Geology of the Craters of the Moon 30’ X 60’ Map Area and New Perspectives on Basaltic Volcanism of the Eastern Snake River Plain, Idaho

Kuntz, Mel; Owen, Douglass; Champion, Duane; Gans, Phillip; Smith, Sara; Brossy, Cooper

Basaltic volcanism was a dominant geologic process in the eastern Snake River Plain (ESRP) in Holocene time, as attested by the fact that eight dominantly late Pleistocene and Holocene (<15 ka) lava fields cover about 13 percent of the ESRP. Because widespread loess deposition essentially terminated at the end of the late Pleistocene, probably owing to abrupt climate change due to retreat of continental and alpine glaciers, the dominantly Holocene lava fields are relatively loess free and have low reflectance in Landsat satellite images (fig. I-1). Three of these lava fields, Craters of the Moon, Kings Bowl, and Wapi, lie along the Great Rift volcanic rift zone. The Great Rift volcanic rift zone is an 85-km-long and 2- to15-km-wide belt of tephra cones, lava cones, shield volcanoes, eruptive fissures and associated tephra deposits, and noneruptive fissures. These three, dominantly Holocene lava fields and the volcanic structures of the Great Rift volcanic rift zone lie within the Craters of the Moon 30' x 60' quadrangle and the northern half of the Lake Walcott 30' x 60' quadrangle (fig. I-1). The Craters of the Moon National Monument was established by President Coolidge on May 2, 1924. Since 1924, the Monument has been expanded through five presidential proclamations. The most recent and largest expansion of the Monument occurred on November 9, 2000, when President Clinton signed a proclamation enlarging the Monument 13-fold, from 55,000 acres to 715,000 acres. The expanded Monument assures the protection of the entire Great Rift volcanic rift zone. It encompasses all of the Craters of the Moon lava field as well as remote areas that include the Kings Bowl lava field, Wapi lava field, and the Bear Trap lava tube. The Monument is managed cooperatively by the National Park Service and the Bureau of Land Management. The National Park Service has primary management authority over the portion of the Monument that includes the dominantly Holocene lava fields (Craters of the Moon, Kings Bowl, and Wapi). The Bureau of Land Management has primary management authority over the remaining portion of the monument. A Visitor Center, camping facilities, and the best access for sightseeing and hiking in the Craters of the Moon lava field are provided by the National Park Service at the north end of the Monument, located off U.S. Highway 20-26-93 between Arco and Carey.