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Results of plate tectonics: 1.volcanism 2.diastrophism 3.earthquakes

Results of plate tectonics: 1.volcanism 2.diastrophism 3.earthquakes. Volcanism. Volcanism. movement of molten rock from earth’s interior through a conduit or opening to, or near, the surface. Types of volcanism:. A. Extrusive 1. Volcanoes a) shield b) composite c) cinder cone

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Results of plate tectonics: 1.volcanism 2.diastrophism 3.earthquakes

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  1. Results of plate tectonics: 1.volcanism 2.diastrophism 3.earthquakes

  2. Volcanism

  3. Volcanism • movement of molten rock from earth’s interior through a conduit or opening to, or near, the surface

  4. Types of volcanism: A. Extrusive 1. Volcanoes • a) shield • b) composite • c) cinder cone 2. Lava Flows • flood basalts B. Intrusive

  5. A. Extrusive Volcanism • Magma reaches the surface (lava) and cools above the surface. 1. Volcanoes: hills or mountains of volcanic material that was released under pressure from a vent • >500 active (4/5 “ Ring of Fire”) - subduction, rift valleys, mid-oceanic ridges, hot spots

  6. Types of Volcanoes: a) Shield Volcanoes • broad, gently sloping surfaces • examples: Hawaii, Azores, Mt. Hekla in Iceland • tallest mountains on earth are shield volcanoes from the ocean floor • effusive eruption • nonviolent eruption due to type of magma • low viscosity; 2200 degrees F, little gas in magma • Iron, magnesium, low in silica: from asthenosphere • Primarily basalt

  7. b) Composite Volcanoes • steep-sided • alternating layers of pyroclastics and lava • pyroclastics: rock pieces ejected: • Tephra: pulverized rock • Scoria: cindery vesicular rock • ash falls and lava flows • subduction zones • examples: Mt. St. Helens, Mt. Rainier, Mt. Fuji, Mt. Hood • explosive eruption due to type of magma • higher viscosity, 1600 F; contains gases • from melting of lithosphere: more silica

  8. Types of volcanism: A. Extrusive 1. Volcanoes • a) shield • b) composite • c) cinder cone 2. Lava Flows • flood basalts B. Intrusive

  9. Composite = stratovolcano

  10. Insert map of volcanoes

  11. CALDERA: landform associated with some composite volcanoes • large bowl-shaped depression left after a composite volcano blows; mountain collapses inward • Example: Crater Lake

  12. c) Cinder Cones • steep, cone-shaped hills of pyroclastics • moderately explosive • most abundant and smallest (<1500 ft. high) • central crater • form rapidly, erode rapidly • example: central Arizona; Paricutin, Mexico; Idaho Snake River Plain

  13. Types of volcanism: A. Extrusive 1. Volcanoes • a) shield • b) composite • c) cinder cone 2. Lava Flows • flood basalts B. Intrusive

  14. 2. Lava Flows • Effusive (nonviolent) eruptions • spreading boundaries and hot spots • lava spreads out over surface; coming out of fissure (rift) • example: Lake Superior shore • 1.2 billion yrs BP • can accumulate layer upon layer : FLOOD BASALT • examples: Columbia Plateau (Washington), Deccan Plateau (India)

  15. B. Intrusive Volcanism • Magma solidifies beneath surface; intrudes into cracks in crust • intrusions can later be exposed at surface; more resistant than surrounding rock

  16. Intrusive landforms • Neck: narrow steep-sided peak , formed in central vent of an extinct volcano • E.g., Ship Rock, Devil’s Tower • Dike: thin layer of igneous rock ; vertical; cuts across other rock layers • Sill: thin layer of igneous rock between rock layers • Plutons: large igneous bodies at depth • batholiths • laccolith: dome-shaped

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