The rocks on the earth can be divided into igneous rocks, sedimentary rocks, and metamorphic rocks. Igneous rocks condensed by silicate slurry constitute the main body of the crust, which is the most calculated by volume and weight. But the most common on the ground are sedimentary rocks. After the earlier formation of the rock was destroyed, it was deposited on the concave surface of the earth after physical or chemical action. After compaction, the cement hardened again. It formed a rock with layered structural characteristics. In the crust, it is much higher than the surface. Under the influence of temperature and pressure, the structure, structure or chemical composition of rocks changes, forming metamorphic rocks different from igneous rocks and sedimentary rocks. What types of rock on the earth does this text mainly introduce? ['Formation conditions.', 'Structural characteristics.', 'Address distribution.', 'Chemical composition.']