Intrusive igneous rock, also known as plutonic rock, is formed from the cooling and solidification of magma beneath the Earth’s surface. This process occurs slowly, allowing large crystals to form, which is a principal characteristic of intrusive rocks.
Examples of intrusive igneous rocks include granite, diorite, and gabbro. These rocks are typically coarse-grained due to the extended cooling period that allows minerals to crystallize. Intrusive igneous rocks often create large formations, such as batholiths and sills, and can be exposed over time through erosion.
In contrast to extrusive igneous rocks, which form from lava that cools quickly on the surface, intrusive rocks provide valuable insights into the geological history of an area due to their formation deep within the Earth. Their study helps scientists understand the processes that shape our planet and the materials that make up its crust.