Today–413.ppt

Today – 4/13 More volcanoes! First Mars shot - hill Matian basalt Martian dune field Frozen Martian Sea Last Time Hotspots – mantle plumes reach the surface; decompression melting to form basaltic magma; Hawaii, Mars, Venus; independent of plate boundaries Intrusive v. extrusive: coarse v. fine texture depends on cooling rate Three kinds of volcano: shield, stratovolcano, caldera – depends on magma type Last Time – Shield Volcano Built up from repeated basalt flows Basalt has high Fe / Mg, high temperature, low Si, low gas content, low viscosity (stickiness) MOR’s, hotspots, areas of continental extension Stratovolcano Built from alternating layers of pyroclastic andesite lava flows Magma – intermediate temperature, gas content, composition, viscosity St. Helens, Monserrat, Pinatubo, Tambora Form above subduction zones Wet melting of the mantle Wet Melting of the Mantle Mount Ngauruhoe, New Zealand PyroclasticFlows- - - - - MayonPhilippines1968- - - - -Hot: 600oCFast: 60 to 100 mph Mt. Vesuvius Pompeii, Italy AD 79 Cascade Volcanic Arc  Lassen Peak Crater Lake Mt.St.Helens Mt. Rainier - - - -Part of Pacific Ring of Fire. Mt. Saint Helens, May, 1980 Eruption Mount St. Helens Volcanocam http://www.fs.fed.us/gpnf/volcanocams/msh/ Space Needle view Seattle, WA and Mount Rainier:Most dangerous volcano in North America? Mount Rainier, Most dangerous volcano in North America? Mount Pinatubo Tectonic Setting Volcanoes – Agents of Climate Change Mt. Pinatubo Ash Circles the Earth Climatic Effects of Volcanism Volcanic particles in stratosphere interact with man-made CFC’s to destroy ozone. Particles settle out in 2-3 years, ozone layer recovers. Volcanoes add CO2 to the atmosphere (10% of anthropogenic emissions), contributing to long-term global warming SO2 in the stratosphere reacts with water to form sulfuric acid, which absorbs solar energy and re-radiates it into space, creating short term cooling. Sulfuric acid droplets settle out after several