Diatremes and uranium deposits in the Hopi Buttes, Arizona

The Hopi Buttes diatremes erupted in a shallow lake that was filled in as volcanic activity progressed in Pliocene time. At the end of the period of volcanism the landscape included low lava domes capping some of the diatremes, a few flows, and numerous craters of the maar type, surrounded by rims of volcanic debris with gentle exterior slopes that merged with the surrounding plain. Erosion, probably chiefly during early and middle Pleistocene, has exposed the diatremes in varying stages of denudation.