Global aspects of volcanism: the perspectives of “plate tectonics” and “volcanic systems”

The concept of plate tectonics provides a general framework to fit the distribution and general characteristics of volcanoes. There remain, however, many details of volcanic activity that are difficult to explain solely by this paradigm. For example, plate tectonics predicts that volcanic activity should take place continuously along all convergent and divergent tectonic margins, where in fact we observe a point-like distribution of volcanic centers that does not fit the predictions. Also, it is observed that many volcanoes share common characteristics despite being located in different tectonic settings, while other volcanoes sharing the same tectonic setting display very different behavior. For instance, so far, there is no congruent explanation offered by plate tectonics about why in similar tectonic conditions volcanism is sometimes polygenetic and elsewhere monogenetic. On the other hand, volcanic activity on a global scale tends to define a series of rules that are independent of the tectonic setting, and therefore should reflect general processes that are not controlled directly by the plate tectonic engine. We show that, by concentrating on the relationship among processes (from the moment of magma generation to the moment of eruption) and by incorporating all of these processes as components of a single system, a coherent picture of volcanism on a global scale emerges and allows us to interpret better many otherwise puzzling aspects of volcanism such as those mentioned above, hence providing a general framework that fills the conceptual gap left between plate tectonics and most (if not all) of the characteristics of volcanic activity at a global scale.