On the great plume debate

Abstract

Geological processes are ultimately consequences of Earth’s thermal evolution. Plate tectonic theory, which explains geological phenomena along plate boundaries, elegantly illustrates this concept. For example, the origin of oceanic plates at ocean ridges, the movement and growth of these plates, and their ultimate consumption back into the Earth’s deep interior through subduction zones provide an efficient mechanism to cool the earth’s mantle, leading to large-scale mantle convection. Mantle plumes, which explain another set of global geological phenomena such as within-plate volcanism, cool the earth’s deep interior (probably the Earth’s core) and represent another mode of Earth’s thermal convection. Plate tectonic theory and mantle plume hypothesis thus complement each other to explain much of the whole picture of Earth processes and phenomena. The above statements represent the mainstream view today on how the Earth works by the majority of Earth scientists, many of whom also recognize that neither plate tectonic theory nor mantle plume hypothesis is perfect, but requires continued developments. However, the mantle plume hypothesis has received great challenges in recent years ‘not without justification’, and the ‘Mantle Plume Debate’ is currently rather heated. This controversy is perhaps one of the greatest in the history of solid Earth Sciences. For this reason, and to properly inform the community exactly what this controversy is about, I invited prominent scientists from both schools to express their views on whether mantle plumes exist or not, whether they exist naturally as a result of Earth’s cooling or whether their existence is purely required for convenience by scientific interpretations of certain Earth phenomena. Don Anderson basically argued that mantle plumes do not exist in the Earth. In this current issue, Geoff Davies, a strong mantle plume advocate, provides A case for mantle plumes, whereas Gillian Foulger, a strong sceptic of mantle plumes, explains Why there is current scepticism of mantle plume hypothesis. In the following, I briefly introduce these two authors and then provide some background information and basic concepts that may help readers better understand the debate in general and the two papers in particular. I do not wish to make specific comments on any argument for or against mantle plume hypothesis in the two invited papers. 2 About the authors