The escarpment called Abert Rim, in south-central Oregon, is the site of a normal fault
where the land in the foreground dropped by several kilometers relative to the plateau behind, one large earthquake at a time. At this point the escarpment is more than 700 meters high. The thick bed of rock at the top is the Steen Basalt, a series of flood basalt flows erupted about 16 million years ago.
Abert Rim is part of the Basin and Range province, where normal faulting due to extension of the crust has created hundreds of ranges, each flanked by basins many of which contain dry lake beds or playas. Abert Rim may be North America's finest example of an escarpment, but the area has several other contenders. The world's premier escarpments, though, are probably in Africa's Great Rift Valley.
This and other pictures of Abert Rim appear in the Oregon Outback Gallery and are also available as free wallpaper images.