Volcanic explosive eruptions emit less carbon than what their tephra deposits sequestrate in soils

Thursday 15 October, 4 PM CET

Prof. PIERRE DELMELLE

Dept. of Environmental Sciences, Earth and Life Institute, UCLouvain

ABSTRACT: Volcanic explosive eruptions release magmatic CO₂ in the atmosphere. These eruptions also blanket the landscape with tephra, sometimes across vast areas. The soils that are buried by tephra may become isolated from surface processes. As a result, the microbial decomposition of organic matter is impeded, leading to the storage of soil organic carbon. The question we ask here is whether explosive eruptions sequestrate more carbon in soils than what they emit in the atmosphere. We first test our hypothesis based on a field study at Atacazo volcano, Ecuador. The results of this work are then used to formulate a model that predicts the storage of soil carbon resulting from explosive activity in the Andean volcanic arc during the Holocene. We conclude that, through time, volcanic eruptions have resulted in a net storage of carbon; the stock being at least two to three times larger than the total magmatic carbon emissions.

BIO: Pierre Delmelle is professor of environmental sciences and geochemistry at UCLouvain, Belgium. His main research interest lies in the environmental effects of volcanic eruptions. His work typically combines field, laboratory and experimental data to describe the various factors and processes dictating the short- and long-term reactivity and impacts of volcanic ash in the environment. He is currently developing researches to better evaluate the risk posed by volcanic eruptions to ancient and contemporaneous agricultural systems.