Scientists have unearthed a new explanation for several low-gravity
spots
detected around the world. They're blaming the anomalies on vast "slab
graveyards" that lie buried deep near the planet's core.
When these slabs of rock were buried long ago, they released water that
reduced the density of overlying rock, Caltech geophysicist Michael
Gurnis
and his colleagues reported online May 9 in Nature Geoscience.
Low-density
rock has less mass, and so less gravitational pull.
Scientists had previously noticed that gravity's tug is smaller where
tectonic plates, or large sections of Earth's crust, once plunged below
the
surface, Gurnis says. The team's new findings, he notes, provide insight
into
the causes of super-low values measured in four regions.
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