The Western or Pacific System forms a part of the vast elevation which extends from the northern to the southern extremity of the western continent. In the United States it is a great plateau of four thousand to ten thousand feet surmounted by a complex system of ranges, in its widest part more than one thousand miles broad. Of this Cordilleran region the Rocky Mountains form the eastern and the Sierra Nevada and Cascade Mountains and the Coast Ranges the western border.
In the ranges of central Colorado alone nearly forty of the summits have an altitude of more than fourteen thousand feet. In the Wind River Mountains, in Wyoming, are the head-waters of the Colorado, the Columbia, and the Mississippi, the three great river-systems of the United States; and in the northwestern corner of the same state is situated the National Park, famous for its hot springs and geysers as well as for its magnificent scenery (see [Yellowstone]).
Between the Wahsatch Range and the lofty masses of mountains in Colorado is a region of peculiar interest, consisting of level plateaus in which the changes of elevation from one plain to another are marked by abrupt descents and steep cliffs. It is furrowed by cañons or gorges, whose sides are nearly vertical; and the bed of the Colorado is in some places more than a mile and a quarter below the surface of the plateau. (See [Grand Cañon] under [Colorado River].)
Between the Wahsatch Range and the Sierra Nevada lies the Great Basin, an immense tract having at best but little rainfall, except upon the summits of the ranges by which it is traversed, and none of whose waters are drained to either ocean. The saline swamps, salt lakes, and sinks of Nevada indicate the former location of one of these lakes; Great Salt Lake is all that now remains of the other.
The Sierra Nevada and the Cascade Range are topographically continuous, and constitute a great mountain-wall, which so far as the height of the peaks and the grandeur of the scenery are concerned, is one of the most striking portions of the Cordilleran system. Most of the peaks of the Sierras are, however, of granite and metamorphic rock, while those of the Cascade Range are volcanic. The greatest altitude is attained with Mt. Whitney as the culminating point. The lofty character of the range is maintained throughout the greater part of California, and the sublimity of the scenery is justly celebrated. (See [Yosemite Valley].)
From this point there extends northward one of the most remarkable groups of extinct or faintly active volcanoes to be found anywhere in the world: the lava overflows in this region cover an area of above two hundred thousand square miles. The most prominent peaks are Mt. Shasta, in California, and Mt. Rainier, in Washington. In three separate places rivers have cut a passage through the volcanic portion of the range. The most notable is the passage of the Columbia River in a grand cañon more than three thousand feet in depth.
The Coast Ranges of Washington, Oregon, and northern California consist of numerous and approximately parallel chains, which as a rule pitch off abruptly toward the sea, leaving no coast-plain. Between the Coast Ranges and the Sierra Nevada and Cascade Range is a series of broad valleys, occupied mainly in Oregon by the Willamette River, and in California by the Sacramento and San Joaquin. In southern California the mountains of the Coast Ranges diminish in height, but throughout their whole extent they are interspersed with picturesque and fertile valleys.
Coast.—The Atlantic coast has a length of about twelve thousand three hundred and sixty miles; the Gulf Coast of five thousand seven hundred and fifty miles, and the Pacific Coast of three thousand two hundred and fifty miles.
On the coast of the New England states there are many indentations which, though small, furnish commodious harbors. Long Island Sound adds greatly to the commercial importance of New York harbor, and farther south are Delaware and Chesapeake Bays; Albemarle and Pamlico sounds, and several small indentations, such as those which form the harbors of Charleston and Savannah. The Chesapeake Bay is the largest indentation of the Atlantic Coast and runs inland in a northward direction for more than one hundred and eighty miles, with an average breadth of about fifteen miles. From Cape Hatteras to Cape Sable, however, the coast is swampy, and, especially in Florida, fringed with lagoons. The harbors of this part of the coast are not good naturally. The coast of the Gulf of Mexico is low and very swampy, but is of special climatic and commercial importance.