He looked at the distinct shape of the Hawaiian chain and concluded that it resulted from the Pacific plate moving over a hot spot region. The heat from the hotspot would produce magma, which is then lighter than the surrounding rock from the plate; the magma would then rise over the mantle and crust and erupt-forming a seamount. This process would continue until the plate movement would then carry the island beyond the hotspot. He describes, "a convection current moving northwesterly over this source may have carried the succession of older volcanoes in turn away to the northwest. Each volcano, as it is carried away from its source, slowly becoming inactive. This source soon created a new volcano in the place of the old" (Wilson, 1963, p. 869). This also allowed an explanation for the age of the islands, "The farther a volcano is from the East Pacific rise, the older it is, [t]he longer a chain, the older is the chain" (Wilson 1963, p. 869).
William Morgan 1971 suggested the deep plume model (Fig.1). Morgan realized the advancements in defining and understanding the concept of hotspots. He proposed that the hotspots were "manifestations of convection in the lower mantle which provides the motive force for continental drift" (p.42). His models reflect deep mantle plumes bringing heat and relatively primordial material up to the asthenosphere flow radially away from the plumes. His assumption was that there were only upwelling points which show unique petrological and kinematic properties and no down swelling-leaving the flow to be uniformly distributed throughout the mantle (Morgan, 1971). Morgan roots his evidence using four features; the "hotspots" are near rise crests and there is a hotspot near each of the ridge triple junctions, agreeing with the notion that asthenosphere currents are pushing the plates away from the rises. "Hotspots" become active before the continents split apart.
