Geo-pic of the Week: Potholes

Pothole

This is a picture of a pothole.  Not the kind that you curse at as you run over it with your car.  This kind of pothole is an erosional feature common in creeks with rocky bottoms. They form by an elegantly simple process.

As a creek flows it carries sediment, such as sand and gravel, downstream.  If there’s a slight pit in the rocky channel bottom, a piece of gravel will sometimes get stuck in the pit.  As water flows over the pit it causes the trapped gravel to roll around.  The tumbling gravel erodes an ever larger pit, which is increasingly better at trapping gravel; the process snowballs.  Eventually, what was a slight pit becomes a smooth, bowl-shaped depression that may be up to several feet deep.

This pothole is in the creek in Duggan Hollow just north of Greer’s Ferry Lake in north Arkansas.

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