The minimum level of gravity can be felt in the ocean near Sri Lanka: this anomaly has been known for a long time, but it was possible to explain it only now, by the influence of the African mantle province and the Indian subcontinent, which is rapidly escaping from it.
On images from space, our Earth looks almost perfectly round, but much is hidden by the water that covers most of its surface. In fact, the planet is full of irregularities, mountain ranges and deep depressions, covered with thick continental tectonic plates, and sometimes with much thinner oceanic plates.
All this creates an uneven distribution of mass in the Earth's lithosphere, and if it were covered with water, would not rotate, if there were no currents or waves in the ocean, then the thickness of the water layer in different regions would be different, and the maximum difference between the highest and in low parts it would approach 200 m. This conditional "sea level" forms the shape of a geoid, which gives a more accurate idea of the shape of our planet than an ideal sphere visible from near-earth orbit.
One of the most notable details will be the Indian Ocean Geoid Low (IOGL), with its deepest point at –106 m, located south of Sri Lanka. Explaining the mass deficit that creates this anomaly remains one of the most interesting problems in modern geophysics. Now, however, it seems to have been solved - through the efforts of Attreyee Ghosh and his colleagues at the Indian Institute of Sciences in Bangalore, as well as from Germany. The article of scientists is published by the journal Geophysical Research Letters, briefly about their work tells the message of the American Geophysical Union (AGU).
Geoid / ESA Surface Map
Geophysicists have modeled convective currents in the Earth's mantle - powerful currents in which hotter and lighter material rises to the surface, while dense and colder material descends. At the same time, the IOGL anomaly was associated with an excess of a less dense and light substance. But where does it come from? As a rule, such areas are associated with the action of mantle plumes, rising hot streams. However, field observations do not find anything suitable nearby.
On the other hand, the African superplume is located a little further to the west. Scientists have shown that India, rather quickly moving away from Africa, directs part of the mantle flows from this vast province to the east. They reach just the center of the anomaly in the Indian Ocean; it looks like the mystery of the largest gravity anomaly has been solved.
Sergey Vasiliev
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