Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, snowflakes take on a variety of shapes, basic among these are platelets, needles and rime. As snow accumulates into a snowpack, it may blow into drifts, over time, accumulated snow metamorphoses, by sintering and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture. In the Southern Hemisphere, snow is confined primarily to mountainous areas, Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds that themselves are part of a weather system.
The physics of snow crystal development in clouds results from a set of variables that include moisture content. The resulting shapes of the falling and fallen crystals can be classified into a number of shapes and combinations. Occasionally, some plate-like and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Two additional and locally productive sources of snow are lake-effect storms and elevation effects, miid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemispheres fall and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall, in the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side, a cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface.
The strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, in cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air, snow transitions to rain in the warm sector behind the front. The same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the air mass is uplifted by the orographic influence of higher elevations on the downwind shores
The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided. Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc, Mont Blanc spans the French–Italian border, and at 4,810 m is the highest mountain in the Alps. The Alpine region area contains about a hundred peaks higher than 4000 metres, the altitude and size of the range affects the climate in Europe, in the mountains precipitation levels vary greatly and climatic conditions consist of distinct zones. Wildlife such as live in the higher peaks to elevations of 3,400 m. Evidence of human habitation in the Alps goes back to the Palaeolithic era, a mummified man, determined to be 5,000 years old, was discovered on a glacier at the Austrian–Italian border in 1991. By the 6th century BC, the Celtic La Tène culture was well established, Hannibal famously crossed the Alps with a herd of elephants, and the Romans had settlements in the region.
In 1800 Napoleon crossed one of the passes with an army of 40,000. The 18th and 19th centuries saw an influx of naturalists, writers, in World War II, Adolf Hitler kept a base of operation in the Bavarian Alps throughout the war. The Alpine region has a cultural identity. The Winter Olympic Games have been hosted in the Swiss, French, at present, the region is home to 14 million people and has 120 million annual visitors. The English word Alps derives from the Latin Alpes, maurus Servius Honoratus, an ancient commentator of Virgil, says in his commentary that all high mountains are called Alpes by Celts. The term may be common to Italo-Celtic, because the Celtic languages have terms for high mountains derived from alp and this may be consistent with the theory that in Greek Alpes is a name of non-Indo-European origin. According to the Old English Dictionary, the Latin Alpes might possibly derive from a pre-Indo-European word *alb hill, Albania, a name not native to the region known as the country of Albania, has been used as a name for a number of mountainous areas across Europe.
In Roman times, Albania was a name for the eastern Caucasus, in modern languages the term alp, albe or alpe refers to a grazing pastures in the alpine regions below the glaciers, not the peaks. An alp refers to a mountain pasture where cows are taken to be grazed during the summer months and where hay barns can be found. The Alps are a crescent shaped geographic feature of central Europe that ranges in a 800 km arc from east to west and is 200 km in width, the mean height of the mountain peaks is 2.5 km. The range stretches from the Mediterranean Sea north above the Po basin, extending through France from Grenoble, the range continues onward toward Vienna and east to the Adriatic Sea and Slovenia. To the south it dips into northern Italy and to the north extends to the border of Bavaria in Germany
A mountain is a large landform that stretches above the surrounding land in a limited area, usually in the form of a peak. A mountain is steeper than a hill. Mountains are formed through tectonic forces or volcanism and these forces can locally raise the surface of the earth. Mountains erode slowly through the action of rivers, weather conditions, a few mountains are isolated summits, but most occur in huge mountain ranges. High elevations on mountains produce colder climates than at sea level and these colder climates strongly affect the ecosystems of mountains, different elevations have different plants and animals. Because of the less hospitable terrain and climate, mountains tend to be used less for agriculture and more for resource extraction and recreation, the highest mountain on Earth is Mount Everest in the Himalayas of Asia, whose summit is 8,850 m above mean sea level. The highest known mountain on any planet in the Solar System is Olympus Mons on Mars at 21,171 m, there is no universally accepted definition of a mountain.
Elevation, relief, steepness and continuity have been used as criteria for defining a mountain, whether a landform is called a mountain may depend on local usage. The highest point in San Francisco, California, is called Mount Davidson, notwithstanding its height of 300 m, Mount Scott outside Lawton, Oklahoma is only 251 m from its base to its highest point. Whittows Dictionary of Physical Geography states Some authorities regard eminences above 600 metres as mountains, in addition, some definitions include a topographical prominence requirement, typically 100 or 500 feet. For a while, the US defined a mountain as being 1,000 feet or taller, any similar landform lower than this height was considered a hill. However, the United States Geological Survey concludes that these terms do not have technical definitions in the US, using these definitions, mountains cover 33% of Eurasia, 19% of South America, 24% of North America, and 14% of Africa. As a whole, 24% of the Earths land mass is mountainous, there are three main types of mountains, volcanic and block.
All three types are formed from plate tectonics, when portions of the Earths crust move, compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity. Volcanoes are formed when a plate is pushed below another plate, at a depth of around 100 km, melting occurs in rock above the slab, and forms magma that reaches the surface. When the magma reaches the surface, it builds a volcanic mountain. Examples of volcanoes include Mount Fuji in Japan and Mount Pinatubo in the Philippines, the magma does not have to reach the surface in order to create a mountain, magma that solidifies below ground can still form dome mountains, such as Navajo Mountain in the US
Siberia is an extensive geographical region, and by the broadest definition is known as North Asia. Siberia has historically been a part of Russia since the 17th century, the territory of Siberia extends eastwards from the Ural Mountains to the watershed between the Pacific and Arctic drainage basins. It stretches southwards from the Arctic Ocean to the hills of north-central Kazakhstan and to the borders of Mongolia. With an area of 13.1 million square kilometres, Siberia accounts for 77% of Russias land area and this is equivalent to an average population density of about 3 inhabitants per square kilometre, making Siberia one of the most sparsely populated regions on Earth. If it were a country by itself, it would still be the largest country in area, the origin of the name is unknown. Some sources say that Siberia originates from the Siberian Tatar word for sleeping land, another account sees the name as the ancient tribal ethnonym of the Sirtya, a folk, which spoke a language that evolved into the Ugric languages.
This ethnic group was assimilated to the Siberian Tatar people. The modern usage of the name was recorded in the Russian language after the Empires conquest of the Siberian Khanate, a further variant claims that the region was named after the Xibe people. The Polish historian Chycliczkowski has proposed that the name derives from the word for north. He said that the neighbouring Chinese and Mongolians would not have known Russian and he suggests that the name is a combination of two words, su and bir. The region is of significance, as it contains bodies of prehistoric animals from the Pleistocene Epoch. Specimens of Goldfuss cave lion cubs and another woolly mammoth from Oymyakon, a rhinoceros from the Kolyma River. The Siberian Traps were formed by one of the largest known volcanic events of the last 500 million years of Earths geological history. They continued for a million years and are considered a cause of the Great Dying about 250 million years ago. At least three species of human lived in Southern Siberia around 40,000 years ago, H. sapiens, H. neanderthalensis, the last was determined in 2010, by DNA evidence, to be a new species.
Siberia was inhabited by different groups of such as the Enets, the Nenets, the Huns, the Scythians. The Khan of Sibir in the vicinity of modern Tobolsk was known as a prominent figure who endorsed Kubrat as Khagan of Old Great Bulgaria in 630, the Mongols conquered a large part of this area early in the 13th century. With the breakup of the Golden Horde, the autonomous Khanate of Sibir was established in the late 15th century, turkic-speaking Yakut migrated north from the Lake Baikal region under pressure from the Mongol tribes during the 13th to 15th century
The Karakoram, or Karakorum is a large mountain range spanning the borders of Pakistan and China, with the northwest extremity of the range extending to Afghanistan and Tajikistan. It is located in the regions of Gilgit–Baltistan and southern Xinjiang, a part of the complex of ranges from the Hindu Kush to the Himalayan Range, it is one of the Greater Ranges of Asia. The Karakoram is home to the four most closely located peaks over 8000m in height on earth, K2, the range is about 500 km in length, and is the most heavily glaciated part of the world outside the polar regions. The Siachen Glacier at 76 kilometres and the Biafo Glacier at 63 kilometres rank as the worlds second, the Karakoram is bounded on the northeast by the edge of the Tibetan Plateau, and on the north by the Pamir Mountains. Karakoram is a Turkic term meaning black gravel, the name was first applied by local traders to the Karakoram Pass. Due to its altitude and ruggedness, the Karakoram is much less inhabited parts of the Himalayas further east.
European explorers first visited early in the 19th century, followed by British surveyors starting in 1856, the Muztagh Pass was crossed in 1887 by the expedition of Colonel Francis Younghusband and the valleys above the Hunza River were explored by General Sir George K. Cockerill in 1892. Explorations in the 1910s and 1920s established most of the geography of the region, the name Karakoram was used in the early 20th century, for example by Kenneth Mason, for the range now known as the Baltoro Muztagh. The term is now used to refer to the range from the Batura Muztagh above Hunza in the west to the Saser Muztagh in the bend of the Shyok River in the east. Floral surveys were carried out in the Shyok River catchment and from Panamik to Turtuk village by Chandra Prakash Kala during 1999 and 2000, the Karakoram is in one of the worlds most geologically active areas, at the plate boundary between the Indo-Australian plate and the Eurasian plate. A significant part, 28-50% of the Karakoram Range is glaciated, compared to the Himalaya, mountain glaciers may serve as an indicator of climate change and receding with long-term changes in temperature and precipitation.
Karakoram glaciers are mostly stagnating or enlarging, unlike in the Himalayas, where there is no such insulation, the rate of retreat is high. In the last ice age, a series of glaciers stretched from western Tibet to Nanga Parbat. To the south, the Indus glacier was the valley glacier. In the north, the Karakoram glaciers joined those from the Kunlun Mountains, while the current valley glaciers in the Karakoram reach a maximum length of 76 kilometres, several of the ice-age valley glacier branches and main valley glaciers, had lengths up to 700 kilometres. During the Ice age, the snowline was about 1,300 metres lower than today. Baltistan has more than 100 mountain peaks exceeding 6,100 metres height from sea level. K1, Masherbrum K2 K3, Gasherbrum IV K3a, Gasherbrum III K4, Gasherbrum II K5, Gasherbrum I K6, Baltistan Peak K7,6,934 m peak near Charakusa Valley K9, approx
It is the second highest summit in Ecuador, reaching a height of 5,897 m. It is one of the worlds highest volcanoes, since 1738, Cotopaxi has erupted more than 50 times, resulting in the creation of numerous valleys formed by lahars around the volcano. The last eruption lasted from August 2015 to January 2016, since the recent eruptions, Cotopaxi has been officially closed for climbing by authorities. On a clear day, Cotopaxi is clearly visible on the skyline from Quito and is part of the chain of volcanoes around the Pacific plate known as the Pacific Ring of Fire. It has an almost symmetrical cone that rises from a plain of about 3,800 metres. It has one of the few glaciers in the world. At its summit, Cotopaxi has an 800 X550 m wide crater which is 250 m deep, the crater consists of two concentric crater rims, the outer one being partly free of snow and irregular in shape. The crater interior is covered with ice cornices and rather flat, the highest point is on the outer rim of the crater on the north side.
Many sources claim that Cotopaxi means Neck of the Moon in an indigenous language, the mountain was honored as a Sacred Mountain by local Andean people, even prior to the Inca invasion in the 15th century. It was worshiped as “rain sender”, that served as the guarantor of the lands fertility, with 87 known eruptions, Cotopaxi is one of Ecuadors most active volcanoes. The first recorded eruption of Cotopaxi was in 1534, cotopaxis most violent eruptions in historical times occurred in the years 1742,1744,1768, and 1877. The 1744 and 1768 events destroyed the town of Latacunga. The city of Latacunga was again leveled completely due to the mudslide deposits, there was a major eruption from 1903 to 1904, and minor activity persisted until at least 1940 and possibly 1942. The same source reported increased thermal/seismic, non-eruptive activity in 1975 and 2002, in the increased activity of 2002, fumarolic activity and sulfuric emissions increased and ice around the inside and on the southeastern side of the cone started to melt.
However, no eruption was observed. In 2015, two large phreatic eruptions in the morning of the 14th of August marked a new phase of volcanic activity, the volcano remains in a very abnormal situation. In August,2,100 earthquakes were recorded and emission rates of sulfur dioxide reach approximately 20,000 tonnes per day, the government estimates some 300,000 people are at risk from the volcano in the provinces of Cotopaxi, Tungurahua and Pichincha. The first European who tried to climb the mountain was Alexander von Humboldt in 1802, however, in 1858 Moritz Wagner investigated the mountain, but he could not reach the summit either
The majority of Southeast Alaskas area is part of the Tongass National Forest, the United States largest national forest. In many places, the border runs along the crest of the Boundary Ranges of the Coast Mountains. The region is noted for its scenery and mild rainy climate, Southeast Alaska is the northern terminus of the Inside Passage, a protected waterway of convoluted passages between islands and fjords, beginning in Puget Sound in Washington state. This was an important travel corridor for Tlingit and Haida Native peoples, in modern times it is an important route for Alaska Marine Highway ferries as well as cruise ships. Southeast Alaska has an area of 35,138 square miles comprising seven entire boroughs. Although it has only 6.14 percent of Alaskas land area, it is larger than the state of Maine, the Southeast Alaskan coast is roughly as long as the west coast of Canada. The 2010 census population of Southeast was 71,616 inhabitants, the largest islands are, from North to South, Chichagof Island, Admiralty Island, Baranof Island, Kupreanof Island, Revillagigedo Island and Prince of Wales Island.
Major bodies of water of Southeast Alaska include Glacier Bay, Lynn Canal, Icy Strait, Chatham Strait, Stephens Passage, Frederick Sound, Sumner Strait, and Clarence Strait. On August 20,1902, President Theodore Roosevelt established the Alexander Archipelago Forest Reserve, Glacier Bay National Park and Preserve Klondike Gold Rush National Historical Park Sitka National Historical Park Wrangell-St. The most common species are sitka spruce and western hemlock. Major cities are Juneau and Sitka, other towns are Petersburg, Metlakatla, Hoonah, Kake, Klawock, Thorne Bay, Yakutat and Gustavus. This region is home to the easternmost town in Alaska. This area is the homeland of the Tlingit, and home of a historic settling of Haida as well as a modern settlement of Tsimshian. The region is connected to Seattle and the American Pacific Northwest economically and culturally. In modern times, southeastern Alaskans can often be identified by their choices, notably Xtratuf boots. Major industries in Southeast Alaska include commercial fishing and tourism and its members include Alcan Forest Products and Viking Lumber, which had been founded in Maine.
Debates over whether to expand logging in the federally owned Tongass are not uncommon, mining remains important in the northern area with the Juneau mining district and Admiralty mining district hosting active mines as of 2015. Gold was discovered in 1880 and played an important part in the history of the region
The Pyrenees is a range of mountains in southwest Europe that forms a natural border between France and Spain. For the most part, the main crest forms a divide between France and Spain, with the microstate of Andorra sandwiched in between. The Crown of Aragon and the Kingdom of Navarre have historically extended on both sides of the range, with smaller northern portions now in France and larger southern parts now in Spain. The demonym for the noun Pyrenees in English is Pyrenean, in Greek mythology, Pyrene is a princess who gave her name to the Pyrenees. The Greek historian Herodotus says Pyrene is the name of a town in Celtic Europe, characteristically drunk and lustful, violates the sacred code of hospitality and rapes his hosts daughter. Pyrene gives birth to a serpent and runs away to the woods, she pours out her story to the trees, attracting the attention of wild beasts who tear her to pieces. After his victory over Geryon, Hercules passes through the kingdom of Bebryx again, and all the rock-cliffs and wild-beast haunts echo back Pyrene.
… The mountains hold on to the name through the ages. Pliny the Elder connects the story of Hercules and Pyrene to Lusitania, the Spanish Pyrenees are part of the following provinces, from east to west, Barcelona, Huesca and Gipuzkoa. The French Pyrenees are part of the following départements, from east to west, Pyrénées-Orientales, Ariège, Haute-Garonne, Hautes-Pyrénées, the independent principality of Andorra is sandwiched in the eastern portion of the mountain range between the Spanish Pyrenees and French Pyrenees. Physiographically, the Pyrenees may be divided into three sections, the Atlantic, the Central, and the Eastern Pyrenees, they form a distinct physiographic province of the larger Alpine System division. In the Western Pyrenees, from the Basque mountains near the Bay of Biscay of the Atlantic Ocean, at the eastern end on the southern side lies a distinct area known as the Sub-Pyrenees. On the French side the slopes of the range descend abruptly. The Pyrenees are older than the Alps, their sediments were first deposited in coastal basins during the Paleozoic and Mesozoic eras, the intense pressure and uplifting of the Earths crust first affected the eastern part and moved progressively to the entire chain, culminating in the Eocene Epoch.
The eastern part of the Pyrenees consists largely of granite and gneissose rocks, the massive and unworn character of the chain comes from its abundance of granite, which is particularly resistant to erosion, as well as weak glacial development. Low passes are lacking, and the roads and the railroads between France and Spain run only in the lowlands at the western and eastern ends of the Pyrenees. A notable visual feature of mountain range is La Brèche de Roland, a gap in the ridge line. Coal deposits capable of being profitably worked are situated chiefly on the Spanish slopes, the open pit of Trimoun close to the commune of Luzenac is one of the greatest sources of talc in Europe
Aerial photography is the taking of photographs of the ground from an elevated/direct-down position. Usually the camera is not supported by a ground-based structure, mounted cameras may be triggered remotely or automatically, hand-held photographs may be taken by a photographer. Aerial photography should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that chase, Aerial photography was first practiced by the French photographer and balloonist Gaspard-Félix Tournachon, known as Nadar, in 1858 over Paris, France. However, the photographs he produced no longer exist and therefore the earliest surviving aerial photograph is titled Boston, as the Eagle, taken by James Wallace Black and Samuel Archer King on October 13,1860, it depicts Boston from a height of 630m. Kite aerial photography was pioneered by British meteorologist E. D. Archibald in 1882 and he used an explosive charge on a timer to take photographs from the air. Frenchman Arthur Batut began using kites for photography in 1888, Samuel Franklin Cody developed his advanced Man-lifter War Kite and succeeded in interesting the British War Office with its capabilities.
The first use of a motion picture camera mounted to an aircraft took place on April 24,1909 over Rome in the 3,28 silent film short. The use of aerial photography rapidly matured during the war, as aircraft were equipped with cameras to record enemy movements. At the start of the conflict, the usefulness of aerial photography was not fully appreciated, germany adopted the first aerial camera, a Görz, in 1913. The French began the war with several squadrons of Blériot observation aircraft equipped with cameras for reconnaissance, the French Army developed procedures for getting prints into the hands of field commanders in record time. Frederick Charles Victor Laws started aerial photography experiments in 1912 with No.1 Squadron of the Royal Flying Corps, in 1916 the Austro-Hungarian Monarchy made vertical camera axis aerial photos above Italy for map-making. The camera was inserted into the floor of the aircraft and could be triggered by the pilot at intervals. In January 1918, General Allenby used five Australian pilots from No.1 Squadron AFC to photograph a 624 square miles area in Palestine as an aid to correcting and improving maps of the Turkish front and this was a pioneering use of aerial photography as an aid for cartography.
Beginning 5 January, they flew with an escort to ward off enemy fighters. The first commercial aerial photography company in the UK was Aerofilms Ltd, founded by World War I veterans Francis Wills, the company soon expanded into a business with major contracts in Africa and Asia as well as in the UK. Operations began from the Stag Lane Aerodrome at Edgware, using the aircraft of the London Flying School, the Aircraft Manufacturing Company, hired an Airco DH.9 along with pilot entrepreneur Alan Cobham. From 1921, Aerofilms carried out vertical photography for survey and mapping purposes, during the 1930s, the company pioneered the science of photogrammetry, with the Ordnance Survey amongst the companys clients. One Fairchild aerial survey aircraft in 1935 carried unit that combined two synchronized cameras, and each camera having five six inch lenses with a ten-inch lenses, each photo covered two hundred and twenty five square miles
Satellite imagery consists of images of Earth or other planets collected by satellites. Imaging satellites are operated by governments and businesses around the world, Satellite imaging companies sell images under licence. Images are licensed to governments and businesses such as Apple Maps, the first images from space were taken on sub-orbital flights. The U. S-launched V-2 flight on October 24,1946 took one image every 1.5 seconds. With an apogee of 65 miles, these photos were from five times higher than the previous record, the first satellite photographs of Earth were made on August 14,1959 by the U. S. The first satellite photographs of the Moon might have made on October 6,1959 by the Soviet satellite Luna 3. The Blue Marble photograph was taken from space in 1972, and has very popular in the media. Also in 1972 the United States started the Landsat program, the largest program for acquisition of imagery of Earth from space, Landsat Data Continuity Mission, the most recent Landsat satellite, was launched on 11 February 2013.
In 1977, the first real time satellite imagery was acquired by the United Statess KH-11 satellite system, all satellite images produced by NASA are published by NASA Earth Observatory and are freely available to the public. Several other countries have satellite imaging programs, and a collaborative European effort launched the ERS, there are private companies that provide commercial satellite imagery. Images can be in visible colours and in other spectra, there are elevation maps, usually made by radar images. Interpretation and analysis of imagery is conducted using specialized remote sensing applications. There are four types of resolution when discussing satellite imagery in remote sensing, spectral and radiometric. GSD is a term containing the optical and systemic noise sources and is useful for comparing how well one sensor can see an object on the ground within a single pixel. For example, the GSD of Landsat is ~30m, which means the smallest unit that maps to a single pixel within an image is ~30m x 30m, the latest commercial satellite has a GSD of 0.41 m.
This compares to a 0.3 m resolution obtained by some early military film based Reconnaissance satellite such as Corona, the resolution of satellite images varies depending on the instrument used and the altitude of the satellites orbit. For example, the Landsat archive offers repeated imagery at 30 meter resolution for the planet, Landsat 7 has an average return period of 16 days. For many smaller areas, images with resolution as high as 41 cm can be available, Satellite imagery is sometimes supplemented with aerial photography, which has higher resolution, but is more expensive per square meter
The Rocky Mountains, commonly known as the Rockies, are a major mountain range in western North America. The Rocky Mountains stretch more than 3,000 miles from the northernmost part of British Columbia, in western Canada, to New Mexico, in the Southwestern United States. Within the North American Cordillera, the Rockies are somewhat distinct from the Pacific Coast Ranges, the Rocky Mountains were initially formed from 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began to slide underneath the North American plate. The angle of subduction was shallow, resulting in a belt of mountains running down western North America. Since then, further tectonic activity and erosion by glaciers have sculpted the Rockies into dramatic peaks, at the end of the last ice age, humans started to inhabit the mountain range. The first mention of their present name by a European was in the journal of Jacques Legardeur de Saint-Pierre in 1752, the Rocky Mountains are commonly defined as stretching from the Liard River in British Columbia south to the Rio Grande in New Mexico.
The United States definition of the Rockies includes the Cabinet and Salish Mountains of Idaho and their counterparts north of the Kootenai River, the Columbia Mountains, are considered a separate system in Canada, lying to the west of the huge Rocky Mountain Trench. This runs the length of British Columbia from its beginnings in the middle Flathead River valley in western Montana to the bank of the Liard River. The Rockies vary in width from 70 to 300 miles, 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 side of the Trench. In Canada geographers define three main groups of ranges, the Continental Ranges, Hart Ranges and Muskwa Ranges, the Muskwa and Hart Ranges together comprise what is known as the Northern Rockies. The western edge of the Rockies includes ranges such as the Wasatch near Salt Lake City, 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 Rocky Mountain System within the United States is a United States physiographic region, the Rocky Mountains are notable for containing the highest peaks in central North America. The ranges highest peak is Mount Elbert located in Colorado at 14,440 feet above sea level, Mount Robson in British Columbia, at 12,972 feet, is the highest peak in the Canadian Rockies. The Continental Divide of the Americas is located in the Rocky Mountains, triple Divide Peak in Glacier National Park is so named because water that falls 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, see Rivers of the Rocky Mountains for a list of rivers. Human population is not very dense in the Rocky Mountains, with an average of four people per square kilometer, the human population grew rapidly in the Rocky Mountain states between 1950 and 1990. The 40-year statewide increases in range from 35% in Montana to about 150% in Utah