description Calvin Overview
The Calvin impact structure is a buried, nearly circular feature in Cass County, southwestern Michigan. It is associated with a Late Ordovician event and is described in geological studies as an impact crater, with estimates of about 6.2 kilometers for the rim-to-rim diameter and 8.5 kilometers for the wider structure. More than 100 oil and gas test wells helped define it, and Devonian oil fields occur in structures associated with the crater.
help Calvin FAQ
Where is the Calvin impact structure?
Calvin is a buried, nearly circular feature in Cass County, in southwestern Michigan. Younger rocks cover the original crater, so it is not visible as an open surface crater.
How wide is the Calvin crater?
Geological studies estimate a rim-to-rim diameter of about 6.2 kilometers. That figure describes the inferred crater boundary beneath the surface.
When did the Calvin impact happen?
Calvin is associated with a Late Ordovician impact event. The supplied catalog description does not establish a precise calendar age, so a more exact date should not be assumed.
What makes Calvin an impact crater rather than an ordinary circular feature?
Its nearly circular buried form is supported by geological studies that interpret it as an impact structure. The identification depends on subsurface evidence rather than a visible crater bowl.
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