Section 2: Volcanic Activity

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Chapter 2 Volcanoes

• Section 2 Volcanic Activity

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How magma reaches Earths surface

• Liquid magma is less dense than the surrounding
  solid material, so it flows upward into any
  cracks in the rock above
• During a volcanic eruption, the gasses dissolved
  in magma rush out, carrying the magma with them

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Inside a volcano
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Characteristics of magma

• The force of volcanic eruption depends partly on
  the amount of gas dissolved in magma
• Other important factors that affect an eruption
  How thick or thin the magma is, the temperature
  and its silica content.
• More silica higher viscosity (thicker)
• Less silica lower viscosity (thinner)

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Types of volcanic eruptions

• The silica content of magma helps to determine
  whether the volcanic eruption is quiet or
  explosive
• High viscosity (thick) causes an Explosive
  eruption
• Low viscosity (thin) causes a Quiet eruption
• A volcano erupts quietly if its lava flows easily
• Two types of lava produced by quiet eruptions
• Pahoehoe -fast moving, hot lava (Low viscosity)
• Aa -slow moving, cooler lava (High viscosity)

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Aa
Pahoehoe
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• Magma rises through the lithosphere because it is
  less dense and it is rising through the solid
  rock. As the magma materials rise, the rock
  cracks and magma goes through.
• Both quiet and explosive eruptions can cause
  damage far from the craters rim.

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3 Stages of a Volcano

• Active - it will erupt or is erupting
• Dormant - there is a possibility that it will
  erupt (may not be for a long time)
• Extinct - it will not erupt

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Other types of volcanic activity

• Hot spring forms when groundwater heated by
  nearby magma, rises to the surface and collects
  in a natural pool
• Pressure can build and cause a geyser- a fountain
  of water and steam that erupts from the ground
• Geothermal Energy a clean, reliable energy
  source caused when water is heated by magma

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Hot Spring
Geyser