Big Cave is a small basalt shield volcano in northern California within the Cascade Volcanic Arc, lying between Big Lake and Bald Mountain and rising a little over 4,130 feet. It is part of a belt of late Quaternary volcanoes that extends north from Lassen Peak, formed by the ongoing subduction of oceanic plates beneath the North American Plate. Its broad, low profile is relatively inconspicuous, with a rough surface covered largely by lava flows and surrounded by an extensive lava field. Young pyroclastic cones appear on its summit and northern flank. Its age remains uncertain, possibly Holocene or as old as the late Pleistocene.