• Question: Why do volcanoes erupt?

    Asked by buzz366den to Elena on 17 Nov 2019.
    • Photo: Elena Maters

      Elena Maters answered on 17 Nov 2019:


      Volcanoes typically erupt when magma (molten rock) rises to the surface. As the magma rises, gases inside the magma begin to form bubbles, but if the magma is thick and the gases cannot easily escape, the bubbles expand and there is a build-up of pressure. When the pressure becomes too much, an eruption can happen at the surface, with the gases finally exploding free of the bubbles and sending pieces of magma flying violently through the air! These magma ‘fragments’ cool quickly to form solid pieces of different sizes which are called volcanic bombs/blocks (bigger than 64 mm), lapilli (between 2 and 64 mm), and ash (less than 2 mm).

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