The Sentinel Plains lava field and associated small shields are early Pleistocene-age, mantle-derived alkali olivine basaltic lavas in the vicinity of the Gila Bend and Painted Rock Mountains, 65 km to 100 km southwest of Phoenix, Arizona (please see 1:100,000-scale map). These volcanic centers are collectively referred to as the Sentinel-Arlington Volcanic Field (SAVF). The SAVF covers ~600 km2 and consists of more than 2 dozen volcanic centers ranging from 4-6 km in diameter and 30-200 m in height. The lavas are partially eroded and dissected by peripheral ephemeral washes, the Hassayampa River, and the Gila River, as well as lightly mantled by aeolian dust, pedogenic calcium carbonate, and basaltic rubble, with a few areas covered by alluvium.