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It seems as though the lithosphere, which makes up the solid plates, averages 70 km thick beneath the oceans and at least 125 to 250 km thick beneath the continents.
Such convection currents do not seem to be consistent with such layering.
It was hoped that seismic tomography would give clear evidence of such convection-cell patterns.
Based on this problem Pavlenkova concludes: "This means that the movement of lithospheric plates over long distances, as single rigid bodies, is hardly possible.
Moreover, if we take into account the absence of the asthenosphere as a single continuous zone, then this movement seems utterly impossible." She states that this is further confirmed by the strong evidence that regional geological features, too, are connected with deep (more than 400 km) inhomogeneities and that these connections remain stable during long periods of geologic time; considerable movement between the lithosphere and asthenosphere would detach near-surface structures from their deep mantle roots." The very process or "driving force" of plate movement is also coming under fire.
It seems like crust is being produced in more areas than it is being subducted. Certain specific examples are also interesting, such as the African plate.
Africa is allegedly being converged on by plates spreading from the east, south, and west, yet it exhibits no evidence whatsoever for the existence of subduction zones.
This might seem like an obvious expectation, except for the fact that it is not observed in real life.
The ocean trenches do not have enough sediment in them if subduction has truly occurred in these areas over the course of millions of years.
It is somewhat like trying to pull a train engine with dental floss.Tags: Adult Dating, affair dating, sex dating