Science:
In geology textbooks, the fate of the oceanic crust seems
straightforward. The ocean floor is created by upwelling of
lighter magma at spreading ridges. The magma cools as it moves
away from the ridge, forming a stiff layer or "plate" called
the oceanic lithosphere. Having increased in density, it then
descends back into the mantle in trench regions.Precise seismic
tomography studies have revealed that many descending slabs
have a more complex evolution and have developed tears,
detached from the surface plate, or even broken up into
fragments.In last week's
Science,
Obayashi
and colleagues not only show clear tomographic evidence for
the development of a vertical tear under southwest Japan, but
have also found evidence for ongoing plate rupturing. The
authors correlated the images directly with measurements of
stress revealed by active seismic sources.
Related Link
Tearing
of Stagnant Slab
