page_title: Mono–Inyo Craters
section_title: Typical evolution
hierarchical_section_title: Mono–Inyo Craters / Geography and description / Typical evolution
caption_attribution_description: Panum Crater with central lava dome, Mono Craters, California, USA
context_page_description: The Mono–Inyo Craters are a volcanic chain of craters, domes and lava flows in Mono County, Eastern California. The chain stretches 25 miles from the northwest shore of Mono Lake to the south of Mammoth Mountain. The Mono Lake Volcanic Field forms the northernmost part of the chain and consists of two volcanic islands in the lake and one cinder cone volcano on its northwest shore. Most of the Mono Craters, which make up the bulk of the northern part of the Mono–Inyo chain, are phreatic volcanoes that have since been either plugged or over-topped by rhyolite domes and lava flows. The Inyo volcanic chain form much of the southern part of the chain and consist of phreatic explosion pits, and rhyolitic lava flows and domes. The southernmost part of the chain consists of fumaroles and explosion pits on Mammoth Mountain and a set of cinder cones south of the mountain; the latter are called the Red Cones.
  Eruptions along the narrow fissure system under the chain began in the west moat of Long Valley Caldera 400,000 to 60,000 years ago. Mammoth Mountain was formed during this period.
context_section_description: Panum Crater is the northernmost volcano in the sequence and is a good example of both a tuff ring and a rhyolite dome. Its structure is twofold; an outer tuff ring (forming a classic crater) and an inner plug, or dome of rhyolite, pumice and obsidian created from lavas. In this case, heat from the magma feeding Panum flashed groundwater to steam to create the tuff ring before lava reached the surface. Other Mono Craters also were formed in this manner, but their plug domes grew larger than their tuff ring craters. The domes have steep sides and are flanked by slopes of scree consisting of large angular and glass-rich rocks. Devil's Punch Bowl, located south of the main dome complex, stopped forming at an earlier stage of development. It is a 1,200-foot (370 m) wide and 140-foot (43 m) deep explosion pit with a much smaller glass dome on its floor.
  The large North and South Coulee and the smaller Northwest Coulee consist of obsidian-rich rhyolite. They were formed from slow-moving lava that had a thin and brittle crust. Once the flow stopped, it formed steep sided tongues of sharp and angular rock that are typically 200 to 300 feet (60 to 90 m) thick and have scree piles along their base. South Coulee is 2.25 miles (3.6 km) long, 0.75 miles (1.2 km) wide and has a volume of 0.1 cubic miles (0.4 km³); making it the largest Mono Craters coulee in volume. South Coulee originates from the crest of the Mono Domes, about 3 miles (5 km) from the southern end, flows down its east and west flanks and terminates at its foot. North Coulee is nearly as large, flows mostly to the east and terminates in a divided pair of lobes. Northwest Coulee is located northwest of North Coulee and was intruded by Upper Dome after the coulee solidified. Permanent pockets of ice from snowmelt have been found 75 to 147 feet (23 to 45 m) inside the coulees and domes.
caption: Aerial photo of Panum Crater
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