Classifying Rocks

Igneous, Sedimentary, and Metamorphic

Igneous Rocks

When hot molten rock known as magma reaches the surface of the Earth it is called Lava and cools down into hard solid rock. This solid rock that is formed is an example of an Igneous rock. Igneous rocks are formed by the cooling and hardening of magma. This cooling and hardening process can also happen underneath the surface of the Earth. When magma cools above the surface it forms Extrusive Igneous Rock and when it cools below the surface of the Earth if forms Intrusive Igneous Rock. Watch the below video to learn more about these two types of Igneous Rock.
Igneous Rocks

Sedimentary Rocks

Sedimentary Rocks are formed by two processes. The first process is weathering and erosion. This is when wind, water, or any other natural event breaks down existing rock into smaller and smaller pieces. The next process necessary to form Sedimentary Rocks is cementation which is when these smaller pieces of rocks are crystallized together. Cementation turns the sediment into Sedimentary Rock. Watch the following the video to learn more about Sedimentary Rocks.
17 - Sedimentary Rocks - The Key to Past Environments

Metamorphic Rocks

Metamorphic Rocks are formed by extreme pressure or extreme temperature below the surface of the Earth. The term metamorphism refers to a change in the structure or composition of a rock in a solid state due to this extreme pressure or temperature. Unlike Igneous Rocks which are formed from magma or lava and unlike Sedimentary Rocks which are formed by compacted sediment, Metamorphic Rocks can be formed from any rock type as long as it's composition or structure is changed. Watch the following video to learn more about Metamorphic Rocks.
Metamorphism of rocks