Tectonics examined: Slabs of the world

[SwordfishMining]

The Earth’s rigid outer shell – the lithosphere – is broken into plates that move relative to one another along discrete plate boundaries – ridges, transforms, and subduction zones. At subduction zone plate boundaries, one plate disappears below another and sinks into the mantle. These sinking plates, called ‘slabs’, are colder than their surroundings, and remain colder for a very long period of time – about 250 million years. As a result, the speed at which seismic waves travel through these bodies of sinking lithosphere is a little higher than from the surrounding hot mantle. Since the 1980’s, the technique of seismic tomography has been developed that provides a 3D image of the seismic velocity structure of the Earth’s crust and mantle, from the surface to the boundary between the mantle and the Earth’s liquid outer core at a depth of 2900 km.
https://www.atlas-of-the-underworld.org/