Rocky mountains

Rocky Mountains

Rocky 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 ffrom 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 bbelts. 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 mm/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 aare 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 iin 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 RRockies, 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 fft) 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 44123 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 rrange 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 RRiver 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 AAthabasca 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 OOklahoma.

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 aand 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 ffor more than 160 km

(100 mi) in 1540-1541. The Colorado and its chief tributary, the Green,

were thoroughly explored for the first time in 1869 by the American

geologist John Wesley Powell. On this survey Powell and his party made the

first recorded passage of the Grand Canyon. The construction of the Glen

Canyon Dam in 1963 dramatically reduced the natural flow of sand and

nutrients down the Colorado River and into the Grand Canyon. In March 1996

the federal government released more than 380 billion lliters (100 billion

gallons) of water from Glen Canyon Dam. This artificial flood added more

than three feet to some beaches downstream and cleared fish spawning

grounds of debris and sediment. Further Reading Columbia (river, North

America), Major River of western North America, rising iin Columbia Lake,

just west of the main range of the Rocky Mountains, in southeastern British

Columbia. The river was formerly known as the Oregon River. The Columbia

River is about 2000 km (1240 mi) long. It initially flows northwest,

through a long, narrow valley called the Rocky Mountain Trench, and then

turns sharply south, skirting the Selkirk Mountains and passing through

Upper Arrow Lake and Lower Arrow Lake. It next receives the Kootenay

(spelled Kootenai in the United States) and Pend Oreille rivers before

entering the state of Washington, where it first flows south and then

traverses a great arc, known as the Big Bend. After receiving the Snake

River, the Columbia turns west and forms much of the boundary between the

states of Washington and Oregon before emptying into tthe Pacific Ocean

through a broad estuary. The river flows through several spectacular

canyons and deep valleys. About one-third of its course is in Canada. The

Columbia and its tributaries together drain a vast basin of about 673,400

sq km (about 260,000 sq mi). Large oceangoing ships can navigate the lower

Columbia River as far as Vancouver, Washington; and, with the aid of locks,

smaller marine vessels can reach The Dalles, Oregon, about 300 km (about

186 mi) upstream. Barges and other shallow-draft boats can navigate a

further 2220 km (137 mi). The Columbia River has immense hydroelectric

potential, and since the 1930s several large power projects have been built

on it. The largest of these, the Grand Coulee Dam, in central Washington,

is the key unit of the Columbia Basin Project, a federal undertaking also

designed to irrigate up to 485,623 hectares (1.2 million acres) of semiarid

land. Other important power projects on the Columbia include Bonneville,

The Dalles, John Day, McNary, Priest Rapids, Rocky Reach, and Chief Joseph

dams, in the United States, and Mica Dam, in Canada. Most of these dams are

also used for flood control and for irrigation. The American explorer

Robert Gray explored the mouth of the Columbia River in 1792. He named the

river for his ship. The Lewis and Clark Expedition explored the lower

Columbia from 1805 to 1806, and David Thompson, a Canadian surveyor and

explorer, followed the river from its source to its mouth in 1811. The

Columbia once had great numbers of salmon and supported a large canning

industry; the fish stock was severely depleted in the 1900s as a result of

dam construction and pollution. In an effort to protect the salmon from

extinction, the Northwest Power Planning Council in 1994 approved a plan to

rebuild salmon stock by increasing the water flow tthrough the dams and by

developing habitat protection standards. Further Reading Continental Divide

(also called the Great Divide), ridge of mountains in North America,

separating the streams that flow west (into the Pacific Ocean) from those

that flow east (into the Atlantic Ocean and its marginal seas). Most of the

divide follows the crest of the Rocky Mountains. It extends from Alaska in

the United States into the Yukon Territory and British Columbia in Canada

and forms part of the border between British Columbia and Alberta, also in

Canada. It then passes through Montana, Wyoming, Colorado, and New Mexico

in the United States and continues south into Mexico and Central America

along the crest of the Sierra Madre Occidental. The term continental divide

may be applied to the principal watershed boundary of any continent.

Fraser, river in southern British Columbia, Canada. The Fraser rises in the

Rocky Mountains, in Mount Robson Provincial Park near the Alberta border,

and flows 1370 km (850 mi) before emptying, through a delta, into the

Strait of Georgia, near Vancouver. The Fraser initially flows northwest

through a section of a deep, narrow valley called the Rocky Mountain

Trench. It then turns south near the city of Prince George, where it

receives its major western tributary, the Nechako River. In its central

section, the volume oof the river increases, and below Quesnel its banks

gradually take on a canyonlike aspect. Important tributaries in this

section include the West Road and Chilcotin rivers, from the west, and the

Thompson River, from the east. From Lytton to Yale the river flows through

a canyon of great scenic beauty. At the canyon’s southern end the Fraser

passes between the Cascade Range to the east and the Coast Mountains to the

west. A little below Yale, at Hope, the river turns sharply west, and the

fertile lower Fraser Valley begins. The Fraser empties into the Strait of

Georgia through three main channels. The river is used by commercial

vessels for a short distance upstream. From May to July the Fraser Valley

is subject to flooding; a series of dikes helps protect the delta. The

Fraser drains an area of about 238,000 sq km (about 91,890 sq mi). Much of

the river basin is heavily wooded, and forest-products industries dominate

the economy of the settlements along the river. The lower Fraser Valley,

including the delta, has highly productive farms. Various species of salmon

spawn in the Fraser, and salmon fisheries are located near the river’s

mouth. The river has great hydroelectric potential, but it remains

undeveloped for fear of detrimental effects on the migratory habits of the

salmon.

The Fraser is highly polluted, especially at its mouth. The first

European to visit the river was Sir Alexander Mackenzie in 1793. It is

named for the fur trader Simon Fraser, who explored much of it in 1808. In

1858 gold was found in alluvial gravels north of Yale, and a major gold

rush ensued. Louise, Lake, glacial lake in southwestern Alberta, Canada.

Lake Louise is located at an elevation of 1731 m (5680 ft) in Banff

National Park, near the town of Lake Louise. The llake is about 2.4 km

(about 1.5 mi) long and 1.2 km (0.75 mi) wide. Sheltered by the Rocky

Mountains, Lake Louise is known for the tranquil beauty of its ...