Definition: Despite sounding like something out of Harry Potter, a batholith is a type of igneous rock that forms when magma rises into the earth's crust, but does not erupt onto the surface.

When was the batholith created?

The SNB formed as a result of igneous activity related to the subduction of the Farallon Plate beneath the North American Plate some 220–80 Ma. Two short-lived magmatic episodes - one at 160–150 Ma and the other at 100–85 Ma built most of the batholith.

Where can batholiths be found?

Batholiths are vast, rising at least 100 square kilometers above the surface of the Earth, which is why they're so hard to miss. They are made up of plutons, which are themselves several kilometers in diameter. Batholiths can be found all over the planet, from Yosemite National Park to Canada's Coast Range.