Bitterwater Slump

May 01, 2006


Provided and copyright by: David Lynch
Summary authors & editors: David Lynch

Along Bitterwater Road in San Luis Obispo County, California there are a large number of landslides. This one shows many classic landslide properties: a steep head scarp at the top where separation begins just below the crown, transverse cracks and ridges, the foot and toe. Note the oft-patched road which is damaged by slow movement along the active slide. Even very old landslides can be identified by their lumpy, hummocky terrain that contrasts sharply with the smoother unbroken surface of the surrounding hillsides. This section of the road with its myriad landslides is about a mile and a half west of the San Andreas Fault, and earthquakes here have contributed to the ground slumping. The region is primarily Pleistocene Paso Robles Formation, poorly consolidated coarse sand and gravel with smaller amounts of fine sand, silt and clay. Landslides have been classified into about 10 different types, and the U.S. Geological Survey maintains an active landslide mapping and mitigation program -- the one shown above would probably be called an earthflow.

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