Friday, April 26, 2013

Geo 365: April 26, Day 116: Mini Canyons

A fun thing to do at the beach during low tide is to look at the short-lived erosional features. Many fluvial landforms can be found, at small scales, changing and evolving over periods of minutes in ways that would take real stream systems years to centuries. In this case, we're seeing sheet wash on the upper "plateau" channeled into a series of distributary "canyons" in response to the rapid drop in base level as the tide went out.

Of course, there's plenty of water percolating through the sand as well. Under the sheet wash, the water table is right at the surface, and that level drops to the left. But the main stream has cut below the water table, so "springs" have formed along the base of the "plateau's" "escarpment." With that former groundwater back on the surface, it can again erode the sand grains in that area, creating an apron similar to a bajada between the main stream and the escarpment.

Photo unmodified. September 21, 2010. FlashEarth Location.

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