• Question: What is a rock made of?

    Asked by beccawilko to Angus, Christian, Hannah, Laura, Simon on 25 Jun 2013.
    • Photo: Laura Roberts Artal

      Laura Roberts Artal answered on 25 Jun 2013:

      It really depends on what type of rock.
      There are three main types of rocks:

      Sedimentary rocks – these are made up of grains eroded away from other rocks and also organic matter (like shell fragments and dead leaves and animals). They form on the surface of the Earth, oceans and lakes. Sedimentary rocks make up between 5%-10% of the rocks in the Earth’s crust. Only about 1% of the total Earth’s volume!

      Igneous rocks- these include all the rocks that can be made by a volcano. They can be cooled and hardend lavas and also by lava that never makes it to the surface to form large structures we call plutons, dykes and sills.

      Metamorphic rocks – these rocks are formed when either sedimantary or igenous rocks are put under a lot of pressure (by burying them usually) and heated to high temperatures (usually above 150 celcius). This changes them and turns them into new rocks!

    • Photo: Simon Holyoake

      Simon Holyoake answered on 26 Jun 2013:

      Mineral wise, most rocks contain silica, calcium carbonate and aluminium, of course there are many other minerals in many other combinations too!

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