High Plains (United States)

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,^[6] 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.^[7] 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—Köppen BSk—receiving between 10–20 in (250–510 mm) of precipitation annually.

Due to low moisture and high elevation, the High Plains commonly experiences wide ranges and extremes in temperature. The temperature range from day to night is usually 30 °F (~16.5 °C), and 24-hour temperature shifts of 100 °F (~55.5 °C) are possible, as evidenced by a weather event that occurred in Browning, 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.^[8] The region is known for the steady, and sometimes intense, winds that prevail from the west. The winds add a considerable wind chill factor in the winter. The development of wind 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 the Farallon plate was subducted 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 dense garnet and other phases into lower density amphibole and mica minerals. The resulting increase in crustal volume raised the elevation about one mile.^[9][10]

Typical plant communities of the region are shortgrass prairie, prickly pear cacti and scrub. Sagebrush steppe is also present, particularly in high and dry areas closer to the Rocky Mountains.

Agriculture in the forms of cattle ranching and the growing of wheat, corn, and sunflower 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 underlying Ogallala Aquifer, which makes it possible to grow water-intensive crops such as corn, which the region's aridity would otherwise not support.^[11] Some areas of the High Plains have significant petroleum and natural gas deposits.

The combination of oil, natural gas, and wind energy, along with plentiful underground water, has allowed some areas (such as West Texas) to sustain a range of economic activity, including occasional industry. For example, the ASARCO refinery in Amarillo, 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 lowest population density in the country after Alaska. In contrast to the stagnant population growth in the northern and western High Plains, cities in west Texas have shown sustained growth; Amarillo and Lubbock both have populations above 200,000 and have continued to grow.^[12] Smaller towns, on the other hand, often struggle to sustain their population.

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  High Plains in Oklahoma west of Guymon (2009)
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  Cimarron County near Boise City. (2009)
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  Grain silos, a common sight on the High Plains. (2009)
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  High Plains in Southeastern Colorado (2009)
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  The High Plains are broken in places by canyons, such as this one in Sabinoso Wilderness in New Mexico.

• High Plains Regional Climate Center High Plains climatological resources
• High Plains information - U.S. Department of the Interior (with map)
• Trains on the High Plains
• Texas counties map showing the ecoregion
• Public domain images of the high plains of the Llano Estacado