The Pleistocene-to-Holocene Indian Heaven volcanic field, located midway between St. Helens and Adams, is an area of low overlapping shield volcanoes with flank vents primarily oriented N-S. Small shield volcanoes topped by cinder and spatter cones dominate the field, which also contains subglacial vents. The shield volcanoes extend from Sawtooth Mountain on the north to Red Mountain on the south; the high point of the field is Lemei Rock shield volcano. Basaltic-to-andesitic lava flows cover much of the field; individual lava flows, many with extensive lava tubes, traveled up to 46 km. The youngest eruption, about 8,200 years ago, produced the voluminous Big Lava Bed, a 0.9 km3 basaltic lava flow that traveled nearly 25 km S of its source from an unnamed cinder cone SE of Red Mountain, to within 8 km of the Columbia River.