National Geographic : 2009 Aug
LOWER MANTLE MANTLE 400 270 New caldera Magma chamber 3,963 mi 3,200 mi 1,800 mi 25 mi Inner core Outer core Mantle Crust DETAIL 3500ºF Plume Beneath the caldera, a vast rocky zone of primordial heat emanates from the mantle. This plume feeds a magma chamber brimming with volcanic fuel just a few miles below the surface. Hot Pockets Current seismic data and geological conditions suggest there may be smaller pockets of hot rock associated with the Yellowstone plume. What Happens the Next Time? Scientists can anticipate the stages of a super-eruption (below). Widespread ecological devastation would follow, and consequences would be felt for years. Before the Eruption Warning signs may appear years in advance. Pressure builds from below, driving seismic activity and doming of the land over the hot spot. The Earth Fractures Gas-filled magma explodes upward; ash and debris soon rain down across hundreds of miles. Fiery ash flows clog rivers and carpet landscapes near and far. Eruptions Continue Periodic blasts go on for weeks or even months, emitting pollutants and causing acid rain. Eventually, the land collapses and a new caldera is born. ALEJANDRO TUMAS, NG STAFF; SHELLEY SPERRY SOURCES: ROBERT B. SMITH, GREGORY P. WAITE, AND MICHAEL JORDAN, GEODYNAMICS OF THE YELLOWSTONE HOTSPOT PROJECT, UNIVERSITY OF UTAH; JACOB B. LOWENSTERN, USGS YELLOWSTONE VOLCANO OBSERVATORY; ROBERT L. CHRISTIANSEN, USGS PLUME ART ; STEPHEN SELF, OPEN UNIVERSITY, MILTON KEYNES, U.K. FUTURE ERUPTIONS ; USGS EARTHQUAKE SWARM Columns of ash may rise 25 miles high, then fall.