~1x. the highest resolution models resolve about 20 discrete llvas below the usual lvz

~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