Science & Technology:

What Goes Up, Must Come Down (and Sometimes Gets Stuck) (Lawrence Berkeley National Laboratory)

Life on Earth is significantly affected by the exchange of mass and energy between the Earth's interior and its surface. Hot upwellings under mid-ocean ridges and hot-spot regions (e.g. Hawaii) are balanced by downward plunges of cold crust at subduction zones (e.g. the Andes range along the West Coast of South America).

To directly "observe" the structure of the Earth's interior, scientists analyze the travel times of earthquake shock waves. One puzzling finding from this data is that subducted slabs of crust penetrate the sharp density boundary between the upper and lower mantle at 660 km (~410 miles), but tend to stall in their descent at around 1000 km (~625 miles), where they thicken and buckle.

Researchers have now found a possible explanation.

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