| Summary: | Presumably, most of the evidence of these early glaciations -- thick glacial sediments and glacial land forms � was removed by erosion over the past several hundred thousand years. The Little Missouri Badlands The Little Missouri Badlands are carved into the strata of the Missouri Plateau. The badlands are a rugged, deeply eroded area along the Little Missouri River that stretches from Bowman County north to the confluence with the Missouri River. The Little Missouri River began to carve the badlands about 600,000 years ago during Pleistocene time (the "Ice Age") when the river was diverted from its northerly route into Canada by glaciers. As a result of this diversion, the Little Missouri River was forced to flow eastward over a shorter, steeper route, thus beginning a cycle of vigorous erosion that continues today. The spectacular variety of landforms found in the Missouri Plateau and Little Missouri Badlands results primarily from the differences in resistance to erosion among Fort Union Group strata. Buttes, for example, form when easily eroded sediments are protected by a hard layer of sandstone or limestone. Where beds of lignite have caught fire and burned, adjacent sediments are baked and fused into a natural brick-like material called clinker. The bright red clinker also shields underlying sediments from erosion. In other places, mineralized groundwater circulated through the sediments, forming flint, petrified wood, silcrete, and concretions and nodules of all shapes and sizes, all of which, being harder than the enclosing sediments, resist erosion and so accumulate at the surface. The Coteau Slope The portion of the Great Plains Province north and east of the Missouri River differs markedly from that south and west of the river, principally because evidence of glaciation is so fresh and clear. The area along and immediately east of the Missouri River is known as the Coteau Slope. The Coteau Slope is a rolling to hilly region that contains both glacial and erosional landforms. Unlike the Coteau that bounds its eastern margin, drainage within the Coteau Slope is generally well developed, so that there are comparatively few potholes (ponds and sloughs without any outlet). The Missouri Coteau The Missouri Coteau trends through the state, parallel to and east of the Missouri River. It consists of hummocky topography � thus the Canadian French coteau meaning "little hill" � characterized by unintegrated drainage (meaning that ponds and sloughs are not connected to one another and no streams flow through the area). The northern and eastern margin of the Missouri Coteau is marked by the Missouri Escarpment, a prominent feature rising as much as 600 feet above the comparatively level terrain of 466 Chapter Ten - Natural History
|
|---|