How are rocks grouped?
Rocks are grouped by how they are formed. There are 3 types of rocks. Sedimentary, Metamorphic, and Igneous rock. Sedimentary rocks are made from broken down rocks, called sediment, which come from all three rocks. Metamorphic rocks come from existing rocks that are changed by heat and pressure. The Igneous rocks are formed from magma that rose up to the surface, also known as lava. When the lava cools and hardens it forms igneous rocks. That is a rock cycle.
