Volcanoes are rumbling as scientists monitor earthquakes at Washington's Mount Rainier and Alaska's Iliamna volcano.

What if the most telling indications of an impending volcanic eruption are buried deep under the ocean, or in a fleeting succession of tiny quakes that no one perceives? As volcanoes of the Pacific ...

Magma from the mantle finds its way to the surface, where it erupts as lava or ash and gas—sometimes in spectacular spurts, ...