Continental displacements of thousands of kilometres point to flow
patterns in the mantle of similar dimensions. As creep depends exponentially on
temperature and as it is known that the temperature of the crust increases
rapidly with depth, we can in this context suppose the mantle to have a sharp
transition between a rigid crust and a fluid mantle at 50 to 100 km depth. Pattern Maker in
India, Pattern Maker in Ahmedabad .Recently the coefficients of the tesseral
harmonics of the geopotential from satellite observations have been determined.
These departures from hydrostatic equilibrium seem to be caused by flow in the
mantle, for from these coefficients can be computed the tractions exerted by
the flow on the crust, assuming Navier-Stokes's equations, and the resulting
pattern accords well with the world-wide tectonic features. Rising flow is
associated with the East Pacific Ocean Rise, the Mid-Atlantic Ridge and the
Mid-Indian Ocean Rise. Pattern Maker in India, Pattern Maker in Ahmedabad.Descending currents coincide with the Andes, the Alps and the
Japan trench. The strong fifth harmonic in the satellite gravity data suggests
that a flow pattern of this degree is at present establishing itself. On the
other hand, continental reconstructions prior to Wegenerian drift suggest the
presence of a strong fourth harmonic in the flow pattern.
