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The Development of Volcanoes

Geography: KS3, topic 11.2.2

Volcanoes

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

Destructive plate margins

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).
Constructive plate margins

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.
Hotspots

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.

The Stages of Volcano Development

Volcanoes exist in one of the following three different states:

Active volcanoes

Active volcanoes

  • Active volcanoes are volcanoes that have a high likelihood of erupting.
Dormant volcanoes

Dormant volcanoes

  • Dormant volcanoes are volcanoes that have the potential to become active but have not actually erupted for at least 10,000 years.
Extinct volcanoes

Extinct volcanoes

  • Extinct volcanoes are volcanoes that are unlikely to ever erupt again and have not erupted for at least 1,000,000 years.

Test yourself on The Development of Volcanoes

  • What do we call an opening in the Earth's crust?

  • Volcano Formation at Destructive Plate Margins

  • Which of the following is NOT a stage of volcano development?

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