Global seismic tomography structural geology at 2,850 km depth and its relationship to the surface continents (part 10) 28 July 2021 by Robert Watchorn Global seismic tomography 2,850 km depth. Structural geology and its relationship to the surface continents. Watchorn ‘working’ hypothesis on the Earth core to crust movement over the last 4 billion years. Like it? Share it!