Basin and Range index map - USGS

The Basin and Range Province is a particular type of topography that covers much of the southwestern United States and northwestern Mexico that is typified by elongate north-south trending arid valleys bounded by mountain ranges which also bound adjacent valleys. Death Valley is a good example of a modified basin and range valley. Basin and Range index map - USGS From: http://wrgis. ... Basin and Range index map - USGS From: http://wrgis. ... Surface of the Earth Topography, a term in geography, has come to refer to the lay of the land, or the physiogeographic characteristics of land in terms of elevation, slope, and orientation. ... Fljótsdalur in East-Iceland A valley is a landform, which can range from a few square miles (square kilometers) to hundreds or even thousands of square miles (square kilometers) in area. ... The most general definition of a mountain range is a group of mountains bordered by lowlands. ... The Panamint Range, Death Valley, and the Black Mountains as seen from the Space Shuttle (NASA image) Death Valley is a valley located in east-central California southeast of the Sierra Nevada range in the Great Basin, comprising much of Death Valley National Park. ...

The basins are down-fallen blocks of crust and the ranges are up-thrust slabs (actually the arrangement is a bit tilted to the east - in profile this would look similar to an encyclopedia leaning to one side - like so ///). The normal arrangement in the basin and range system is that each valley (i.e. basin) is bounded on each side by a normal fault that runs parallel to the range. Old fault exposed by roadcut near Harrisburg, Pennsylvania. ...

This arrangement is very similar to the horsts and grabens seen in divergent plate boundaries such as the Mid-Atlantic Ridge or in failed rifting areas such as the Western Rift of the Great Rift Valley in East Africa. However the extent of the rifting in the Basin and Range is not concentrated into a single valley but is spread out over a very large area creating much smaller grabens laying roughly parallel to each other in a north-south direction (which leads to a rain shadow effect resulting in exceedingly dry conditions in this province). USGS image In physical geography and geology, a horst is the raised fault block bounded by normal faults. ... USGS image A graben is a depressed block of land bordered by parallel faults. ... In plate tectonics, a divergent boundary (divergent fault boundary or divergent plate boundary) is a linear feature that exists between two tectonic plates where the plates are moving away from each other. ... Courtesy USGS The Mid-Atlantic Ridge is a mostly underwater mountain range of the Atlantic Ocean that runs from 87°N (about 333 km South of the North Pole) to subantarctic Bouvet Island, where it turns into Atlantic-Indian-Ridge and continues further East through Crozet Plateau to the Southwest... Northern section of the Great Rift Valley. ... East Africa is a region generally considered to include: Djibouti Eritrea Ethiopia Kenya Somalia Tanzania Uganda Burundi, Rwanda, Madagascar, Malawi, Mozambique, and Sudan are sometimes considered a part of East Africa. ... // A rain shadow (or more accurately, precipitation shadow) is a dry region on the surface of the Earth that is leeward or behind a mountain with respect to the prevailing wind direction. ...

Geography

The province extends east from the Sierra Nevada all the way to the Colorado Plateau and extends south over northern parts of the Baja California peninsula. This covers parts of the U.S. states of Arizona, California, Idaho, New Mexico, Texas, and Utah and almost all of Nevada. Basin and Range topography also dominates large parts of the Mexican states of Sonora, Chihuahua, and Baja California. The arid Great Basin is part of this province as well as the Sonoran Desert and the Mexican Highlands. The Sierra Nevada is a mountain range that is almost entirely in eastern California. ... The Colorado Plateau, also called the Colorado Plateaus Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. ... Baja California (highlighted) Alternative use: Baja California (state) Baja California or Lower California is a peninsula in the west of Mexico. ... A U.S. state is any one of the 50 states which have membership of the federation known as the United States of America (USA or U.S.). The separate state governments and the U.S. federal government share sovereignty. ... State nickname: The Grand Canyon State, The Copper State Other U.S. States Capital Phoenix Largest city Phoenix Governor Janet Napolitano (D) Senators John McCain (R) Jon Kyl (R) Official language(s) English Area 295,254 km² (6th)  - Land 294,312 km²  - Water 942 km² (0. ... State nickname: The Golden State Other U.S. States Capital Sacramento Largest city Los Angeles Governor Arnold Schwarzenegger (R) Senators Dianne Feinstein (D) Barbara Boxer (D) Official language(s) English Area 410,000 km² (3rd)  - Land 404,298 km²  - Water 20,047 km² (4. ... State nickname: Gem State Other U.S. States Capital Boise Largest city Boise Governor Dirk Kempthorne (R) Senators Larry Craig (R) Mike Crapo (R) Official language(s) none Area 216,632 km² (14th)  - Land 214,499 km²  - Water 2,133 km² (0. ... State nickname: Land of Enchantment Other U.S. States Capital Santa Fe Largest city Albuquerque Governor Bill Richardson (D) Senators Pete Domenici (R) Jeff Bingaman (D) Official language(s) English and Spanish Area 315,194 km² (5th)  - Land 314,590 km²  - Water 607 km² (0. ... ... Utah is one of the Four Corners states, and is bordered by: Idaho (at 42°N) and Wyoming (at 41°N and 111°W) in the north, by Colorado (at 109°W) in the east, at a single point by New Mexico to the southeast (at the Four Corners Monument... State nickname: Silver State, Battle Born State (official) Other U.S. States Capital Carson City Largest city Las Vegas Governor Kenny Guinn (R) Senators Harry Reid (D) John Ensign (R) Official languages None Area 286,367 km² (7th)  - Land 284,396 km²  - Water 1,971 km² (0. ... Sonora is a state in northwestern Mexico, bordering the states of Chihuahua to the east, Sinaloa to the south, and Baja California to the northwest. ... The state of Chihuahua is the largest of the 31 states of Mexico and is located in the northwestern part of the country. ... Other Mexican States Capital Mexicali Other major cities Tijuana Ensenada list of municipalities Area 69,921 km² Ranked 12th Population (2000 census) 2,487,700 Ranked 15th Governor (2001-07) Eugenio Elorduy Walther (PAN/PVEM) Federal Deputies (6) PAN = 6 Federal Senators PAN = 2 PRI = 1 ISO 3166-2 Postal... Map showing the Great Basin in orange The Great Basin is a large, arid region of the western United States, commonly defined as the contiguous watershed region, roughly between the Rocky Mountains and the Sierra Nevada, that has no natural outlet to the sea. ... Sonoran Desert wildlife Mountains in the Sonoran Desert The Sonoran Desert is a North American desert which straddles part of the border between the United States and Mexico and covers large parts of the states of Arizona, California and Sonora. ...

Geology

Full extent of the Basin and Range

This unique topography has formed as the result of extension (literally the Earth's crust is being pulled apart) that is thought to be caused by the effect of the Pacific Plate moving north relative to the North American Plate (this is the same force behind the creation of the San Andreas Fault) and by other forces (see below). The crust here has been stretched up to 100% of its original width. In fact, the crust underneath the Basin and Range, especially under the Great Basin, is some of the thinnest in the world. Along the roughly north-south-trending faults mountains were uplifted and valleys down-dropped, producing the distinctive alternating pattern of linear mountain ranges and valleys of the Basin and Range province. A map showing these stretch marks, and noting their association with earth movements, is at the USGS report on the Pleasant Valley (Nevada) Earthquake. Image File history File links NPS image from http://www. ... The Pacific plate is shown in pale yellow on this map The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean. ... The North American plate is shown in brown on this map The North American Plate is a continental tectonic plate covering the continent of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... View of the San Andreas Fault on the Carrizo Plain in central California The San Andreas Fault is a geological fault, known as a right-lateral strike-slip fault, that spans a length of roughly 800 miles (1287 kilometers) through California. ... Map showing the Great Basin in orange The Great Basin is a large, arid region of the western United States, commonly defined as the contiguous watershed region, roughly between the Rocky Mountains and the Sierra Nevada, that has no natural outlet to the sea. ...

Although there are other types of faults in the Basin and Range province, the extension and crustal stretching that have shaped the present landscape produce mostly normal faults. The upthrown side of these faults form mountains that rise abruptly and steeply, and the down-dropped side creates low valleys. The fault plane, along which the two sides of the fault move, extends deep in the crust, usually an angle of 60 degrees. In places, the relief or vertical difference between the two sides is as much as 10,000 feet (just over 3000 m). Old fault exposed by roadcut near Harrisburg, Pennsylvania. ...

Kingston Range

Subsequent to the mountain building episode a large part of the mountain belt created in the Laramide orogeny and previous orogenies (the Sevier, and part of the Nevadan) went through a long period of extension that persists today. Image File history File links Download high resolution version (1800x1200, 236 KB) Looking southeast from Emigrant Pass in the Nopah Range towards Kingston Range, Mojave Desert, California, taken March 2005 by User:Stan Shebs File links The following pages link to this file: Mojave Desert Basin and Range ... Image File history File links Download high resolution version (1800x1200, 236 KB) Looking southeast from Emigrant Pass in the Nopah Range towards Kingston Range, Mojave Desert, California, taken March 2005 by User:Stan Shebs File links The following pages link to this file: Mojave Desert Basin and Range ... The Laramide orogeny was a 30 million year period of mountain building in western North America that started in the Late Cretaceous, 70 million years ago, and ended in the Late Paleogene 40 million years ago. ... The Sevier orogeny was a mountain-building event that affected western North America between aproximately 150 million years ago (Ma), and 80 Ma. ... The Nevadan Orogeny was a major mountain building event that took place along the western edge of ancient North America between the Mid to Late Jurassic(between about 180 and 146 million years ago). ...

As the rocky ranges rise, they are immediately subject to weathering and erosion. The exposed bedrock is attacked by water, ice, wind and other erosional agents. Rock particles are stripped away and wash down the mountain sides, often covering young faults until they rupture again. Sediment collects in the adjacent valleys, in some places burying the bedrock under thousands of feet of rock debris. Our earth is composed of three main types of rock, each having been formed in its own special way. ... Weathering is the process of decomposition and/or disintegration of rocks and their minerals in situ, that is, in place. ... Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock, and so forth) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). ... Water (from the Old English word wæter; c. ... A natural, 4 tonne, block of ice on a beach in Iceland Icicles Ice is the solid form of water. ... Wind is the quasi-horizontal movement of air (as opposed to an air current) caused by Howard Sterns asshole. ...

There are several hypotheses trying to explain how the continental crust of North America responded to the great deal of compaction it went through with the Laramide orogeny. There is at least some evidence to support all of these ideas but it is very possible that more than one is correct: The continental crust is the layer of granitic and sedimentary rock which forms the continents and the areas of shallow seabed close to their shores, known as continental shelves. ...

1. Movement of the Pacific Plate is stretching the North American Plate toward the West.
2. As the spreading center (divergent plate boundary) of the subducting Farallon Plate moved beneath the North American plate, it formed a "slab gap", which caused heat from the mantle plume feeding the spreading zone to thin out the continental crust above it and cause the spreading (see slab gap hypothesis).
3. After the Laramide orogeny, the crust under the Rockies got overthickened and the Great Basin spread out in response.
4. The continental root of the proto-Rockies was so deep that the bottom part broke off and was incorporated into the asthenosphere.

The Pacific plate is shown in pale yellow on this map The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean. ... The North American plate is shown in brown on this map The North American Plate is a continental tectonic plate covering the continent of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... In plate tectonics, a divergent boundary (divergent fault boundary or divergent plate boundary) is a linear feature that exists between two tectonic plates where the plates are moving away from each other. ... The Farallon Plate is an ancient tectonic plate which began subducting as Pangaea broke apart during the Jurassic period. ... A mantle plume is a manifestation of a type of geological phenomenon originally proposed by W. Jason Morgan in 1971. ... In geology, the slab gap hypothesis is one of the explanations put forward to explain several instances of extension that have seemingly paradoxically occurred near subduction zones (which otherwise would typically compact crust, not stretch it out). ... Map showing the Great Basin in orange The Great Basin is a large, arid region of the western United States, commonly defined as the contiguous watershed region, roughly between the Rocky Mountains and the Sierra Nevada, that has no natural outlet to the sea. ... Dont be afraid of big words. ...

References

• Steven M. Stanley, Earth System History (W.H. Freeman and Company; 1999) pages 537, 540-543, 545 ISBN 0-7167-2882-6
• Plummer, McGeary, Carlson, Physical Geology, Eight Edition (McGraw-Hill: Boston, 1999) pages 321, 513, 514 ISBN 0-697-37404-1
• USGS - Geologic Provinces of the United States: Basin and Range Province (adapted public domain text)

Further reading

• Basin and Range by John McPhee, Noonday Press, 1990. ISBN 0374516901
• Geology of the American Southwest : A Journey Through Two Billion Years of Plate Tectonic History by W. Scott Baldridge, Cambridge University Press, 2004. ISBN 0521016665