The volcanoes featured in the NOVA program "Volcano's Deadly Warning"—Galeras, Nevado del Ruiz, Popocatepetl, and Mt. Redoubt—as well as many other famous volcanoes, including Mt. St.

On volcanoes, a fissure is an elongated fracture or crack at the surface from which lava erupts. Fissure eruptions typically dwindle to a central vent after a period of hours or days. Occasionally ...