Aden Crater is a small shield volcano in southern New Mexico within the Aden-Afton basalt field of the Potrillo volcanic field, shaped by volcanism along the Rio Grande rift. Built by repeated eruptions of very fluid olivine basalt, it formed a broad, low shield with a summit crater containing remnants of a lava lake, a spatter cone, and a collapse pit. Its lava flows include early fluid flows that spread widely and later thicker flows that built the shield. Nearby are explosion craters, collapse pits, hornitos, spatter cones, and distinctive herraduras. The volcano’s most recent activity dates to about 16,000 years ago, and a deep fumarole on the crater rim preserved a fossil ground sloth and coprolites.