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 are rocks made?

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.

How are rocks formed step by step?