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It is somewhat like trying to pull a train engine with dental floss.
The theory of subduction has other problems as well.
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.
As it turns out, the plates are not really solid, intact, plates at all, but are instead composed of broken-up pieces of various shapes, sizes, structure, and strength.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.However, recent seismic tomography of the oldest parts of the continents have very deep roots that extend to depths of around 400 to 600 km with no asthenosphere beneath them.Antarctica, too, is almost entirely surrounded by alleged "spreading" ridges without any corresponding subduction zones.Also, if subduction has been occurring over 200 million years, one might expect that a lot of oceanic sediment would be scraped off the ocean floor and piled up against the overlying plate, filling up the trenches.
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.