* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download VOLCANOES form where molten rock is vented at Earth`s surface.
Mono–Inyo Craters wikipedia , lookup
Lōʻihi Seamount wikipedia , lookup
Axial Seamount wikipedia , lookup
Craters of the Moon National Monument and Preserve wikipedia , lookup
Itcha Range wikipedia , lookup
Mount Pinatubo wikipedia , lookup
Mount Meager massif wikipedia , lookup
Mount Pleasant Caldera wikipedia , lookup
Mount Garibaldi wikipedia , lookup
Llullaillaco wikipedia , lookup
Level Mountain wikipedia , lookup
Large igneous province wikipedia , lookup
Potrillo volcanic field wikipedia , lookup
Lascar (volcano) wikipedia , lookup
Mount Edziza volcanic complex wikipedia , lookup
Mount St. Helens wikipedia , lookup
Olympus Mons wikipedia , lookup
Volcanology of Io wikipedia , lookup
Nevado del Ruiz wikipedia , lookup
Mount Pelée wikipedia , lookup
Mount Vesuvius wikipedia , lookup
Wells Gray-Clearwater volcanic field wikipedia , lookup
Cascade Volcanoes wikipedia , lookup
Volcano (1997 film) wikipedia , lookup
Cerro Azul (Chile volcano) wikipedia , lookup
Shield volcano wikipedia , lookup
VOLCANOES form where molten rock is vented at Earth’s surface. BIG Questions Where do volcanoes form in the context of plate tectonics? Volcanoes aren’t equally dangerous.... how do their hazards differ, and why? What comes out of a volcano? Ash What comes out of a volcano? Gas Most common: H2O CO2 SO2 HCl What comes out of a volcano? Lava Mauna Loa (Hawai’i): A typical shield volcano Mt. St. Helens: A typical composite volcano Mt. St. Helens after its 1980 eruption Composite Volcano • • • Cinder Cone Built from ejected lava fragments Steep slope angle Rather small size Sunset Crater, near Flagstaff, AZ A size comparison of the three types of volcanoes Volcanologists recognize many types of volcanoes, but we only need to worry about two: Explosive (“Clogged”) Andesitic composition Composite volcanoes Non-explosive Basaltic composition Shield volcanoes (“Runny”) Volcanic eruptions Factors that determine the violence of an eruption • • • Composition of the magma Temperature of the magma Dissolved gases in the magma Viscosiy of magma Viscosity is a measure of a material's resistance to flow Volcanic eruptions Viscosity of magma – factors • • • Temperature (hotter magmas are less viscous) Composition [Si02 (silica) content] - High silica – high viscosity (e.g., rhyolitic lava) - Low silica – more fluid (e.g., basaltic lava) Dissolved gases - Mainly water vapor and carbon dioxide – - Gases expand near the surface More silica = more linkage = more viscous Magma compositions affect properties Volcanic Hazards Lava flows Ash fall Pyroclastic flows Mudflows Volcanic Gases Tsunami Plate-tectonic setting of volcanism Explosive (andesitic) volcanoes form at subduction zones. Plate-tectonic setting of volcanism At spreading centers, low pressure triggers mantle melting—fluid basaltic magma rises. Plate-tectonic setting of volcanism Within plates, rising plumes of hotter mantle feed hot spots; varied volcanoes result (basaltic on Hawaii).