Geophysicists at ETH Zurich are using models of the lower mantle to identify areas where earthquake waves behave differently than previously assumed. This indicates the presence of zones of rocks that are colder, or have a different composition, than the surrounding rocks. This finding challenges our current understanding of the Earth’s plate tectonics—and presents the researchers with a major mystery.
No one can see inside the Earth. Nor can anyone drill deep enough to take rock samples from the mantle, the layer between the Earth’s core and outermost, rigid layer, the lithosphere, or measure temperature and pressure there. That’s why geophysicists use indirect methods to see what’s going on deep beneath our feet.
For example, they use seismograms, or earthquake recordings, to determine the speed at which earthquake waves propagate. They then use this information to calculate the internal structure of the Earth. This is very similar to how doctors use ultrasound to image organs, muscles or veins inside the body without opening them up.
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