Experimental studies of the earth's mantle

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The Earth's mantle, the 80% of our planet between the crust and the core, plays a fundamental role in the dynamic Earth system. Processes in the mantle directly affect our surface environment through earthquakes, volcanic eruptions, and the cycling of material from the surface to the mantle and back. We need to understand the workings of the mantle to better understand their impacts on the surface environment. My research focuses on how "volatiles" - compounds like water and carbon dioxide - behave in the mantle, and how they are transported between the mantle and the surface. They come to the surface from the mantle via volcanic eruptions, and are returned to the mantle by subduction, when oceanic crust is thrust back into the mantle where two of the lithospheric plates that make up the Earth's outer shell converge. Over geological time scales of billions of years, subduction could transport all of the surface water and carbon dioxide down into the mantle, so understanding the processes that allow them to return to the surface after subduction is vital to understanding the long-term balance and cycling of these volatiles. In the mantle, water and carbon dioxide can be present in minerals, or as fluids or melts. These fluids and melts interact with, and modify, the mantle. One outcome of this interaction, for example, is crystallization of diamond, but the nature of the fluids or melts involved is not well constrained. My primary research approach is to duplicate the pressure and temperature conditions that exist inside the Earth's upper mantle in my laboratory. In effect, I make my own mantle rocks. Studying these "do-it-yourself" samples allow me to simulate the processes in the mantle, to give us a better understanding of how water and carbon dioxide behave, and what types of fluids and melts can exist in the mantle, including those that form (or destroy) diamond. The experiments allow us to test hypotheses, derived from observations of natural mantle samples, of how these melts and fluids interact with the mantle, and thereby provide an important way to "ground-truth" these ideas.