Extrusive Igneous Rock Formation: Extrusive igneous rocks form when magma reaches the Earth's surface and erupts as lava through volcanic activity. Once the lava is exposed to the cooler temperatures of the atmosphere or ocean, it cools and solidifies quickly, resulting in the formation of extrusive igneous rocks. Common examples include basalt and pumice.
Intrusive Igneous Rock Formation: Intrusive igneous rocks form from magma that cools and solidifies beneath the Earth's surface. This process occurs slowly, allowing larger crystals to form within the rock. Granite is a common example of an intrusive igneous rock.
Which Cools Faster? Extrusive igneous rocks cool faster than intrusive igneous rocks because they are exposed to the lower temperatures of the surface environment.
Which Has Crystals? Intrusive igneous rocks typically have larger crystals due to the slower cooling process that allows more time for crystal growth. In contrast, extrusive igneous rocks usually have smaller crystals or may even be glassy, as they cool too quickly for significant crystal formation.