Igneous rocks are formed when molten rock (magma or lava) cools and solidifies. This can happen on the surface of the Earth, such as when lava cools after a volcanic eruption, or deep underground, such as when magma cools slowly within the Earth's crust. Igneous rocks are classified according to their texture and composition. Some common types of igneous rocks include granite, basalt, and obsidian.
Sedimentary rocks are formed from sediments, which are bits of rock, mineral, or organic material that have been deposited by water, wind, ice, or gravity. Over time, these sediments are compacted and cemented together by minerals to form solid rock. Sedimentary rocks are classified according to their composition, grain size, and texture. Some common types of sedimentary rocks include sandstone, limestone, and shale.
Metamorphic rocks are formed when existing rocks are changed by heat, pressure, or chemical reactions. This can happen when rocks are buried deep underground, where they are subjected to high temperatures and pressures, or when they come into contact with hot magma. Metamorphic rocks are classified according to their texture, composition, and the type of metamorphism they have undergone. Some common types of metamorphic rocks include marble, slate, and quartzite.
