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Vocabulary


volcano- a weak spot in crust where molten material, or magma, comes to the surface

magma- a molten mixture of rock forming substances

lava- magma that reaches the surface

Ring of Fire- a major volcanic belt

island arc- a string of islands created by erupting volcanoes

hot spot- an area where magma from deep within the mantle melts through the crust like a blowtorch

Outline


T

Volcanoes and Plate Tectonics=
  • What is a Volcano?

    • weak spot in crust
    • spews out lava
    • volcanic activity adds rock to land
  • Location of Volcanoes

    • 600 active volcanoes
      • more lie beneath the sea
    • volcanoes occur in belts
      • major belt= Ring of Fire
    • volcanic belts form along boundaries of Earth's plate
      • crust weak fracture at boundaries
    • most volcanoes occur along diverging plate boundaries
  • Volcanoes at Diverging Plate Boundaries

      • form along mid- ocean ridge= diverging plate boundary
        • along ridge, lava pours out of cracks on ocean floor
  • =Volcanoes at Converging Boundaries=
    • many volcanoes form near plate boundaries
      • oceanic crust returns to the mantle in boundaries
    • the crust melt= forms magma, rises toward surface
      • magma erupts as lava, and volcanoes formed
    • volcanoes occur on....
      • islands
      • near boundaries
        • older, denser, lower plate creates deep ocean trench
        • lower plate sinks into asthenosphere, and melts
      • melted plate forms magma
        • magma seeps upward through crust's cracks
          • magma breaks through ocean floor, creating volcanoes
            • volcanoes create string of islands= island arc
            • island arc's curve echo's deep ocean trench
              • major island arc= New Zealand, Japan, Indonesia, Carribean Islands, etc.
      • Subduction occurs where edge of continental plate collides w/ oceanic plate
        • collisions produced Andes Mt. volcanoes
  • Hot Spot Volcanoes

    • some volcanoes formed from hot spots
      • hot spot= area where magma from deep within the mantle melts through crust
      • hot spots lie in middle of of continental or oceanic plates
    • volcanoes from hot spots not from subduction
      • hot spots also can form under continents
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