Unit 4: Minerals and rocks                                                       1   2   3   4

3. Rocks

   The solid part of the Earth is made up of rocks.

   Rocks are any natural, inorganic materials made up of minerals.

   Most part of them is compounded by several minerals and is solid.

   But some rocks are made of a single substance and others can be

   found in liquid form, for example, oil.

   According to their origin rocks can be classified as:

- Sedimentary rocks:

  They are formed by the accumulation and compaction of sediment.

  These sediments can be:

      - fragments of the rocks are carried to where they are them

        deposited. For example: conglomerate, sandstone, etc.

      - accumulated chemical substances in the bottom of seas,

        lakes, etc. For example: Gypsum.

- Metamorphic rocks:

      Forces inside the Earth cause that a rock change into another

      type, without melting.

      They are formed from other rocks by the effects of high

      temperature and pressure.

           - due to the high pressure. For example: slate.

           - due to the high temperature For example: marble.

    - Magmatic (or igneous) rocks:

      They are formed from cooled magma.

      Magma is molten rocky material below the Earth's surface.

       When the magma cools down:

          - slowly, inside the terrestrial crust, for example: granite.

          - quickly, when it surfaces from volcanoes, for example: basalt.

3.1. Answer these questions:

a. What is a rock

b. We can classify them in three types, which are they?

c. What criteria do we used to do it?

3.2. Match these columns:

3.3. Listen and indicate what type of rock  is described: