Volcanoes
Geography: Edexcel IGCSE, topic 1.4.7
Where Do Volcanoes Happen?
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.
Convergent plate margins
- The denser oceanic plate is forced under the continental plate at convergent plate 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).
Divergent plate margins
- At divergent 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 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.
Test yourself on Volcanoes
What do we call an opening in the Earth's crust?
Volcano Formation at Destructive Plate Margins