Spread over western North America, the Rocky Mountains stretch more than 4,830 km from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States. This mountain range must have been formed from 80 million to 55 million years ago by the Laramide orogeny. Since then, erosion by water and glaciers has sculpted the mountain range into dramatic valleys and peaks. At the end of the last ice age, humans started to inhabit the mountain range. Today much of the mountain range is protected but still it is a popular tourist destination mainly for hiking, camping, mountaineering, fishing, and hunting, skiing, and snowboarding.
Before the mountains were raised by tectonic forces, the rocks in the Rocky Mountains were formed. The oldest rock is Precambrian metamorphic rock that forms the core of the North American continent. There is also Precambrian sedimentary argillite, dating back to 1.7 billion years ago. In the southern Rocky Mountains, near present-day Colorado, these ancestral rocks were disturbed by mountain building approximately 300Ma, during the Pennsylvanian. This mountain building produced the Ancestral Rocky Mountains. They consisted largely of Precambrian metamorphic rock forced upward through layers of the limestone laid down in the shallow sea. The mountains eroded throughout the late Paleozoic and early Mesozoic, leaving extensive deposits of sedimentary rock.
The current southern Rockies were forced upwards through the layers of Pennsylvanian and Permian sedimentary remnants of the Ancestral Rocky Mountains. Such sedimentary remnants were often tilted at steep angles along the flanks of the modern range; they are now visible in many places throughout the Rockies, and are prominently shown along the Dakota Hogback, an early Cretaceous sandstone formation that runs along the eastern flank of the modern Rockies. Immediately after the Laramide orogeny, the Rockies were like Tibet: a high plateau, probably 6,000 metres above sea level. In the last 60 million years, erosion stripped away the high rocks, revealing the ancestral rocks beneath, and forming the current landscape of the Rockies. Periods of glaciation occurred from the Pleistocene Epoch to the Holocene Epoch. The ice ages left their mark on the Rockies, forming extensive glacial landforms, such as U-shaped valleys and cirques.
The Rockies vary in width from 70 to 300 miles. Also west of the Rocky Mountain Trench, farther north and facing the Muskwa Range across the trench, are the Stikine Ranges and Omineca Mountains of the Interior Mountains system of British Columbia. A small area east of Prince George, British Columbia on the eastern side of the Trench, the McGregor Plateau, resembles the Rockies but is considered part of the Interior Plateau. The eastern edge of the Rockies rises dramatically above the Interior Plains of central North America, including the Front Range of Colorado, the Wind River Range and Big Horn Mountains of Wyoming, the Absaroka-Beartooth ranges and Rocky Mountain Front of Montana, and the Clark Range of Alberta. The western edge of the Rockies includes ranges such as the Wasatch near Salt Lake City and the Bitterroots along the Idaho-Montana border. The Great Basin and Columbia River Plateau separate these sub-ranges from distinct ranges further to the west, most prominent among which are the Sierra Nevada, Cascade Range and Coast Mountains. The range's highest peak is Mount Elbert located in Colorado at 14,440 feet (4,401 m) above sea level. Mount Robson in British Columbia, at 12,972 feet (3,954 m), is the highest peak in the Canadian Rockies.
The Continental Divide is located in the Rocky Mountains and designates the line at which waters flow either to the Atlantic or Pacific Oceans. Triple Divide Peak in Glacier National Park (U.S.) is so named because water that falls on the mountain reaches not only the Atlantic and Pacific, but Hudson Bay as well. Human population is not very dense in the Rocky Mountains, with an average of four people per square kilometer and few cities with over 50,000 people. Since the last great ice age, the Rocky Mountains were home first to the indigenous peoples, including the Apache, Arapaho, Bannock, Blackfoot, Cheyenne, Crow, Flathead, Shoshone, Sioux, Ute, Kutenai, Sekani, Dunne-za, and others. Paleo-Indians hunted the now-extinct mammoth and ancient bison in the foothills and valleys of the mountains.
Rockies’ precipitation ranges from 250 mm per year in the southern valleys to 1,500 mm per year locally in the northern peaks. Average January temperatures can range from 20 °F in Prince George, British Columbia to 43 °F in Trinidad, Colorado. Ecologists divide the Rocky Mountain into a number of biotic zones. Each zone is defined by whether it can support trees, and the presence of one or more indicator species. Two zones that do not support trees are the Plains and the Alpine tundra. The Great Plains lie to the east of the Rockies, and is characterized by prairie grasses. The Rocky Mountains are habitat for wildlife, such as elk, moose, mule and white-tailed deer, pronghorns, mountain goats, bighorn sheep, black bears, grizzly bears, coyotes, lynxes, and wolverines. The status of most species in the Rocky Mountains is unknown, due to incomplete information.
There are abundant economic resources in Rocky Mountains such as significant deposits of copper, gold, lead, molybdenum, silver, tungsten, and zinc. The Wyoming Basin and several smaller areas contain significant reserves of coal, natural gas, oil shale, and petroleum. The Rocky Mountains contain several sedimentary basins that are rich in coal bed methane. Coal bed methane is natural gas that arises from coal, either through bacterial action, or through exposure to high temperature.
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