The way rocks form determines their classification. Igneous rocks are formed when magma cools and hardens. This process can take place either on the Earth’s surface or underground. The precise location of the rock’s formation determines the type of igneous rock it is.
Extrusive igneous rock is formed when magma rises to the Earth’s surface and hardens.
Extrusive igneous rock has a glassy texture due to the speed with which it forms.
Pumice and basalt are examples of extrusive igneous rock.
Pumice is an extrusive igneous rock that is used in a variety of products such as toothpaste, cement, and cosmetics.
Basalt is an extrusive igneous rock that is used to build structures and statues.
Extrusive rocks are also known as volcanic rocks due to the role volcanoes play in their formation.
An intrusive igneous rock forms when magma cools and hardens beneath the Earth’s surface.
Because the formation of intrusive igneous rock is a slow process, these rocks have a grainy texture.
Granite and gabbro are examples of intrusive igneous rock.
Granite is an intrusive igneous rock that is used to make gravestones, statues, and countertops due to its durability.
Gabbro is a type of intrusive igneous rock that contains valuable amounts of gold, chromium, and silver.
Plutons are intrusive rock bodies that are typically composed of granite.
Batholiths are huge bodies formed by intrusive rocks, such as those found in the cores of mountains.
Igneous rock makes up 95 percent of the Earth’s crust.
Over 700 different types of igneous rocks have been identified.
