How are igneous rocks formed?

Igneous rocks are formed through the cooling and solidification of magma or lava. This process occurs either beneath the Earth's surface, leading to the formation of intrusive igneous rocks, or on the surface following a volcanic eruption, resulting in extrusive igneous rocks. When magma cools slowly underground, it allows large crystals to form, resulting in rocks like granite. On the other hand, when lava cools quickly upon reaching the surface, it forms smaller crystals, leading to rocks like basalt.

Understanding the formation process is fundamental in geology, as it highlights how different environmental conditions affect the characteristics of rocks. This difference in cooling rates explains why igneous rocks can vary significantly in their texture, composition, and appearance. This rigorous process of cooling is critical for identifying and classifying igneous rocks in various geologic environments.