There are three main types of rocks: sedimentary, igneous, and metamorphic. Each of these rocks are formed by physical changes—such as melting, cooling, eroding, compacting, or deforming—that are part of the rock cycle. Sedimentary rocks are formed from pieces of other existing rock or organic material.
What Are the Three Groups of Rocks?
Rocks are classified into three distinct groups: igneous, sedimentary, and metamorphic. Igneous rocks are those that form from solidified lava or magma.
Sedimentary rocks are those that form from the accumulation of sediments, such as sand or pebbles. Metamorphic rocks are those that have been altered by heat or pressure.
Igneous rocks are the most common type of rock on Earth. They are formed from the solidification of lava or magma. Lava is molten rock that has been erupted from a volcano.
Magma is molten rock that is found below the Earth’s surface. Igneous rocks can be either intrusive or extrusive. Intrusive igneous rocks are those that form from magma that cools and solidifies below the Earth’s surface.
Extrusive igneous rocks are those that form from lava that cools and solidifies on the Earth’s surface. The most common type of intrusive igneous rock is granite.
Granite is a hard, durable rock that is often used in the construction of buildings and monuments. Granite is made up of large crystals of quartz, feldspar, and mica.