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~1X
The highest resolution models resolve about 20 discrete LLVAs below the usual LVZ
Heated from below gives narrow upwellings and broad downwellings. Cooling from the top and internal heating give the opposite.
Fig. 11. Numerical simulation of convection in a fluid with viscoelastic rheology and a yield stress showing temperature (top) and the second invariant of stress rate (bottom). For a suitable range of Rayleigh number and yield stress the surface velocity, vx, breaks up into a number of distinct ‘plates’.
Heated from below gives narrow upwellings and broad downwellings. Cooling from the top and internal heating give the opposite.
Fig. 11. Numerical simulation of convection in a fluid with viscoelastic rheology and a yield stress showing temperature (top) and the second invariant of stress rate (bottom). For a suitable range of Rayleigh number and yield stress the surface velocity, vx, breaks up into a number of distinct ‘plates’.
Hawaii
ridgesuperswell
Ridge Related Upwellings
Shallow lateral flow (fingers) either away from ridges (ridge centered upwellings) or toward ridges/thin spots (off axis upwellings).
Cooled from above…
Low sound speed(?) but dense
1, Hawaii; 2,Samoa; 3, Marquesas; 4, Tahiti 5, Pitcairn; and 6, Macdonald.
Hawaii
Galapagos Easter
fingers
superswell
42
S.Of AlaskaW. Of Calif.
-2%+3%
Downwellings?
cold warm cool cold
Most hotspots, backtracked LIPs & kimberlites fall within the ~ -2% contour surrounding ridges (p=10-8)
Harvard
In spite of being ‘passive’, ridge-related upwellings are not ambient or ‘representative’ shallow mantle
Dziewonski&Ekstrom
HawaiiTonga
ridge
800