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09-Apr-2018 03:06

The slab-pull is thought to be the "dominant" mechanism.

It refers to the gravitational sinking of the subducted slabs as they slide under the edges of continental shelves.

It has long been theorized that the driving forces of plate movements are deep convection currents that well up beneath the mid-ocean ridges and then circle back down beneath the ocean trenches.

The problem with this theory is that the mantle appears to be horizontally layered.

Scholl and Marlow (1974), who support plate tectonics, admitted to being "genuinely perplexed as to why evidence for subduction or offscraping of trench deposits is not glaringly apparent." In order to maintain their theory, plate tectonicists have had to resort to the notion that unconsolidated deep-ocean sediments can easily slide under overlying plates without being scraped off or leaving any other significant trace behind.

Also, these trenches often show a very low level of seismicity and often have flat-lying sediments at their bases that are not angled as if they were being subducted.

For example, the mid-ocean ridges, where new crust is thought to be produced, total 80,000 km in collective length.

However, only about 40,000 km of ocean trenches and "collision zones" exist.

Some scientists claim that these instruments have unequivocally supported the theory of plate tectonics.

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.

Of course, subduction does not happen for the edges of plates that are largely continental because continental crust cannot be subducted due to its relatively low density.

This is a problem because subduction cannot be used to explain the movement of certain massive continental plates such as the Eurasian plate.

Some scientists claim that these instruments have unequivocally supported the theory of plate tectonics.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.Of course, subduction does not happen for the edges of plates that are largely continental because continental crust cannot be subducted due to its relatively low density.This is a problem because subduction cannot be used to explain the movement of certain massive continental plates such as the Eurasian plate.The existence of deep continental roots and the absence of a continuous, global asthenosphere to "lubricate" plate motions, have rendered the classical model of plate movements untenable.