[The unusual agricultural pattern of eastern Washington’s “channeled scablands” can be traced to a (series of) massive glacial outburst flood(s) which cut the deep into the region’s volcanic basalt, leaving fertile plateaus and barren, rocky valleys.  Mammoth looked at that event, the Missoula Floods, in a post last year, “a glacier is a very long event”.  (You’ll want to scroll down to “Jokulhlaups”.)  We might add that, if contemporary land use patterns are determined by Ice Age floods, a flood can also be a very long event.]