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Vocabulary


magma chamber- a pocket in which magma collects

pipe- a long tube in the ground that connects the magma chamber to the Earth's surface

vent- an opening where molten rock and gas leave

lava flow- an area covered by lava as it pours out of a vent

crater- a bowl shaped area that may form at the top of a volcano around the volcano's central vent

Silica- a material that is formed from elements oxygen and silicon

Pahoehoe- fast moving, hot lava

aa- cooler, slower moving lava

pyroclastic flow- occurs when explosive eruption hurls out ash, cinders, bombs and gases

active- the term for a live volcano, having the ability to erupt in the near future

dormant- a 'sleeping' volcano, opposite of active, may be able to erupt in the future

extinct- a dead volcano, which is unlikely to erupt again

hot spring- formed when groundwater heated by nearby body of magma rises to the surface and collects in a natural pool

geothermal energy- water heated by magma produces this clean energy

Outline


T= Volcanic Activity

  • How Magma Reaches Earth's Surface

    • lava begins as magma
    • magma forms in asthenosphere
      • materials of asthenosphere under great pressure
  • Magma Rises

    • liquid magma is less dense than surrounding solid material, it flow upward into cracks
    • magma floats up until trapped or reaches the surface
  • A Volcano Erupts

    • dissolved gases trapped in magma under tremendous pressure
      • as magma rises toward the surface, pressure decreases
        • volcano erupts when opening develops in weak rock
        • once magma reaches surface, becomes lava and gases bubble out
  • Inside a Volcano

    • beneath a volcano, magma collects in magma chamber
      • magma moves through a pipe
      • molten rock and gases leave the volcano through a vent
  • Characteristics of the Magma

    • the force of a volcanic eruption depends on
      • gas content of magma
      • thickness of magma
      • how much silica the magma contains
  • Types of Volcanic Eruptions

    • The silica content in magma helps determine whether the eruption is quiet or explosive
  • Quiet Eruptions

    • a volcano erupts if the magma flows easily
      • Quiet Eruptions produce two eruptions=
        • Pahoehoe
          • fast moving, hot lava
          • surface of lava looks like rope- like coils
        • aa
          • when hardens, it forms a rough, jagged chunks of lava
  • Explosive Eruptions

    • If thick and sticky, the magma will erupt explosively
      • the pressure will build until it explodes
        • hurtles out=
          • bombs
          • fine sand grains
        • pyroclastic flow
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Scan10006.JPG
A diagram of a volcano