It was like a scene conjured by a Hollywood special effects shop. In September 2005 Afar herders in northern Ethiopia watched in amazement as the Earth yawned open and swallowed their goats and camels. Chunks of obsidian burst from subterranean caverns and flew through the air, said one local, "like huge black birds." For three days a cloud of billowing ash dimmed the sun as the region's largest volcano, Erta Ale—"smoking mountain" in the Afar language—erupted.
What set off these startling events? Miles below the surface a mammoth burp of magma had welled up between two tectonic plates, prying them farther apart. Aboveground, hundreds of faults and fissures opened along a 40-mile stretch of desert, swallowing unlucky livestock. More than a dozen smaller burps have shaken the area in the years since.
East Africa's Afar depression is one of the world's most geologically hyperactive regions. Fly over it in an airplane—or in a one-person motorized paraglider, as photographer George Steinmetz did countless times—and it may appear as frozen and still as Arctic ice. But the Afar's timeless visage hides its true nature. Below the surface, Earth's rocky rind is ripping apart, and underground chambers of magma are fueling 12 active volcanoes as well as steaming geysers, boiling cauldrons, and a fiery lake of lava.