Why does granite form deep underground?

Granite is an intrusive igneous rock, meaning it solidifies from molten material below Earth’s surface. Because the magma is insulated by surrounding rock, it cools over thousands to millions of years rather than quickly at the surface. That slow cooling allows large crystals of quartz, feldspar, and mica to grow, which is why granite looks speckled and coarse-grained. When uplift and erosion expose these rocks at the surface, we can see the frozen remains of ancient magma chambers. Many continental crustal regions contain huge granite bodies called plutons or batholiths.