GRE Reading Comprehension: PPO-GRE阅读PPO - 91JNJ20GFVGQ4H4KS

(This passage is adapted from material published in 2002.) In 1971, hot on the heels of plate-tectonic theory's acceptance, J. W. Morgan suggested that hotspots – areas of intense volcanism such Hawaii, Yellowstone, and Iceland – are fueled by plumes of hot material arising in the deep mantle and punching through the mobile shallow mantle and crust to the surface. Morgan's theory was developed to explain the time-progressive trails of volcanoes associated with some hotspots and the hotspots' apparent fixity relative to one another. If the sources of the volcanism were rooted in the immobile deep mantle, they would not move relative to one another and the plates at the surface would drift above, bearing away trails of volcanism. According to a recent article by geologist G. R. Foulger, however, although hotspots do exist, they do not have time-progressive volcanic trail and are not fixed relative to one another.