TOPIC 7 ROCKS

WHAT ARE ROCKS?

Rocks contain one or more minerals. Rocks make up the continents and the ocean floor.

Types of rocks

1. Sedimentary rocks

They are formed on the surface of the Earth over millions of years. Sedimentary rocks are layers of broken rock, minerals and the remains of living things. 

E.g. Sandstone, clay, coal and petroleum

Coal

Sandstone

                                2. Igneous rocks

Granite

Basalt

They are formed deep inside the Earth where it is so hot that rock melts! When melted rock cools, it makes igneous rocks. 

E.g. granite and basalt.

Marble

3. Metamorphic rocks

Slate

They are formed when rocks deep inside the Earth change. This happens because of heat and pressure.

E.g. marble and slate

         

  What do we use rocks for?

      We make many objects from rocks:

        

• We use clay, granite, marble and slate as building materials.
• We use coal and petroleum as fuel.
• We use lots of rocks in industry, for example, to make glass, paper, cement, plastics, paints...etc.