A hot spot occurs because of the intense heat of the outer core. This heat radiates through the mantle bringing hot solid rock upward to the hot spot. These areas of rising solid rock are called mantle plumes. Because of lower pressure in the upper region of the mantle the rock begins to melt. This forms magma which rises inch by inch until it reaches the surface forming a volcano.

In 1971 W. Jason Morgan added to the hot spot theory. When the rising solid rock (mantle plume) reaches the plates it splits and spreads horizontally. This split or flow causes the plates to drift.

Morgan proposed that there are 20 different hot spots in the world. Most hot spots are located at mid-ocean ridges, but there are a few located in the middle of plates, like Hawaii and Yellowstone.

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