At http://phys.org.print282845516.html … we learn that a chunk of continental plate is lodged underneath central California and is responsible for the so call Isabell Anomaly. This was indicated by a large piece of cool dehydrated material deep within the crust. It is now thought to be a surviving slab of oceanic plate – most of which should have been driven deeper still into the Earth's mantle. IN fact, large chunks of ancient tectonic plate are beneath California and appear to have failed to subduct, a prerequisite of the consensus Plate Tectonics theory (see PNAS March 18th 2013).
Meanwhile at http://phys.org/print282748497.html … earthquakes and the formation of gold.