Igneous rocks formed beneath the surface of the Earth are called intrusive igneous rocks.

Here's why:

* Intrusive means that the magma (molten rock) cooled and solidified *inside* the Earth's crust.

* Extrusive igneous rocks, on the other hand, form when lava (magma that reaches the surface) cools and solidifies.

Intrusive rocks often have larger crystals than extrusive rocks because they cool more slowly. This gives the minerals more time to grow.