The explosiveness of a volcanic eruption depends on how many gas bubbles form in the magma—and when. Until now, it was thought that gas bubbles were formed primarily when the ambient pressure dropped while the magma was rising.

Scientists have uncovered a long-missing piece of the volcanic puzzle: rising magma doesn’t just form explosive gas bubbles when pressure drops—it can do so simply by being sheared and “kneaded” inside a volcano’s conduit.

Discover why volcanoes erupt, how magma and gases cause eruptions and why volcanoes are essential for life on Earth.