Lenses of relatively resistant stone just a few inches thick permeate otherwise soft and very easily eroded clay sediments in Theodore Roosevelt National Park. Every winter, the expansion of ice in freeze-thaw cycles pries particles and chunks of clay apart. Every summer, the expansion of clay on the parched side of wet-dry cycles does the same. The chunks crumble and fall with aid from both gravity and sporadic torrents of rain. Within a hundred thousand years or so--just a fraction of a tick of the geologic clock--this bluff could recede far into the background and evolve into a gentle, grassy slope utterly unrecognizeable to anyone who could travel there in a time machine. Until then, the natural abstract art of the Badlands landscape presents itself in different ways with the changing of the light throughout the day, and differently from spot to spot.
2 NE Medora SD (16 Jun 12) Looking down