Large masses of magma that solidify far below Earth's surface form igneous rocks that have a coarse-grained texture.

Here's why:

* Slow Cooling: Magma deep underground cools very slowly. This gives the minerals ample time to grow into large crystals.

* Large Crystals: The slow cooling process results in the formation of visible crystals, giving the rock a coarse-grained texture.

Examples of coarse-grained igneous rocks formed this way include:

* Granite: A common, light-colored rock with large crystals of quartz, feldspar, and mica.

* Gabbro: A dark-colored rock with large crystals of pyroxene and plagioclase feldspar.

In contrast, igneous rocks that form quickly near the surface (like volcanic rocks) have a fine-grained texture because the crystals have less time to grow.