The Inyo Craters are a 12-km-long chain of silicic lava domes, lava flows, and explosion craters along the eastern margin of Sierra Nevada south of Mono Craters near the town of Mammoth.  Inyo Craters overtop the NW rim of the Pleistocene Long Valley caldera and extend onto the caldera floor, but are chemically and magmatically part of a different volcanic system.  Postglacial explosion pits of Mammoth Mountain to the south are an extension of Inyo Craters (Bailey 1980).  The latest eruptions at Inyo Craters took place about 600 years ago, when explosive eruptions accompanied formation of the South Deadman, Obsidian Flow, and Glass Creek rhyolitic lava domes and lava flows.  The Inyo Crater Lakes are small phreatic craters that formed during this eruption on the south flank of the Pleistocene Deer Mountain rhyolite dome of the Long Valley caldera.