Panum Crater

Panum Crater is a volcanic cone that is part of the Mono-Inyo Craters, a chain of recent volcanic cones south of Mono Lake and east of the Sierra Nevada, in California, United States. Panum Crater is between 600 and 700 years old, and it exhibits all of the characteristics of the textbook rhyolitic lava dome.Rhyolitic volcanoes are characterized by having large amounts of silica (quartz) in their lava. The content of silica at Panum is about 76 percent. It makes the lava very viscous, or thick, and very glassy. Products of this rhyolitic eruption are pumice and obsidian, the volcanic glass that Native Americans used to make arrow points and scrapers.Panum Crater formed in a sequence of events. The first event was caused by magma rising from deep within the Earth's crust. When this extremely hot, liquid rock made contact with water just below the surface, the water expanded into steam and a large, violent eruption occurred. The material that was thrown into the air by the steam, mainly old lake bottom sediments, was deposited around the new vent in little mounds. So much debris was blown out that a gaping crater was left behind.Once this debris was blown out, a fountain of cinders shot up a great distance into the sky. As this huge amount of ash and pumice began to fall back towards the earth, it formed a pumice ring, or cinder cone, about the original vent. This cinder cone is still visible today.