There are three main types of rocks: sedimentary, igneous, and metamorphic. Each of these rocks are formed by physical changes—such as melting, cooling, eroding, compacting, or deforming—that are part of the rock cycle. Sedimentary rocks are formed from pieces of other existing rock or organic material.

How rocks are created?

When soil and surface materials erode over time, they leave layers of sediments. Over long periods of time, layer upon layer of sediments form, putting intense pressure on the oldest layers. Under great pressure and heat, lower layers of sediments eventually turn into rocks.

What is a rock and how are they formed?

A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition and the way in which it is formed. ... Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed.