Recycling

Our studies in Costa Rica are crucial to understanding not only how volcanoes work — including how volatiles influence the eruption process, but also how certain elements are cycled via volcanic pathways between the Earth’s underlying mantle and surface reservoirs such as the crust, hydrosphere and atmosphere. The down-going plate carries with it marine sediments: exactly how much of this material actually makes it down into the Earth’s mantle and back out via volcanism is very poorly constrained. By looking at the type and amounts of sediments being subducted, and comparing them chemically and isotopically to the gases which are fluxing out of the adjacent volcanoes, we hope to be able to quantify the percentage of each volatile species that makes it around the cycle.

One species of particular interest is carbon dioxide, well-known as a greenhouse gas contributing to global warming. Knowledge of how much CO₂ is lost via volcanoes not only allows us to establish a baseline for natural fluxes of CO₂ to the atmosphere but also provides constraints on the inventory of carbon in the Earth’s largest reservoir — the mantle. This CO₂ flux, however, is not an easy parameter to quantify but one useful approach is to couple CO₂ measurements to the rare isotope of helium (helium-3) whose flux from the mantle to the atmosphere is well known. Therefore, we will be using our measurements of the CO₂/³He ratio at the various volcanoes in Costa Rica to derive CO₂ flux estimates for the region.

Isotopes - Geochemical Tracers>>