The crater dates to the late Eocene geological time period (about 35 million years ago), and may have been formed by the same event as the larger Chesapeake Bay impact crater, to the southwest at the mouth of Chesapeake Bay, and also dating to the late Eocene.
Seismic reflection profiles, studied by USGS scientists, show that the crater was formed by an object or objects which struck from the southwest at a glancing angle and formed a long, oval crater. Since impact, sediment filled part of the crater, giving it its present triangular shape.
Poag, C. Wiley. Chesapeake Invader: Discovering America's Giant Meteorite Crater. Princeton, NJ: Princeton University Press, 1999. ISBN 0-691-00919-8