Subvolcanic rocks form when magma intrudes into the shallow crust but does not erupt onto the surface. They cool faster than deep plutonic rocks but slower than extruded volcanic rocks, resulting in an intermediate, often porphyritic texture. Geologists study these formations to understand the plumbing systems of ancient volcanoes and the formation of shallow ore deposits.
Heard on the job
The drill core shows a subvolcanic porphyry, indicating we're right above the old magma chamber.
Also heard as
- hypabyssal