruction. The higher the rocks were elevated the more powerfully

those agencies acted. The top of the dome was soon broken and its

internal structure revealed.

[Illustration: FIG. 18.--Ideal east-and-west section through the Black

Hills. The vertical scale is about six times the horizontal. The dotted

lines indicate the portion of the uplift removed by erosion. After Henry

Newton.

1. Archean slates and schists.

2. Granite.

3. Potsdam, sandstone, resting unconformably on 1 and 2.

4. Carboniferous, mostly limestone.

5. Red Beds (Trias), sandstone with included limestone.

6. Jura, shales.

7. Cretaceous, shales.

8. White River Tertiary, shales, resting unconformably on 7.]

By reference to the accompanying generalized section through the Black

Hills, which as the uplift is rudely circular would be essentially the

same if taken in any direction through the elevated region, it will be

seen that there is a central core of slate, schists, and granite which

has been forced upward so as to stand in its present eroded condition;

it rises well above the surface of the adjacent plateau. About this

central core the upturned edges of the sedimentary rocks form concentric

zones, the oldest in the series being next the schists, and the youngest

10 to 40 or 50 miles distant. It is the presence in the central part of

the hills of an area of resistant crystalline rocks which have weathered

into rugged forms, and the series of encircling and concentric belts of

rock of varying degrees of hardness and solubility, that has given to

the uplift its present peculiar relief and its generally beautiful

scenery. The edges of the harder belts form bold hills and ridges, while

the softer belts have been eroded into valleys. This series of

sharp-crested ridges and intervening valleys forms concentric circles

completely surrounding the central group of rugged mountains. The

largest and most interesting of the ring-like valleys is underlaid by

red sandstone, and is remarkable for its flaming colour as well as for

its exceptional form. In this Red Valley one may ride entirely around

the rugged central mass of the hills, on a generally level surface,

which is inclosed on its outer border by a precipitous wall of yellowish

sandstone and shale 300 or 400 feet high. The distance about this

"race-course," as it is sometimes termed, is about 200 miles. This

series of concentric ridges and intervening valleys, surrounding a high

and rugged region of more resistant rock, furnish an admirable

illustration of the influence of rock texture, hardness, etc., on

topography.

Another instructive geographical lesson afforded by the Black Hills is

the manner in which the portion of the dome rising above the level of

the rivers which flow across the surrounding plain has been dissected by

stream erosion. The streams originating in the central portion of the

uplift flowed outward in all directions, and have cut deep narrow gorges

through the ridges of hard rock in the base of the truncated dome. Some

20 streams originating in the central portion of the uplift cross Red

Valley and escape through notches in its outer wall, about 16 of which

are well-defined gateways leading to the encircling plateau. This is one

of the most beautiful and most instructive examples of _consequent_

drainage--that is, of streams whose direction has been determined by the

inclination of the surface over which they flow--thus far discovered.

Still another feature of much geographical interest is furnished by the

rivers on the adjacent plain, two of which, branches of the Cheyenne

River, cross the north and south extensions, respectively, of the Black

Hills dome. These streams flow directly across the arched strata, in

canyons of their own making, and, as explained by G. K. Gilbert, are

illustrations of _superimposed_ drainage--that is, the portions of the

dome crossed by the branches of the Cheyenne after the rocks were

upheaved were covered by soft horizontal lake beds, over which the water

flowed as consequent streams. The rivers deepened their channels and

cut through the soft cover of horizontal rock and into the arched

beds beneath. The course of the streams initiated on the covering of

soft beds were maintained, as the flowing water charged with sand cut

downward into the harder, upturned beds beneath, and now, the covering

of soft beds having been eroded away, the rivers flow directly across

(or through) the flanks of the great arch, but are not deflected by it.

In the neighbourhood of the Black Hills, and especially about their

northern and northwestern border, there are secondary hills formed by

the upward protrusion of molten rocks into the generally horizontally

stratified rocks underlying the plateau. These intrusions did not reach

the surface in such a way as to form volcanoes, but were forced upward,

raising domes above them, in which the structure is similar to that in

the great Black Hills dome. These secondary domes have been eaten away

by erosive agencies in varying degrees. In some of them, as the Little

Sundance Hill, near the town of Sundance, Wyoming, the dome of

stratified rock is unbroken, and no igneous rock is to be seen; other

neighbouring domes in which the plutonic magmas rose higher have been

eroded so as to expose the summit portion of the inner core; and in one

instance, known as Mato Tepee, the uncovering of the plug of plutonic

rock which caused the uplift is so complete that it now forms a

prominent fluted column over 600 feet high above its immediate base.

_Volcanic Mountains and Table-Lands._--In the south-central portion of

the Great plateaus in southwestern Colorado and eastern New Mexico,

there are several typical cinder cones with lava-flows associated with

them, which impart novel topographic forms to the general monotony of

the broad plateau surfaces. The highest of the extinct volcanoes in this

region is Mount Capulin, situated in northeastern New Mexico, about 200

miles east of the Rocky Mountains, which rises 2,750 feet above the

surrounding plain, and has an elevation of about 9,000 feet above the

sea. At the summit of this conical mass there is a well-defined crater a

mile in diameter. In the same region there are several other

similar volcanic cones, from which lava streams have descended. As has

been pointed out by R. T. Hill, these are the most easterly volcanoes of

recent geological age in North America. They were formed after the

Tertiary rocks of the Llano were laid down.

The Raton Mesa, situated between Mount Capulin and the front range of

the Rockies, is capped by a lava flow of more ancient date than the

volcanoes just referred to, which has protected the softer rocks beneath

from erosion, and now stands as a prominent table-land with precipitous

borders.

THE PACIFIC MOUNTAINS

To the west of the Continental basin is a vast cordillera composed of

numerous mountain chains which extends from south-central Mexico

northward to the Arctic Ocean, and in its broadest part is about 1,000

miles wide. As already explained, we speak of this region in its

entirety as the Pacific cordillera, or less technically as the Pacific

mountains. It is a highly complex group of mountain chains, each of

which contains two or more distinct mountain systems; each system,

again, is usually composed of many ranges, and each range is frequently

made up of a multitude of ridges, peaks, buttes, mesas, etc.; there are

also many plateaus more or less completely dissected by erosion, and

broad valleys, as well as numerous canyons, gulches, ravines, arroyas,

and other secondary topographic forms. This vast cordillera not only

contains mountains produced by the folding of the rocks of the earth's

crust, in a general way similar to the Appalachians in structure, but

also upturned blocks many miles in extent, bounded by breaks or faults,

and volcanic mountains, vast lava-flows, and elevations due to the

injection of molten rock into the earth's crusts so as to elevate domes.

In fact, scarcely any topographic form and no important geological

structure that is known is lacking in this great family of mountains

which dominates the western portion of the continent.

The Pacific mountains begin abruptly at the south, along a generally

east and west line passing some 75 miles south of the City of

Mexico, where the precipitous border of the table-land of central Mexico

overlooks a lower region to the south which is diversified by many

volcanic mountains. But little accurate information is available

concerning the geology and geography of Mexico, but in general, as is

well known, there are three main mountain belts which traverse that

republic. One of these mountain belts is adjacent to the Gulf of Mexico,

and another is situated near the Pacific coast of the main portion of

the republic, while the third forms the rugged and irregular axis of the

peninsula of Lower California. Between the leading mountain belts of the

mainland there are numerous short ranges and many nearly level-floored

valleys. The general level of this inland region is in the neighbourhood

of 6,000 feet, while the more prominent peaks and crests attain

elevations of from 10,000 to 12,000 feet. The general trend of the main

mountain belts, and of the numerous subordinate ranges, is about

northwest and southeast. For this reason, and also because the valleys

have become deeply filled with _debris_ from the mountains, travelling

in directions leading north and south is facilitated by the topography,

while in passing from one coast of the republic to the other the rugged

bordering mountain belts have to be crossed and detours made in order to

pass around the central mountain ranges.

The more elevated portion of central and northern Mexico, together with

the peninsula of Lower California, has an arid climate, to which many of

the conspicuous features in the geography of the land are due. The

precipitation over large areas is insufficient to maintain permanent

streams, the vegetation is nearly all of a desert-like character, and

several basins exist which do not drain to the sea. In the interior

basins there are saline and alkaline lakes, and numerous dry lake beds

or _playas_, which are whitened by saline efflorescences. The rocks

exposed in the mountains are largely of sedimentary origin, but a

characteristic feature is the geology, especially to the west, in the

presence of extensive volcanic areas and lofty mountains of igneous

rocks.

The Pacific cordillera begins in southern Mexico with a width of some

300 miles and broadens when traced northward. At the boundary between

Mexico and the United States it has a width of fully 700 miles, but

reaches its greatest breadth in the latitude of San Francisco and

Denver, where it is about 1,000 miles across. In its better known, but

as yet incompletely studied portion embraced within the boundaries of

the United States there are several important subdivisions, such as the

Rocky Mountain belt on the east; a less lofty, but yet rugged central

region, termed the Great Basin, characterized by having a dry climate

and by the fact that the streams do not reach the ocean; and a western

mountain chain which includes the Sierra Nevada and Cascade Ranges. To

the west of the mountains just named lies the great valley of

California, and similar regions in Oregon and Washington occupied in

part by Puget Sound. To the west, again, are the several ranges

bordering the Pacific coast from Lower California to Vancouver Island,

and termed in a general way the coast mountains. Each of the great

divisions of the Pacific mountain region has its indefinitely known

southern terminus in Mexico, and extends northward to beyond the

Canadian boundary. As this central portion of the most westerly of the

larger geographical divisions of the continent is well developed in the

United States, and has there been more carefully explored than

elsewhere, a review of its leading features will serve to give as good

an idea of the entire Pacific mountain region as is now practicable.

_The Rocky Mountains._--The limitations to the north and south of the

region to which this name is more or less specifically applied are not

well defined. Perhaps the most accurate statement at present permissible

is that the Rocky Mountains begin at the south, in northern Mexico, and

extend northward across the United States and Canada to near the shore

of the Arctic Ocean. On the east it is sharply defined by its junction

with the Great plateaus. Its western border, although less definite than

the eastern, is easily traced, at least across the greater portion of

the United States, by the marked contrast it presents to the

geographical conditions characteristic of the Great Basin region,

but owing to the many difficulties met with in attempting to adjust and

make use of the current nomenclature in classifying geographical regions

more or less artificial boundaries have to be accepted. The Great Basin

is so designated because it is a region of interior drainage--that is,

it does not send any tribute to the sea. Its boundaries are therefore

the crest-lines of the surrounding divides or water-partings. The Rocky

Mountains, on the other hand, are defined as an elevated region, the

boundaries of which are determined by relief and not by drainage. The

basis of classification in these two instances is not the same, and one

province overlaps the other. The streams flowing westward from the Rocky

Mountains into the Great Basin--such, for example, as Bear, Provo, and

Sevier Rivers in Utah--have their sources well within the Rocky Mountain

province as defined by uplift, but yet lie wholly within the Great Basin

province as defined by drainage. In spite of this inconsistency,

geographers recognise as the western border of the Rocky Mountains the

irregular and in part indefinite line where the elevated region breaks

down and meets the broad level-floored valleys characteristic of the

Great Basin. This line, or more properly belt of country, although

indefinite at the south, may for convenience be taken as beginning at

the head of the Gulf of California, and extending up the Colorado River

for about 300 miles, to where that river makes an abrupt bend, turning

southward after a westerly course through the Grand Canyon. From the

locality indicated, the boundary passes through central Utah, and is

sharply defined for most of the way by the bold western escarpment of

the Wasatch Range. In the neighbourhood of Great Salt Lake the border of

the mountain belt trends more and more to the northwest, crosses Idaho

diagonally, and in northern Washington merges with or closely approaches

the Cascade Mountains. In this northern region the border of the Rocky

Mountains is again indefinite, and until the geological structure of

western Canada is more thoroughly studied can only be located

provisionally.

The unsatisfactory condition of the nomenclature at present applied to

the larger topographic features of North America is illustrated by the

fact that to the north of the United States-Canadian boundary the term

_Rocky Mountains_ is much more restricted than is the custom in the

United States. In Canada this name is applied to the most easterly of

the ranges or chains of the Pacific cordillera. This difference in the

significance of the name referred to on the opposite sides of the

international boundary is unfortunate, but is due in large part to our

ignorance of the geography and geology not only immediately along the

boundary line, but generally throughout the rugged region of the

northwest portion of the continent.

One of the most important geographic features in the central part of the

United States is the presence in Wyoming of a broad, generally flat,

region known as the Laramie plateau (plains) and its extension westward

across nearly the entire width of the Rocky Mountains. The general

elevation of these "plains" is about 7,000 feet, or approximately 1,000

feet greater than that of the western border of the Great plateaus. The

Laramie plateau and country to the west having a similar topography,

furnished a convenient pass for the Union Pacific, the oldest of the

transcontinental railroads, and divides the Rocky Mountain belt into two

portions, which may be termed in a general way the northern and southern

Rocky Mountains respectively.

To the north of the Union Pacific Railroad there are several important

mountain groups, termed collectively the Stony Mountains by Lewis and

Clark in the report of their bold explorations across the continent in

1804, but not generally used since that time. This name has recently

been revived by J. W. Powell as a convenient term by which to designate

this large division of the Rocky Mountain belt, but unfortunately is not

recognised and has no significance to the north of the international

boundary. What the natural limitations of the Stony Mountains may be in

Canada remains to be determined.

The Stony Mountain system includes the Big Horn Mountains in

north-central Wyoming, the sharp and lofty Teton Range to the

south of the Yellowstone National Park, and several other rugged uplifts

of great extent in Montana and Idaho, and should the name be extended to

the north of the international boundary until a natural limit is

reached, it will include the Rocky Mountains of Canadian geographers

(the most eastern of the great uplifts constituting the Rocky Mountain

belt), together with the several ranges of the Gold Mountains. These

several mountain ranges and groups of ranges appear to have diverse

geological structure, but their histories are by no means thoroughly

understood. Some of them, as stated by Powell, are carved out of broad

folds, and involve both originally deeply seated igneous and metamorphic

rocks and upturned and folded sedimentary beds; while others are due to

movements along lines of fracture and in part of overthrust.

The Stony Mountains form a portion of the continental divide which parts

the waters flowing to the Pacific from those that find their way to the

Atlantic. The thousands of streams tributary to the Missouri head

against the equally numerous fountains supplying the westward-flowing

Columbia. The broad valleys between the several ranges have a general

elevation of between 7,000 and 8,000 feet, and the bold, massive

mountains rise from 10,000 to over 13,000 feet above the sea. Owing to

the considerable elevation even of the valleys, and the northern

position of the region here considered, as well as its distance from the

equalizing influence of the sea, the extremes of climate are strongly

marked. The summer season is comparatively short, and in the valleys the

heat is intense (ranging from 90 deg. to 112 deg. F.) and the rainfall small or

none at all, while the winter season is cold (temperatures of from -15 deg.

to -30 deg. F. being frequent) and accompanied by an abundant snowfall,

especially on the mountains. Agriculture, although carried on in the

valleys, is of comparatively small importance, and is usually dependent

on irrigation. The mountains are snow-covered through much of the year,

and small glaciers occur about the lofty summits of the Teton Range and

on the mountains near the international boundary and in Canada. The

valleys are generally destitute of trees except along the

streams, where white-trunked cottonwoods spread their green leaves in

summer and become a tracery of golden yellow in the autumn, marking the

courses of the life-giving waters. The lower mountain slopes are covered

with dark forests of pine, spruce, and juniper, which increase in

density and extent as one follows the ranges northward until the

influence of the high northern latitude is felt, and in northern Canada

the zone of the subarctic forest is reached.

In the central part of the Stony Mountains is situated the justly famed

Yellowstone National Park, which is truly remarkable for its fine

scenery, its deeply carved and gorgeously colored canyons, and most of

all for its numerous hot springs and spouting geysers. This is the only

geyser region on the continent, and the most extensive of the three now

existing in the world.

The finest scenery of the northern division of the Rocky Mountain belt

lies to the north of the international boundary, and within recent years

has been rendered accessible by the building of the Canadian Pacific

Railroad. It is in this region that the mountains are highest, most

rugged, and clothed most completely with the dark, sombre, evergreen

northern forests. Here, too, high up among the bare serrate mountain

tops, and mostly above the timber-line, are found the largest of the

glaciers in the Rocky Mountain belt. This wonderful region of rugged

mountains, deep and formerly glacier-filled valleys, impetuous rivers,

and dense forests has only recently become known to the world at large.

Vast areas, no doubt as attractive as those about Banff, Lake Louise,

Glacier House, etc., already famous, remain to be discovered and

described.

In the fastnesses of these wild northern Rockies moose, elk, deer, bear,

mountain-sheep, and mountain-goat still abound. The buffalo (bison) is

protected in the Yellowstone National Park, and will probably be

preserved from extinction. A small herd also survives in Canada. The

streams, except those flowing from glaciers, are bright, clear, and

swift, and are well stocked with fish. The trout, represented by several

species, there finds the cool retreats so essential to its life. To the

sportsman and skilled angler the northern Rockies are a paradise.

Among the lofty mountains and in the larger valleys there are many

lakes, more especially in northern Idaho and Montana and in Canada. Many

of these, and particularly those near the heads of the valleys and about

the more lofty peaks, are true rock-basin lakes, worn out by the

grinding of sand-charged glacial ice when the glaciers were far more

extensive than now. The large lakes situated in the trunk portions of

the broad-bottomed valleys are in many instances retained by dams of

glacially deposited detritus and record the changes in the aspect of the

land inherited from the Glacial epoch. These numerous lakes present a

vast variety of scenery, and in many instances reflect from their placid

mirror-like surfaces as beautiful and inspiring pictures of rugged

grandeur as can be found in the world. The natural beauties of the

classical lakes of Switzerland and Italy are rivalled by many of the

charming water bodies of the northern Rockies, which but few men

appreciative of the beauties of nature have ever seen.

To the south of the Laramie plateau the mountains of the Rocky Mountain

system are more irregular and more lofty than those to the north of that

break. The many rugged ranges in southern Wyoming, Colorado, and

northern New Mexico form a great group, to which the name Park Mountains

has been applied by J. W. Powell. The several ranges composing this

group have a general north and south trend, to which, however, an

exception is furnished by the Uintah Mountains in southwestern Wyoming

and eastern Utah, which consists of a deeply dissected east and west

fold or broadly uplifted plateau. Intervening between several of the

adjacent ranges there are wide, nearly flat-bottomed valleys, which owe

their leading characteristics to the deep filling of depressions by

_debris_ carried from the bordering mountains by the wind and streams.

These broad valleys surrounded by rugged peaks are known as parks, and

the numerous ranges among which they are situated are hence designated

the Park Mountains. The term by which the valleys are known is in some

respects misleading, as the word _park_ usually carries the idea of a

diversified and in part forested region, with mild, picturesque

scenery. Perhaps a city park or the beautiful rural estates of England

are most usually brought to mind when the term referred to is mentioned.

But in the great mountains of the central portion of the continent one's

idea must expand to keep in harmony with his surroundings. The natural

parks of that region are broad, generally treeless, valleys with winding

streams, the uplands are grass-covered and rolling, and in distant views

the courses of the streams are marked by narrow belts of verdure. The

picture is framed by a succession of mountain domes and embattled

cliffs. Over all arches the dark blue, cloudless sky of a nearly

rainless region. In the clear air distances are deceptive, and what

appear to be miles to the novice must be extended to leagues in order to

acquire adequate conceptions of the magnitude of the scene.

The most famous of the great tracts of generally level land surrounded

by the high ranges of the Park Mountains is San Luis Park, situated in

southeastern Colorado and extending southward into New Mexico, which has

a length from north to south of about 130 miles, and is from 20 to

nearly 40 miles wide. Its general elevation is between 7,000 and 8,000

feet. This great valley, level-floored with soft deposits swept in from

the bordering highlands, and almost completely surrounded by rugged

mountains, although more desolate than the majority of the numerous

similar valleys in the same region, is typical of its class. The Rio

Grande winds through its entire length and many streams rising in the

bordering mountains flow to the valley during the winter season, but in

summer, owing to the high temperature, active evaporation, and small

rainfall, only a few of the larger of these mountain-born torrents reach

the main, southward-flowing river. In the southern portions of the

valley large areas are covered with drifting sand, which is fashioned by

the winds into ever-changing dunes of a creamy whiteness. Some of the

streams from the mountains expand on the plain and form the San Luis

lakes, from which the water escapes by evaporation, thus causing them to

become alkaline. The land bordering the lakes is whitened as with

snow by saline incrustations. On the lower portion of the rim of this

mountain-inclosed basin there are scattered groves of pines and

junipers, and at higher elevations the mountains are dark with forests.

The more lofty peaks, however, rise far above the upper limit of the

forests and are rugged and magnificent even under the glare of a

cloudless sky.

To the east of the San Luis Park, and rising about 7,000 feet over it,

and over 14,000 feet above the sea, stands Sierra Blanca, one of the

finest of the many majestic mountains of Colorado. In summer immense

cloud banks frequently gather about this cold, isolated peak, and local

storms, accompanied by fierce lightning and echoing thunder, beat upon

its shrouded sides. These tempests raging on the mountain top, while the

adjacent valleys are flooded with sunlight, recall the scriptural

accounts of the storms of Mount Sinai. In fact, the southwestern portion

of the United States and the adjacent region in Mexico, so far as

scenery and climatic peculiarities are concerned, have much in common

with Palestine.

The other great parks in Colorado, which have suggested a name for the

group of mountains in the midst of which they are sheltered, are less

arid and less desert-like than the one just described; but like it,

derive their magnificence and fascination from their vast extent, the

sublimity of the bordering mountains, and the wonderful transparency of

the air above them, rather than from the topography of their nearly

level floors or the vegetation that strives ineffectually to clothe

their nakedness.

The individual summits as well as the separate ranges composing the Park

Mountains are remarkable for their massiveness and the great height of

their bare rounded summits rather than for picturesque details. Several

of the peaks are among the highest in the United States. One conspicuous

feature is the considerable elevation of the valleys, usually over 7,000

feet, and the large number of lofty summits. Of the peaks that have been

measured, over 30 exceed 14,000 feet in height. The portion of the Park

Mountains above an elevation of 10,000 feet, as is indicated on

the map reproduced on page 65, is far greater in area than

any other region of similar altitude on the continent.

In the Park Mountains, and generally throughout the southern Rockies,

even to central Mexico, the forms that meet the eye are the remnants of

vast upheaved folds and domes of the earth's crust sculptured and

degraded by erosion. The nearly horizontal rocks of the Great plateaus

on meeting the eastern border of the mountains are bent abruptly upward,

and in many places stand on edge or have been overturned so as to dip

westward. This abrupt upward bending and the presence of remnants of the

same beds on the summits of some of the higher mountains shows that the

strata have not been simply folded into anticlinals and synclinals, but

that there has been a thickening and upswelling of the rocks beneath.

In the northern Rockies, except in western Idaho and adjacent portions

of Washington and Oregon, evidences of recent volcanic activity are

rare, although igneous rocks cover great areas, and in the Yellowstone

Park numerous geysers and hot springs bear evidence to the presence of

abnormal heat in the earth's crust. In the southern Rockies, however,

volcanic mountains which still preserve their forms are numerous in

certain regions, and in Mexico there are mighty volcanic piles and many

lesser elevations built up by extrusion of molten material, some of

which are still active. Examples are furnished of volcanic mountains

ranging from perfect cones with curved slopes typical of the forms

produced by the piling up of various sized fragments about the vents

from which they were extruded, to irregular serrate peaks which reveal

the anatomy of the dissected volcanic masses, and even the dikes which

remain after the surface elevation of a volcano has been removed. The

most modern volcanoes in this great group of mountains are situated in

central Mexico, but others nearly as perfect in form occur in New Mexico

and Arizona, and in the plateaus to the east of the Park Mountains. The

Spanish peaks in southeastern Colorado are instructive illustrations of

the topographic forms produced when a volcanic mountain has been deeply

dissected.

In the formation of volcanic mountains there is an extrusion of molten

and fragmentary material accompanied by an escape of great volumes of

steam at the surface. Closely related to this phase of vulcanism is the

injection of molten material into the earth's crust from below, so as to

force its way between stratified beds and produce intruded sheets. In

this latter process the sheets of injected material may be thin in

comparison to their lateral extent or thick lens-shaped masses. In the

production of either of these forms of intrusion the cover above the

injected material is lifted and a change is made in the topography of

the surface. The intrusions, which are thick in comparison to their

lateral extent, are known as _laccoliths_. At times intrusions of this

nature are of such thickness that they produce true mountain forms. If

unmodified, these elevations would be domes, but when their surfaces are

broken by erosion and their dissection and removal progresses they

frequently assume rugged, serrate forms.

The type of laccolithic mountains made known some years since by the

studies of G. K. Gilbert is furnished by the Henry Mountains, in

southern Utah. More recently it has been found that this interesting

phase of mountain building is illustrated by many other examples in the

Rocky Mountain region and elsewhere.

The rocks exposed at the surface in the southern Rockies, as in the

northern division of that great chain, embrace almost every variety

which enters into the composition of the earth's crust. The central

cores of many of the now deeply eroded ranges consist of granite and

other similar rocks, and are surrounded by sedimentary beds which range

in age from the oldest stratified rocks now known to the youngest.

Igneous rocks in great variety and in all forms incident to an extruded

or volcanic and intruded or plutonic origin are present. The many

disturbances that have occurred have led to the formation of mineral

veins and the impregnation of rock masses with ores of various

kinds--such as gold, silver, lead, copper, etc.--which have been mined

with great success at many localities.

_The High Plateaus._--To the west and south of the Park Mountains, and

situated in the western portions of Colorado and New Mexico, eastern and

southern Utah, and northern Arizona, there is an extensive region having

a general surface level of 6,000 to 7,000 feet above the sea, known as

the High plateaus. This region has suffered great erosion and is deeply

trenched by stream-carved canyons. Although not mountainous in the

ordinary acceptance of the term, its surface is rugged and difficult to

traverse, particularly on account of the deep canyons that intersect it

in every direction.

The High plateaus are a part of the Rocky Mountain region and bear a

somewhat similar relation to the Park Mountains that the Alleghany

plateau does to the Appalachian Mountains. Streams flowing westward from

the Park Mountains and from the southwestern portion of the Stony

Mountains unite to form the Colorado River--the one great drainage

channel of the region. The importance of this remarkable river in the

history of the land has led to the adoption of the name Colorado plateau

by Powell and others for the region under consideration. As with so many

of the grander geographical units of the continent, the precise limits

of the one here considered are difficult to define; but in spite of this

uncertainty as to meets and bounds, the now classical writings of

Newberry, Powell, and Dutton especially have shown that a strange and

wonderful land exists in the southwest part of the United States, which

is of unusual interest to geologists and geographers.

The High plateaus are underlaid by nearly horizontal rocks. The larger

elements in the structure are great blocks of the earth's crust

measuring some 60 to 100 miles on their various borders, which are

bounded by breaks (faults), or by what are termed monoclinal folds or a

change from one plateau to another by a single bend in the strata. The

rocks in each of the separate plateaus are usually gently tilted. Their

eroded edges stand as lines of massive, gorgeously coloured, and

frequently fantastically sculptured cliffs. These cliffs, when seen from

below, appear as rugged mountain ranges, but to an observer standing on

their deeply sculptured crests are easily recognised as the

upturned edges of large gently tilted blocks of the earth's crust.

The basement rocks beneath the High plateaus are very ancient granites,

schists, etc., which formed a land surface and were greatly eroded

before the first of the superimposed stratified beds were deposited upon

them. The first of the sheets of sediment laid down by the primeval

ocean belong to the oldest rocks containing records of life that have as

yet been recognised--the Algonkian (pre-Cambrian) terranes of modern

geology. Above these come other deposits of sandstone, shales,

limestone, etc., representing a wide range of geological history, and

including as the upper member of the series the sediments of large

Tertiary lakes. This vast succession of stratified rocks, some 13,000

feet in thickness, has been upraised in a broad way, without the

crumpling and folding, but broken, as stated above, into great blocks

which are now variously inclined, but still preserve a plateau-like

character.

Besides the movements in the earth's crust which raised the plateaus and

caused fractures and simple or monoclinal folds in the rocks of which

they are composed, there occurred volcanic eruptions which produced

numerous cinder cones, extensive lava-flows, and widely spread sheets of

comminuted material known as lapilli, dust, and so-called ashes.

Although the history recorded in the rocks forming the High plateaus is

one of fascinating geological interest, the easier and more obvious

lesson that the region has to offer, more especially to the geographer,

has been engraved and etched on its surface by streams and wind-blown

sand.

On the High plateaus the rainfall is comparatively small, and the

streams originating there mostly ephemeral. But on the mountains to the

east and north the precipitation is more abundant and rivers are formed

which flow across the plateau region. The Green and Grand Rivers, fed by

many tributaries, unite to form the Colorado, which flows southwestward

for some 700 miles and discharges its muddy waters into the Gulf of

Lower California. This great river year by year and century after

century has deepened its channel through the plateau region where the

rainfall is small, more rapidly than the general surface has been

lowered by erosion. The main conditions are a broad area of nearly

horizontal rocks, raised high above the sea or above the base level of

erosion, and an arid climate; crossing this region is the ever-flowing

river, which, acting like an endless saw, cuts deeper and deeper into

the blocks of the earth's crust which have been raised athwart its

course. Resulting from these conditions is a mighty trench or canyon,

which is by far the most magnificent of its kind in North America, if

not in the world. Not only has the main river sunken its channel into

the earth to a depth of more than a mile throughout a large portion of

its course, but each tributary stream has been engaged for a long period

of time in a similar task. Although most of the streams originating on

the surface of the plateaus are ephemeral, they work rapidly when the

occasional heavy rains flood their channels. This deepening of the

stream channels, while their borders and the intervening portions of the

plateau surface suffered but comparatively slight erosion, has produced

a wonderful system of deep steep-sided trenches in the borders of which

the edges of the dissected rocks are exposed in nearly vertical

precipices.

[Illustration: FIG. 19.--Grand Canyon of the Colorado River. After W. H.

Holmes.]

Aside from the lessons of interest to the geologist and geographer so

plainly engraved on the surfaces of the plateaus crossed by the

Colorado, the region has a wonderful fascination for the purely aesthetic

feelings more or less latent in every human breast. To one traversing

the open pine forests, in places clothing the plateaus and inclosing

many grassy glades and flower-decked parks, in which timid deer may

frequently be seen feeding in the early morning, and emerging on the

brink of the Grand Canyon, the scene that meets the eye is marvellous

beyond all description. C. E. Dutton, to whom we owe some of the most

graphic and inspiring descriptions of natural scenery ever written,

states that those who have long and carefully studied the Grand Canyon of

the Colorado do not hesitate for a moment in pronouncing it the most

sublime of all earthly spectacles. "If its sublimity," writes

Dutton, "consisted only in its dimensions, it could be sufficiently set

forth in a single sentence. It is more than 200 miles long, from 5 to 12

miles wide, and from 5,000 to 6,000 feet deep. But it is not magnitude

alone that gives this marvellous canyon its prominence; it is the

gorgeous and varied colouring of its mighty walls, the endless details

in the sculpturing of its battlements and towers, the ever-changing

atmospheric effects of its profound depths, and the wonderful stimulus

to the imagination with which it feeds the mind. Standing on the brink

of the Grand Canyon, the prosaic search for causes and effects for a time

at least must be laid aside, and give place to the emotions."

Wonderfully grand as are the scenes beheld in traversing this region of

high plateaus, with its magnificent cliffs and profound canyons, one is

constantly reminded that it is an arid land. The higher portions of the

plateau, it is true, are in places forested, but over vast areas the

rocks are bare. Water is everywhere scarce except in the bottom of the

larger excavations. Thirsty, and perhaps perishing, the traveller,

Tantalus like, looks down on the shining silvery threads of water in the

canyons, hundreds and even thousands of feet below, but separated from

them by impassable barriers. To the south the plateaus descend to the

desolate valleys of southern Arizona, where strange gigantic

cactus-plants and scattered clumps of thorny shrubs alone break the

dreary monotony of the hot gravelly deserts. Agriculture is there

impossible without irrigation, but where the life-giving waters can be

utilized, as in the Gila Valley, marvellous productiveness follows.

THE GREAT BASIN

To the west of the Rocky Mountain belt in the United States there exists

a region embracing about 210,000 square miles, which sends no stream to

the ocean. This vast and in large part desert tract is known as the

Great Basin. The climate is characterized by its aridity. The annual

precipitation is small and evaporation active. All the water reaching

the land is returned to the air by evaporation, either directly or from

the streams and lakes. Many of the lakes do not overflow and are more or

less alkaline and saline, while some of them, as Great Salt Lake, Utah,

and Mono and Owens Lakes, California, are dense with mineral matter in

solution.

[Illustration: FIG. 20.--The Great Basin.]

The Great Basin is not a single level-floored depression, as one might

infer from its name, but is traversed by rugged mountain ranges, which

divide it into a large number of minor valleys. Some of these secondary

basins have lakes and streams which escape from them into lower

depressions, but in many instances under present climatic conditions

they have no surface water, all the moisture that reaches them being

absorbed by the thirsty soil or evaporated without forming lakes. The

Great Basin proper, as it may be termed, embraces nearly the whole of

Utah and Nevada, together with small portions of the southern parts of

Idaho and Oregon and a large area in southeastern California. While the

drainage conditions limit the application of the name to this group of

associated basins which send no tribute to the sea, the climatic and to

a less extent the topographic and geological conditions that

characterize it have much wider, although indefinite boundaries. This

wider region which resembles the Great Basin proper, extends from

British Columbia southward to beyond the city of Mexico, and includes

the eastern half of Washington and Oregon, a large part of Idaho, and

much of Arizona, New Mexico, and western Texas. In this outer region

both to the north and south of the Great Basin proper there are

drainless valleys, as those of central Mexico, in which the conditions

characteristic of the desert valleys of Utah and Nevada are repeated.

The greater region of arid valleys and desolate mountains surrounding

the Great Basin proper is crossed at the north by the Columbia and in

the central part by the Colorado. Each of these large rivers has its

source in the Rocky Mountains and flows to the Pacific.

The most obvious features of the Great Basin and of the northward and

southward extensions of the belt of country having much in common

with it, depend on climatic conditions. The rainfall is small throughout

the entire belt from the Canadian boundary to south-central Mexico. The

average mean annual precipitation, judging from such observations as are

available, is probably less than 15 inches, but this broad statement

does not truly represent the diverse conditions. The rainfall is

confined almost entirely to the winter season, and frequently comes in

short heavy downpours. During the summer season, the valleys especially,

become so parched that only such plants can grow as are adapted to

long-continued droughts. The topography is rough and diversified by many

mountain ranges, and the precipitation is more abundant on the uplands

than in the valleys. Over large areas in Nevada and southeastern

California the mean annual rainfall is less than 5 inches. The author,

while carrying on geological work in this region, was informed by some

of the older settlers that at times for fully eighteen consecutive

months no rain whatever fell in certain of the valleys. From the

accounts of travellers in central Mexico, it seems as if some of the

interior basins in that region must be fully as arid as those just

referred to.

One conspicuous result of the lack of moisture is the absence of

forests. Except on the mountains mainly at the north the Great Basin and

its extensions, as defined above, is nearly destitute of trees. The

valleys are in many instances thickly covered with desert shrubs,

notably the sage-brush, but the floors of the driest basins are in many

instances almost absolutely without vegetation, and are frequently white

with saline incrustations.

Many of the depressions in the Great Basin, as well as some of the

outlying valleys referred to, have rivers and lakes which exhibit

certain interesting features that are unfamiliar to people dwelling in

humid lands. The streams are fed in part by the small precipitation on

the desert valleys, and by springs, frequently of heated water, but

mainly by the rain and melting snow on the mountains. Many rills and

rivulets are born on the valley sides of a single storm, but are

absorbed by the thirsty soil or evaporated during the succeeding hours

of sunshine. Other streams have a greater lease of life and flow

down to valleys and basins, suffering evaporation and absorption as they

progress, which cause them to diminish in volume, and finally to vanish.

The stronger streams, such as Sevier and Bear Rivers in Utah, the

Humboldt River in Nevada, and the Truckee River in California, maintain

their existence throughout the year, and expand into lakes in which the

inflow is balanced by evaporation.

The lakes of the Great Basin present even greater diversity than the

streams. Some of those situated principally in the mountains are of

pure, limpid, wholesome water, supplied by cool, sweet brooks and rills

or by the melting of the winter's snows, and overflow throughout the

year. These lakes, usually of small size, are similar in all respects to

the ordinary lakes of humid lands. In eastern Utah, adjacent to the west

base of the Wasatch Mountains, the Provo River and other streams supply

Utah Lake, the outlet of which, the Jordan River, empties into Great

Salt Lake. Utah Lake is well within the Great Basin, and situated at a

low elevation for the region, namely, 4,500 feet, or about 280 feet (in

1873) above the level of lake of brine into which it discharges. This is

the largest of the fresh lakes in the valleys of the Great Basin, and

owes its existence to the fact that a depression there occurs which is

filled to overflowing by the streams from the mountains. Bear Lake, in

northeastern Utah, is another exceptional example of a fresh lake of

considerable size at a comparatively low altitude, in the same region.

On the western rim of the Great Basin, at an elevation of 6,247 feet,

and surrounded by the forested peaks of the Sierra Nevada, lies Lake

Tahoe, "the gem of the Sierra," a water body of remarkable purity, which

discharges through Truckee River into Pyramid and Winnemucca Lakes.

These lower lakes, situated in desert valleys at an elevation of 3,780

feet above the sea, are without outlets and alkaline and bitter. The

most characteristic lakes of the Great Basin, however, are those that do

not overflow, and on account of concentration by evaporation are more or

less highly charged with mineral matter in solution. These saline and

alkaline lakes may be divided into two classes, in reference to

their duration, but the line of separation is indefinite. Certain of

them have maintained their existence for many years, and probably have

not been evaporated to dryness for several centuries, and may be classed

as perennial lakes; others are evaporated to dryness each year, or

during certain exceptionally dry and hot seasons, and may be termed

ephemeral lakes. In many instances the beds of the ephemeral lakes are

normally in a state of desiccation, and appear as broad, level, mud

plains, usually with a white fringe of saline matter. Frequently these

mud plains, or _playas_, as they are termed, are transformed into

shallow lakes during a single storm, but the waters are absorbed by the

clays beneath or evaporated within a few days or perhaps a few hours

after the rain ceases. The largest and most characteristic of the

perennial saline water bodies is Great Salt Lake, the counterpart in

many ways of the Dead Sea. The streams discharging into this salt sea

have the usual purity of river-waters, and carry but a small fraction of

one per cent of saline matter in solution. The lake is supplied also in

part, but to an unimportant extent, by springs, the most of which are of

essentially fresh water. The source of the salts which make the waters

of the lake a brine is evidently, therefore, the small percentage of

mineral material brought in by the tributary streams. After reaching the

lake these fresh waters, in the ordinary meaning of the term, are

concentrated by evaporation. This is the explanation of the leading

facts in the chemistry of all of the saline and alkaline lakes of the

Great Basin region, such as Pyramid, Winnemucca, and Walker Lakes in

Nevada, Mono and Owens Lakes in California, and the saline lakes of

Mexico.

The volume of a lake without an outlet, or an "inclosed lake," is

determined mainly by the ratio of the inflow (including the rain falling

directly on its surface and the tribute from springs) and evaporation.

Its volume, and consequently its area, fluctuates from season to season,

and frequently varies also during periods embracing several years. With

variations in volume there are fluctuations in the percentage of saline

matter in solution, even if precipitation of one or more of the

contained salts does not take place during the periods of more than

usual concentration. In most instances inclosed lakes are concentrated

by evaporation in summer seasons, and perhaps become nearly saturated

solutions, but are diluted during the rainy winter seasons. Fluctuations

in volume, area, depth, salinity, etc., are thus characteristic of

inclosed water bodies. They are sensitive to climatic changes which

ordinary weather records fail to detect, and are modified in a

conspicuous manner when the country about them becomes inhabited and

irrigation is practised.

Some of the lakes of the Great Basin are dense brines from which various

substances are being precipitated. The economic importance of these

natural reservoirs of brine and of various soda salts is great, and will

become more and more important as transportation facilities increase.

Great Salt Lake, it has been estimated, contains 400,000,000 tons of

common salt and 30,000,000 tons of sodium sulphate in solution. During

the past ten years about 40,000 tons of common salt have been harvested

from it annually. Mono Lake contains some 245,000,000 tons of saline

matter in solution, of which about 92,000,000 tons are sodium carbonate

and bicarbonate. Owens Lake is similar to Mono Lake in composition, and

is now the basis of a large soda industry.

A marked difference between a region which drains to the ocean and one

where the streams enter inclosed basins where their waters are

evaporated is that in the former the waste from the land carried by the

streams as an invisible load in solution or as a visible load consisting

mainly of silt and sand in suspension is contributed to the ocean and

widely distributed before being deposited--much of the material in

solution, in fact, may be said to be a permanent contribution to the

salinity of sea-water; but in most instances where streams enter

inclosed basins all of the material contributed both in solution and

suspension is sooner or later precipitated. The area within an inclosed

basin, on which the inflowing streams lay down their loads, is as a rule

less extensive than the area that is being denuded to supply the

material. The receiving basins are thus filled in or _aggraded_, and

there is a concentration both of the mechanical wash from the land and

of the substances taken in solution by the waters of streams and

springs. A marked result of this process of concentration, particularly

of the fine waste of the uplands and mountains, is seen in the

approximately level floors of inclosed valleys. Throughout the Great

Basin the valleys have been filled to a depth in many instances of

hundreds of feet. Some of the lower mountain ranges in Utah have been so

nearly buried beneath these valley deposits that only their summits,

termed _lost mountains_, appear above the even surface of the desert

plains. This _debris_, deeply filling the valleys referred to, is

usually a fine yellowish dust-like material, similar in many ways, and

probably in mode of origin, to the _loess_ of China in which geologists

have taken much interest. With the concentration and deposition of the

fine mechanical wash of the uplands there has also been a concentration

of the more soluble saline constituents of rocks, which causes the soils

of arid regions to differ in an important way from those of humid lands.

The leached and characteristically red-tinted soils of warm humid

countries, consisting of the oxidized residue of deeply weathered rocks,

are absent from arid regions; in their place we find minutely

disintegrated, usually light-coloured, and not chemically impoverished

soils. In warm humid regions chemical decay of the rocks is the

conspicuous feature; in equally warm arid lands mechanical

disintegration is carried to an extreme, without the removal of the more

soluble constituents. In fact, concentration of saline matter, notably

common salt, sodium sulphate, gypsum, etc., is one of the functions, so

to speak, of arid climates, when the requisite evaporation basins are

present. Among the important industries of the Great Basin region is the

gathering and purifying of the various salts contained in the existing

water bodies and in the basins of desiccated lakes.

In addition to the characteristics of the region referred to above,

which are mainly the result of climatic conditions, the Great Basin has

certain geological features, in the main, so far as North America

is concerned, peculiar to itself. The leading structural features of the

rocks, so far as they find expression in the surface relief, is the

presence of a large number of extensive faults trending in general about

northeast and southwest. These faults are breaks or cracks along which

the rocks have been moved up and down. One side of a fault sometimes

stands higher than the opposite side, and forms a narrow and frequently

high and rugged mountain range. The number of these faults within the

Great Basin is as yet unknown, but they certainly number many hundreds.

In a cross profile of the region between the Wasatch Mountains on the

east and the Sierra Nevada on the west the number of mountain ridges due

to faulting is at least a score. The precipitous western border of the

Wasatch Mountains is itself a great fault scarp, as is also the eastern

border of the Sierra Nevada. The faults that determine the steeper sides

of these mountain ranges are not to be considered as single clean-cut

gashes, but as irregular and intersecting fractures traversing a narrow

belt of country. The faults referred to divide rocks of all ages, and

are evidently due to the most recent disturbances that have affected the

region. It is not probable that the break in any given instance was

formed all at once. Such vast convulsions would be out of harmony with

the rules of nature. But rather many small movements and adjustments of

pressure have occurred along the same belt of fracture. This conclusion

is sustained by the fact that many of the faults have experienced

movements in very recent times. In places fault scarps a score or more

feet in height cross the alluvial cones at the mouths of the small

high-grade valleys in the mountains. These scarps in loose

unconsolidated gravel and similar material, even under an arid climate,

could not be expected to preserve their freshness for many years. At

times the breaks cross the courses of streams and cascades, and rapids

are formed by the waters flowing down escarpments thus produced in loose

material. One characteristic fault scarp in Inyo Valley, California, is

known to have been formed during an earthquake that shook that portion

of the country in 1872. The many small earthquakes that have been

felt in the Great Basin region are believed to have been caused by

slight movements along the breaks that traverse the region. This and

other evidence indicates that the faults to which so much of the

characteristic scenery of the Great Basin is due have grown by repeated

minor displacements, and that such movements are a common cause of

earthquakes.

The most conspicuous topographic features of the better known portion of

the Great Basin are long, narrow, and frequently sharp-crested ridges,

with a gentle slope on one side and a steep escarpment on the other. The

steeper side in a large number of instances is known to be the upraised

side of a fault. Each of these basin ranges, as they are termed, may be

considered as the upturned edge of a block of the earth's crust, in

general from 60 to 100 or more miles long, and 10 to perhaps 20 miles

wide. The crest-lines of the tilted blocks are frequently serrate, on

account of differences in the hardness and texture of the rocks and the

effects of weathering. There is frequently, however, an older structure

revealed in them, showing that the region was folded and otherwise

disturbed previous to the later movements which produced the leading

features in the present topography. It is probable that this older

structure in some instances has had an important bearing on the forms of

some of the ranges, but our knowledge in this direction is too limited

to warrant presentation in a popular treatise.

Many of the basin ranges are imposing on account of their height and

ruggedness, when seen from the adjacent, deeply filled valleys, although

scarcely more than half of their actual elevation above the sea is

revealed from such points of view. Exceptions to this general statement

occur, however, in southeastern California, where, in Death Valley, the

land is 480 feet below sea-level. This is the only region in North

America which, like the basin of the Dead Sea, is below the level of the

ocean's surface. On the border of Death Valley the mountain ranges rise

from 6,000 to 10,000 feet, and the highest summit, known as Telescope

Peak, is reported to have an elevation of nearly 11,000 feet

above the sea. In the central and northern portions of the Great Basin

the valley floors have a general elevation of from 5,000 to 6,000 feet.

The mountains rise from these valleys to a height of from a few hundred

to 4,000 or 5,000 feet. Among the highest, if not actually the

culminating peaks well within the Great Basin are White Mountain, on the

California-Nevada boundary, about 30 miles southeast of Mono Lake, which

has a summit elevation of 13,000 feet, and Jeff Davis Peak, in eastern

Nevada, which rises 13,100 feet above the sea and 8,000 feet above the

adjacent valleys.

The numerous sharp-crested ranges of the region under review are

frequently remarkable for the richness of the colours of the naked

rocks. The mountain slopes and towering angular summits when outlined

against the morning or evening sky are frequently as brilliantly dyed as

are the New England hills when clothed in the harlequin foliage of

autumn. Before sunrise and after sunset each serrate crest-line is the

sharply cut border of a silhouette of the deepest and richest purple.

The diversity of scenery in the Great Basin is increased by mountains of

volcanic origin, including several modern craters, some of which hold

lakes, and by lava-flows of recent date, and by great alluvial fans or

detritus cones which stream out into the valleys from the mouths of

gorges in the bordering mountains.

The Great Basin proper, with its rugged topography and arid climate, is

not an agricultural region. Small portions of it, however, when water

can be had for irrigation, have been transformed into fruitful farms and

gardens which yield bountiful returns. But even a century hence, when

all has been accomplished in the way of reclaiming the arid valleys that

can be done by utilizing the available water for irrigation, only a

small per cent of the whole will be under cultivation.

SIERRA NEVADA AND CASCADE MOUNTAINS

To the west of the Great Basin, and extending from southern California

northward to beyond the United States-Canadian boundary, there is a

lofty and extremely rugged belt of mountains consisting of two

ranges--the Sierra Nevada at the south and the Cascade Mountains at the

north. Topographically, these two ranges form a single elevated belt of

country, but custom, and as is now generally understood the geological

structure and history, draws a dividing line between them in northern

California. The Sierra Nevada-Cascade range extends far into Canada, and

is there known as the Coast Range. No adjustment of the nomenclature in

use on the two sides of the international boundary has been made, and in

order to conform with current usage, it is necessary to consider

separately the two portions of the range on opposite sides of the

forty-ninth parallel.

The Sierra Nevada has its southern terminus at Tejon Pass, in southern

California, and extending from there northward to Lassen Peak, in the

northern part of the same State. With the exception of a small area to

the east and north of Lake Tahoe, the entire range is included within

the boundaries of California. This is geographically one of the best

defined of the larger mountain ranges in the United States. Its eastern

border especially is easy to trace, as for the most part it is

determined by a great escarpment, corresponding to the fault scarp which

borders one side of so many of the basin ranges. The Sierra Nevada, in

fact, may be considered as one of the basin ranges of great size and

forming the western wall of the region of interior drainage lying to the

eastward. This abrupt eastward-facing mountain slope is in reality a

great fault scarp, formed mainly by the upheaval of the west side of an

intersecting system of fractures. It is not known, however, how much of

the escarpment is due to the upheaval of the west side of the belt of

fracture, or how much to the sinking of the eastern side. There have no

doubt been many up and down movements along this belt, of which

the present mountain wall is the algebraic sum. The escarpment rises in

general from 5,000 to 6,000 feet above the desert valleys to the

eastward, and reaches a maximum of about 14,000 feet in the vicinity of

Death Valley. It is exceedingly precipitous and rises to an irregular

serrate crest-line, from which the general slope westward to the Great

Valley of California is gentle.

The best idea of the generalized topographic form as well as of the

origin of the Sierra Nevada, which the reader may be asked to hold in

mind, is that the range consists of a block of the earth's crust about

500 miles long and from 70 to 100 miles broad, which has been upraised

along its eastern edge so as to give its surface a westward inclination.

From this vast monolith the profound canyons and multitude of sharp

tapering spires which give to the range its magnificent scenery have

been sculptured. Like most generalized pictures of great geographical

features, however, this outline of the form and structure of the great

mountain range of California has to be modified when studied in detail.

From extensive and most painstaking studies by H. W. Turner, of the

United States Geological Survey, the conclusion is reached that "the

Sierra Nevada may be described as a monogenetic range, composed of

highly compressed schists and slates with large areas of associated

igneous rocks, chiefly granite and diabase, upon which lie uncomfortably

a series of later Cretaceous and Tertiary sediments and volcanic rocks."

Could the profound valleys carved in the long western slope of the

Sierra Nevada be filled so as to restore the conditions as they existed

when the mountain block was first upraised and tilted, we would have an

inclined plane in which the edges of previously folded rocks would be

exposed. In other words, the western slope is a tilted peneplain,

bearing on its surface remnants of older uplands. High up on the range

there are detached areas of well-worn gravel, which were deposited when

the slopes were less inclined than at present, and before the existing

peaks and canyons came into existence. Certain of the valleys carved

during a portion of the earlier stage of erosion were subsequently

filled by lava-floods, which buried gold-bearing gravel beneath thick

layers of basaltic rock. Erosion has since cut away the softer beds

bordering these ancient lava-sheets, and left them in bold relief as

table mountains, underneath which miners have excavated tunnels in order

to reach the stream-deposited gravels of the ancient canyons. In these

instances valleys have been changed to uplands, owing to the resistance

to erosion afforded by the volcanic rocks discharged into them.

The long gentle slope on the west side of the Sierra Nevada has been

dissected by westward-flowing rivers, which have sunk their channels

2,000 or 3,000 feet or more into the rocks. Other streams having much

shorter courses flow down the steep eastern slope of the range and have

also excavated canyons. These two systems of drainage, one leading

westward to the Great Valley of California and the other eastward to the

valleys of the Great Basin, extended their head branches until they came

into rivalry with each other, and cut deep notches in the crest of the

range. During a late stage in its history the higher portions of the

mountains were covered with a great field of perennial snow, from which

glaciers flowed both eastward and westward. These ice-streams, by

deepening and broadening the previously water-cut channels, still

further increased the diversity of the topography and impressed upon it

characteristics such as only glaciers can produce.

The highest and most typical part of the Sierra Nevada is in its

south-central portion, and is known as the High Sierra. This region,

although at present not accurately defined, is well worthy of

recognition. Throughout its entire extent, from the neighbourhood of

Lake Tahoe on the north to Tehichipe Pass at the south, a distance of

about 240 miles, it is diversified by rugged serrate peaks and narrow

stream-cut valleys of great depth. Many of the mountains attain

elevations of from 12,000 to over 13,500 feet. The highest summit is

Mount Whitney, in the southern part of the range and near its eastern

border, which rises 14,522 feet above the sea and has the added

distinction of being the highest mountain in the United States,

exclusive of Alaska. It is a notable fact that this great mountain-peak

should be situated only about 100 miles from Death Valley, the lowest

depression on the continent.

Another of the remarkable features of the Sierra Nevada is the great

depth and the wonderfully precipitous walls of some of the valleys

carved by the westward-flowing rivers. The most famous of these is the

sublime Yosemite Valley, now world-renowned. This cleft as it appears in

solid light-coloured granite, over a mile deep, is believed by Turner,

the last of several geologists to discuss its origin, to be due to

stream erosion. The fact seems well established, however, that glacial

ice has assisted in the great task. The Yosemite is not such an unique

feature as was at one time supposed, but is approached if not equalled

in depth and magnificence by Hetch Hetchy Valley, through which flows

the Tuolumne River, and is duplicated, in part at least, by other

similar stream-cut gulfs.

Among the chief elements in the glorious scenery of the Sierra Nevada is

the multitude of lakes left as a rich inheritance by the departed

glaciers. These occur not only high up amid the bare peaks where their

basins were excavated by the flowing ice, but also in the lower valleys

where the ancient ice-streams built morainal dams.

The High Sierra was swept nearly clean of soil and _debris_ by the

ancient glaciers, and the hard rocks thus exposed were rounded and

burnished by the ice that flowed over them. But little disintegration or

decay of the rocks has taken place since an amelioration of climate

changed the drainage from a solid to a liquid form. On account mainly of

the general absence of soil the forests are less dense than might be

expected from the height of the regions where they occur and its general

climatic conditions. The more lofty peaks reach far above the forests

and are riven and shattered by frost. The crests and cliffs at somewhat

lower altitudes are also bare, but in the canyons and on the meadow-like

valley bottoms smoothed by the glaciers, open park-like groves of pine

and spruce grow in picturesque disorder. On the ledges of the great

precipices, and on many of the secondary summits, gardens of

alpine flowers blossom in late summer, and at times impart a rich warm

glow to the heights that support them. The views of nature, unmarred by

the hand of man, which reward the persistent mountaineer in this silent

wonderland of the upper world, are not only grand beyond all

description, but beautified by a delicacy of decoration where

snow-fields and alpine gardens meet, that is undreamed of by the

dwellers in the denser air of the plains and seaside. Lovers of nature

who are unable to climb the towering summits of the High Sierra and see

for themselves the marvellous beauty there so lavishly displayed can at

least find a glowing pen picture of it in John Muir's fascinating book

The Mountains of California. On the lower western slope of the Sierra

Nevada the forests become continuous and luxuriant, the trees are of

large size, and the lovely flowers carpeting the valleys and hillsides

take on a more familiar appearance than the gorgeous blossoms of the

alpine meadows. It is in this region that the gigantic _Sequoia_ still

lingers as a remnant of a nearly extinct flora.

Statements of heights and depths, of geological structures, and of

topographic forms are perhaps necessary to enable one to form a mental

picture of a snow-crowned mountain range which will bear some faint

resemblance to the mighty original; but when one threads his way through

the resinous forests on the lower slopes of the Sierra Nevada, ascends

some one of the profound water-cut rifts in its side, scales the steep

cliffs, traverses the crystal surfaces of the small glaciers, and

finally stands on a spire-like summit covered only by the dark blue of

the dome above, all thoughts of the arches and walls that support the

mighty cathedral are lost in wrapt wonder and admiration of the

magnificent scene about him. It is this intense feeling for the sublime

and beautiful in nature that the student of geography should strive to

cultivate, as well as to acquire skill in reading the prosaic history

written everywhere on the mountains. This important lesson can seldom be

studied to greater advantage than amid the silent awe-inspiring peaks of

California.

The Cascade Mountains, as previously stated, are a direct continuation,

so far as the relief is concerned, of the Sierra Nevada. The geological

structure of the region in northern California, where the two ranges

approach each other, has been studied by J. S. Diller, of the United

States Geological Survey, who concludes that they present characteristic

differences. In the Cascade Mountains in northern California, Oregon,

and southern Washington the rocks exposed at the surface are mainly, if

not entirely, of volcanic origin, and were poured out in a molten

condition as lava-flows, or as fragmental ejections from volcanoes, and

in part rose through fissures and formed what are termed fissure

eruptions. The rocks thus extruded are mainly composed of dark, heavy

basic material, such as basalt and andesite. These outpourings of molten

rocks were on a grand scale, and a large number of volcanic mountains

were formed which still remain as the dominant peaks of the rugged and

densely forested Cascade Range. Although the evidence now available

seems to show that there is a striking difference between the Sierra

Nevada and the Cascade Mountains, another significant change occurs when

one follows the Cascade Mountains into northern Washington. Where the

Northern Pacific Railroad crosses the range the volcanic rocks are

succeeded northward by granites, schists, serpentine, etc., and

Cretaceous and Tertiary sedimentary beds of much the same character as

those in the Sierra Nevada.

The study of the Sierra Nevada-Cascade region has not progressed far

enough to warrant a decision, but the fact referred to above strongly

suggests that the two ranges, as we now term them, are essentially a

single uplift, a large portion of which, extending from Lassen Peak, in

California, northward across Oregon and into Washington as far as the

Northern Pacific Railroad, is buried beneath a great blanket, so to

speak, of lava-flows. The tract of elevated and rugged country in

northern Washington embraced in the Cascade Mountains, as has been

observed by the writer, passes into Canada without a marked change in

either its geology or geography, and there is no occasion for a

change of name when the international boundary is crossed.

The Cascade Mountains in Oregon and southern Washington, where the

surface rocks are mainly and perhaps wholly of volcanic origin, are

rugged for two principal reasons: First, volcanic energy has built up

great individual peaks; and second, erosion has carved deep valleys and

numerous ravines and gorges. The volcanoes are now extinct, or have long

been dormant, and their cold summits are in several instances crowned

with perennial snow and small glaciers. The forms given to the more

prominent elevations by the eruptions which built them have to a great

extent been defaced by erosion. As they stand to-day they furnish an

instructive series of more or less deeply dissected volcanic mountains.

[Illustration: FIG. 21.--Crater Lake in the summit of Mount Mazama,

Oregon.]

Not only has erosion changed the characteristic slopes of the peaks

built of lava-flows and ejected fragments, but in at least one

remarkable instance the volcanic energy itself greatly altered the

structure it had previously raised. Mount Mazama, situated in southern

Oregon in the summit region of the Cascades, is a truncated volcanic

cone in the top of which there is an immense depression now partially

filled by the waters of Crater Lake (Fig. 21). The main features in the

history of this unique mountain with a lake in its summit, as

interpreted by Messrs. Dutton and Diller, of the United States

Geographical Survey, are as follows: It once stood as a conical peak,

similar to several other mountains of volcanic origin in the same

region, some 15,000 feet in height; it was then an active volcano with a

summit crater filled with lava, but subsequently, for a time at least,

became dormant and was occupied by glacial ice. At a later period an

escape for the lava was furnished by a fissure or other opening which

admitted of a surface discharge at a more or less distant locality, in a

manner similar to the escape of the molten rocks from the great

volcanoes of the Hawaiian Islands within historic times. This drawing

off of the lava from the crater removed the support afforded its walls

from within, and the summit portion of the mountain, embracing about

three-fourths of its height above the adjacent valleys, fell in

and was engulfed. The mountain was thus truncated, and presents the

general appearance of similar cones the upper portions of which are

known to have been blown away by explosions. But in the case of Mount

Mazama, the hypothesis of truncation by explosion seems to be disproved

by the absence of the fragments of the portion removed on the slopes

remaining or on the surrounding region. After the falling in of the

summit of the mountain comparatively mild volcanic explosions followed

which built a cone within the great pit or _caldera_ in the summit of

the truncated mountain, but without filling it. The space left vacant is

now occupied by water, and thus transformed into a lake. The cone built

after the catastrophe referred to now forms Wizard Island, near the

southwest border of Crater Lake.

Some idea of the magnitude of the changes wrought in Mount Mazama by the

events recorded in its geology and topography may be obtained from the

following facts: Crater Lake has a surface elevation of 6,239 feet above

the sea, and is nearly 2,000 feet deep in its deepest part; the

precipices surrounding it are from 520 to 1,987 feet high. The whole

depth of the depression is therefore 4,000 feet. This _caldera_, as such

basins of volcanic origin are termed, is nearly circular, with an east

and west diameter measuring 6 miles, and a north and south diameter of 5

miles. The volume of the pit is nearly 12 cubic miles.

Not only is Mount Mazama with its wonderful lake one of the most unique

natural features of North America, but it has its full share of the

artistic details of lake and mountain scenery which appeal so forcibly

to the finer instincts within us. The outer slopes of the mountain are

clothed with the all-embracing coniferous forests which cover the

Cascades as with a mantle throughout their entire extent, while the

precipitous inner slopes are for the most part bare precipices of

angular and extremely rugged rock. The lake itself is of the most

marvellous blue, in which the encircling cliffs, the crater-island, and

the sky above are reflected.

[Illustration: FIG. 22.--Mount Rainier, Washington.]

Other peaks along the crest-line of the Cascades to be numbered by the

score, although with less romantic histories than Mount Mazama,

have instructive answers to give when properly questioned. Among the

remarkably picturesque summits rising above the dark coniferous forests

of western Oregon are the following, with their respective heights above

the sea expressed in feet: Mount Pitt, 9,760; Mount Mazama, 8,228; Mount

Union, 7,881; Mount Scott, 7,123; Three Sisters, Mount Jefferson,

10,200; and Mount Hood, 11,225. Of these peaks, the best known, on

account of its proximity to the city of Portland, and at the same time

one of the most picturesque and beautiful, is Mount Hood, situated about

25 miles south of the Columbia River. The concave slopes so

characteristic of volcanic cones are no longer conspicuous on the sides

of this once symmetrical mountain, and only remnants of its crater

remain. The part it played as a safety-valve for the pent-up energy

beneath was long since finished, although heated vapours still escape

from an opening near the summit. Similar manifestations of heat have

also been observed about several other ancient craters in the Cascades,

but these occurrences are not considered as indicating that actual

connections still exist with reservoirs or bodies of molten rocks below

the surface: they are evidently due to the residual heat of the once

molten rock in the conduits of the now extinct or dormant volcanoes.

The lava-flows and volcanic mountains typically displayed in the

Cascades throughout the breadth of Oregon continue northward and form at

least the surface portion of the same range in Washington as far as the

Northern Pacific Railroad, or about 100 miles north of the Columbia. The

more important volcanic mountains in western Washington are, in their

order from south to north; as follows, the height of each being given in

feet: Mount Adams, 9,570; Mount St. Helens, 9,750; Mount Rainier,

14,525; Glacier Peak, 10,436; and Mount Baker, 10,877. Only two of these

ancient volcanoes, namely, Mount Adams and Glacier Peak, are situated on

the crest-line of the Cascade Mountains; the others are to the westward

and more or less completely detached from the main range.

The Cascade Mountains are in general parallel with the shore of the

Pacific, and rise as a prominent barrier athwart the path of the

prevailing westerly winds. Precipitation on their seaward slopes is

copious, but their landward sides overlooking the arid plains of central

Washington are far less humid. The westward, or rainy slope, is clothed

with a magnificent forest of giant trees, while the eastward, or sunny

side, is largely without forests, but abounds in natural meadows and

pastures. Large portions of the mountains are still almost entirely

unknown, and retain their primitive wildness, except that forest fires,

particularly near the international boundary, have in places made

desolate the once beautiful valleys and precipitous slopes. Elk, deer,

bear, the mountain-goat, and mountain-sheep still roam the forests. The

large streams abound in salmon, and each cool, clear brook and rushing

creek is a favourite haunt of the trout. No more delightful

camping-ground for lovers of nature and searchers for recreation can be

found than the grassy, park-like valleys on the sunny side of these

magnificent mountains.

Many of the details in the scenery of the Cascades are due to the work

of ancient glaciers. Numerous lakes, held in rock-basins in the higher

portions of the mountains, and many still larger sheets of water

retained by morainal dams in the lower valleys, give a superlative charm

to many a wild and rugged landscape. The largest and most interesting

lake in the entire Cascade region is Lake Chelan, situated in a deep

valley on the eastern side of the mountains in north-central Washington.

This beautiful sheet of water, a mile or two wide, extending like a

placid river for some 70 miles into the mountains, resembles in many of

its features the far-famed lakes of northern Italy. The mountains

inclosing this hidden gem of the Cascades rise abruptly from the water's

edge to great heights, and with one exception are unbroken by deep

side-valleys. For fully 50 miles the blue plain of water is overshadowed

on each side by crags and precipices from 5,000 to 6,000 or more feet in

height. The lower slopes are dark with forests of pine and fir, and the

bare serrate spires above are white with snow long after the

spring flowers have faded in the lower vales. The water of the lake is

clear and sparkling, and has the deep-blue colour of the open ocean. The

sounding-line has shown a depth of 1,400 feet, and the bottom is about

300 feet below sea-level. This wonderful lake, clasped in the embrace of

the eastward extended arms of the Cascades, is but 2 or 3 miles from the

Columbia River, into which it discharges its surplus waters through

Chelan River, and may be easily reached from Wenachee, on the Great

Northern Railroad, by steamers on the Columbia. Although at present

scarcely known to the world of tourists, Lake Chelan is destined to take

as an important place in the lives of those who seek rest and recreation

as does Lake George in northern New York at the present day.

Before attempting to trace the Pacific mountains northward through

Canada and Alaska, let us glance at the leading geographical features to

the west of the Sierra Nevada-Cascade uplift.

THE GREAT VALLEY OF CALIFORNIA AND THE PUGET SOUND BASIN

To the west of the Sierra Nevada-Cascade Mountains, and bordered on the

west by another and very nearly parallel series of elevations, known in

a general way as the Coast Mountains, there is a succession of long,

relatively narrow basins, situated end to end, and constituting what may

be termed a valley-chain. This series of basins extends from southern

California northward far into Canada, and includes, in their order from

south to north, the great Valley of California, the Willamette and

Cowlitz Valleys in Oregon and Washington, and the Puget Sound basin,

together with its great but indefinitely defined northward extension.

The Great Valley of California has a length of about 500 miles and an

average width of approximately 40 miles, and is greater in area than

either Belgium, Denmark, or Switzerland. It is divided in reference to

drainage into two portions, the San Joaquin Valley at the south and the

Sacramento Valley at the north, named respectively after the

rivers that drain them. These two streams unite and discharge into San

Francisco Bay, the outlet of which is through the Golden Gate to the

Pacific. This central basin of California has a generally flat bottom

composed of a great depth of unconsolidated gravel, sand, and clay,

which are believed to owe their deposition mainly to the streams flowing

from the bordering mountains, although in part they may have been

deposited when the land was more depressed than now and the basin was a

great sound, connected with the ocean by a single narrow opening. The

rock-waste swept into the valley served not only to add to the

accumulations forming its floor, but to give the bottom some

irregularities. A portion of its southern end, shut off by alluvial

deposits brought down from the Sierra Nevada, is occupied by the shallow

alkaline waters of Tulare Lake. When the great valley was first visited

by white men it was without trees, except along the immediate borders of

some of the streams, and for the most part was a luxuriant meadow of

wild grasses and flowers. On the uplands oak-trees grew in scattered

park-like groves with gorgeously flower-decked hills and vales between.

This favoured land, clothed in its natural beauties, came as near being

an Eden as perhaps any portion of the continent. The changes that have

followed the settlement and cultivation of this great mountain-inclosed

basin are simply marvellous. Cities and villages have been built,

orchards and vineyards planted which yield most bountiful harvests, and

the once grass-covered plains are now seemingly boundless wheat-fields.

The unkept natural garden of half a century ago has become a granary not

only for the people of America, but for those of Asia as well.

To the north of the Klamath Mountains, which shut in the central Valley

of California at the north, lies the beautiful Willamette Valley, about

150 miles long, drained by the northward-flowing river of the same name,

which joins the Columbia where the thriving city of Portland now stands.

The depression between the mountains of which the Valley of the

Willamette forms a part, extends north of the Columbia, and is there

drained by the southward-flowing Cowlitz River. The relation of

these two valleys is much the same, although on a smaller scale, as that

existing between the San Joaquin and Sacramento Valleys, except that the

Columbia, after passing through the Cascade Mountains, receives the

Willamette and Cowlitz rivers as tributaries, one from each side of its

course. This Willamette-Cowlitz depression is surrounded by densely

forested hills and the snow-capped summits of ancient volcanoes. The

soil was originally highly fertile, and although now somewhat

impoverished, still furnishes a substantial basis for agriculture, and

renders the region one of the most productive as well as most beautiful

in the United States.

To the geographer the Willamette-Cowlitz Valley seems scarcely distinct

from the great depression farther north in the same valley-chain, which

now holds the waters of Puget Sound, except that there is a low

water-parting between. This divide, as previously suggested, is thought

to be due largely to stream and glacial deposits, which have been laid

down in the previously nearly level-floored intermontane trough.

The Puget Sound basin has a length from south to north of about 150

miles, and extends from the Olympic Mountains on the west to the Cascade

Mountains on the east, a distance of some 60 miles. The sound terminates

at the north at the Strait of Fuca (at Port Townsend, in Fig. 23), but

the depression in which it lies continues northward, with similar

geographical and geological characteristics. In a general way the same

depression may be said to extend northward to southeastern Alaska, but

is there deeply water-filled, and its western border is discontinuous

and broken into many islands.

There are several features in the Puget Sound basin which especially

impress the traveller: Next to the magnificence of the lofty volcanic

cones that stand like Titan watch-towers along the western slope of the

Cascades and the dense forest of gigantic firs and cedars, the most

conspicuous feature of the region is the extreme irregularity of the

sound itself. Even such general maps of Puget Sound as are

usually available indicate that it is exceptional and different from all

other water bodies on the continent, not including the extension of the

same series of basins northward. Not only is Puget Sound extremely

irregular, and inconsistent with any theory that would ascribe its

origin to the subsistence and drowning of stream-eroded valleys, but its

waters are deep and the channels narrow. The uplands between the

waterways are low plateaus composed of clay, gravel, and glacial

moraines. The explanation of these unique conditions is that glacial ice

formerly occupied the basin and deposited moraines and gravel-plains and

clay-plains about its margins; when the branching and irregular sheet of

stagnant ice melted its place was taken by the waters of the sea. This

simplified outline of the later history of Puget Sound has many

modifications, the most important being that there were at least two

periods of ice occupation, with an intervening stage of mild climate

between, during which the previously formed glacial deposits were forest

covered and thick beds of peat formed.

[Illustration: FIG. 23.--Puget Sound.]

The ice which occupied Puget Sound was the extreme southern portion of a

great but irregular Piedmont glacier which fringed the rough and ragged

coast of the continent all the way to southern Alaska. A remnant of this

former ice body still exists near Mount St. Elias, and constitutes the

very instructive Malaspina glacier.

THE MOUNTAINS BORDERING THE PACIFIC

In a preceding chapter the rugged topography of the western margin of

the continent has been briefly described, and a general explanation

given of the contrasts which it presents to the coastal plains and

plateaus on the Atlantic border.

The long, narrow peninsula known as Lower California, as yet unstudied

in the light of modern geography, is known to be mountainous throughout.

Although nearly surrounded by the waters of the ocean, the climate of

the peninsula is hot and arid and its surface desert-like. The Gulf of

California, which separates such a large portion of the Pacific border

of Mexico from the main body of the republic, has the characteristics of

a drowned intermontane or orogenic valley. But whether the great

depression was ever dry land or not is unknown. The waters of the gulf

are shallow, however, and a moderate upward movement of the earth's

crust in that region would transform it into a great valley similar in

its general features to the central basin of the State of California.

What are frequently designated collectively as the Coast Mountains begin

at the south and adjacent to the shore of the Pacific, in the vicinity

of Santa Barbara, Cal., and extend northward along the immediate

seaboard far into British Columbia. A continuation or branch of this

series of elevations follows the south coast of Alaska, and is prolonged

so as to form the Aleutian Islands. The length of the mountain system or

succession of ranges referred to is between 3,500 and 4,000 miles. The

detailed study of this long, narrow, and in many parts excessively

rugged region is as yet in its infancy, and only a brief account of its

salient features can be attempted at present.

In southern California the structure of the mountains and the deep

stream-deposited gravel, etc., in the intervening valleys, as well as

the aridity of the climate and character of the vegetation, correspond

closely with the similar conditions in the Great Basin. In fact, the

Great Basin region, as the term has been used on a previous page, there

meets the Pacific, and the islands rising from the adjacent

portion of the ocean seem to be the summits of mountains of the Basin

Range type. Owing to the dryness of the climate in southern California

and adjacent portions of Mexico, the deeply alluvial-filled valleys are

treeless, and agriculture is only possible with the aid of irrigation.

Where water can be had, however, there are wonderfully productive

orchards, vineyards, and gardens, in which the fruits and flowers of

both the temperate and torrid zones flourish side by side with

marvellous luxuriance. The palm there casts its shadow on fragrant

bowers of the most superb roses. The grass-clothed mountain slopes are

either bare of trees or but scantily forested, while the upland valleys

produce a dense jungle of native trees and shrubs.

To the north of the irregular and diversified portion of southern

California, where the Great Basin region extends southwestward to the

Pacific, rises the southern Coast Range of California. The indefinite

beginning of this range is in the neighbourhood of Point Conception, to

the north of Santa Barbara, and its northern terminus is at the Golden

Gate. The same belt of mountains extends northward, however, and forms

the northern Coast Range, which extends to the Klamath Mountains in

northern California. The coast ranges of California as a whole are about

500 miles long and from 30 to 40 miles broad, and comprise several

seemingly distinct uplifts, some of which have culminating peaks from

4,000 to about 7,000 feet high. In general this elevated region is

conspicuously sculptured, and in part at least has the characteristics

of an eroded plateau. The suggestion has been offered that the northern

portion of the Coast Range is a dissected peneplain.

The Coast Ranges, although generally bare of trees to the south of the

Golden Gate, become more and more densely forested when followed

northward. It is in this northern division that the great forests of

redwood occur, now so largely used for lumber. Reference is here made

not to the "big trees," which grow in certain restricted areas on the

west slope of the Sierra Nevada, but to the far more extensive forests

of a related species.

Considering mountain forms simply, it is difficult if not impossible to

determine where the Coast Mountains of California terminate at the

north, but, as has been shown especially by J. S. Diller, there are

reasons based on geological structure for separating them from the

irregular group of ranges and peaks in northern California and southern

Oregon recently named the Klamath Mountains. The coast system is

continued north of the Klamath Mountains by the Coast Mountains of

Oregon, which extend to the Columbia River, and consist of irregular

ridges or series of ridges, with bold lateral spurs, especially on the

ocean side. It varies conspicuously in height from place to place, yet

nowhere attains a great altitude. The elevations of the bolder summits,

although not accurately measured, seldom exceed 3,000 feet.

The Coast Mountains of Oregon are considered as terminating at the

northern boundary of the State, there defined by the Columbia River, but

no reason is apparent, however, for not including in the same group the

elevated land lying in southwestern Washington and adjacent to the

Pacific coast. Between the Columbia and Chehalis River in Washington

there is a rugged region which attains an elevation of over 4,000 feet,

and is separated from the Olympic Mountains to the northward by Chehalis

Valley. Although the geology of this group of ridges and peaks is

entirely unknown, its position and general appearance, when seen from a

distance, suggest that it might properly be considered as a direct

extension of the Coast Mountains of Oregon.

Following the general belt of the Coast Ranges still farther northward,

we come to the splendid group of forest-clothed mountains, with usually

snow-covered summits, situated to the west of Puget Sound, and known as

the Olympic Mountains. This magnificent range is in full view from

Victoria, Seattle, and Tacoma, and would be far-famed for its grandeur

were it not for its near rival, the still more lofty Cascade Range.

There are several fine, sharp peaks in the Olympics that have never been

scaled, the highest of which, Mount Olympus, rises 8,150 feet

above the sea. Owing to the excessive humidity and other favourable

climatic conditions, these mountains are clothed with magnificent

forests up to an elevation of about 7,000 feet. On account of the

ruggedness of the country, the extreme density of the tangled

undergrowth, and the obstructions formed by the fallen moss- and

lichen-covered trees, this region is extremely difficult to traverse,

and to-day is the least known of the continental portion of the United

States. On the north the excessively rugged Olympic peninsula is

bordered by a deep, broad fiord known as the Strait of Fuca. To the

north of this formerly ice-filled channel lies Vancouver Island, the

central and northern portion of which is mountainous. The highest summit

on the island rises about 7,500 feet above the sea, and a considerable

area in its central part has an elevation of over 2,000 feet.

The Olympics, together with the mountains of Vancouver and Queen

Charlotte Islands, and the northern extension of the same belt, embraced

in part within the mainland of British Columbia and southeastern Alaska,

have been termed the "Vancouver Mountains" by Canadian geographers. The

northern boundary of this mountain system, justly named in honour of the

celebrated English explorer who mapped large portions of the northwest

coast about a century since, remains indefinite, and cannot be

determined until geologists have made more thorough explorations of the

land it occupies. The leading geographical features of this region, as

remarked in a preceding chapter, are due to the deep dissection, by

streams and glaciers, of an elevated table-land. When the ice-streams

melted, the sea was permitted to enter the valleys, so as to form

numerous deep, narrow, steep-walled fiords (Fig. 11). The coast is, in

fact, the most ragged of any portion of the border of the continent. All

but the higher summits are clothed with a dense mantle of vegetation,

the upper limit of which decreases in elevation when followed northward,

from about 7,000 feet in the Olympics to approximately 2,500 feet in

southern Alaska. Perennial snow exists in the higher valleys and

amphitheatres of the Olympics, but the presence of true glaciers

in that group of peaks has not been demonstrated. When followed

northward the snow-line becomes lower and lower, and well-defined alpine

glaciers are known to exist in many of the valleys, more especially on

the mainland of British Columbia and southeastern Alaska. There streams

of ice descend lower and lower with increase in latitude, and to the

north of Stickeen River, in a number of instances, enter the fiords

which connect with the ocean and become tide-water glaciers.

To the west of Lynn Canal, and extending to beyond Copper River, is the

most rugged portion of North America, and contains also some of the

highest mountain-peaks on the continent thus far measured.

The region of high mountains in Alaska and the adjacent portion of

Canada begins on the east in the group of magnificent peaks which

cluster about Mount Fairweather as a centre and extend westward, with a

breadth of some 80 miles, to beyond Mount St. Elias. Farther westward,

beyond Copper River, other great mountains are known to exist. One of

these, Mount McKinley, has an elevation of 20,400 feet, and so far as

now known is the highest peak in North America.

The highest summit to the east of Copper River is Mount Logan, 19,500

feet. This superb ice-sheathed peak is situated in Canada about 40 miles

from the coast and 12 miles east of the one hundred and forty-first

meridian. Second in rank is Mount St. Elias, 18,070 feet, situated close

to the one hundred and forty-first meridian, and within the territory

belonging to the United States. These two summits are the highest in a

land of lofty snow-covered mountains, and for this reason have claimed a

large share of attention. There are many neighbouring peaks, however,

that are wonderfully magnificent, but only a few of them have been

measured and many of them are still unnamed. Only one of the high

mountains of Alaska, namely, Mount St. Elias, has been climbed. This

splendid feat of mountaineering was accomplished by Prince Luigi, of

Savoy, in 1899.

In southern Alaska the snow-line is only about 2,500 feet above

tide, and a large number of magnificent glaciers descend to sea-level,

and many of them actually enter the ocean. All of the valleys and basins

among the higher summits are occupied by snow-fields and glaciers. The

general covering of ice and snow as well as the ruggedness of the land

makes this the most difficult of all the mountainous portions of North

America to traverse.

In the St. Elias region the mountains have been produced by upheaval,

and are not volcanic in their origin. The frequently repeated statement

that Mount St. Elias is a volcano is incorrect. Although igneous rocks

occur near its summit, they are of the nature of dikes or intrusions,

probably of ancient date, and not lava-flows. The principal volcanic

mountains of Alaska are farther west in the region of the Alaskan

peninsula and the Aleutian Islands. This western extension of the

continent is excessively rugged, but the mountains rise directly from

the ocean and in part form a chain of precipitous islands with irregular

topographic forms.

There are mountain ranges also in the central and northern portions of

Alaska and the adjacent part of Canada, but this region awaits

exploration, and but little accurate information concerning its

topography is on record.

_The Mountains of Western Canada._--Reference has already been made to

the differences in the nomenclature applied to the portions of the

Pacific mountains on opposite sides of the United States-Canadian

boundary, and at present this lack of harmony cannot be adjusted. As is

well known, the great Pacific cordillera crosses the boundary nearly at

right angles, and there is no abrupt change in the topography of the

land. From the western border of the Great plateaus to the Pacific,

between the forty-fifth and fifty-sixth parallels, as stated by the

Geological Survey of Canada, the cordillera has an average breadth of

about 400 miles, and is composed of four great mountain chains, named in

their order from east to west, the Rocky, Gold, Coast, and Vancouver

Mountains. These four great chains are nearly parallel and have

irregular northwest and southeast trends.

The Canadian Rockies rise abruptly from Great plateaus in which the

rocks are nearly horizontal, and have a complex structure, due to the

folding and other disturbances that have affected the strata. Deep

dissection by stream erosion has occurred, as is the case generally

throughout the Pacific cordillera, and the peaks and ridges remaining

are remarkable for their grandeur. Although less elevated than the

higher portions of the same great belt in the United States, many of the

summits are from 8,000 to 10,000, and, as reported, in a few instances

reach 13,000 feet in height, while the passes range is elevated from

about 4,000 to 7,000 feet. The western border of the Rocky Mountain

range is well defined for a distance of some 700 miles to the northward

of the international boundary by a remarkably straight, wide valley,

which is occupied by the head waters of several large rivers, namely,

the Kootenay, Columbia, Fraser, Parsnip, and Findley. To the west of the

great valley just referred to rises the Gold system, composed

principally of the Selkirk, Purcell, Columbia, and Caribou Ranges. It is

in this rugged region that some of the most remarkable of the splendid

scenery of western Canada occurs.

To the west of the Gold system is a broad region of valleys and lesser

mountains, known as the interior plateau of British Columbia, which is a

northward extension of the Great Basin region of the United States. The

breadth of this belt of comparatively low country is about 100 miles.

Like the similar region in Washington and Oregon, it is without forests,

but favourable as a grazing country. In part it is occupied by extensive

lava-flows, similar to the Columbia River lava of the northwestern part

of the United States.

The Coast Mountains of Canada, although stated by geologists to be

distinct from the Cascade Mountains, are in part at least, as determined

by the present writer, a direct northward extension of that range. The

average elevation of the higher peaks in the Canadian Coast Range, as it

is termed, is between 6,000 and 7,000 feet, while the culminating points

reach an elevation of about 9,000 feet. How far northward the

nomenclature applied to the Pacific mountains in southwestern Canada

will be found applicable can not be stated, as the region to the north

of the fifty-sixth parallel is almost wholly unknown.

THE ANTILLEAN MOUNTAINS

As has been clearly pointed out by R. T. Hill, the Pacific cordillera

ends at the south in south-central Mexico, while the Andean cordillera

at its northern end terminates in the rugged mountains of Venezuela to

the south of the Caribbean Sea. These two great cordilleras do not

overlap, but there is a difference of about 10 degrees of latitude

between them, and if extended they would pass each other at a distance

of nearly 1,000 miles. In the space thus indicated, measuring some

600,000 square miles, is included the southern portion of Mexico,

Central America, and the West Indies. The rocks in these countries

present a great series of folds which trend in an easterly and westerly

direction, and thus present a conspicuous exception to the major

structural features of both North and South America. To this newly

recognised division of the larger geological and geographical

characteristics of the New World the name _Antillean mountains_ has been

given.

The folds or corrugations in the rocks of the Central American and

Caribbean region extend in an east and west direction along the seaward

margin of Venezuela and Colombia from the Orinoco westward to the

Isthmus of Panama, and thence continue westward through Costa Rica, the

eastern portions of Nicaragua, Guatemala, and Honduras, and reach

southern Oaxaca in Mexico. The same system of plications is revealed

also on the larger West India islands. The rocks of this great region

include granite and allied metamorphosed terranes, old lavas, and

sedimentary beds.

One of the most conspicuous features of this region with a structure and

relief commonly found in mountains is that to a great extent it is

depressed beneath the sea, and only the higher summits are in view. Some

of the larger inequalities of the rock surface have been

discovered by means of the sounding-line. By referring to Fig. 3, it

will be seen that two submarine ridges extend in an east and west

direction beneath the Caribbean Sea, from the West Indies to the Central

American coast, and are separated by Bartlett Deep. These ridges

correspond in trend with the longer axes of the folds in the Antillean

mountains, and suggest a common origin for the leading geographical

features of the land and of the still more remarkable topography of the

sea-floor.

In addition to mountains produced by corrugation and upheaval, there are

also in the middle American region numerous volcanic mountains. Of these

there are two well-defined belts, each trending in general north and

south, or directly across the longer axes of the folds of the Antillean

mountains. One of these belts of volcanic cones and craters is situated

on the Pacific coast of Central America and Mexico, and includes some 25

active volcanoes, and the other is defined by the numerous volcanic

islands of the Lesser Antilles. The association of these belts of

fracture through which molten rock has been extruded and where

earthquakes are of common occurrence, with the junction of the east and

west belt of plication to which the Antillean mountains are due, with

the north and south belts of mountains forming the Pacific and Andean

cordilleras, is significant in connection with the study of the origin

of the larger features of the relief of the solid earth.

* * * * *

Varied as is the relief of North America when studied in detail, an

outline sketch of its major features may be readily retained in mind. On

the east side of the main continental area are the Atlantic mountains,

extending from near the Gulf coast northward to beyond Hudson Strait; in

the central part is the broad continental basin, a vast region of low

relief reaching from the Gulf of Mexico to the Arctic Ocean; west of the

continental basin are the Pacific mountains, the greatest of all the

elevations on the continent, which begin abruptly in south-central

Mexico and extend northward, expanding to a width of about 1,000

miles in the United States and reach the Arctic Ocean and Bering Sea.

The movements in the earth's crust, which blocked out these major

physiographic features, were produced by forces acting in east and west

directions, and gave origin to folds and faults with their longer axes

trending north and south. To the south of the main body of the

continent, in middle America, are situated the Antillean mountains, also

a cordillera comparable with the Atlantic and Pacific cordilleras, in

which the longer axes of the folds and faults trend east and west, and

are due to forces acting in north and south directions. The Antillean

mountains in a general way connect or intervene between the Pacific and

the Andean cordilleras. Where the Antillean mountains cross the axes of

the Pacific and Andean cordilleras are situated the volcanoes of

southern Mexico and Central America, and those of the Lesser Antilles.

Geographers will recognise that this outline is drawn boldly, but

although it will no doubt have to be modified as detailed studies

progress, it should serve to emphasize the leading geographic divisions

of the North American continent when viewed as a whole.

LITERATURE

The following list of publications relating to the physiography of North

America is here presented largely because the books mentioned contain

bibliographies or references which indicate sources of more special

information:

_American Geographical Society, Bulletin._ Published annually.

_Canadian Geological Survey_, Ottawa, Canada. Index to reports

from 1863 to 1884, published in 1900.

DARTON, N. H. _Catalogue and Index of Contributions to North

American Geology, 1732 to 1891._ United States Geological

Survey, Bulletin No. 127, Washington, 1896.

DAVIS, W. M. _Physical Geography._ Ginn & Co., Boston, 1898.

Contains a valuable bibliography.

DRYER, C. R. _Lessons in Physical Geography._ American Book

Company, New York, 1901. Contains a valuable bibliography.

_Geological Society of America, Bulletin._ Published annually

since 1890 at Rochester, N. Y. Index to vols. i-x, published in

1900.

_International Geography._ Edited by H. R. Mill. D. Appleton and

Company, New York, 1900. Contains several chapters on North

America by various authors.

_Journal of Geology._ Edited by T. C. Chamberlin and published at

the University of Chicago, Chicago, Ill.

MERRILL, G. P. _Rocks, Rock-Weathering, and Soils._ The Macmillan

Company, New York, 1897.

_National Geographic Magazine._ Washington, D. C.

_National Geographic Monographs._ American Book Company, New York,

1895. One volume published.

POWELL, J. W. _Exploration of the Colorado River of the West._

Published by the Smithsonian Institution, Washington, 1875.

POWELL, J. W. _Canyons of the Colorado._ Flood & Vincent,

Meadeville, Pa., 1895.

RUSSELL, I. C. _Lakes of North America_, Ginn & Co., Boston, 1895;

_Glaciers of North America_, Ginn & Co., Boston, 1897;

_Volcanoes of North America_, The Macmillan Company, New York,

1897; _Rivers of North America_, Putnam's Sons, New York, 1898;

_The Names of the Larger Geographical Features of North

America_, in _Bulletin of the Geographical Society of

Philadelphia_, vol. ii, 1899, pp. 55-68.

SHALER, N. S. _Nature and Man in America._ Scribner's Sons, New

York, 1891.

_Stanford's Compendium of Geography and Travel._ North America:

Canada and Newfoundland, by S. E. Dawson; United States, by H.

Gannett; Central America and West Indies, by A. H. Keane.

Published by Edward Stanford, London.

TARR, R. S. _Elementary Physical Geography._ Macmillan & Co.,

1895.

_United States Geological Survey._ Bibliography and Index,

contained in Bulletins No. 100, 127, 177, 188, and 189, issued

by the Survey. The reader is referred especially to the

_Geological Atlas_ and the _Topographic Atlas_, published by the

Survey.

WARMAN, P. C. _Bibliography and Index to the Publications of the

United States Geological Survey._ United States Geological

Survey, Bulletin No. 100, Washington, 1893. (Relates to

publications of the United States Geological Survey issued

previous to 1892; continued in Bulletin No. 177 by the same

author.)

WARMAN, P. C. _Catalogue and Index of the Publications of the

United States Geological Survey, 1880 to 1901._ United States

Geological Survey, Bulletin No. 177, Washington, 1901.

WEEKS, F. B. _Bibliography of North American Geology,

Paleontology, Petrology, and Mineralogy for the Years 1892-1900,

inclusive._ United States Geological Survey, Bulletins No. 188

and 189, Washington, 1902.

WHITNEY, J. D. _The United States._ 2 vols. Little, Brown & Co.,

Boston, 1889 and 1894.