Mass Wasting in the Appalachian Plateau
Among Appalachian provinces, the Appalachian Plateau has the greatest abundance of conspicuous slope failures. Here, such failures have ahigh frequency, low magnitude compared to thethose typical of the Blue Ridge and Ridge and Valley provinces. Most slope failures on the Appalachian Plateau are earthflows and slump-earth flows, but earth slumps, debris slides, debris flows, topples and rockfalls are also common. Failuresare most abundantin the region underlain by subhorizontal cyclothemic sedimentary rocks (shale, mudstone, claystone, siltstone, sandstone, and coal) of Pennsylvanian to Permian age.
Most slope failures on the Plateau occur in colluvium and weathered fine-grained rocks. Different parts of the Plateau are characterized by distinct kinds of slope failures. For example, southeastern Ohio, central and western West Virginia, and northeastern Kentucky commonly have slow-moving earth flows in addition to slump-earthflows and slumps. Large parts of eastern Kentucky and southwestern West Virginia are characterized by debris slides and flows because of steep slopes and large amounts of coarse clastic rock material.
Rock type and structure are important determinants of failure mechanisms, sizes, and rates. Several argillaceous rocks of the Appalachian Plateau are particularly weak and prone to failure. For example, the red mudstones of the Conemaugh and Monongahela formations and the Permian Dunkard Group account for nearly 95 percent of slope failures mapped in eastern Ohio, and for the majority of failures in West Virginia. Instability of redbeds stems from their fine particle size, their tendency to contain swelling clays, and high-angle slickensided surfaces that reduce rock strength and enhance permeability and weathering. Gray and green shales and underclays in the Pennsylvanian-Permian rocks are also relatively weak.
Encyclopedia ID: p1566
