In 1985, Nevado del Ruiz erupted in Colombia, burying the sleeping townspeople of Armero under six feet of mud and water. 25,000 people died. Scientists knew that unless they found a way to more accurately predict when a volcano would erupt, the potential for future catastrophe would be huge. Now, one scientist may have met that challenge.

Geophysicist Bernard Chouet discovered that a mysterious type of seismic signal given off by quaking volcanoes might be the key warning sign before an eruption. As proof of his theory, Chouet predicted the explosion of Alaska’s Redoubt volcano to within hours. And in 2000, tens of thousands of people were safely evacuated just before an eruption of Mexico’s Popocatépetl volcano.

Join NOVA and experience spectacular volcanic eruptions, including the tragic eruption of the Colombian volcano Galeras that killed a group of scientists studying the volcano. Discover what causes volcanic eruptions; and meet the man whose scientific breakthrough could save thousands of lives.