Interior Plains
The Interior Plains is a vast physiographic region that spreads across the Laurentian craton of central North America, extending along the east flank of the Rocky Mountains from the Gulf Coast region to the Arctic Beaufort Sea. In Canada, it encompasses the Canadian Prairies separating the Canadian Rockies from the Canadian Shield, as well as the Boreal Plains and Taiga Plains east of the Mackenzie and Richardson Mountains; while in the United States, it includes the Great Plains of the West/Midwest and the tallgrass prairie region to the south of the Great Lakes extending east to the Appalachian Plateau region.[1]
Glacial history[edit]
2.6 million years ago at the start of the Pleistocene Epoch, the Laurentide Ice Sheet began to spread southwards to cover North America down to the northern Great Plains on the western side of the Interior Plains and down into most of Minnesota and Wisconsin.[11] The Laurentide Ice Sheet had a large influence on the morphology of the Interior Plains during the end of the Pleistocene. During the retreat, the Laurentide scoured numerous pockets of sediment. Upon the plate’s melting, those pockets were filled, resulting in the kettle lakes. The Great Lakes[12] and both Great Slave Lake and Great Bear Lake[13] of Canada were formed by the Laurentide. During the retreat, the Laurentide gouged and filled the glacial paleolake McConnell in northern Canada.[14] As the region uplifted and rebounded isostatically from the mass of the ice sheet, paleolake McConnell was split into Great Slave Lake and Great Bear Lake. Great Slave Lake's basin formed under the 4-kilometer thick Keewatin Dome that today is the deepest lake in North America.[15] A vast amount of smaller lakes were formed as well and serve an integral part of ethos in the surrounding regions. For example, Minnesota is often referred to as “the Land of 10,000 Lakes”[16] due to the number and widespread recreational use of the state’s lakes.
Much of the loess distributed within the Interior Plains has its origin in glaciers. In glaciated conditions, sand and silt-laden meltwater originating from alpine glaciers in the Rocky Mountains generated alluvial deposits at their base. This alluvium was then distributed throughout the Interior Plains by strong winds.[11]
Current land use[edit]
Grassland and shrubland make up the largest portion of the Interior Plains within the United States, at 44.4 percent.[26] The western margin is mainly shortgrass prairie dominated by blue grama and buffalograss. Prairies on the eastern side of the Interior Plains are dominated by tall grass varieties including big bluestem and switchgrass. The two regions are separated by mixed-grass prairie, which contains both short and long grass varieties as well as little bluestem and western wheatgrass.[27] Land used for cattle-grazing is included under this classification, which sustains nearly 50 percent of all United States beef cattle.[28]
In Canada, provinces located within the Interior Plains produce nearly 60 percent of all beef cattle.[28]
Much of the land in the Interior Plains is used for agriculture. In the year 2000, 43.8 percent of the Great Plains portion of the Interior Plains were used for agriculture.[26] By far, wheat comprises the largest portion of the agricultural yield in region; combined, wheat exports from the Interior Plains make up more than half of the world’s exports.[28] Other significant crops produced in the region include barley, corn, cotton, sorghum, soybeans, and canola, which is particularly important to Canadian exports.[28]
Other sources comprise much smaller portions of the land. In decreasing percentage, forests make up 5.8%, wetland makes up 1.6%, developed land makes up 1.5%, barren land makes up .6%, and land used for mining makes up .1%.[26]