Inyo Craters:
The Inyo Craters are either phreatic (steam explosion) volcanoes or domes. The two southernmost Inyo Craters are in a forested area and are open pits about 600 feet (180 m) across, each with small ponds covering their floors. The magma that created these craters never reached the surface. These craters were formed when heat from the rising magma superheated groundwater until the overlying dirt and rock could no longer contain the pressure, resulting in a massive steam explosion. They last erupted 650 years ago.