Petrology

Deep beneath Alaska’s Aleutian Islands, down where the pressure and temperatures have become so high that rock starts to flow, new continental crust is being born. Scientists have long believed that continental crust forms in volcanic arcs – they know the magma brought up in the arcs’ volcanoes is geochemically very similar to continental crust. The lingering question has been how exactly that happens. While the magma that reaches the surface is similar to continental crust, the lower crust beneath volcanic arcs is quite different from the lower half of continental crust.