1.2.6

Volcanoes

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Volcanoes

A volcano is an opening in the Earth's crust that is formed when magma rises from inside the Earth and erupts through the Earth's crust. Volcanoes can be formed at constructive plate margins and destructive plate margins.

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Destructive plate margins

  • The denser oceanic plate is forced under the continental plate at destructive margins.
  • The friction and pressure cause cracks (vents) to form in the continental plate. The magma rises to the surface of the Earth through the cracks in the continental plate.
  • This usually creates highly explosive volcanoes (e.g. Mount Vesuvius in Italy) that produce a lot of gas and lava (magma above the surface).
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Constructive plate margins

  • At constructive plate margins:
    • Tectonic plates move apart (diverge) because the convection currents in the mantle diverge, creating outward pressure.
  • Magma bubbles up to fill the gap between the plates, creating a volcano.
  • This kind of volcano is common in Iceland.
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Hotspots

  • Hotspots do not happen at plate boundaries. But they still count as volcanic activity.
  • Hotspots happen on parts of the Earth's crust over hotter parts of the Earth's mantle.
  • The rising hot air weakens the Earth's crust and magma can reach the surface, bubbling up through the weakness in the crust.
  • The Hawaiian islands all formed as a result of a mid-Pacific hotspot.

Jump to other topics

1The Challenge of Natural Hazards

1.1Natural Hazards

1.2Tectonic Hazards

1.3Weather Hazards

1.4Climate Change

2The Living World

3Physical Landscapes in the UK

3.1The UK Physical Landscape

3.2Coastal Landscapes in the UK

3.3River Landscapes in the UK

3.4Glacial Landscapes in the UK

4Urban Issues & Challenges

5The Changing Economic World

6The Challenge of Resource Management

6.1Resource Management

6.2Food

6.3Water

6.4Energy

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