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Images: Hitting the Hotspots

A hotspot created the island of Iceland and its characteristic volcanic landscape. Hotspots are relatively small regions on the earth where unusually hot rocks rise from deep inside the mantle layer.

A map of the world's major hotspots shows that many of them are integrally connected to the global mid-ocean ridge system (red lines). Green lines indicate subduction zones, where plates plunge back into the mantle. Not shown is the Jan Mayen hotspot north of Iceland.

By measuring precise travel times of seismic waves passing through mantle rocks beneath Iceland, scientists have recently identified a surprisingly narrow and deep cylindrical "root" of anomalously hot rocks, extending to a depth of at least 400 kilometers, and probably farther. (From: Wolfe, Bjarnason, VanDecar, and Solomon, 1996)

Recently declassified satellite gravity data reveal bulges of unusually thick and elevated oceanic crust (red, yellow and green on the map) extending hundreds of kilometers from the Iceland and Azores hotspots. The two hotspots may be feeding huge supplies of magma to nearly the entire northern segment of the Mid-Atlantic Ridge. Map produced by Jennifer Georgen, MIT/WHOI Joint Program, with data from of David Sandwell, Scripps Institution of Oceanography, and Walter Smith, NOAA

A theoretical geodynamic model shows that a narrow hotspot "root," such as the one recently discovered beneath Iceland, would generate a vigorous source of heat (light colors) and produce a huge volume of magma that would migrate laterally along and across the ridge axes hundreds of kilometers away from the hotspot source.

Satellite gravity map of the western Indian and southern Atlantic Ocean basins, as revealed by satellite gravity data. A string of hotspots (Tristan, Gough, Discovery, and Shona) aligned with the southern Mid-Atlantic Ridge (MAR) may be contributing magma supplies that maintain the ridge. The Bouvet hotspot may play a critical role in maintaining the triple junction, where three mid-ocean ridge branches and the three boundaries (white lines) separating the South American, Antarctic, and African plates all intersect. Farther east, the Kerguelen, Crozet, and Marion hotspots may have extensively shaped the seafloor of the southern ocean. SEIR is the Southeast Indian Ridge, CIR is the Central Indian Ridge, and SWIR is the Southwest Indian Ridge. Map produced by Jennifer Georgen, MIT/WHOI Joint Program, with data from David Sandwell, Scripps Institution of Oceanography, and Walter Smith, NOAA.