Variation in volcanic activity- different margins and lava

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  • Created by: Lilly
  • Created on: 20-04-14 16:35

Constructive Margin

  • Basaltic Magam- runny due to low silica content, does not trap gases.
  • Eruptions low level of violence, gases can escape easily therefore pressure does not build up.
  • Eruption height reaches from 1km onwards- not as much as destructive margins because of the lack of silica in the magma.
  • Mostly lava is ejected.
  • Eruptions are fairly regular and continuous- not trapped gases- lava can flow freely.
  • A constructive margin can form a lava plateau and shield volcano.
  • Classification- Icelandic and onwards.
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Destructive Margin

  • Magma is andesitic to rhyolitic. The lava is increasing in viscosity due to a higher silica content, which traps gases, making the lava more sticky and less able to flow.
  • Eruptions can potentially be explosive, due to the build up of pressure. This build up of pressure can mean that eruptions can reach heights of over 17km to the tropopause (the lowest major atmostpheric layer.)
  • Materials produced- Tephra and pyrcolastic flows.
  • Eruptions are spardic, with periods of dormancy.
  • Destructive margins form acid lava domes and composite cone volcanoes.
  • Classification- Vulcanian > Plinian.

Q) In what way does volcanic activity vary in relation to the type of plate margin along which it occurs?  (10)

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