• Question: Hi Becky. I'm Edward, I'm 6 y.o and I do Science at the Romanian School. I want to ask why do volcanoes have a hole in the middle? Why do volcanoes explode and why after explosion there is smoke? And why does smoke goes everywhere? Why are volcanoes mountains? I know they are mountains but I don't know why. Thank you very much.

    Asked by to Becky on 27 Jun 2014. This question was also asked by .
    • Photo: Rebecca Williams

      Rebecca Williams answered on 27 Jun 2014:


      Hi Edward,
      That’s lots of questions! Thank you for asking some great ones.

      Volcanoes have a hole in the middle because that’s where the eruptions come out of. The magma (molten rock) inside the volcano forces itself out of them, sometimes explosively, which can make a crater. In the really big volcanic eruptions, the magma chamber gets emptied so much, this leaves a space under the volcano, so the top of the volcano collapses in – this is called a caldera.

      The smoke from an explosion is actually volcanic gases like steam, carbon dioxide and sulphur dioxide mixed in with ash which are tiny particles of frozen magma. The ash cloud will rise up into the air until it is the same density as air and then it starts to spread out. It can then get blown about by the wind. Take a read of my answer to Rhiana’s question here about why volcanoes erupt: /praseodymiumj14-zone/2014/06/23/what-makes-volcanos-erupt/

      Volcanoes are mountains because they are growing all of the time. They are making new rocks and building up layer upon layer, so they get higher and higher. Volcanoes like Mauna Loa in Hawaii have built up from the bottom of the sea floor in this way! Volcanoes also form at places called subduction zones – here two tectonic plates crash into other and this forces one of the plates up into the air as mountains. The volcanoes then grow in these mountain ranges. The longest mountain chain in the world is the chain of volcanoes on the seafloor which are made because two tectonic plates are moving apart. I talk more about plate tectonics here, and this may help you to understand: /praseodymiumj14-zone/2014/06/24/where-is-the-lava-coming-from/

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