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Volcanoes

Volcanoes. Eruptions and Forms of Volcanoes. Types of Eruptions. Violent and explosive Quiet and flowing Depends on trapped gases and magma composition. Trapped Gases. Water vapor and carbon dioxide are trapped in magma

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Volcanoes

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  1. Volcanoes Eruptions and Forms of Volcanoes

  2. Types of Eruptions • Violent and explosive • Quiet and flowing • Depends on trapped gases and magma composition

  3. Trapped Gases • Water vapor and carbon dioxide are trapped in magma • At low pressure, they escape quietly when they reach the surface • At high pressure, they escape violently when they reach the surface

  4. Magma Composition • Two types: • Basaltic – less silica and very fluid; produces quiet eruptions • Granitic – lots of silica, high water vapor content, and very thick; produces very violent eruptions

  5. Forms of Volcanoes • Three forms: • Shield • Cinder Cone • Composite

  6. Shield Volcano • Formed by quiet eruptions • Basaltic lava builds up in flat layers • Gently sloping sides • Ex: Hawaiian Islands

  7. Cinder Cone Volcano • Caused by explosive eruptions • Granitic lava thrown high into the air • Lava cools into different sizes of volcanic material called tephra • Steep-sided, loose slopes

  8. Composite Volcano • A mix of the other two types • Quiet or violent • Basaltic or granitic • Steep or gentle slopes • Layered or tephra

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