38th parallel structures

American Midwest landscape depressions

The 38th parallel structures, also known as the 38th parallel lineament, are a series of seven circular depressions or deformations stretching 700 kilometres (430 mi) across southern Illinois and Missouri and into eastern Kansas, in the United States, at a latitude of roughly 38 degrees north. Estimated at 300 million years old, two are believed to be impact events from meteorites, but other structures are possibly remnants of volcanos.

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