• Question: how do volcanoes erupt

    Asked by to Andrei, Ekbal, Gemma, Helen, Ruth on 16 Jun 2014. This question was also asked by , .
    • Photo: Ekbal Hussain

      Ekbal Hussain answered on 16 Jun 2014:

      Hi @sinclairm,

      The main reason volcanoes erupt is because the pressure inside the volcano builds up so much that the stuff inside bursts out.

      A really easy way to see this is with a fizzy drink bottle. I’m sure you’ve seen it happen before, where if you shake the bottle before opening it and the try and open the bottle cap all the drink gushes our very fast.

      By shaking the bottle you are making all the air inside the drink come out of the liquid and make air bubbles. These push on the bottle and put lots of pressure on the lid. And as soon as there is a little gap all the air gushes out and brings all the drink with it.

      That’s exactly how an explosive volcano erupts.

      Here’s a little video my friend made of an experiment you can try at home and learn about volcanic eruptions: https://www.youtube.com/watch?v=BqYguj-Lsso#t=67

    • Photo: Helen Gath

      Helen Gath answered on 19 Jun 2014:

      Quite right. The pressure of the magma build up due to chemical reactions, and as the magma increases in temperature, it expands. Similarly to when you heat water, the water molecules gain much more energy and expand, becoming gaseous.

      As the magma it gets more energy and tries to expand. This reaches a point where the rock around it are not string enough to contain the pressure. The magma tires to find the path of least resistance, which means it is more likely to choose heading towards earth’s open surface rather than deeper into the ground!

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