Mixing & Melting

A new study changes our understanding of how lavas are formed at volcanic arcs, and may have implications for the study of earthquakes and the risks posed by volcanic eruption. WHOI researchers discovered a previously unknown process involving the melting of intensely-mixed metamorphic rocks—known as mélange rocks—that form through high stress during subduction at the slab-mantle boundary. It was long thought that fluids from a subducted tectonic plate and melted sediments percolated into the mantle where they mixed (triggering more melting) and eventually erupted at the surface (left). Mixing and melting are reversed in the new mélange model (right). (Illustration by Jack Cook, WHOI Graphic Services)