Magma Supply, Transport, and Storage through the Upper Mantle and Crust: A General Model for Volcanoes
Senior Advisor, Energy Sciences
Lawrence Berkeley National Laboratory
There are a variety of types of volcanoes and volcanic phenomena. Although there is much known about the final stages of eruption of magma, most of what happens beneath the surface must be inferred from disparate observations plus what is known about the properties of magma and of the Earth’s crust and upper mantle. There is not general agreement about what these deep processes look like, but there are certain constraints and models that can be used to provide a useful framework. A key constraint is the rate at which magma can be produced, which tends to govern the possible outcomes. Magma generation starts typically at a depth of about 100km in the Earth, and the rate can vary over about 5 orders of magnitude. When these generation rates are combined with other reasonably well-known properties of magma, characteristics of potential transport processes, properties of the upper mantle and lower crust, and thermal constraints, useful generalizations can be arrived at to explain why volcanism can take so many different forms. The objective is to understand the difference between small distributed basalt cinder cones, large central volcanoes, mega-volcanoes like Hawaii, lava plateaus, and in particular, so-called super-eruptions, where >1000 km3 of magma is erupted at one time. Key concepts are presented in Jellinek and DePaolo (Bull. Volc., 2003); and DeGruyter and Huber (EPSL, 2014).