The Sonoran Desert is a North American desert which covers large parts of the Southwestern United States in Arizona and California and of Northwestern Mexico in Sonora, Baja California, Baja California Sur. It is the hottest desert in Mexico, it has an area of 260,000 square kilometers. The western portion of the United States–Mexico border passes through the Sonoran Desert. In phytogeography, the Sonoran Desert is within the Sonoran Floristic Province of the Madrean Region in southwestern North America, part of the Holarctic Kingdom of the northern Western Hemisphere; the desert contains a variety of unique and endemic plants and animals, such as the saguaro and organ pipe cactus. The Sonoran desert wraps around the northern end of the Gulf of California, from Baja California Sur, north through much of Baja California, excluding the central northwest mountains and Pacific west coast, through southeastern California and southwestern and southern Arizona to western and central parts of Sonora.
It is bounded on the west by the Peninsular Ranges, which separate it from the California chaparral and woodlands and Baja California Desert ecoregions of the Pacific slope. To the north in California and northwest Arizona, the Sonoran Desert transitions to the colder-winter, higher-elevation Mojave, Great Basin, Colorado Plateau deserts. To the east and southeast, the deserts transition to the coniferous Arizona Mountains forests and Sierra Madre and Sierra Madre Occidental pine–oak forests at higher elevations. To the south the Sonoran–Sinaloan transition subtropical dry forest is the transition zone from the Sonoran Desert to the tropical dry forests of the Mexican state of Sinaloa; the desert's sub-regions include the Colorado Desert of southeastern California. In the 1957 publication Vegetation of the Sonoran Desert, Forrest Shreve divided the Sonoran Desert into seven regions according to characteristic vegetation: Lower Colorado Valley, Arizona Upland, Plains of Sonora, Foothills of Sonora, Central Gulf Coast, Vizcaíno Region, Magdalena Region.
Many ecologists now consider Shreve's Vizcaíno and Magdalena regions, which lie on the western side of the Baja California Peninsula, to be a separate ecoregion, the Baja California Desert. Within the southern Sonoran Desert in Mexico is found the Gran Desierto de Altar, with the Reserva de la Biosfera el Pinacate y Gran Desierto de Altar, extending 2,000 square kilometers of desert and mountainous regions; the Pinacate National Park includes the only active erg dune region in North America. The nearest city to the Reserva de la Biosfera el Pinacate y Gran Desierto de Altar is Puerto Peñasco in the state of Sonora, Mexico. Sub-regionsSonoran Desert sub-regions include: Colorado Desert Gran Desierto de Altar Lechuguilla Desert Tonopah Desert Yuha Desert Yuma Desert The Sonoran Desert includes 60 mammal species, 350 bird species, 20 amphibian species, over 100 reptile species, 30 native fish species, over 1000 native bee species, more than 2,000 native plant species; the Sonoran Desert area southeast of Tucson and near the Mexican border is vital habitat for the only population of jaguars living within the United States.
The Colorado River Delta was once an ecological hotspot within the Sonoran desert, fueled by the flow of fresh water through the Colorado river in this otherwise dry area, but the delta has been reduced in extent due to the damming and use of the river upstream. Many plants not only thrive in the harsh conditions of the Sonoran Desert. Many have evolved to have specialized adaptations to the desert climate; the Sonoran Desert's biseasonal rainfall pattern results in more plant species than any other desert in the world. The Sonoran Desert includes plant genera and species from the agave family, palm family, cactus family, legume family, numerous others; the Sonoran is the only place in the world. Cholla, hedgehog, prickly pear, nightblooming cereus, organ pipe are other taxa of cacti found here. Cactus provides food and homes to many desert mammals and birds, with showy flowers in reds, pinks and whites, blooming most from late March through June, depending on the species and seasonal temperatures.
Creosote bush and bur sage dominate valley floors. Indigo bush and Mormon tea are other shrubs. Wildflowers of the Sonoran Desert include desert sand verbena, desert sunflower, evening primroses. Ascending from the valley up bajadas, various subtrees such as velvet mesquite, palo verde, desert ironwood, desert willow, crucifixion thorn are common, as well as multi-stemmed ocotillo. Shrubs found at higher elevations include whitethorn acacia, fairy duster, jojoba. In the desert subdivisions found on Baja California, cardon cactus, elephant tree, boojum tree occur; the California fan palm is found in the Colorado Desert section of the Sonoran Desert, the only native palm in California, among many other introduced Arecac
Course of the Colorado River
The Colorado River is a major river of the western United States and northwest Mexico in North America. Its headwaters are in the Rocky Mountains. Located in north central Colorado it flows southwest through the Colorado Plateau country of western Colorado, southeastern Utah and northwestern Arizona where it flows through the Grand Canyon, it turns south near Las Vegas, forming the Arizona–Nevada border in Lake Mead and the Arizona–California border a few miles below Davis Dam between Laughlin and Needles, California California before entering Mexico in the Colorado Desert. Most of its waters are diverted into the Imperial Valley of Southern California. In Mexico its course forms the boundary between Sonora and Baja California before entering the Gulf of California; this article describes most of the major features along the river. The Colorado River rises on the Continental Divide at La Poudre Pass, in Rocky Mountain National Park, about 40 km north of Lake Granby, as a tiny stream draining a wet meadow.
At the river's headwater, the Continental Divide forms the boundary between the Gulf of Mexico and Pacific Ocean watersheds of North America, between Colorado's Grand and Larimer counties, the northern boundary of Rocky Mountain National Park. The river's first diversion is here at its headwater; the Grand Ditch redirects water from the Never Summer Mountains, which would have flowed into the Colorado River, to instead flow across the divide through La Poudre Pass to irrigate farmland to the east. About a mile downstream from its source, the Colorado River has carved its first canyon, the narrow, deep Little Yellowstone Canyon, it flows through the broad Kawuneeche Valley, where it is joined by U. S. Highway 34, which will parallel it to the town of Granby, it exits Rocky Mountain National Park, flowing into Shadow Mountain Lake and into Lake Granby, which are portions of the Colorado-Big Thompson Project, a large trans-basin water storage and delivery project that diverts water from the Colorado River under the Front Range mountains to provide an agricultural and municipal water supply for the northern Front Range and plains of Colorado.
Starting in Granby, the river is paralleled by U. S. Highway 40 to the town of Kremmling, by the tracks of the Union Pacific Railroad until about the Utah border, carrying the Amtrak California Zephyr passenger train; the canyons and valleys of the Upper Colorado River are among the scenic attractions for passengers on this rail route. Just downstream from Granby, the Colorado is joined by the Fraser River and flows through Windy Gap Reservoir, where more water is diverted to the Front Range via the Windy Gap Project. At Hot Sulphur Springs the river flows through Byers Canyon and is joined by the Williams Fork from the left and Muddy Creek from the right shortly thereafter. Just below Kremmling it is joined by the Blue River from the left before flowing through Gore Canyon, famous for its challenging rapids for the sport of whitewater rafting, where it drops until State Highway 131 crosses at the village of State Bridge, where the Piney River joins from the left; the Eagle River joins from the left in the town of Dotsero, from where Interstate 70 will parallel the Colorado until it enters Utah.
Below Dotsero the Colorado flows through Glenwood Canyon, emerging at the city of Glenwood Springs where the swift flowing Roaring Fork River, its second largest tributary in Colorado joins from the left. West of Glenwood Springs, the Colorado runs through a wider valley along the northern foothills of the Grand Mesa, passing the towns of New Castle, Rifle and De Beque, it flows through De Beque Canyon, where it is joined by Plateau Creek. The Colorado enters the Grand Valley, where its waters are used to irrigate over 40,000 acres of agricultural land. Here it passes Grand Junction, the largest town on the upper Colorado, where it is joined by the Gunnison River, its largest tributary within Colorado and second largest overall; the Gunnison drains from the northern San Juan Mountains, Elk Mountains and Sawatch Range – which includes Colorado's highest peak, 14,440-foot Mount Elbert – and carves the Black Canyon of the Gunnison before joining the Colorado. In the Grand Valley the Colorado becomes a meandering river in contrast to the steep mountain canyons above Grand Junction.
It ranges from 6 to 30 ft in depth with occasional deeper areas. From there the Colorado turns northwest, past Fruita and entering Ruby Canyon as it approaches the Colorado Plateau, it turns southwest once again just before entering Utah. In Utah the Colorado enters the high desert canyon country of the Colorado Plateau, flowing swiftly southwest through Westwater Canyon. Near Dewey it picks up the Dolores River, which together with its tributary the San Miguel drains the western slope of the San Juan Mountains, it passes the Fisher Towers and forms part of the southern border of Arches National Park before entering the Moab Valley at Moab. Just below Moab it carves through a 1,000-foot deep mountain pass known as "The Portal"; the Colorado passes by Dead Horse Point State Park before entering the backcountry of Canyonlands National Park where it is joined from the north by the Green River, its biggest tributary. The Green, flowing from the Wind River Range of western Wyoming, drains 48,000 square miles in southwest Wyoming, northeast Utah and northwest Colorado.
It is much longer than the Colorado above their confluence and carries a larger load of silt, though the Colorado has a greater flow. Before an act of Congress changed the name in 1921 this confluence marked the official beginning of the Colorado River prop
Berthoud Pass is a high mountain pass in the Rocky Mountains of central Colorado in the United States. The pass is located west of Denver, provides a high route between upper Clear Creek Canyon to the upper valley of the Fraser River in Middle Park to the north; the pass traverses the continental divide at the Front Range, on the border between Clear Creek County and Grand County. The pass is named for Edward L. Berthoud, the chief surveyor of the Colorado Central Railroad during the 1870s. Accompanied by Jim Bridger, Berthoud discovered the pass in July 1861 while surveying a possible route for the railroad. Berthoud concluded that the pass was suitable as a wagon road, but not as a railroad, was hired by the Central Overland California and Pikes Peak Express Company to survey a route over the pass to Salt Lake; the pass is the route of U. S. Highway 40, north of its junction with Interstate 70 in Clear Creek Canyon, it provides the fastest road access to Winter Park and a secondary route to Steamboat Springs from Denver and the Colorado Front Range.
However, the pass is one of the most notoriously difficult passes in Colorado for motorists, based on its height as well as the steep grades on both sides and the large number of switchbacks on the southern side of the pass. At least 55 avalanche paths have been mapped on Berthoud Pass. S. Highway 40, a smaller subset of paths intersecting the roadway at multiple points on the pass. In 2015, CDOT installed an automated propane-fueled avalanche mitigation system consisting of five units that create concussive blasts to mitigate snow slab buildup on avalanche path #5, Stanley. In 1902, the 3.5 mile Berthoud Pass Ditch began diverting water from the headwaters of the Fraser River over the continental divide into the basin of Clear Creek. This water was used for irrigation, but the cities of Northglenn and Golden purchased the ditch in the mid-1980s; the ditch has a capacity of 53.4 cubic feet per second, The ditch was blocked in 1999 by the collapse of the tunnel under the parking lot at the summit of the pass, but it was repaired the next year.
In the decade since the repairs, the ditch has diverted on the order of 500 acre-feet per year. Once home to the now-defunct Berthoud Pass Ski Area, the pass is a destination for local backcountry skiers and snowshoers due to its abundance of steep and challenging terrain and plentiful snow averaging 500 inches annually; the twisting road on both sides of the pass makes "car shuttles" possible, eliminating the need for skiers and snowboarders to hike back to the top of the pass after each run. The ski resort was closed in 2002 due to financial problems caused by lack of water and sewage at the top of the pass. In 2003 the lifts were taken down, while some people continued to ski using snowcats for lift transportation. In 2005 the Colorado DOT began using a fund to restore the area to its natural state. First on the list was the demolition of the historic lodge. A new warming hut was opened at the top of the pass in May 2008, along with an expanded parking area, two scenic viewing areas and a new summit marker sign.
The ski lodge and facilities had been in use since the early 1950s and the new warming hut includes modern features such as composting toilets, radiant floor heating and green construction. Berthoud Ski resort is claimed by some to lift in Colorado; some say it was the first resort to welcome snowboarders. The summit of Berthoud Pass is located at 39°47′53.70″N 105°46′36.88″W. Founded in 2003, Friends of Berthoud Pass is a grassroots collective of backcountry enthusiasts committed to preserving the legacy of public recreation at Berthoud Pass, they are a non-profit 501c tax exempt organization managed by a volunteer executive board and supported by a diverse and active member base. Berthoud Pass is a unique environment, where a major highway crosses the Continental Divide in a topographically and climatically ideal location that lends itself to a lengthy season of challenging deep powder skiing; this combination of elements at Berthoud Pass creates a unique set of circumstances for land managers, FOBP has played a pivotal role in giving public voice to the policy process.
In its short history Friends of Berthoud Pass has endeavored to fashion a new paradigm in winter recreation on public land. They have mobilized public involvement in lobbying the US Forest Service to incorporate the needs and wishes of winter backcountry users in redevelopment plans and positioned themselves as a key stakeholder in the public policy process; the Friends of Berthoud Pass avalanche education curriculum has expanded from two classroom sessions in 2004 that reached 100 people, to a 2008 roster of eight classroom lectures educating more than 1,000 individuals in basic avalanche awareness and more than 150 participants in an on-snow practical course. 9. Jack Kerouac. Berthoud Pass, Colorado USGS TopoZone listing Friends of Berthoud Pass Berthoud Pass Ski Area's History
Middle Park (Colorado basin)
Middle Park is a high basin in the Rocky Mountains of north-central Colorado in the United States. It is located in Grand County, on the southwest slope of Rocky Mountain National Park 50 miles west of Boulder; the basin surrounds the headwaters of the Colorado River on the west side of the Front Range. It extends southwestward from the source of the Colorado at Grand Lake, downstream past Granby, Hot Sulphur Springs and Kremmling, it terminates on the western end where the Colorado passes Gore Canyon at the southern end of the Gore Range. The valley extends into the lower valleys of side tributaries on the upper Colorado such as the Fraser River, Williams Fork, Willow Creek; the valley of the Fraser contains the towns of Winter Park. The lower Blue River downstream of Dillon Reservoir is included as part of Middle Park; the valley receives its name from being the middle of the three large mountain valleys in Colorado on the western side of the Front Range. The other two are South Park. U. S. Highway 34 traverses the valley from the northeast to the southwest, connects to U.
S. Highway 40 at Granby; the valley is surrounded on the north and south by mountains that form the continental divide, thus it forms a slight pocket eastward in the drainage basin of the Pacific Ocean in this part of the Rockies. North Park, to the north, is drained by the North Platte River and separated from the valley by low passes, Muddy Pass and Willow Creek Pass; the passes on the east and south, connect to the basin of the South Platte River. They are both in the Front Range proper and thus are higher and more to be snow-covered. Milner Pass is near the height point on Trail Ridge Road and is open only during summer months, allowing a seasonal connection by road between Estes Park and Grand Lake. Berthoud Pass, at the headwaters of the Fraser south of Winter Park, connects the valley via U. S. Highway 40 to Interstate 70 in Clear Creek Canyon; this latter route is the most direct route between Denver. The valley contains several reservoirs on the Colorado and its tributaries, including Lake Granby, which inundates a large portion of the northeastern part of the valley.
Unlike North Park and South Park, which are wide flat basins at the headwaters of the North and South Platte Middle Park is a narrower basin, allowing for less agricultural use as pasturelands. The main industry in the valley is tourism, including alpine skiing at Winter Park Ski Resort. Much traffic between Denver and the destination resort of Steamboat Springs passes through the valley as well, allowing for secondary tourism industries to proliferate in the smaller towns; the smaller demand for water allows much of the water in the upper Colorado basin to be transported eastward across the continental divide to the Colorado Front Range as part of the Colorado-Big Thompson Project
Wyoming is a state in the mountain region of the western United States. The state is the 10th largest by area, the least populous, the second most sparsely populated state in the country. Wyoming is bordered on the north by Montana, on the east by South Dakota and Nebraska, on the south by Colorado, on the southwest by Utah, on the west by Idaho and Montana; the state population was estimated at 577,737 in 2018, less than 31 of the most populous U. S. cities including Denver in neighboring Colorado. Cheyenne is the state capital and the most populous city, with an estimated population of 63,624 in 2017; the western two-thirds of the state is covered by the mountain ranges and rangelands of the Rocky Mountains, while the eastern third of the state is high elevation prairie called the High Plains. Half of the land in Wyoming is owned by the U. S. government, leading Wyoming to rank sixth by area and fifth by proportion of a state's land owned by the federal government. Federal lands include two national parks—Grand Teton and Yellowstone—two national recreation areas, two national monuments, several national forests, historic sites, fish hatcheries, wildlife refuges.
Original inhabitants of the region include the Crow, Arapaho and Shoshone. Southwestern Wyoming was in the Spanish Empire and Mexican territory until it was ceded to the United States in 1848 at the end of the Mexican–American War; the region acquired the name Wyoming when a bill was introduced to the U. S. Congress in 1865 to provide a "temporary government for the territory of Wyoming"; the name was used earlier for the Wyoming Valley in Pennsylvania, is derived from the Munsee word xwé:wamənk, meaning "at the big river flat". The main drivers of Wyoming's economy are mineral extraction—mostly coal, natural gas, trona—and tourism. Agricultural commodities include livestock, sugar beets and wool; the climate is semi-arid and continental and windier than the rest of the U. S. with greater temperature extremes. Wyoming has been a politically conservative state since the 1950s, with the Republican Party candidate winning every presidential election except 1964. Wyoming's climate is semi-arid and continental, is drier and windier in comparison to most of the United States with greater temperature extremes.
Much of this is due to the topography of the state. Summers in Wyoming are warm with July high temperatures averaging between 85 and 95 °F in most of the state. With increasing elevation, this average drops with locations above 9,000 feet averaging around 70 °F. Summer nights throughout the state are characterized by a rapid cooldown with the hottest locations averaging in the 50–60 °F range at night. In most of the state, most of the precipitation tends to fall in early summer. Winters are cold, but are variable with periods of sometimes extreme cold interspersed between mild periods, with Chinook winds providing unusually warm temperatures in some locations. Wyoming is a dry state with much of the land receiving less than 10 inches of rainfall per year. Precipitation depends on elevation with lower areas in the Big Horn Basin averaging 5–8 inches; the lower areas in the North and on the eastern plains average around 10–12 inches, making the climate there semi-arid. Some mountain areas do receive a good amount of precipitation, 20 inches or more, much of it as snow, sometimes 200 inches or more annually.
The state's highest recorded temperature is 114 °F at Basin on July 12, 1900 and the lowest recorded temperature is −66 °F at Riverside on February 9, 1933. The number of thunderstorm days vary across the state with the southeastern plains of the state having the most days of thunderstorm activity. Thunderstorm activity in the state is highest during early summer; the southeastern corner of the state is the most vulnerable part of the state to tornado activity. Moving away from that point and westwards, the incidence of tornadoes drops with the west part of the state showing little vulnerability. Tornadoes, where they occur, tend to be small and brief, unlike some of those that occur farther east; as specified in the designating legislation for the Territory of Wyoming, Wyoming's borders are lines of latitude 41°N and 45°N, longitude 104°3'W and 111°3'W, making the shape of the state a latitude-longitude quadrangle. Wyoming is one of only three states to have borders along only straight latitudinal and longitudinal lines, rather than being defined by natural landmarks.
Due to surveying inaccuracies during the 19th century, Wyoming's legal border deviates from the true latitude and longitude lines by up to half of a mile in some spots in the mountainous region along the 45th parallel. Wyoming is bordered on the north by Montana, on the east by South Dakota and Nebraska, on the south by Colorado, on the southwest by Utah, on the west by Idaho, it is the tenth largest state in the United States in total area, containing 97,814 square miles and is made up of 23 counties. From the north border to the south border it is 276 miles; the Great Plains meet the Rocky Mountains in Wyoming. The state is a great plateau broken by many mountain ranges. Surface elevations range from the summit of Gannett Peak in the Wind River Mountain Range, at 13,804 feet, to the Belle Fourche River val
The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is 277 miles long, up to 18 miles wide and attains a depth of over a mile; the canyon and adjacent rim are contained within Grand Canyon National Park, the Kaibab National Forest, Grand Canyon-Parashant National Monument, the Hualapai Indian Reservation, the Havasupai Indian Reservation and the Navajo Nation. President Theodore Roosevelt was a major proponent of preservation of the Grand Canyon area, visited it on numerous occasions to hunt and enjoy the scenery. Nearly two billion years of Earth's geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. While some aspects about the history of incision of the canyon are debated by geologists, several recent studies support the hypothesis that the Colorado River established its course through the area about 5 to 6 million years ago.
Since that time, the Colorado River has driven the down-cutting of the tributaries and retreat of the cliffs deepening and widening the canyon. For thousands of years, the area has been continuously inhabited by Native Americans, who built settlements within the canyon and its many caves; the Pueblo people considered the Grand Canyon a holy site, made pilgrimages to it. The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540; the Grand Canyon is a river valley in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata, is one of the six distinct physiographic sections of the Colorado Plateau province. It is not the deepest canyon in the world. However, the Grand Canyon is known for its visually overwhelming size and its intricate and colorful landscape. Geologically, it is significant because of the thick sequence of ancient rocks that are well preserved and exposed in the walls of the canyon; these rock layers record much of the early geologic history of the North American continent.
Uplift associated with mountain formation moved these sediments thousands of feet upward and created the Colorado Plateau. The higher elevation has resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid; the uplift of the Colorado Plateau is uneven, the Kaibab Plateau that Grand Canyon bisects is over one thousand feet higher at the North Rim than at the South Rim. All runoff from the North Rim flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon; the result is deeper and longer tributary washes and canyons on the north side and shorter and steeper side canyons on the south side. Temperatures on the North Rim are lower than those on the South Rim because of the greater elevation. Heavy rains are common on both rims during the summer months. Access to the North Rim via the primary route leading to the canyon is limited during the winter season due to road closures.
The Grand Canyon is part of the Colorado River basin which has developed over the past 70 million years, in part based on apatite /He thermochronometry showing that Grand Canyon reached a depth near to the modern depth by 20 Ma. A recent study examining caves near Grand Canyon places their origins beginning about 17 million years ago. Previous estimates had placed the age of the canyon at 5–6 million years; the study, published in the journal Science in 2008, used uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon. There is a substantial amount of controversy because this research suggests such a substantial departure from prior supported scientific consensus. In December 2012, a study published in the journal Science claimed new tests had suggested the Grand Canyon could be as old as 70 million years. However, this study has been criticized by those who support the "young canyon" age of around six million years as " attempt to push the interpretation of their new data to their limits without consideration of the whole range of other geologic data sets."The canyon is the result of erosion which exposes one of the most complete geologic columns on the planet.
The major geologic exposures in the Grand Canyon range in age from the 2-billion-year-old Vishnu Schist at the bottom of the Inner Gorge to the 230-million-year-old Kaibab Limestone on the Rim. There is a gap of about a billion years between the 500-million-year-old stratum and the level below it, which dates to about 1.5 billion years ago. This large unconformity indicates a long period. Many of the formations were deposited in warm shallow seas, near-shore environments, swamps as the seashore advanced and retreated over the edge of a proto-North America. Major exceptions include the Permian Coconino Sandstone, which contains abundant geological evidence of aeolian sand dune deposition. Several parts of the Supai Group were deposited in non–marine environments; the great depth of the Grand Canyon and the height of its strata can be attributed to 5–10 thousand feet of uplift of the Colorado Plateau, starting about 65 million years ago. This uplift has steepened the stream gradient of the Colorado River
The Rocky Mountains known as the Rockies, are a major mountain range in western North America. The Rocky Mountains stretch more than 4,800 kilometers from the northernmost part of British Columbia, in western Canada, to New Mexico in the Southwestern United States. Located within the North American Cordillera, the Rockies are somewhat distinct from the Pacific Coast Ranges, Cascade Range, the Sierra Nevada, which all lie farther to the west; the Rocky Mountains formed 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began sliding underneath the North American plate. The angle of subduction was shallow, resulting in a broad belt of mountains running down western North America. Since further tectonic activity and erosion by glaciers have sculpted the Rockies into dramatic peaks and valleys. At the end of the last ice age, humans began inhabiting the mountain range. After Europeans, such as Sir Alexander Mackenzie, Americans, such as the Lewis and Clark expedition, began exploring the range and furs drove the initial economic exploitation of the mountains, although the range itself never experienced dense population.
Public parks and forest lands protect much of the mountain range, they are popular tourist destinations for hiking, mountaineering, hunting, mountain biking and snowboarding. The name of the mountains is a translation of an Amerindian name, related to Algonquian; the first mention of their present name by a European was in the journal of Jacques Legardeur de Saint-Pierre in 1752, where they were called "Montagnes de Roche". The Rocky Mountains are defined as stretching from the Liard River in British Columbia south to the Rio Grande in New Mexico; the Rockies vary in width from 110 to 480 kilometres. The Rocky Mountains are notable for containing the highest peaks in central North America; the range's highest peak is Mount Elbert located in Colorado at 4,401 metres above sea level. Mount Robson in British Columbia, at 3,954 metres, is the highest peak in the Canadian Rockies; the eastern edge of the Rockies rises above the Interior Plains of central North America, including the Sangre de Cristo Mountains of New Mexico and Colorado, 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 subranges from distinct ranges further to the west. In Canada, the western edge of the Rockies is formed by the huge Rocky Mountain Trench, which runs the length of British Columbia from its beginnings in the middle Flathead River valley in western Montana to the south bank of the Liard River. Geographers define three main groups of the Canadian Rockies: the Continental Ranges, Hart Ranges, Muskwa Ranges; the Rockies do not extend into central British Columbia. Other mountain ranges continue beyond the Liard River, including the Selwyn Mountains in Yukon, the Brooks Range in Alaska, but those are not part of the Rockies, though they are part of the American Cordillera; the Continental Divide of the Americas 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 is so named because water falling on the mountain reaches not only the Atlantic and Pacific but Hudson Bay as well. Farther north in Alberta, the Athabasca and other rivers feed the basin of the Mackenzie River, which has its outlet on the Beaufort Sea of the Arctic Ocean. Human population is not dense in the Rocky Mountains, with an average of four people per square kilometer and few cities with over 50,000 people. However, the human population grew in the Rocky Mountain states between 1950 and 1990; the forty-year statewide increases in population range from 35% in Montana to about 150% in Utah and Colorado. The populations of several mountain towns and communities have doubled in the last forty years. Jackson, increased 260%, from 1,244 to 4,472 residents, in forty years; the rocks in the Rocky Mountains were formed. The oldest rock is Precambrian metamorphic rock. There is Precambrian sedimentary argillite, dating back to 1.7 billion years ago. During the Paleozoic, western North America lay underneath a shallow sea, which deposited many kilometers of limestone and dolomite.
In the southern Rocky Mountains, near present-day Colorado, these ancestral rocks were disturbed by mountain building 300 Ma, during the Pennsylvanian. This mountain-building produced the Ancestral Rocky Mountains, they consisted 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. Terranes began colliding with the western edge of North America in the Mississippian, causing the Antler orogeny. For 270 million years, the focus of the effects of plate collisions were near the edge of the North American plate boundary, far to the west of the Rocky Mountain region, it was. The current Rocky Mountains arose in the Laramide orogeny from between 55 Ma. For the Canadi