Speed dating in yakima washington Adult chat rooms wales
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.
The hypothesizes directional movements of the plates themselves are also being questioned using "space-geodetic techniques" such as "very long baseline interferometry (VLBI), satellite laser-ranging (SLR), and the global positioning system (GPS).
Some scientists claim that these instruments have unequivocally supported the theory of plate tectonics.
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.
There is no consensus on the thickness of the "plates" and no certainty as to the forces responsible for their supposed movement.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 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.