| High Plains | |
|---|---|
 Abuffalo wallow on the High Plains.[1] | |
 Physiographic regions of the United States. The High Plains region is the center yellow area designated 13d.[2] | |
| Floor elevation | 1,500–6,000 ft (460–1,830 m)[3] |
| Length | 800 mi (1,300 km) |
| Width | 400 mi (640 km) |
| Area | 174,000 sq mi (450,000 km2) [4] |
| Geography | |
| Country | United States |
TheHigh Plains are a subregion of theGreat Plains, mainly in theWestern United States, but also partly in theMidwest states of Nebraska, Kansas, and South Dakota, generally encompassing the western part of the Great Plains before the region reaches theRocky Mountains. The High Plains are located ineastern Montana, southeasternWyoming, southwesternSouth Dakota, westernNebraska,eastern Colorado, westernKansas,eastern New Mexico, theOklahoma Panhandle, and theTexas Panhandle.[5] The southern region of the Western High Plains ecology region contains the geological formation known asLlano Estacado which can be seen from a short distance or on satellite maps.[6] From east to west, the High Plains rise in elevation from around 1,500 to 6,000 ft (460 to 1,830 m).[3]
The term "Great Plains", for the region west of about the 96th or 98th meridian and east of the Rocky Mountains, was not generally used before the early 20th century.Nevin Fenneman's 1916 study,Physiographic Subdivision of the United States,[7] brought the term Great Plains into more widespread usage. Prior to 1916, the region was almost invariably called the High Plains, in contrast to the lower Prairie Plains of the Midwestern states.[8] Today, the term "High Plains" is usually used for a subregion instead of the whole of the Great Plains.
The High Plains has a"cold semi-arid" climate—KöppenBSk—receiving between 10–20 in (250–510 mm) of precipitation annually.
Due to low moisture and high elevation, the High Plains commonly experience wide ranges and extremes in temperature. The temperature range from day to night is usually 30 °F (17 °C), and 24-hour temperature shifts of 100 °F (56 °C) are possible, as evidenced by a weather event that occurred inBrowning, Montana, from January 23–24, 1916, when the temperature fell from 44 to −56 °F (7 to −49 °C). This is the world record for the greatest temperature change in 24 hours.[9] The region is known for the steady, and sometimes intense, winds that prevail from the west. The winds add a considerablewind chill factor in the winter. The development ofwind farms in the High Plains is one of the newest areas of economic development.
The High Plains are anomalously high in elevation. An explanation has recently been proposed to explain this high elevation. As theFarallon plate wassubducted into the mantle beneath the region, water trapped in hydrous minerals in the descending slab was forced up into the lower crust above. Within the crust, this water caused the hydration of densegarnet and other phases into lower densityamphibole andmica minerals. The resulting increase in crustal volume raised the elevation by about one mile.[10][11]
Typical plant communities of the region areshortgrass prairie,prickly pear cacti andscrub.Sagebrush steppe is also present, particularly in high and dry areas closer to the Rocky Mountains.
Agriculture in the forms ofcattleranching and the growing ofwheat,corn, andsunflower is the primary economic activity in the region. The region's aridity necessitates either dryland farming methods or irrigation; much water for irrigation is drawn from the underlyingOgallala Aquifer, which makes it possible to grow water-intensive crops such as corn, which the region's aridity would otherwise not support.[12] Some areas of the High Plains have significantpetroleum andnatural gas deposits.
The combination of oil, natural gas, and wind energy, along with plentiful underground water, has allowed some areas (such asWest Texas) to sustain a range of economic activity, including occasional industry. For example, theASARCO refinery inAmarillo, Texas has been in operation since 1924 due to the plentiful and inexpensive natural gas and water that are needed in metal ore refining.[citation needed]
The High Plains has one of the lowest population densities of any region in the continental United States;Wyoming, for example, has the second lowestpopulation density in the country afterAlaska. In contrast to the stagnant population growth in the northern and western High Plains, cities inwest Texas have shown sustained growth;Amarillo andLubbock both have populations above 200,000 and have continued to grow.[13] Smaller towns, on the other hand, oftenstruggle to sustain their population.
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