Granite is an igneous rock that forms deep underground, but it's not a single continuous layer. It's formed in large bodies called plutons. These plutons can extend for miles in all directions, but their depth varies significantly depending on the specific formation.

Here's a breakdown:

* Shallow Plutons: These can be found just a few kilometers below the surface. They often form near the edges of continents or beneath volcanic areas.

* Deep Plutons: These can extend down to depths of tens of kilometers. They are typically found beneath mountain ranges or areas with active tectonic activity.

So, the depth of granite is not fixed. It depends on the specific pluton and the geological history of the region.

It's important to note that granite is exposed at the surface due to erosion and uplift. This means that the granite we see today is just the tip of the iceberg. The vast majority of the original pluton remains buried deep beneath the Earth's surface.