Types of rocks
Rocks can be classified in many ways, depending on the characteristics that are taken into account.
For example, according to their composition they could be classified as simple, if they are only made up of the same type of mineral, and compound, if they are made up of several different types of minerals.
But the usual way of classifying rocks is based on how they originated. The rocks have been formed as a result of geological processes such as volcanoes, sedimentation in seas, lakes, rivers, etc., they come from other rocks formed previously, etc.
According to the origin of the rocks, they are classified into three groups:
- Sedimentary rocks. They are formed from sediments.
- Metamorphic rocks. They are formed from other rocks by changes in pressure and temperature, but without actually melting.
- Magmatic or igneous rocks. They form when magma from inside the Earth cools and solidifies.