Geology topics
Robert Schuster
Publications and source records attributed to Robert Schuster.
Overview of catastrophic landslides of South America in the twentieth century
This chapter summarizes the processes and effects of the most notable catastrophic mass movement events in South America in the twentieth century. We present 23 case histories of individual and regional landslide events, beginning at the northeast terminus of the Andes Mountains in Venezuela, proceeding counterclockwise down the Pacific Coast to the southern Andes of Chile and Argentina, and ending with discussion of catastrophic regional mass movements in the Brazilian Highlands. The types of landslides involved in these disasters ranged from high-velocity rockslides and rock or debris avalanches to high-to medium-velocity debris flows and mudflows. Most casualties were caused by high-velocity debris avalanches and high-to medium-velocity, highly mobile, long-runout debris flows. A common, and particularly devastating, regional occurrence consisted of earthquake-triggered slides on steep slopes covered with saturated residual soils; these slides were rapidly transformed into very fluid, high-velocity debris avalanches, which in turn changed into devastating debris flows that ran out into populated areas on valley bottoms.
LANDSLIDE DAMMED LAKES AT MOUNT ST. HELENS, WASHINGTON.
The collapse of the north face of Mount St. Helens on May 18, 1980, and the debris avalanche that resulted blocked outflow from Spirit Lake and Coldwater and South Fork Castle Creeks. Spirit Lake began to increase in size and lakes began to form in the canyons of Coldwater and South Fork Castle Creeks. Coldwater and Castle Lakes would have overtopped their respective blockages in late 1981 or early 1982. Catastrophic flooding would have occurred from the breakout of Coldwater Lake while serious flooding probably would have resulted from the breakout of Castle Lake. As a result, the level of both lakes was stabilized with spillways in 1981. The three blockages are stable against liquefaction and gravitationally induced slope failure. The existence of groundwater in the blockages was observed in piezometers installed between 1981 and 1983. Groundwater mounds with water levels above lake level exist under the crest of all of the blockages.