Abstract

Deposits resulting from mass-wasting processes along the Missouri River trench near Pierre, South Dakota, have been studied and mapped. Landslides in Pierre shale are typically of the slump variety in which the surface of movement is concave and in which movement is chiefly rotational. Landslides in glacial drift are mostly of the debris-slide type, although in favorable topographic positions, unit blocks of drift evidently have moved laterally on gently sloping, relatively flat surfaces. Deposits due to rapid flowage are less conspicuous than slumps but have as great or greater areal distribution.

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