Thare's a "gravity hole" in the Indian Ocean, where Earth's gravity is lower than average. The sea level of the Indian Ocean there is 106 meters lower than the global average.

Researchs say they know the reason. A mantle structure called the "African blob", which is a large low shear velocity province" causes hot, low-density material to flow from underneath Africa to underneathr the Indian Ocean. The African blob in turn is probably formed by "Tethyan slabs" deep in the mantle.

"Geologists think these slabs are ancient remnants of seafloor from the Tethys Ocean, which was located between the supercontinents of Laurasia and Gondwana more than 200 million years ago. Both Africa and India were part of Gondwana, but what is now India moved north into the Tethys Ocean -- creating the Indian Ocean behind it -- about 120 million years ago."

"Plumes [of molten rock] arise when subducted slabs belonging to the old Tethys Ocean sink inside the mantle and reach the core-mantle boundary."

Giant "gravity hole" in the ocean may be the ghost of an ancient sea

#geology