Figure 14.17

SCIENTIFIC INQUIRY: Can scientists predict dangerous volcanic eruptions? Careful monitoring of Mount St. Helens allowed scientists to predict its eruption in 1980 and warn people to get out of harm’s way. Changes in the gases emitted by a volcano, widening cracks, swelling of the volcano’s surface, and increasing earthquake activity can all be signs that magma is moving upward through the magma chamber. Given the growing body of data that pointed to an impending eruption, scientists urged local authorities to close the mountain to the public before the eruption, saving thousands of lives.

(1. USGS, photo by Thomas Casadevall; 2. U.S. Geological Survey, photo by Lyn Topinka; 3. U.S. Geological Survey, photo by Lyn Topinka; 4. U. S. Geological Survey, photo by P. W. Lipman; 5. U.S. Geological Survey, Volcano Hazards Program, photo by Mike Doukas)