On the physics of crystal-rich mush

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There is great uncertainty about the processes that occur under volcanoes, yielding eruptions and other unseen processes that form the Earth's crust. Both the chemical composition of erupted materials and the related 'frozen' bodies of rock, suggests that the natural state of these magmas (molten rock) is a mushy, or crystal-rich material. An obstacle to understanding the processes that produce the diversity in volcanoes and chemical compositions is that there is only a poor understanding of the physical behavior of these mushes. The objective of this research is to illuminate in new detail how the physical processes occurring in crystal mush can control volcanic and plutonic systems. The broader impacts of this work are that it will enhance our ability to understand, anticipate and communicate hazards and to explain why certain processes have particular timescales. It will also bring new concepts from material science into the study of geological processes, and train students in new problem solving skills of wide application.This research effort is one part of a collaboration involving a total fourteen researchers at five institutions, in the USA and France. The research objective is to describe and rationalize the behavior of magma mush by a combination of novel, linked experimental and numerical modeling techniques. This will be the first time that high resolution numerical and laboratory experiments will be employed in an initially coordinated fashion using natural materials at the same scale. The specific research products from the experimental work provide kinematic elements of mush description: local and system fabric (expressed by their tensors calculated by image analysis) and bulk rheology. The numerical experiments provide information unavailable from the lab experiments: force tensors and fabric. Combining these two descriptions yields a unified, extensible framework to reveal the controls on mush behavior without ad hoc assumptions across a wide variety of magmatic compositions and conditions. The experimental work includes both high-pressure apparatus, The Griggs rig, as well as more moderate pressure, the Paterson press. Thus the project will explore a pressure range from the Moho to the near surface with shared elements of description.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.