• Question: when lava dries does the rock that it creates float

    Asked by anon-174234 to Alex, Carl, Hayley, Melanie, Tim, Yewande on 19 Jun 2018.
    • Photo: Carl Barford

      Carl Barford answered on 19 Jun 2018:


      It can, if there are lots of bubbles, it is called pumice

    • Photo: Alex Seeney

      Alex Seeney answered on 19 Jun 2018:


      Yes – when magma cools, it forms a type of rock called igneous rock. The inside of this rock is affected by how much gas escapes during the eruption, which means that some rocks like pumice (as Carl mentioned) can be so light that it floats!

    • Photo: Tim Craig

      Tim Craig answered on 19 Jun 2018:


      Generally, no – rock is much more dense than water. The only real exception (as mentioned) is Pumice, which has a very high content of void space filled with gas. But pumice is only a small proportion of rock formed – it forms when you cool lava really, really quickly, by quenching it in water, for example.

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