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Volcanoes Plate tectonics part 2

Volcanoes Plate tectonics part 2. Mt. Arenal, Costa Rica. Hawaii. Surtsey, Iceland. Basaltic -hottest,most fluid, low[gas],lowSiO 2 ……….CALMEST………. Devil’s Tower, SD. Andesitic- over subduction zones;intermediate. Mt. St. Helens. Tambora Indonesia.

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Volcanoes Plate tectonics part 2

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  1. Volcanoes Plate tectonics part 2 Mt. Arenal, Costa Rica

  2. Hawaii Surtsey, Iceland Basaltic-hottest,most fluid, low[gas],lowSiO2 ……….CALMEST………. Devil’s Tower, SD

  3. Andesitic-over subduction zones;intermediate Mt. St. Helens Tambora Indonesia

  4. Rhyolitic-coolest,least fluid,high[gas],highSiO2 ….MOST EXPLOSIVE…. Yellowstone National Park

  5. Volcano types • shield volcanoes Broad, gently-sloped sides, circular base; formed by basaltic lava layering Mauna Loa, Hawaii Cleveland Volcano Aleutian Islands

  6. 2) Cinder cone volcanoes Ejected material falls back to earth, piles up around vent; usually small, with steep sides; usually <500m high Paricutin, Mexico Lava Butte, OR Sunset Crater, AZ

  7. 3) Composite volcanoes Formed by alternate layers of lava, volcanic fragments; tend to be larger, more explosive than cinder cones (magma commonly with large amounts of silica, water, and gases Mt. St. Helens Mt. Vesuvius - Italy Mt. Fuji - Japan

  8. Volcanic material (tephra) Classified by size DUST =<0.25mm ASH = 0.25-2.0mm LAPILLI (“little stones,” Italian) = 2mm-64mm BLOCKS = large pieces (can be as large as houses!), BOMBS = large pieces that are rounded as the lava cools PYROCLASTIC FLOWS = masses of hot gasses, ash, tephra that can move @ 200km/hr

  9. Modeling volcanoes 1) convergent volcanoes Subduction zones – note the Circum-Pacific belt, the “ring of fire,” extending along S. America, up across Aleutians, along E. Asian continent; note also the Mediterranean Belt

  10. Ring of Fire (cont)

  11. 2) Divergent vulcanism Occurs at rift zones (much of this vulcanic activity occurs as underwater eruptions; note above-water divergent vulcanism in Iceland Underwater Pillow lava

  12. 3) Hot spots Located above “Mantle Plumes;” plumes “burn holes” in the crust (Hawaiian Islands are a great example!)

  13. Over millions of years, the Pacific Plate has moved over the Hawaii hotspot, creating a trail of underwater mountains stretching across the Pacific Ocean

  14. Olympus Mons Mars!!

  15. Olympus mons *Height 88,580 feet *Approx. 3X elevation of Mt. Everest above sea level *2.6X height of Mauna Kea above base

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