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Williams national park service 1977 montgomery 1987

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Unformatted text preview: r related to high viscosity felsic magma viscosity Form by violent eruption or collapse Enormous calderas 10s of km in diameter can Enormous form over continental hotspots (“supervolcanoes” form “supervolcanoes” such as Yellowstone) such Photograph by M. Williams, National Park Service, 1977 Montgomery, 1987 Calderas The Toba Caldera in Sumatra, Indonesia formed from a massive supervolcanic eruption estimated at that occurred 69,000 to 77,000 years ago. Largest known explosive eruption on Earth in the last 25 million years. Caldera is 100 km long, 30 km wide. Blocking of sunlight by ash is thought to have led to a volcanic winter (temperature dropped avg. 3 to 5 oC globally, and as much as 15 oC at higher latitudes). Speculated to have nearly led to human extinction! So what if Yellowstone caldera (~ 60 km dia.) blew it’s top again? Note: 3 major eruptions associated with Yellowstone hotspot are known to have occurred 2.1 million, 1.3 million, and 640,000 years ago. Estimated area of ashfall from the last major eruption of Yellowstone supervolcano (640,000 years ago) End of Lecture Reading: Make sure you have read Chapter 4 (Volcanoes and Volcanic Processes) In preparation for next lecture, read… Chapter 5 (Weathering and Soil (excluding section on soil)) Chapter 6 (Sedimentary Rocks)...
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