Presentation on theme: "The Myth of Whole Mantle Convection JUDGE FOR YOURSELF… Don L. Anderson."— Presentation transcript:
The Myth of Whole Mantle Convection JUDGE FOR YOURSELF… Don L. Anderson
Fs/RitsemaWebSuppl_Accepted.pdf The large, red, 2000-km-wide feature extends from the southern hemisphere under the Shona and Bouvet volcanic regions to the Afar region, some 7000 km distant. It has been assumed to be a continuous hot feature that penetrates the whole mantle.
Ritsema, J., Global seismic maps, Web supplement, (http://www.mantleplumes.org/TopPages/TheP3Book.html)http://www.mantleplumes.org/TopPages/TheP3Book.html Ritsema, J., van Heijst, H. J., and Woodhouse, J. H., Complex shearwave velocity structure imaged beneath Africa and Iceland, Science, 286, 1925–1928, References
Evidence for whole mantle convection Visual impression of a few color-saturated tomographic cross- sections
Images that suggest whole mantle convection
Images that suggest slab flattening
The transition zone is a crust-slab-water filter but it filters from above, not below Upper mantle 1000-km Mesosphere Abyss D” D’ LOWERMANTLELOWERMANTLE VISUAL INTERPRETATIONS ARE NOT ALWAYS THE BEST, BUT....
“It is now well established that oceanic plates sink into the lower mantle at subduction zones…”
Transition Zone thickness is independent of hotspot and ‘megaplume’ locations
With this color scheme there are no whole mantle slabs
Cartoons are used to interpret the images as slabs and plumes
References Fukao, Y., Widiyantoro, S., and Obayashi, M., Stagnant slabs in the upper and lower mantle transition region, Rev. Geophy. 28,291–323, 2001.
Saturated images showing slab-like features
Correlations between seismic velocities (solid) and between velocities and densities (dots and dashes)