The theory of plate tectonics explains many earth features, like ocean floor trenches and sediment-free mid-ocean ridges made of hardened magma. The popular theory holds that continents drift slowly across earth's surface atop deeply buried molten rock, and that plate movements creep along at leisurely paces. But new research by Yale University geologists calls that into question.

On May 18, 1980, a tremendous landslide on the northern side of Mount St. Helens in Washington state uncapped a violent volcanic eruption, completely altering the surrounding landscape. It is the most studied volcano in history and has reshaped thinking regarding catastrophic earth processes.

Volcanic activity in 2005 accompanied the formation of a deep, wide rift in Ethiopia on part of the 4,000-mile-long north-to-south trending Great Rift Valley fault. Studies show that the injection of mantle material that “unzipped” the earth along the fault operated the same way as similar material does in less-accessible undersea rifts.