Wilson thought the hot spot was located in the center of a mantle
convection cell where movement was slow. The upper, faster moving part
of the convection cell helped carry the Pacific Plate to the northwest.
By the early 1970s, the plate tectonic theory and the presence of hot
spots was generally accepted. In 1971, W. Jason Morgan suggested a more
important role for hot spots. He proposed that hot spots result from
hot, narrow plumes of material that rise from deep within the mantle.
As the hot mantle plume reaches the base of the lithosphere, it spreads
laterally. The laterally spreading of the hot mantle helped to move the
Earth's rigid outer plates. In all, Morgan proposed 20 different hot
spots, some located along mid-ocean ridges and others, like Hawaii and
Yellowstone, located within plates.