• Question: If volcanoes keep errupting, wouldn't the core of the Earth run out of magma?

    Asked by to Becky on 25 Jun 2014. This question was also asked by .
    • Photo: Rebecca Williams

      Rebecca Williams answered on 25 Jun 2014:

      Hi Alberteinstein!

      So, to answer this question there are two things you need to know about. Where magma comes from and plate tectonics.

      Magma is molten rock (lava when it is still under the ground). I say how magma is made here in answer to Rhiana’s question. Go read that first /praseodymiumj14-zone/2014/06/24/where-is-the-lava-coming-from/

      So, magma doesn’t come from the core. The heat comes from the core that helps melt the mantle to make magma. So, if volcanoes kept erupting would we run out of mantle?

      Well, the answer to that lies in plate tectonics. The earths crust is broken up like a jigsaw. In some places, the plates move away from each other and make new crust through volcanoes (at mid-ocean ridges). In other places, the plates crash into each other to make mountains. Here, one plate gets forced underneath the other one – this is called subduction. When the plate gets forced into the mantle it joins up with the mantle – some of it melts and the rest of it hangs around as a cold bit in the mantle. So, whilst volcanoes erupt melted mantle, subduction returns the crust back into the mantle. Its like recycling!
      There is a picture of that here:

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