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. 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. Loess, as much as thick thins toward the east, covers most uplands. Pleistocenetill lies beneath the loess, covering the bedrock up to deep. Along the edges, it thins to less than. The Mississippi and Missouri floodplains have up to of unconsolidated Tertiary and Quaternary alluvium over the bedrock, thinner in the river valleys. Bedrock appears along the margins. Cretaceousshale 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.
Location (Geography)
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 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.
Missouri – The northern tier from the Missouri Valley between St. Louis and Kansas City north to the Iowa border.
Nebraska – Thirty eastern counties from the Missouri River to about the 98 latitude or about of the state.
South Dakota – An ‘L’ shaped section along the Sioux River from north of Sioux Falls down to its junction with the Missouri River and then west up the Missouri for about.
Minnesota – Three counties in the southwestern corner along the Sioux River and eight counties in the southwest in the Mississippi River hill country around Rochester.
