Magma Rheology, Transport, and Eruption: Field, Experiments and Models

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This research program comprises 3 distinct but complementary themes in volcanology. A) A Model for Silicate Melt Viscosity: Redux Viscosity is the most important physical property governing transport and eruption of magma. In 2008, we published the "GRD model" for predicting the viscosity of natural hydrous silicate melts. Although widely accepted as the best model available, due to the increasing diversity of scientists using the model a new 2nd generation model is overdue. The new model will: i) be more accurate (relative to the experimental database), ii) span a wider range of melt compositions (e.g., kimberlite), iii) account for higher pressures, iv) add the volatile CO2, and v) allow for iron as both species Fe3+ and Fe2+. Most importantly, the model will be based on the Adams-Gibbs theory for cooperative relaxation of melts, which connects transport (viscosity) and thermodynamic properties (entropy, heat capacity). The resulting model will capture virtually all silicate melts found on Earth and other planets, and have a stronger theoretical basis allowing for prediction of other thermochemical properties. B) Rheological behaviour of lava domes: Experiments it lies at the interface between the fields of rock mechanics and experimental volcanology. The goal of this experimentation is to establish the rheological properties of volcanic materials at the elevated conditions attending volcanic eruption. The resulting datasets are used to build constitutive equations that predict the flow of natural magmas as a function of stress, strain-rate, temperature, and crystal content. The constitutive relationships are key to more sophisticated and accurate modelling of volcanic eruptions. C) Particle Attrition in Fluidized Volcanic Systems During ascent and eruption, magmas commonly become high velocity, gas-rich, particle-laden suspensions. These environments support “attrition” - that is, vigorous, sustained particle-particle interactions causing grain size reduction and reshaping of the suspended cargo. The shapes and surface properties of crystals and rock fragments in natural volcanic deposits directly inform on the conditions attending magma transport and eruption, including, flow regime (laminar vs. turbulent), ascent velocity, and residence time. We will use experiments to study attrition in gas and fluid jets at conditions comparable to volcanic systems. The experiments elucidate the mechanisms and rates of attrition as a function of particle density, energy, and time. Our goal is to create a paradigm for using the properties of the "milled” (i.e. attrited) lithics and crystals in volcanic deposits to infer transport and eruption conditions.