Answer:
Rocks are classified as igneous, sedimentary, or metamorphic, based primarily on their method of formation.
Step-by-step explanation:
Rocks are naturally formed solid material made up of minerals. They are classified into different types by its chemical composition, the minerals included, and the method of formation. The three main types of rock based primarily on their method of formation are sedimentary, metamorphic, and igneous rocks. These rocks make up the earth’s lithosphere.
Igneous rocks are formed by the cooling and hardening of magma (molten rock deep within the earth) inside the earth or erupts onto the surface from volcanoes as lava. Examples of igneous rocks are basalt and obsidian.
Sedimentary rocks are formed from the particles of sand, shells and other particles called sediment which are the products of weathering on the earth’s surface. These sediments accumulates and gradually hardens into rock. It is the only type of rock that contains fossils. Conglomerate and limestone are the examples of this type of rocks.
Metamorphic rocks are formed by the intense temperature and pressure changes under the surface of the earth. These rocks have ribbon like layers and shiny crystals formed by minerals growing on their surface slowly over time. Gneiss and marble are the examples.