The Earth's mantle and core comprise more than 99 percent of the mass of the planet. As such, the physical and chemical properties of these regions are critical in determining the processes by which the planet has evolved to its current state. In short, we and everything we see occupy a miniscule layer of scum at the surface of the planet—my group tries to figure out what goes on below the scum (or, as some call it, the biosphere). My research is centered on experimentally examining the structural and thermodynamic properties of minerals, melts, and fluids at both ambient and high pressures. In particular, the melting relations of deep Earth materials, the ability of deep Earth minerals (and melts) to retain water and carbon dioxide, the mineralogy of subduction zone materials, and the structural constraints that determine whether silicate magmas buoyantly rise or sink at different depths in the Earth are among his primary interests. Such properties not only control the thermal regime in the deep Earth (and thus the driving force of plate tectonics), but also are vital in determining the mechanisms and degree to which the planet has differentiated.
The principal tool I use to study these problems is the high-temperature diamond anvil cell, a device which generates pressures corresponding to those present throughout the deep Earth. Because of the transparency of diamond, probes such as Raman spectroscopy are used to examine the bonding properties of materials in situ at simultaneous high pressure and temperature. Such data yield insight into the local bonding environments of ions in crystals, melts, and solutions, and the changes in these environments with pressure and temperature.