Plateaus.— The great plateau region in cluded in the Rocky Mountain system is in southern Wyoming, eastern Utah, eastern Ari zona, western New Mexico and western Colo rado. The lands in Colorado and New Mexico east of the mountain ranges belong to the Great Plain. The Plateau region is bounded on the north by Sweetwater and Wind River Moun tains. The general elevation of the whole plateau is about 7,000 feet above sea-level, but in Colorado it has an elevation of 10,000 feet. The Continental divide crosses this plateau; and within its limits are the waters of the three great river systems of the United States, the Mississippi, the Colorado and the Columbia. The southern part of the plateau has in places an abrupt ending, a steep, almost perpendicular escarpment. The ranges crossing, divide the plateau region into sections to which have been given the names Kaibab, Kaiparowits, Aqua rius, Colorado, Markagunt, Paunsagunt, Paria, Shiwits, Tavaputs, Uinkaret, and others not so well defined as those named. On these broad plateaus are groups of mountains, buttes and isolated ranges and peaks. There are seven peaks over 13,000 feet above sea-level; five over 12,000 feet and less than 13,000 feet; and 20 over 10,000 feet and less than 12,000 feet.
Parks.— The parks of Colorado are high mountain valleys, known as North, Middle, South and San Luis, with an elevation of from 6,000 to 10,000 feet, surrounded by ranges of mountains from 3,000 to 4,000 feet higher. The west border of the San Luis Park is formed by San Juan Range, with its high peaks, more than 100 of them over 13,000 feet, border ing it like giant watch towers. The Uinta Range is west of North Park. The Parks, or enclosed mountain valleys in Idaho and Wyoming, are not so high as the Parks of Colorado. The most famous park in the whole Rocky Mountain System is Yellowstone Park (q.v.) in Wyoming, now a government reser vation. The ranges on the boundaries of the Parks and rising from the Park Valleys, are P grouped together as the Park Ranges or ark System. The mountains so designated are bounded an the north by the Laramie Plains, and on the east by the Great Plains. The southern and western boundaries are indefinite. Other noted parks are Monumental Park and the Garden of the Gods, near Colorado Springs. The 500 acres are covered with an extraordinary rock formation, like giant spires and pillars, and some like vast cathedrals. The Yosemite Valley (q.v.) is often classed with the Parks.
Desert Region.— Within the area called by this name are vast arid regions, bare bleak mountains, and localities of almost barren lands, some of which might be made fertile by irriga tion, and some fertile valleys. It includes the southern parts of Idaho and Oregon, the west ern parts of Utah and Nevada, the southeastern part of California, the southwestern part of New Mexico, the southern part of Arizona and the north central part of Mexico. The Sierra Nevada and Cascade ranges are on the Western boundary; and the plateau drained by the Colo rado River is on the eastern boundary. The greater part of this region is known as the Great Basin (q.v.) which has no apparent out lets to the ocean. The ranges, as in Nevada, are simple and narrow and separated by broad, level desert valleys. Geologically this basin is probably not strictly within the Rocky Moun tain system.
Passes.— Several depressions in the ranges are called Passes, and some have been used for routes for railroads. A famous pass is the Lewis and Clark's, in lat. 47°. Through this pass the Northern Pacific Railroad has been built, and at Mullan's Pass it goes through a tunnel 3,850 feet long. The Truckee Pass, 6,000 feet above sea-level; the South Pass of the Wind River Range, Evan's Pass in the Front Range, which is crossed by the Union Pacific Railroad, are well known. In Canada
the pass between Mount Hooker and Mount Brown, Athabasca Portage, is 7,300 feet above the sea. In the California mountains there are a number of passes. Where the rivers have cut their channels through the mountains, passes have been formed.
Lakes, Rivers and Glaciers.— The great est rainfall is on the western slope, where the moisture brought by the winds from the Pacific Ocean falls. In the valleys and on the plateaus, especially where the waters fall down the es carpments, the rivers run through deep canons, the most perpendicular sides of which are thou sands of feet above the river beds. The rivers of the plateaus have their sources in the Park and Wind River Mountains, and in the Wah satch Range. They have carved out deep gorges, which divide the region into a series of distinct plateaus. Some of the famous canyons of this region are the Grand of the Colorado, the Kanab and the Marble. The principal riv ers within this region are the Green, Colorado, Sevier, Paria, Uinta and White. The rivers whose head waters are in the Sierra Nevada Range, flow to the Pacific, except a few, which flow east and are lost in the sands. The Sacramento and the San Joaquin are in the valley between the Sierra Nevada and the Coast Range. The one river comes from the north, the other from the south, almost parallel with the ranges until they unite, when they burst through the mountains and discharge their united waters into the Pacific Ocean. The Columbia is one of the great rivers of this re gion. Rising on the east side of the Cascade Mountains it flows south for some distance un til finally it plunges through the mountains in a series of magnificent cascades, whence the name of the range. The Front Range in north ern Montana bears upon its crest for many aides the continental divide which separates the headwaters of .the' Missouri and the Columbia rivers. The Bitter Root Range separates the Missouri from the Salmon. The greatest water systems of North America have head-waters in the Rocky Mountains. The Colorado toward the south, the Yukon on the north, and the Columbia are the largest streams that flow toward the Pacific; the Mississippi, the Great Lakes and the Saint Lawrence, and the streams that flow into the Hudson Bay all reach the Atlantic Ocean; and the Mackenzie and its tributaries flow into the Arctic. The Rocky Mountains have many small lakes, formed by springs, and depressions which serve as basins. In the Great Basin are several bodies of salt water, the largest of which is Salt Lake (q.v.). The only crater lake in the United States id Crater Lake in the National Park. The glaciers of the Rocky Mountains are numerous. In Alaska are the largest and greatest numbers among which are Muir and Malaspina. Mount Rainier (q.v.) has over 30 glaciers, extending over a space of 100 square miles, and some of the ice walls reach a depth of 1,060 feet. The Puyallup and Mowich rivers drain five of the largest 'glacier rivers of Mount Rainier. A notable feature of these rivers is what is known as glacial tides, which are quite marked in summer time. Between midday and a few hours before sunset, there is an increase in the flow of water at the head of each river ; about two feet in the narrowest part of the rivers. The vastness of Mount Rainier may be con ceived when it is known that the surface, in cluding the hill country at its base, has an area of 3,000 square miles. In other parts of the Rocky Mountains are found vast glaciers, and many of the peaks are ever whitecapped with snow.