How does radioactive decay related to radiometric dating


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.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.

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Evidence for significant amounts of submerged continental crust in the present-day oceans provides another major challenge to plate tectonics.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.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.For example, the mid-ocean ridges, where new crust is thought to be produced, total 80,000 km in collective length.

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