• Question: how does the magma in volcanoes come out when a volcano erupts?

    Asked by lesperges to James V on 2 Jul 2012.
    • Photo: James Verdon

      James Verdon answered on 2 Jul 2012:


      Hi lesperges,
      There are a number of ways this can happen, so it’s a good question. Usually, the magma will be sitting in the magma chamber, a cavern below the volcano where the magma is stored. If more and more magma keeps coming up from below, then there is only so much the chamber can store before the pressure becomes too much, and the magma is forced up a vent to cause an eruption.

      Bubbles in the magma can play a huge role in an eruption as well. Most magma has gasses dissolved in it. If, for some reason, the pressure in the magma is suddenly reduced (perhaps the magma rises up a bit), the bubbles will come out of solution. The bubbles will immediately try to escape. This is just like when you shake a coke bottle and then open it – you have a liquid at pressure with gas dissolved in it. When you release the pressure, all the bubbles come out and you have an explosion of coke. So it’s the same in volcanoes, you release the pressure and the bubbles come out of solution, leading to an explosion, except you get hot magma going everywhere!!

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