Ever since the plume hypothesis was proposed by Jason Morgan, geologists have jumped at the opportunity to use his theory to describe other previously misunderstood geological events. Mantle plumes promised a deeper understanding of the earth’s interior composition and helped geologists to find an absolute direction and speed of tectonic plates. Central to Morgan’s hypothesis was the idea that mantle plumes are the source of midplate tectonic activity often referred to as hot spots.
While mantle plumes were a convenient explanation for multiple geological processes, apparent evidence to the contrary began to pop up. Absolute motions of different plates did not match up, and plumes are hard to detect in tomographic images of the mantle. Scientists recently discovered a series of midplate volcanoes near Japan that cannot have been formed by mantle plumes because of their location near to the subduction zone of the Pacific Plate. This evidence definitely illuminates some underlying issues with Morgan’s hypothesis, but in my opinion, it does not completely discredit his theory.
These scientists have proved that at least one chain of “hot spot” volcanoes was not produced by a mantle plume; however, jumping to any conclusions that this disproves Morgan’s entire hypothesis is too rash. The interior dynamics of the earth have proven to be difficult to unravel. Although it is hard to detect plumes in tomographic images of the mantle, evidence of upwelling material from the lower to upper mantle can be found underneath some hot spots when advanced techniques are used. Just because one mountain range that we previously believed to be created by mantle plume activity has been shown instead to be created by a crack in an oceanic plate does not mean that every midplate mountain range is now under suspicion.
Instead, I believe that the earth continually proves to be more complicated than we imagine. Mantle plumes likely do exist; there is too much evidence to be ignored. Might we be discovering new processes that result in midplate tectonic activity? Yes, and it is exciting! Geologists do not need to choose between one explanation and another. Instead, they should recognize the limit of our knowledge and celebrate every discovery that adds to this body of knowledge.