Rocky mountains
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Rocky mountains

Rocky MountainsRocky Mountains or Rockies, great chain of rugged mountain

ranges in western North America, extending from central New Mexico to

northeastern British Columbia, a distance of about 3220 km (about 2000 mi).

The Great Basin and the Rocky Mountain Trench, a valley running from

northwestern Montana to northern British Columbia, border the Rockies on

the east by the Great Plains and on the west. The Rocky Mountains form part

of the Great, or Continental, Divide, which separates rivers draining into

the Atlantic or Arctic oceans from those flowing toward the Pacific Ocean.

The Arkansas, Colorado, Columbia, Missouri, Rio Grande, Saskatchewan, and

Snake rivers rise in the Rockies. The Rockies may be divided into four

principal sections—Southern, Central, Northern, and Canadian. The Southern

Rockies, which include the system’s broadest and highest regions, extend

from central New Mexico, through Colorado, to the Great Divide, or Wyoming,

Basin, in southern Wyoming. This section, which encompasses Rocky Mountain

National Park, is composed chiefly of two northern-southern belts of

mountain ranges with several basins, or parks, between the belts. The

component parts include the Sanger de Crisco and Laramie mountains and the

Front Range, in the east, and the San Juan Mountains and the Swatch and

Park ranges, in the west. The Southern Rockies include the chain’s loftiest

point, Mount Elbert (4399 m/14,433 ft high), in central Colorado. More than

50 other peaks of the Rockies rising above 4267 m (14,000 ft) are in

Colorado; these include Longs Peak (4345 m/14,255 ft high) and Pikes Peak

(4301 m/14,110 ft high). The Central Rockies are in northeastern Utah,

western Wyoming, eastern Idaho, and southern Montana. They encompass the

Bighorn; Bear tooth, and Unite Mountains and the Absaroka, Wind River, Salt

River, Teton, Snake River, and Wasatch ranges. The Unite Mountains are the

only major portion of the Rockies that extends east west rather than north

south. Among the peaks of the Central Rockies, which include Grand Eton and

Yellowstone national parks, are Gannett Peak (4207 m/13,804 ft high), Grand

Eton (4197 m/13,771 ft high), and Fremont Peak (4185 m/13,730 ft high). The

Northern Rockies are in northern Idaho, western Montana, and northeastern

Washington. They include the Saw tooth, Cabinet, Salmon River, and

Clearwater Mountains and the Bitterroot Range. The loftiest points in the

section, which includes Glacier National Park, are Granite Peak (3901

m/12,799 ft high) and Borax Peak (3859 m/12,662 ft high). The Canadian

Rockies, located in southwestern Alberta and eastern British Columbia, are

composed of a relatively narrow belt of mountain ranges that terminates at

the Lizard River lowland in northeastern British Columbia. The peaks of the

section, which takes in Banff, Jasper, Kootenay, Waterton Lakes, and Yoho

National Parks, include Mount Robson (3954 m/12,972 ft high), Mount

Columbia (3747 m/12,294 ft high), and The Twins (3734 m/12,251 ft high).

Slopes generally are very steep, and there are numerous glaciers. The Rocky

Mountains are a geologically complex system with jagged peaks as well as

almost flat-topped elevations. The Rockies were formed mainly by crustal

uplifts in comparatively recent times, during the late Cretaceous and early

Tertiary periods, and later were reshaped by glaciation during the

Pleistocene Epoch. Today the Rockies receive moderate amounts of

precipitation, most of which occurs in the winter. Lower levels are covered

chiefly by grassland, which gives way to extensive forests, principally of

conifers. Above the woodland is a zone of grasses and scattered shrubs.

Most peaks have little vegetation around the summit, and some have a year-

round cap of snow and ice. The Rockies are sparsely populated for the most

part and contain few cities. The principal economic resources of the

mountains are minerals, such as coal, copper, gold, iron ore, lead,

molybdenum, petroleum and natural gas, silver, and zinc. Important mining

centers include Leadville and Climax, Colorado; Atlantic City, Wyoming;

Kellogg, Idaho; Butte, Montana; and Fernie and Kimberley, British Columbia.

Major forest products industries, especially lumbering, are concentrated in

the Northern and Canadian Rockies, and large numbers of sheep and cattle

are raised in the Rockies of Colorado, Wyoming, and Montana. The chain has

many centers for outdoor recreation and tourism. Bighorn Mountains,

isolated range of the Rocky Mountains, lying east of the Bighorn River and

extending generally north from central Wyoming into southern Montana. The

range averages more than 2134 m (7000 ft) in elevation; the highest summit

is Cloud Peak (4019 m/13,187 ft) in Wyoming. Along the upper levels are

large coniferous forests, which are part of Bighorn National Forest.

Bitterroot Range, mountain range, northwestern United States, a chain of

the Rocky Mountains, extending about 700 km (about 435 mi) along the

Montana-Idaho border. Rugged and forested, with an average elevation of

2740 m (about 9000 ft), it remains one of the most inaccessible areas in

the United States. In 1805 the Lewis and Clark Expedition traveled west

through Lolo Pass (1595 m/5233 ft) in the range. Guadalupe Mountains,

mountain range, southwestern United States, a branch of the Rocky

Mountains, extending from southern New Mexico to western Texas. Guadalupe

Peak (2667 m/8749 ft above sea level), the highest in the chain, is in

Texas. Laramie
Mountains, range of the Rocky Mountains, western United

States, extending from southeastern Wyoming into northern Colorado. The

highest point, Laramie Peak, is 3131 m (10,272 ft) above sea level. Coal,

the principal mineral, is found in the foothills. San Juan Mountains,

mountain range, southwestern United States, in southwestern Colorado and

northwestern New Mexico. Part of the Rocky Mountains, it is of volcanic

origin and is rich in minerals. The highest peaks are in Colorado and

include Uncompahgre Peak (4361 m/14,309 ft), Mount Sneffels (4313 m/14,150

ft), and Wetterhorn Peak (4272 m/14,017 ft). Sangre de Cristo Mountains,

mountain range, western United States, the southernmost range of the Rocky

Mountains, in south central Colorado and north central New Mexico. The very

high and narrow range extends southeast and south for about 354 km (220

mi), from Salida, Colorado, to Santa Fe County, New Mexico. Blanca Peak

(4372 m/14,345 ft), in Colorado, is one of the highest mountains of the

Rockies. Sawatch Range, mountain range, central Colorado, a branch of the

Rocky Mountains. The range extends for about 177 km (about 110 mi) and

reaches a height of 4399 m (14,433 ft) at Mount Elbert, the highest point

in the state. Teton (mountain range), range of the Rocky Mountains, in

northwestern Wyoming, and southwestern Idaho, just south of Yellowstone

National Park, west of Jackson Lake and the Snake River. The highest peak

is Grand Teton (4197 m/13,771 ft), located in Grand Teton National Park.

Teton Pass (2569 m/8429 ft) and Phillips Pass (3261 m/10,700 ft) are just

south of the park. Uinta Mountains, mountain range, western United States,

mainly in northeastern Utah and partly in southwestern Wyoming, part of the

Rocky Mountains. The peaks of the Uinta Mountains are mostly flat because

of erosion by glaciers and the waters of the Yampa and Green rivers. The

range is about 240 km (about 150 mi) long and 48 to 64 km (30 to 40 mi)

wide. The highest elevation is Kings Peak, which is 4123 m (13,528 ft) high

and is also the highest point in Utah. Wasatch Range, mountain range,

western United States, in the Rocky Mountain system. The range is about 240

km (about 150 mi) long; part of the Central Rockies, it begins in

southeastern Idaho and runs southward, east of the Great Salt Lake and

through the center of Utah, gradually ending in southwestern Utah. The

average height of the range is about 3050 m (about 10,000 ft), and the

highest peak, Mount Nebo, is 3620 m (11,877 ft) high. Wind River Range,

range of the Rocky Mountains, western Wyoming, forming part of the

Continental Divide. The Green River rises in the southwestern slope of the

range, and many tributaries of the Wind River flow off on the northeastern

side. The range contains Fremont Peak (4185 m/13,730 ft) and Gannett Peak

(4207 m/13,804 ft); the latter is the highest point in Wyoming. Arkansas

(river, United States), river, western U.S., a major tributary of the

Mississippi River, 2350 km (1460 mi) long. Rising in central Colorado, in

the Sawatch Range of the Rocky Mountains, at an altitude of about 4270 m

(about 14,000 ft), the river flows generally east and forms a turbulent

stream passing over rocky beds and through deep canyons such as the Royal

Gorge. As it flows through the plains of Kansas, the river broadens to a

wider, less turgid stream until it enters Oklahoma; at that point it

receives two chief tributaries, the Cimarron and the Canadian rivers.

Except for a large northern bend in Kansas, the Arkansas River follows a

southeastern course, merging with the Mississippi River above Arkansas

City, Arkansas. The water levels of the river are extremely variable, and

several dams have been built for flood control and irrigation and to create

hydroelectric power; one of the most impressive, the John Martin Dam in

southeastern Colorado, was built in 1948. The Arkansas River Navigation

System, completed in the early 1970s, made the river navigable to Tulsa,

Oklahoma. Athabasca, river and lake, in western Canada, that form part of

the Mackenzie River system. The Athabasca River, 1231 km (765 mi) long,

begins in Jasper National Park in southwestern Alberta. Its source is the

Columbia Icefield, high in the Rocky Mountains. The river flows northeast

across Alberta and empties through a shallow delta into Lake Athabasca in

northeastern Alberta. The river was once an important route for fur

traders. Lake Athabasca, which straddles the AlbertaSaskatchewan- border,

is about 320 km (about 200 mi) long and covers about 7936 sq km (about 3064

sq mi). Fort Chipewyan, which was built along the southwestern shore of the

lake in 1788, became one of the region’s most important fur-trading posts.

Today Lake Athabasca is used for commercial fishing. It is drained to the

north by the Slave River. Large deposits of petroleum-bearing sand are

located along the lower Athabasca River, near Fort McMurray. Long known but

untapped because of high extraction costs, the deposits are now mined using

new technology and efficient methods. In 1994 the output amounted to one-

quarter of Canada’s crude oil production. Canadian, also South Canadian,

unnavigable river, southwestern United States, 1460 km (906 mi) long. The

Canadian River is formed in northeastern New Mexico by the union of several

branches from the southern Rocky Mountains. The river flows south through

New Mexico and then turns east, crossing the Texas Panhandle into Oklahoma.

Following a meandering course, it
finally joins the Arkansas River. The

river’s only major tributary is the North Canadian River, 1260 km (784 mi)

long, which runs almost parallel to the Canadian River in Oklahoma. The

tributary joins the Canadian River at Eufaula in eastern Oklahoma to form

the Eufaula Reservoir. In northeastern New Mexico, a semiarid region, the

Canadian River provides an important water source at the Conchas Dam, a

flood-control and irrigation project. Colorado (river, North America),

river, in southwestern United States and northwestern Mexico, 2330 km (1450

mi) long, the longest river west of the Rocky Mountains. The Colorado rises

just west of the Continental Divide, in northern Colorado, and, for the

first 1600 km (about 1000 mi) of its course, passes through a series of

deep gorges and canyons that were created by the eroding force of its

current. The river flows in a generally southwestern direction across

Colorado into southeastern Utah, where it joins its chief tributary, the

Green River. After crossing the northern portion of Arizona, the Colorado

flows west for 446 km (277 mi) through the majestic Grand Canyon. It then

flows in a generally southerly direction and forms the boundary between

Arizona and the states of Nevada and California. Near Yuma, Arizona, the

river crosses the international border into Mexico and flows for about 145

km (90 mi) to its mouth on the Gulf of California, an inlet of the Pacific

Ocean. Besides the Green River, the most important tributaries of the

Colorado include the Dolores and Gunnison rivers, in Colorado; the San Juan

River, in Utah; and the Little Colorado and Gila rivers, in Arizona. With

its tributaries, the Colorado drains portions of seven states, a total

area, in Colorado, Wyoming, Nevada, Utah, Arizona, New Mexico, and

California, of about 626,800 sq km (about 242,000 sq mi) and 5180 sq km

(2000 sq mi) more in Mexico. To control the tremendous flow of the

Colorado, particularly under flood conditions, an extensive series of dams,

many of them constructed by the U.S. Bureau of Reclamation, has been built

along the river and its tributaries. Notable is the Hoover Dam, which

impounds the river at the Black Canyon to form Lake Mead, one of the

largest artificial lakes in the world. The Glen Canyon Dam, in north-

central Arizona just south of the Utah border, is the third highest dam in

the U.S. In addition to regulating the flow of water, dams on the Colorado

harness hydroelectric power and provide storage reservoirs for irrigation

projects. As such, they have been instrumental in reclaiming the semiarid

and arid regions through which the river flows. The Imperial Valley of

southern California is an excellent example of land reclaimed by the waters

of the Colorado. A number of reservoirs have been incorporated into

national recreation areas. The Glen Canyon National Recreation Area in Utah

encompasses Lake Powell, formed by the Glen Canyon Dam. Lakes Mead and

Mohave (the latter formed by Davis Dam) are part of Lake Mead National

Recreation Area in Arizona. The Colorado was first explored by the Spanish

navigator Hernando de Alarcón, who ascended the river for more than 160 km

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