High-precision timeline helps clarify an ancient magma surge in the North Cascades

Where oceanic crust subducts beneath continental crust, belts of volcanoes known as continental arcs can form. Located around the world, these arcs may undergo episodic magma flare-ups—dramatic surges in the flow of magma into the continental crust at rates up to 20 times higher than normal. However, what triggers these extreme surges, which last tens of millions of years, can be unclear.