See the photo gallery for an illustrated look at how scientists are using technology to better forecast volcanic eruptions

Humans are fleeting visitors on this roiling rock in the universe. On December 26, 2004, at 58 minutes and 49 seconds past midnight GMT, Mother Earth reacquainted us with this immutable fact. For millions of years, a creeping slab of Earth’s crust—the India Plate—had been grinding headlong into a similarly stubborn chunk of rock called the Burma Plate. Like a clash of Brobdingnagian armies, millennia of pent-up kinetic energy suddenly exploded from the seabed, a scant 100 miles from Sumatra, Indonesia.

It takes Scott Kiser only a split second to name the one city in the U.S., and probably the world, that would sustain the most catastrophic damage from a category-5 hurricane. "New Orleans," says Kiser, a tropical-cyclone program manager for the National Weather Service. "Because the city is below sea level—with the Mississippi River on one side and Lake Pontchartrain on the other—it is a hydrologic nightmare." The worst problem, he explains, would be a storm surge, a phenomenon in which high winds stack up huge waves along a hurricane’s leading edge.