When magma cools slowly beneath the surface, it forms intrusive igneous rocks.

Here's why:

* Intrusive means the rock formed inside the Earth's crust.

* Igneous means the rock formed from cooled and solidified magma or lava.

Some common examples of intrusive igneous rocks include:

* Granite: A light-colored, coarse-grained rock.

* Diorite: A medium-grained rock with a mix of light and dark minerals.

* Gabbro: A dark-colored, coarse-grained rock.

The slow cooling process allows the minerals in the magma to form larger crystals, resulting in the coarse-grained texture of intrusive igneous rocks.