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It was later postulated that hotspots are fed by streams of hot mantle rising from the Earth's core–mantle boundary in a structure called a mantle plume. [6] Whether or not such mantle plumes exist has been the subject of a major controversy in Earth science, [4] [7] but seismic images consistent with evolving theory now exist. [8]
There is an ongoing discussion about whether the hotspot is caused by a deep mantle plume or originates at a much shallower depth. [3] Recently, seismic tomography studies have found seismic wave speed anomalies under Iceland, consistent with a hot conduit 100 km (62 mi) across that extends to the lower mantle.
[13] [14] The theory predicts mushroom-shaped mantle plumes with heads of about 2000 km diameter that have a critical time (time from onset of heating of the lower mantle to formation of a plume) of about 830 million years for a core mantle heat flux of 20 mW/m 2, while the cycle time (the time between plume formation events) is about 2000 ...
An example of plume locations suggested by one recent group. [38] Figure from Foulger (2010). [3] Many different localities have been suggested to be underlain by mantle plumes, and scientists cannot agree on a definitive list. Some scientists suggest that several tens of plumes exist, [38] whereas others suggest that there are none. [3]
The mantle plume hypothesis proposes that areas of volcanism not readily explained by plate tectonics, called hotspots, are a result of thermal upwelling within the mantle. Some researchers have proposed an upper mantle source above the 660km discontinuity for these plumes, [ 32 ] while others propose a much deeper source, possibly at the core ...
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Yellowstone hotspot Nördlinger Ries (14.5-14.3) Burdigalian: 20.44 Aquitanian: 23.03 * Shield volcanoes of Ethiopia [h] Antarctic ice sheet complete Paleogene: Oligocene: Chattian: 28.1 Ethiopian and Yemen traps (31–30) [h] Fish Canyon Tuff (27.51) [i] Rupelian: 33.9 * Chesapeake Bay impact crater (35.5) [j] Antarctic ice sheet expands ...