Monday, May 21, 2018

Mima Mounds

Parts of the prairie landscape south of Olympia are bumpy - quite regularly so. Theories range from gophers to earthquakes to soil processes to wind and vegetation. The debate has kept some geologists busy and kept many others entertained for most of a century.

During the last ice age, the Puget Lobe reached almost this far south - suggesting some connection between the glacier and this landscape, although I don't think anyone thinks it was the ice itself. It's something about the dirt in this area of glacial outwash that lends itself to pimples.

It turns out Mima Mounds are not just found here; they also occur in a variety of other places around the world. In those places they're typically called something else and there are additional hypotheses. And then there all sorts of patterned ground (self-organization of soils in cold and/or arid regions) and bioturbation features that have similarities, but take on significantly different appearances.

I like the idea that they represent an emergent landscape process that happens when the right combination of plants, animals and soils are left alone for a few thousand years. Complexity leads to regularity.

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