Some changes in the earth's surface are abrupt while other changes happen very slowly. Today we are going to learn how this rock formed, where it is found and how we can go about classifying it. Rocks are found everywhere. They are on top of the earth's surface as well as below earth's surface. Rocks are composed of chemical substances known as minerals .
Minerals usually occur naturally in the ground and are made of non-organic substances.
However, sometimes minerals contain organic substances such as coal. There are approximately 2000 minerals with new ones still being discovered. The rocks present in the earth's crust are classified as igneous, sedimentary and metamorphic. Each of the three kinds of rocks is related to the other two. Igneous rocks compose the majority of the rock in the earth's crust.