Calvin is an
impact crater
An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...
located in
Calvin Township,
Cass County, in the
U.S. state
In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...
of
Michigan
Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...
. It was discovered in 1987 by
Randall Milstein of the
Michigan Geological Survey
The Michigan Geological Survey is a scientific agency of the U.S. state of Michigan. The survey is headed by the State Geologist of Michigan.
The survey has been composed of three individual surveys: the first from 1837 through 1845, the second fr ...
while examining data from about 100 test wells drilled in the area.
It is in diameter and the age is estimated to be 450 ± 10 million years (
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...
).
The crater is not exposed to the surface. It lies about 100 to 400 feet (30–120 m) below today's ground level.
References
External links
Exploration of the Calvin impact structure
Landforms of Cass County, Michigan
Impact craters of the United States
Landforms of Michigan
Ordovician impact craters
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