Volcano Crystals Hold Clues to Next Big Eruption

Volcano Crystals Hold Clues to Next Big Eruption

Pablo Coazzaglio/AFP/Getty Images

The Tungurahua Volcano spews incandescent rocks and lava on Dec. 4, 2011 as seen from the town of Runtun, Ecuador. Volcanos often erupt with little clear warning, and efforts to predict them rely on monitoring seismic activity, ground deformations, gas emissions and changes in water levels and chemistry, according to the U.S. Geological Survey.