What is a crustal hot spot?

Answer 1

A hot spot is a place where incredibly hot rock from the mantle rises toward the surface of a crustal plate, usually far away from the plate boundaries, causing a melting of the crust with the associated volcanism. A hot spot, unlike other forms of volcanism that rely on plate subduction or divergence, is due to rising heat from a specific location in the mantle, or core mantle boundary, which is very localized, not broadly regionalized. The Hawaiian Islands are a great example of the resultant landforms created by a hot spot that exists under oceanic crust. While the crust moves over the hot spot due to plate tectonics, volcanic mountains build up on the ocean floor, eventually breaching the surface of the water. As the crust moves away, the existing volcanic mountains become inactive and are replaced with newer volcanic mountains, the older ones slowly eroding below the surface of the ocean.

Hot spots occur under continental crust as well, the Yellowstone caldera being a good example. Hot spots and plume theory are heavily debated topics in geology at this time. New scientific data is continually being added toward the understanding of their geophysics.

Answer 2

The term "hot spot" refers to the surface expression of an upwelling column of hot molten rock from the asthenosphere.

The asthenosphere is the viscous layer of plastic rock that underlies the solid, cold crust.

In some locations, under Hawaii, for example, exceptionally hot asthenosphere from deep within the mantle streams upward and burns a hole in the crust. That hole becomes a volcano, an area of hydrothermal activity, a site where the crust ruptures and spreads apart, or other large geolic features.