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18-Dec-2017 21:06

However, seismic tomography has actually provided strong evidence against the existence of convection currents that are large enough and strong enough to move continental plates.

In fact, many geologists now think that the small upper layer mant Currently, the favored mechanisms used to explain plate movements are the "ridge-push" and the "slab-pull" methods.

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.

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.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.

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