National Geographic : 2009 Aug
PLUME PLUME PLUME Juan de Fuca Plate YELLOWSTONE N.P. Juan de Fuca Plate Juan de Fuca Plate New Fields Snake River Plain North American Plate North American Plate North American Plate First Volcanic Fields Pacific Ocean Pacific Ocean Pacific Ocean Snake Great Salt Lake OREGON IDAHO WYOMING UTAH NEVADA MONTANA Boise Twin Falls Pocatello Logan Ogden Cody Idaho Falls ROCKY MOUNTAI NS ABSAROKA RANGE WIND RIVER RANGE SNAKE RIVER PLAIN Volcanic field name Age in years Plate movement 2.1 million 1.3 million 640,000 6.65 million 10.3 million 10.8 million 13.8 million 13.8 million 15.5 million 15.4 million YELLOWSTONE N.P. 18-16.5 million PICABO HEISE YELLOWSTONE PLATEAU OWYHEE- HUMBOLDT MCDERMITT TWIN FALLS 12.5 million BRUNEAU- JARBIDGE 15 86 84 15 15 80 80 84 0mi 50 0km 50 Line of Fire A 350-mile-long string of volcanic fields---each a site of multiple eruptions--- gouges the Snake River Plain and beyond, tracing the motion of the crust across a fixed plume of superheated rock, or hot spot. Sliding southwest at about 1.8 inches a year, the North American tectonic plate has been scarred by volcanic events for millions of years (graphics, right). 18 to 13.8 million years ago As the edge of one tectonic plate grinds under another, the plume breaks through, causing eruptions that form vast calderas on the surface. 12.5 to 6.65 million years ago Plate drift continues, with new blasts occurring northeast of earlier sites. Ashfall causes massive wildlife die-offs hundreds of miles away. 2.1 million years ago to today The plume drives three huge eruptions, then settles into a calmer phase, powering Yellow- stone's geysers, mud pots, and hot springs.