in the Cumberland Plateau. Missionary Ridge, one of the high longitudinal ridges in the valley, is parallel to the Tennessee River and passes a short distance to the east of the city. Its position makes it a vital part of the military key of this region, and caused it to be one of the most fiercely contested battle grounds of the Civil War. Lookout Mountain at the southern edge of the city rises 1500 feet above the river, and from its summit, which is reached by an incline railroad, a wonderful panoramic view of the Great Valley, Walden Ridge and the Unakas is obtained. Chattanooga lies in the heart of the coal regions with iron ore and limestone. Its chief manufacturing interests are concerned with assembling these raw materials and producing foundry and machine shop products. The richness of mineral deposits, their occurrence in such favorable conditions for mining and the minimum of transportation required are factors which will give this region great advantage in the future expansion of its iron ore industry. Chattanooga is near the center of the best hardwood timber of the South. Furniture factories, coffin works, box factories, wagon works, hardwood finish shops, and cooperage plants constitute some of the wood working industries which rank third in the city. Other important lines of industry are flour milling, food products, brewing, and tanning.

Knoxville is in the center of the Valley of East Tennessee; it was formerly the capital of the state and its position at the head of the Tennessee River and near the junction of the Holstein and French Broad rivers gave it importance in early river traffic. Its chief industries are the quarrying and preparation of marble for the market. The surrounding land is well adapted to farming and truck gardening. Early vegetables are raised in large quantities for the northern markets.

DIAGRAM-MAP OF WESTERN WAR ZONE

The March issue of the Bulletin of the American Geographical Society contains an article on "Geographic Aspects of the War," by Professor D. W. Johnson, illustrated by a block diagram of the western war zone. The topographic peculiarities of the Vosges and Ardennes Mountains, the plateau of western Germany cut by the gorges of the Rhine, Meuse and Moselle rivers, the cuesta escarpments of north-eastern France, and the principal valleys which have affected the campaign, are clearly represented. With the aid of this bird's-eye view of the entire western theatre of war one can readily trace the positions of the contending armies, and note many striking examples of the influence of landforms upon detailed movements of armies and general plans of campaign. Enlarged copies of the drawing, size about 29x17 inches, can be secured at a cost of fifty cents each by writing to the Columbia University. Bookstore, New York City.

THE CASCADE MOUNTAINS*

By Minna J. Telker

University of Cincinnati

LOCATION, EXTENT, ETC.

N the western part of the Pacific States, trending parallel with the coast and extending from northern California northward beyond the United States-Canadian boundary, there is a lofty and extremely rugged belt of mountains known as the Cascade Range. The belt attains its greatest width, 100 miles, near the international boundary, and from there southward its east-west extent varies between 25 and 75 miles.

Until recent years, the term "Cascades" was applicable only as far south as the Oregon border. The Lassen Peak Ridge of northern California was then considered the northern termination of the Sierra Nevadas. Recent study has shown, however, that this ridge consists entirely of volcanic material, and therefore presents a marked contrast to the Sierras both in its rocks and in its manner of growth; while its volcanic origin is accepted as evidence that it should be considered the southern extension of the Cascades, noted for their immense development of igneous rocks.

Southern Cascades distinguished.-The mountains of the two northern states, as will be noted in the following pages, owe their existence primarily to uplift and dissection, while in the development of the Lassen Peak Ridge, uplift has played but a minor part. The piling up of lava and other ejecta about more than a hundred volcanic vents has given rise to this ridge. Owing to this great difference in the physiographic history of the two parts of the range, it is deemed best to consider them separately, and therefore, in this article, only that part of the range lying in Washington and Oregon and commonly known as the Cascades will be the subject of discussion.

TOPOGRAPHIC DESCRIPTIONS

Characteristic features.—Before going into detail concerning the history of this portion of the range and the forces to which it owes its existence, let us consider briefly the general topographic features that gradually suggest themselves upon crossing the mountainous tract and viewing the mountains from the summits of a number of peaks. At first the range seems "a puzzling complex of ridges and peaks," (I. C. Russell) but soon one is impressed with the general uniformity of altitude. One soon realizes that the Cascades are not a sharp-crested uplift, but a deeply dissected plateau, and that the sharp divide, which parts the eastward and westward flowing streams, is due to the headwater extension of the opposite flowing rivers.

Summary description. For a generalized view of the northern and central Cascades, therefore, it is well to hold in mind as the leading topographic

*Prepared under the direction of Professor N. M. Fenneman.

feature an elongated, flat-topped dome, about 600 miles long, 40 to 100 miles wide, 8500 feet high near the international boundary, declining gradually to about 4000 feet near the Oregon border, its gently sloping sides merging with the lower regions adjacent on the east and west, its borders crenulated, and its summit crowned with a long line of volcanic peaks, all so completely dissected and sculptured by river and ice, as to produce the most beautiful mountain scenery the continent affords.

Northern subranges described.-The wildest and most picturesque scenery of the Cascade Mountains is found in the triple set of subranges in which the range terminates on the north. Here the mountains reach their greatest development. They rise to uniform elevations of 8500 to 9000 feet, into the region of perennial snows. The scenery is typically Alpine. The deep and complete dissection of these subranges is due to the rapid descent of the streams that leave the crest, and which, throughout the greater part of their length, flow through deep canyons, which at many places are so narrow as to barely permit the passage of the streams. Precipitous slopes prevail everywhere and much of the region is impassable even to prospectors. Between the canyons stand the sharp, serrate ridges with their high, jagged, pyramidal peaks. These "Matterhorn" peaks are the result not of stream erosion, but of the headward extension of the glaciers whose remnants, even now, linger in protected spots.

The main range.-The same rugged topography found along the northern border is continued in the main range and in the higher portions of the subranges found along the border as far south as Wenatchee. (Lat. 47°30′). These ridges represent secondary elevations whose trend is almost at right angles to the main range. Altitudes here vary from 4000 to 8000 feet. In the higher parts, dissection has attained maturity. The valleys are deep and canyon-like and the divides narrow. Sharp peaks and pinnacles, steep slopes ending in glacial amphitheatres, still occupied by glaciers, and wild, cascading streams are characteristic of this section of the range.

The southern half.-Farther to the south, the topography becomes more subdued. Elevations of 5000 to 6000 feet are reached near the divide, but out upon the flanks of the range, they rarely exceed 3000 feet. On the higher slopes, near the crest of the main range, where precipitation is comparatively great, erosion has been active and has produced rugged mountains, but out near the borders, where uplift was not so great and precipitation scanty, the ridges are broad and featureless in detail. The gulches that score the sides are barely noticeable in general view. The long, gentle slopes present an almost unbroken sweep from the broad, even-topped crests to the adjacent valley floors. Such scenery is typical of the east side of the Cascades in Oregon.

HISTORY

Geologic history.-The history of this great mountain range is an interesting one. Its birth probably dates back far in geologic history. The

events of greatest interest, however, occurred in comparatively recent geologic times and began with the great eruptions which completely covered northern California, with most of Oregon and Washington (as far north as the parallel 47°30′) with a series of lava sheets averaging, perhaps, 2000 feet in thickness. This period of igneous activity and base-leveling seems to have been. followed by an epoch in which the lava sheets together with the region of older rocks north of the above mentioned parallel were uplifted, and it is to these mountain building movements that the Cascades owe their present elevation.

Character of uplift.-As has been noted, this uplift was not of a broad, general nature, resulting in a great, flat-topped anticline with gentle slopes, but was effected with local warpings along the margin, which resulted in the series of parallel ridges found along its borders. This complex warping was no doubt occasioned by north-south and east-west pressure brought to bear simultaneously upon the great block of the earth's crust involved.

River history.-Evidence that the main drainage lines of the region were established previous to the initiation of the present relief, is abundant. In Washington the Yakima River crosses not one, but several of the high, eastern subranges, in a deep canyon in which the original meanders of the stream are well preserved. The Skagit River crosses the higher portion of the main range near the Canadian boundary in one of the narrowest, deepest and wildest canyons of the continent, while the Columbia has not only maintained its course across the eastern subranges, but has cut its way through the Cascade Range cleaving it from summit to sealevel. The Frazer River of British Columbia and the Pitt River of northern California also pierce the main range on their way to the sea. That the courses of these streams were established upon the Cascade lowland cannot be doubted. Not only do they furnish conclusive evidence of the lowland ancestry of the Cascades, but they throw an important light upon the rate of uplift, showing that warping must have been effected at a rate which permitted these master streams to maintain their courses without change.

Partial cycles. For a complete understanding of the sculpturing of the Cascades of today from this great, diastrophic plateau, it is necessary to trace, briefly, the various stages of its topographic development. Uplift inaugurated a new cycle of erosion, gave opportunity for new streams to form and intrench themselves. That warping was arrested and halted for a long period is indicated by the broad, open valleys with rounded intervening ridges produced during this time. This was followed by a renewal of uplift, upon which the streams, now rejuvenated, began cutting their channels deep into the uplifted mass. The canyons to which the Cascades owe their wild, rugged and picturesque beauty were carved during this epoch. The relative position of the features produced during these early stages can be seen very clearly in the Columbia Valley just north of Wenatchee. Here the valley consists of two

parts, a deep, inner canyon and a broad outer valley, which opens gradually onto the old plateau surface, above which rise the residual hills or monadnocks.

Glacial period.-The canyon cutting stage was brought to a close by a great climatic change which led to vast accumulations of snow in this region. There is abundant evidence that great glaciers formed in the elevated plateau region of the Cascades, from whence they flowed eastward and westward through previously excavated valleys. Though of great size, these were truly Alpine glaciers. The sharp peaks, the hundreds of amphitheatres with their precipitous walls, the many lakes, the U-shaped valleys, the deserted stream channels or coulees, the moraines, all are the result of this ice invasion.

Perhaps the most noteworthy feature in this connection is Lake Chelan, a narrow river-like sheet of water, 65 miles long, located on the east side of the Cascades in northern Washington. This lake is situated in the heart of the highest mountains and is fed by the glaciers lingering on their slopes. At its northern limit it is barely 2 miles wide and for many miles southward steeply sloping walls 5000 to 6000 feet high rise abruptly from the clear blue waters. Farther south, its width increases to three miles and the landscape becomes more subdued. Its surface is only 1079 feet above sea level, yet soundings have revealed depths of 1419 feet, showing that in such places the bed of the lake is 340 feet below sea level.

It is believed that in pre-glacial times, this great gash in the earth was a stream canyon of ordinary depth. Glacial effects in this vicinity testify that ice from an area of about 350 square miles, found its way into this narrow valley. It is to the concentration and corrosive action of this ice, known to have attained a thickness of 1000 to 5000 feet, that the marvelous depth of the valley is attributed.

As this glacier slowly melted back it left a terminal moraine across the entrance of the valley where Chelan City now stands. With its retreat came the gradual expansion of the lake, which now occupies the Chelan Valley.

Volcanic peaks. In addition to the leading topographic feature due to uplift and dissection, there are the prominent individual ice-capped peaks that rise far above the dark, coniferous forests and add so much to the scenery of this region. Some of these, like Mt. Stuart, are monadnocks, remnants upon an older topographic surface, but the long line of individual peaks found along the summit of the range is of volcanic origin. Enumerating them in order from north to south the principal ones are: Mt. Baker, 10877 ft.; Glacier Peak, 10436 ft.; Mt. Rainier, 14525 ft.; Mt. St. Helens, 9750 ft.; Mt. Adams, 9570 ft., in Washington, and Mt. Hood, 11225 ft., Mt. Jefferson, 10220 ft., Mt. Mazama, 8220 ft., and Mt. Pitt, 9760 ft., in Oregon. These peaks, it is thought came into existence after the time of uplift, and are therefore, of later date than the range itself. All were built by the accumulation of viscous lavas, volcanic ash and other ejecta about old centers of volcanic disturbance.