Robert sent in this link – go to www.dailymail.co.uk/sciencetech/article-4998508/Scientists-create-incred… … Scientists claim to have mapped most of the tectonic plates, ancient and recent, which they define as slabs of crust in the Mantle under Earth's surface geology. Modeling has invariably been used – but so too has some interesting field research. Some of these slabs, we are informed, sank into the Mantle at depths such as 10,000 miles. This is perhaps a guesstimate as it conforms to Plate Theory a bit too neatly.
The mapping is the product of earth scientists at Utrecht University and it is published in the journal Tectonophysics – which may be all you need to know. Some of the slabs are ancient tectonic plates, it is thought, and they came to this conclusion by using seismic tomography to create a 3D image – a mirror inside the Mantle. If the process is valid they have confirmed Plate Tectonics as fact rather than the theoretical status it currently enjoys. Bouncing signals that hit anomalies in the Mantle is however open to misconceptions. The speed of seismic waves travelling through the inner parts of the Earth has come across obstacles of some kind that seismic waves pass through more slowly. The potential remnants of plate slabs differ from the surrounding hot Mantle and appear to be cooler – as one might suspect if surface rocks had been submerged in the hotter mixture making up the Mantle. One should try to be positive on this but I suppose other geologists will eventually have something to say, particularly at the New Concepts in Global Tectonics journal.