The Black Rock Desert volcanic field in western Utah’s Great Basin, in Millard County, is a cluster of volcanoes and lava features formed within a faulted landscape by repeated eruptions over about 2.7 million years. During roughly the past 1.5 million years, eruptions from nearly twenty-four vents produced both rhyolitic and basaltic cones as lava rose along geologic faults, creating a varied volcanic field rather than a single central volcano. Its best-known recent activity, the Ice Springs eruption sometime between 1140 and 1440 AD, combined an explosive event with lava flows that overlapped older lava from Pahvant Butte. These flows are Utah’s youngest known lava flows.