Rocks on the earth can be divided into igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks condensed from silicate solution constitute the main body of the earth's crust, which is the most in terms of volume and weight. But the most common thing on the ground is sedimentary rock. It is a rock with layered structure formed after the earlier rock is destroyed, deposited in the depression of the earth's surface by physical or chemical action and then compacted and cemented and hardened again. In the crust, the structure or chemical composition of rocks change under the action of temperature and pressure much higher than the surface, forming metamorphic rocks different from igneous rocks and sedimentary rocks.
passage?
Conditions of formation.