Simple features of mantle-wide convection and the interpretation of lower-mantle tomograms |
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| Authors: | Norman H Sleep |
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| Institution: | Department of Geophysics, Stanford University, Stanford, CA 94305, USA |
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| Abstract: | Simple fluid dynamic constraints aid in the interpretation of lower mantle tomograms. The geothermal gradient away from slabs and plumes is subadiabatic between the upper (lithosphere) and lower (D″) boundary layers by ～400 K. Slabs widen proportionally with the square root of the viscosity as they sink through the lower mantle. The time scale for the persistence of slab graveyards at the base of the mantle is comparable to the time for plate motions to reorganize ～120–200 Myr. At most a few starting plume heads currently exist in the lower mantle. Tomographic inversions may include more sophisticated numerical-modeling versions of these constraints. |
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| Keywords: | Mantle convection Slabs Subduction Tomography Geothermal gradient Plumes Plume heads Convection mantélique Lithosphère plongeante Subduction Tomographie Courbe géothermique Panaches Têtes de nouveaux panaches |
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