KS3 Science Revision

There are three types of rock:

 

Sedimentary:

Sedimentary rocks are formed from tiny pieces of rock and sand called sediments. These sediments are washed into the rivers and build up in layers. The pressure of the water above compacts them and makes them very tight. The water gets inbetween the sediments and cements tem together. Limestone, sandstone and mudstone are examples of sedimentary rocks. Sedimentary rocks are usually quite soft and can contain fossils.

 

Igneous:

Igneous rocks are formed when magma solidifys. This can happen over or underground. If the magma solidifys underground, then it will take time and conatin large crystals. If it is overground, then it will be very fast and have small crystals. Basalt and granite are exaples of igneous rock.

 

Metamorphic:

Metamorphic Rocks are sedimentary or igneous rocks that have been changed by pressure or heat to form a new rock. Marble, slate and quartzite are examples of metamorphic rock.

 

Rocks can be weathered and destroyed in three different ways. Chemical weathering involves acid rain and is where a rock is corroded. Biological weathering involves plants growing in the cracks of a rock. It involves plants, animals or microbes. Physical weathering is where earthquakes and boulders brake up rocks.