It is about  across, a little longer N-S than E-W. Its floor is about  below the surrounding ground level and has a rim that rises  above, the highest point on the east side. The crater formed during the late Pleistocene, between 13,500 and 18,000 years ago, at which time the Fort Rock basin was a lake and the location was near the shore.
The crater measures roughly  in width, stretching more north-south than east-west. Its floor is about  below ground level, with a rim that rises  above it, reaching its highest point on the eastern side. The crater formed during the late Pleistocene, between 13,500 and 18,000 years ago, when the Fort Rock basin was a lake and situated near the shore.