Serpent Mound Crater - The Earth Impact Database, maintained by the University of New Brunswick, lists the Serpent Mound impact crater as an 8 kilometer structure exposd at the surface in sedimentary rock. The database lists an age of less than 320 million years. (Mississippian or younger.) Wikipedia places the crater in Ohio's Adams, Pike, and Highland counties.
Diagnostic Evidence For This Crater
The impact origin of each location listed on this website has been supported by unambiguous diagnostic evidence of hypervelocity impact that has been reported in a scientific (usually peer reviewed) context. Without such evidence, a geological structure is not a confirmed impact crater. This section, which is included for each crater on this website, is not an exhaustive list of such published evidence, but is meant to demonstrate that appropriate work has been done for each listing.
Nature of diagnostic evidence:
Other significant evidence: breccia, morphology.