Kilbourne Hole is a volcanic maar in southern New Mexico within the Potrillo volcanic field and the Rio Grande rift. Formed when rising magma struck groundwater-saturated sediments, it erupted violently and excavated a deep basin, later undergoing some collapse. The crater is notable for its broad depression, basalt cliffs, dunes, and dry lakebed, but its greatest scientific importance lies in ejecta rich in xenoliths from the lower crust and upper mantle, including lherzolite, charnockite, and anorthosite. These rare samples of Earth’s interior have made the site valuable to geologists, and its stark terrain also served NASA in Apollo astronaut training and later instrument testing.