Devils Postpile National Monument, Inyo County, California

Devils Postpile National Monument (Inyo County) is appropriately named for the large, blocky talus slope below cliff of columnar basalt. The rock columns formed from a lava flow that flowed down an ancient valley in the eastern Sierra Nevada Range. The cliff slope formed when a glacier and stream erosion later scoured out the valley. Rockfalls in the high mountains of the west are mostly initiated by water freezing and expanding in cracks, and the collapse of steep slopes in over-steepened valleys carved by glaciers in the recent Ice Ages of the Pleistocene Epoch (roughly between 11,000 and 2 million years ago).

The URL of this page is http://3dparks.wr.usgs.gov/landslide/big/3.htm