The Interior Plains constitute a major physiographic region of North America, extending from the Gulf of Mexico in the south to the Arctic Ocean in the north. The region occupies the central portion of the continent between the Appalachian Mountains to the east and the Rocky Mountains to the west. It includes the Canadian Shield’s interior lowlands, the Great Plains of the United States, and the Arctic Lowlands of northern Canada.
Geography
The Interior Plains are characterized by relatively low relief, extensive sedimentary basins, and broad, gently rolling to flat terrain. Major sub‑regions include:
- The Great Plains – a vast expanse of grassland and prairie covering parts of Texas, Oklahoma, Kansas, Nebraska, the Dakotas, and extending into the Canadian Prairies.
- The Central Lowlands – a region of fertile agricultural soils, river valleys, and glacial deposits that includes the Mississippi River basin and the Ohio River basin.
- The Arctic Lowlands – a sparsely vegetated area of permafrost, tundra, and wetlands in northern Canada and Alaska.
Geology
The plains rest upon a thick sequence of sedimentary rocks, principally sandstones, shales, limestones, and coal seams deposited over the Phanerozoic eon. The underlying lithology reflects a long history of marine transgressions, riverine deposition, and glacial sculpting. The region’s geology is a major source of hydrocarbons (oil and natural gas), coal, and potash, contributing significantly to North American resource extraction.
Climate
Climate varies from semi‑arid continental in the southern Great Plains to humid continental in the central lowlands, and sub‑arctic to polar in the northern Arctic Lowlands. The area experiences pronounced seasonal temperature fluctuations, with hot summers, cold winters, and, in many locales, strong southerly winds such as the Chinook and the Prarie‑derived tornado activity.
Ecology
Historically, the Interior Plains supported grassland ecosystems dominated by tallgrass, mixed‑grass, and shortgrass prairies, interspersed with wetlands, riverine forests, and sagebrush steppe. Large herbivores such as bison (Bison bison) and a diversity of avian species once roamed the region. Extensive agricultural development and urbanization have transformed much of the native prairie, though conservation areas and prairie restoration projects aim to preserve remnant ecosystems.
Human Use
The Interior Plains are a core agricultural zone, producing significant portions of North America’s wheat, corn, soybeans, and cattle. The region also hosts major urban centers, transportation corridors (including the transcontinental railways and interstate highways), and energy infrastructure. Historically, indigenous peoples such as the Sioux, Cheyenne, Blackfoot, and Cree inhabited the plains, and their cultural heritage remains integral to the region.
References
- United States Geological Survey (USGS). “Physiographic Provinces of the United States.”
- Natural Resources Canada. “Canadian Physiographic Regions.”
- White, R. (2010). The Great Plains: A Natural History. University of Nebraska Press.
This entry reflects information available from established geographic and scientific sources.
