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Discovery of the origin of the huge gravity well in the Indian Ocean

It should be said that to reconstruct the early stages of post-geoid formation, a longer-term view was needed; Therefore, Paul and Gash trace geoid formation by displacement modeling tectonic plates They traced the past 140 million years on the earth’s crusty and hot mantle.

At that time, the Indian tectonic plate was just beginning to break away from the Gondwana supercontinent to begin its northward journey. As the Indian plate advanced, the ancient ocean floor called the “Tethys Sea” went down and was buried in the Earth’s mantle and the Indian Ocean opened up behind it.

Pal and Gash performed several simulations using computer models of plate and mantle motion and compared these models’ predictions of ocean subduction with observations of subduction.

The models that predicted the Indian Ocean gravity low as it is today all had one thing in common: plumes of hot, low-density magma moving upward under the gravity low. These columns, along with the different structure of the mantle in this region, are the cause of geoid depression; Of course, according to Paul and Gus, if they get high enough.

“In short, to adapt,” they wrote [شکل و بزرگی] “The results of our simulations, with observations from the postgeoid, suggest that the plumes should be buoyant enough to rise deep into the middle mantle.”

The first columns appeared 20 million years ago in the south of the geoid of the Indian Ocean; That is, 10 million years after the ancient Tethys sea sank into the lower mantle. With the expansion of the columns under the ore sphere and its creep towards the Indian subcontinent, the depression intensified.

Since the results were in line with the components of Gash’s previous modeling in 2017, the two researchers suggest that the plumes moved upward after the Tethys Sea floor sank into the lower mantle, expanding the “African bubble.”

Needless to say, some scientists who were not present in this research are not convinced. From their point of view, so far there is no clear seismological indication of the existence of these simulated columns under the Indian Ocean.

Such data may be available soon; Of course, there is no rush. Post geoid is expected to remain in place for millions of years to come.

This research in the publication Geophysical Research Letters It has been published.


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