For almost 40 years, experts have developed different hypotheses to explain this phenomenon, which reaches its deepest point at 106 meters below average sea level.
Geoscientists Debanjan Pal and Attreyee Ghosh of the Indian Institute of Science believe they are certain of the types of planetary phenomena that could be involved in the formation of the Indian Ocean Low Geoid (IOGL).. These experts concluded that the accumulation of light material from the African super feather is the cause of the IOGLas they exposed in an article recently published in Geophysical Research Letters.
The african super featherweight it is a massive upwelling of the Earth’s mantle that rises from the depths of the planet below southwestern Africa, running northeast across the continent, becoming shallower as it extends northward.
The Earth is not perfectly shaped, but more like a potato, so the gravitational levels of its surface differ due to the uneven distribution of mass in its depths. This circumstance causes variations in the gravity of some places on our planet, known as ‘geoid anomalies’. One of the points where it is lowest is in the IOGL.
Since the early 1980s, scientists have developed different hypotheses to explain this phenomenon, which reaches its deepest point at 106 meters below average sea level. So far there is no consensus on its origin.
Pal and Ghosh simulated plate tectonic movement in 19 global mantle convection models, from the Mesozoic to the present (the last 140 million years), to trace the formation of this low geoid. The results of the simulations of half a dozen computer models indicated that it originated more than 1,000 kilometers below the Earth’s crust about 30 million years ago.
As the Indian Plate progressed, the cold, dense seafloor of an ancient ocean called the ‘Tethys Sea’ sank into Earth’s hot mantle, below Africa. Then the Indian Ocean opened up behind him.
The researchers conjecture that the flow induced by the subsidence of the Tethys slabs disturbed the large African province, giving rise to plumes/columns of hot, low-density magma that reached the upper mantle. The authors of the paper maintain that these plumes, along with the mantle structure near the low geoid, are responsible for the formation of this anomaly. As the plumes extended below the lithosphere and inched toward the Indian peninsula, the depression intensified.
No seismographic evidence
However, Pal told New Scientist that there is no clear seismographic evidence that the simulated plumes are actually present beneath the Indian Ocean. He also believes that there are still other undiscovered factors behind the low geoid, such as the precise position of the ancient Tethys slabs. “In simulations it is not possible to exactly imitate nature“, he stresses.
For his part, Bernhard Steinberger, from the German Research Center for Geosciences, argues that the new model shows that the low geoid has more to do with the columns and slabs that surround it than with any particular structure below the Indian Ocean. “It’s basically this hole where there’s nothing,” he pointed out.