Q. 88: Can you explain why plate motions are still occurring today?

CPT Q. #88 – 101 Q&A on Catastrophic Plate Tectonics

Question: 88. Can you explain why plate motions are still occurring today?

Response: Seismic observations clearly reveal today the presence of subducting slabs that penetrate the upper mantle and in some cases some or all of the lower mantle as well. What the existence of these slabs implies is that, when the CPT runaway process during the Flood came to a stop, there were slabs still in the process of sinking. These slabs were effectively frozen in place as the mantle’s viscosity rapidly rose to its non-runaway value. Although this non-runaway value of mantle viscosity is about a billion times higher than it was during the interval during which CPT was occurring, it nevertheless is not infinite. The mantle still undergoes deformation in response to the stresses these slabs generate, despite the fact that the sinking rates of the slabs are only on the orders of a few millimeters per year.

To recap, the plate motion occurring today is a consequence of slabs of cold lithosphere which presently exist in the mantle. These slabs were in the process of sinking through the mantle when CPT shut down and were effectively frozen in place as the mantle rapidly recovered its strength. These slabs, because of their strong negative buoyancy, that is, higher density due to lower temperature, continue to sink today, but the sinking rates are quite small. Mantle rock is strong, but not infinitely so. The stresses these slabs exert cause the surrounding mantle to deform and the slabs to move through it, typically, at rates of only millimeters to centimeters per year.