Global Geological And Climatic Events

Gravity Hole in the Indian Ocean


From UPSC perspective, the following things are important :

Prelims level: Gravity Hole

Mains level: Not Much

gravity hole
The true shape of our Earth

Central Idea

  • One intriguing phenomenon recently discovered is the presence of a significant “gravity hole” in the Indian Ocean, where the gravitational pull is notably weaker.
  • Recent research sheds light on the possible causes behind this anomaly.

What is a Gravity Hole?

  • A “gravity hole” refers to a region on Earth where the gravitational pull is significantly weaker compared to the surrounding areas or the global average.
  • It is characterized by a dip or low gravity anomaly.
  • In such areas, the sea level may be lower than average due to the weaker gravitational force acting upon the water.
  • This term is often used to describe specific locations, such as the Indian Ocean geoid low (IOGL), where the gravitational pull is notably diminished compared to nearby regions.
  • The exact causes of gravity holes can vary and may involve factors such as variations in the Earth’s mass distribution or underlying geological features.

What is Indian Ocean Geoid Low (IOGL)?

  • It is located approximately 1,200 kilometers southwest of the southernmost tip of India.
  • IOGL is an area in the Indian Ocean where the sea level is about 106 meters below the global average.

Unraveling the Causes of IOGL

  • Discovering the Anomaly: Geophysicist Felix Andries Vening Meinesz first identified the IOGL during a survey in 1948. Since then, it has been confirmed by subsequent ship-based experiments and satellite measurements.
  • Ancient Ocean Hypothesis: Researchers from the Indian Institute of Science conducted computer-simulated models spanning 140 million years. They discovered remnants of an ancient ocean, located approximately 965 kilometers below the Earth’s crust, just beneath Africa.
  • Molten Rock Plumes: The simulations revealed molten rock plumes below Africa, potentially caused by tectonic plates subducting into the mantle. These plumes are believed to be a contributing factor to the IOGL.
  • Possible origination: Researchers said that the IOGL comprises slabs from the Tethys Sea, a long-lost sea that plunged into the depths of the planet millions of years ago. Tethys Sea, which once separated the supercontinents of Gondwana and Laurasia is believed to have perturbed the African Large Low Shear Velocity province.

Future Perspectives

  • Lack of Seismic Evidence: While the simulated models suggest the presence of molten rock plumes beneath the Indian Ocean, seismographic evidence has yet to confirm their actual existence.
  • Additional Factors at Play: The researchers emphasize that other factors contributing to the gravitational anomaly in the Indian Ocean need to be further explored before reaching a definitive conclusion.
  • Further Research: Continuation of studies, including seismic surveys and detailed modelling, is necessary to gain a comprehensive understanding of the IOGL and its causes.

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