Pleistocene And Recent Topographic Changes In The Pacific Coast States

Abstract

In comparison with the eastern half of North America, great topographic changes have occurred, in the Pacific Coast States during the last three periods of geological time—the Pliocene, Pleistocene, and Recent. During these later periods of geological history the eastern mountains and plains have apparently suffered only relatively gentle upbowing or downwarping, but since the beginning of the Pliocene the western mountains and plateaus have not merely been uplifted thousands of feet but have been strongly folded and broken by faults. In the West, neighboring areas have moved in opposite directions. Some have gone up great distances and now form the high ranges; others have sunk and now either form the valleys into which the erosional detritus from the ranges is being in part deposited or they form estuaries or sounds if, lying near the Coast, they sank below sea-level.