Test Review 2

Test Review 2 - -Chapter 8 (5 Qs)-Volcanoes - Distribution...

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------------------------------------------------Chapter 8 (5 Q’s)--------------------------------------------------------------- Volcanoes - Distribution of most volcanoes is related to boundaries between tectonic plates, Volcanic eruptions affect climate and were responsible for forming Earth's atmosphere. Igneous processes form a variety of mineral deposits and contribute geothermal energy. Volcano : constructional feature built up around a vent in which magma escapes to the surface, Multiple flows build up cone, After eruption: Magma withdrawal --> collapse --> depression Caldera : large depression Crater Lake (Oregon) Crater : small depression, Mt. Etna (Sicily, Italy) Lava - Shield volcanoes : very broad volcano with surface slopes of <10° produced by eruption of basaltic lava, Hawaii or Mars, are commonly present at hot spots Cinder (tephra) cones : generally small volcanoes built up of pyroclastic material, generally of andesitic to rhyolitic composition, with surface slopes of 25° to 50°, Kilauea or Nicaragua Composite volcanoes (stratovolcanoes) : very large volcano composed of alternating lava flows and pyroclastic material, generally of andesitic composition, with surface slopes of 30° at the summit and 6°-10° at the base, Mt. Fiji Japan or Mt. St. Helens/Rainer Washington, more destructive than shield volcanos Lava dome : bulbous mass of highly viscous, gas-poor lava out like toothpaste from a volcano Flood basalts : regional lava flows that come from fissures (long, linear cracks in the earth's surface); thick accumulations build lava plateaus, Northern Iceland Splatter Cones – Small cones which lava flows from, tiny volcanoes, in lines Gases produced from eruptions: CO 2 , H 2 O, SO 2 , H 2 S, HCl, N 2 Pyroclastic (fragmental) material , e.g., ash, bombs Pahoehoe lava : billowy and ropelike (hotter), basaltic lava Kilauea Aa: rough surface composed of blocks and fragments (cooler), basaltic lava Kilauea Pillow lava : spheroidal masses produced by underwater eruptions, basaltic lava, associated with submarine basaltic eruptions Viscosity : resistance to flow, increases as silica content increases, Rhyolite -- high viscosity; does not flow easily Basaltic magma - Dry partial melting of mantle rocks at mid-ocean ridges & hotspots. can be altered to andesitic & rhyolitic magma through contamination from continental crust, Basalt -- low viscosity; flows easily, gas escapes readily-->quiet eruptions George Julius Poulett Scrope “expansive forces of some elastic aëriform fluid struggling to escape from the interior of a subterranean body of lava.”— Considerations on Volcanoes , 1825. Pumice, scoria --volcanic rock containing numerous cavities filled with gas Ash --shards of volcanic glass formed in explosion, fine volcaniclastic debris (ash) suspended in air when volcano is erupting Magma - contains dissolved gases, Rising magma --> pressure reduction --> gas release --> eruption.
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Test Review 2 - -Chapter 8 (5 Qs)-Volcanoes - Distribution...

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