Igneous rocks are classified based on their formation process and the location where they solidify. The two main types of igneous rocks are intrusive and extrusive, each with distinct characteristics.
Intrusive igneous rocks, also known as plutonic rocks, form beneath the Earth’s surface when magma cools and solidifies slowly over a long period. Because of this slow cooling process, intrusive rocks typically have a coarse-grained texture, meaning their mineral crystals are large and easily visible. Examples of intrusive igneous rocks include granite and diorite.
On the other hand, extrusive igneous rocks, or volcanic rocks, form at the Earth’s surface from lava that cools and solidifies quickly after a volcanic eruption. The rapid cooling contributes to a fine-grained texture, resulting in smaller crystals that are often not visible without magnification. Common examples of extrusive igneous rocks are basalt and pumice.
In summary, the key difference between these two types of igneous rocks lies in where and how they form: intrusive rocks solidify slowly underground and have a coarse texture, while extrusive rocks cool quickly on the surface and exhibit a fine texture.