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The Dissected Till Plains are physiographic sections of the Central Lowlands province, which in turn is part of the Interior Plains physiographic division of the United States, located in southern and western Iowa, northeastern Kansas, the southwestern corner of Minnesota, northern Missouri, eastern Nebraska, and southeastern South Dakota. [1]
The Dissected Till Plains were formed during the Pre-Illinoian Stage. Glacial scouring and deposition by the Laurentide Ice Sheet and the later accumulation of loess during the Wisconsin Stage left behind the rolling hills and rich, fertile soils found today in the region.
The region is also the western edge of the Corn Belt.
As a part of the Central Lowland geomorphic province. It is a glacier till plain from flat to rolling plain that slopes towards either the Missouri or Mississippi rivers. It is moderately dissected. Local relief is 20 to 165 feet (6.1 to 50.3 m). The region is pocketed by small human landform, i.e., strip-mines among a hummocky or ridge-swale topography. Streams drain and erode the area, moving soils and depositing them downstream. Elevation ranges from 600 to 1,500 feet (180 to 460 m). [2]
Loess (unconsolidated aeolian silt), as much as 25 feet (7.6 m) thick thins toward the east, covers most uplands. Pleistocene (pre-Illinoisan) till lies beneath the loess, covering the bedrock up to 300 feet (91 m) deep. Along the edges, it thins to less than 30 feet (9.1 m). The Mississippi and Missouri floodplains have up to 150 feet (46 m) of unconsolidated Tertiary and Quaternary alluvium (gravel, sand, silt, and clay) over the bedrock, thinner in the river valleys. [2]
Bedrock appears along the margins. Cretaceous shale and sandstone occur in the northwestern corner, the Nebraska, Minnesota and Iowa boundary section. Permian sandstone is along the western margin or the Missouri Valley. Pennsylvanian shale, limestone, and coal is beneath nearly the entire geologic unit. Mississippian, Devonian and Ordovician shale and carbonate are the bedrock along the eastern and southern areas. Bedrock is visible along the deeper drainage's and in eroded "windows" of the unconsolidated surface soils. [2]
The Dissected Till Plains is a sub-unit of the Central Lowlands in the Interior Plains of North America. It is centered on the Iowa-Missouri state line. The eastern border is the Mississippi River and bounded on the south by the Missouri River Valley across central Missouri. Its western boundary is about 100 miles (160 km) west of the Missouri Rivers border along the Kansas/Missouri – Nebraska/Iowa state line. Its northern border is a line dipping from the Sioux River valley of South Dakota and Minnesota, south into Iowa along a line demarking the Missouri valley from the interior lowlands of Iowa, then curving northward again on a line demarking the interior lowlands of Iowa, from the Mississippi River valley on the east. [3]
The Great Plains are a broad expanse of flatland in North America. The region is located just to the east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include the mixed grass prairie, the tallgrass prairie between the Great Lakes and Appalachian Plateau, and the Taiga Plains and Boreal Plains ecozones in Northern Canada. "Great Plains" or Western Plains also describe the ecoregion of the Great Plains, or alternatively the western portion of the Great Plains.
Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type. Temperate grassland regions include the Pampas of Argentina, Brazil and Uruguay, and the steppe of Ukraine, Russia, and Kazakhstan. Lands typically referred to as "prairie" tend to be in North America. The term encompasses the area referred to as the Interior Lowlands of Canada, the United States, and Mexico, which includes all of the Great Plains as well as the wetter, hillier land to the east.
Missouri, a state near the geographical center of the United States, has three distinct physiographic divisions:
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.
The Driftless Area, also known as Bluff Country and the Paleozoic Plateau, is a topographical and cultural region in the Midwestern United States that comprises southwestern Wisconsin, southeastern Minnesota, northeastern Iowa, and the extreme northwestern corner of Illinois. The Driftless Area is a USDA Level III Ecoregion: Ecoregion 52. The Driftless Area takes up a large portion of the Upper Midwest forest–savanna transition. The Blufflands refers to the eastern section of the Driftless area in Minnesota, due to the steep bluffs and cliffs around the river valleys. The western half is known as the Rochester Plateau, which is flatter than the Blufflands. The Coulee Region refers to the southwestern part of the Driftless Area in Wisconsin. It is named for its numerous ravines.
The Loess Hills are a formation of wind-deposited loess soil in the westernmost parts of Iowa and Missouri, and the easternmost parts of Nebraska and Kansas, along the Missouri River.
The Smoky Hills are an upland region of hills in the central Great Plains of North America. They are located in the Midwestern United States, encompassing north-central Kansas and a small portion of south-central Nebraska.
The geology of Minnesota comprises the rock, minerals, and soils of the U.S. state of Minnesota, including their formation, development, distribution, and condition.
Buffalo Ridge is a large expanse of rolling hills in the southeastern part of the larger Coteau des Prairies. It stands 1,995 feet (608 m) above sea level. The Buffalo Ridge is sixty miles (97 km) long and runs through Lincoln, Pipestone, Murray, Nobles, and Rock counties in the southwest corner of Minnesota, and Minnehaha, Moody, and Lincoln counties in southeast South Dakota.
The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.
The geology of Kansas encompasses the geologic history and the presently exposed rock and soil. Rock that crops out in the US state of Kansas was formed during the Phanerozoic eon, which consists of three geologic eras: the Paleozoic, Mesozoic and Cenozoic. Paleozoic rocks at the surface in Kansas are primarily from the Mississippian, Pennsylvanian, and Permian periods.
The Missouri River Valley outlines the journey of the Missouri River from its headwaters where the Madison, Jefferson and Gallatin Rivers flow together in Montana to its confluence with the Mississippi River in the State of Missouri. At 2,300 miles (3,700 km) long the valley drains one-sixth of the United States, and is the longest river valley on the North American continent. The valley in the Missouri River basin includes river bottoms and floodplains.
The geography of Iowa includes the study of bedrock, landforms, rivers, geology, paleontology and urbanisation of the U.S. state of Iowa. The state covers an area of 56,272.81 sq mi (145,746 km2).
The Ozark Highlands is a Level III ecoregion designated by the Environmental Protection Agency (EPA) in four U.S. states. Most of the region is within Missouri, with a part in Arkansas and small sections in Oklahoma and Kansas. It is the largest subdivision of the region known as the Ozark Mountains, less rugged in comparison to the Boston Mountains in Arkansas, the highest part of the Ozarks.
The environment of Iowa has been heavily affected by agricultural production since it became a U.S. state in 1846. However, there remain natural areas in Iowa that reflect a wide varieties of environmental niches.
The Ogallala Formation is a Miocene to early Pliocene geologic formation in the central High Plains of the western United States and the location of the Ogallala Aquifer. In Nebraska and South Dakota it is also classified as the Ogallala Group. Notably, it records the North American Land Mammal Ages (NALMAs) Hemphillian, Clarendonian, and Barstovian. It also includes an excellent record of grass seeds and other plant seeds, which can be used for biostratigraphic dating within the formation. The Ogallala Formation outcrops of Lake Meredith National Recreation Area preserve fish fossils. Similar specimens from the same unit are found at Alibates Flint Quarries National Monument in Texas.
The Graneros Shale is a geologic formation in the United States identified in the Great Plains as well as New Mexico that dates to the Cenomanian Age of the Cretaceous Period. It is defined as the finely sandy argillaceous or clayey near-shore/marginal-marine shale that lies above the older, non-marine Dakota sand and mud, but below the younger, chalky open-marine shale of the Greenhorn. This definition was made in Colorado by G. K. Gilbert and has been adopted in other states that use Gilbert's division of the Benton's shales into Carlile, Greenhorn, and Graneros. These states include Kansas, Texas, Oklahoma, Nebraska, and New Mexico as well as corners of Minnesota and Iowa. North Dakota, South Dakota, Wyoming, and Montana have somewhat different usages — in particular, north and west of the Black Hills, the same rock and fossil layer is named Belle Fourche Shale.
The geology of Missouri includes deep Precambrian basement rocks formed within the last two billion years and overlain by thick sequences of marine sedimentary rocks, interspersed with igneous rocks by periods of volcanic activity. Missouri is a leading producer of lead from minerals formed in Paleozoic dolomite.
The Western Corn Belt Plains is a Level III ecoregion designated by the Environmental Protection Agency (EPA) in seven U.S. states, though predominantly in Iowa.