Indian Ocean Geoid Low

The Indian Ocean Geoid Low (IOGL) is a gravity anomaly in the Indian Ocean. A circular region in the Earth's geoid, situated just south of the Indian peninsula, it is the Earth's largest gravity anomaly.[1][2] It forms a depression in the sea level covering an area of about 3 million km2 (1.2 million sq mi), almost the size of India itself. Discovered in 1948 by Dutch geophysicist Felix Andries Vening Meinesz as a result of a ship's gravity survey, it remains largely a mystery. A May 2023 study presented a potential explanation for the weak local gravity through a hypothesis that used computer simulations and seismic data.[1]

Location, characteristics, and formation

The gravity anomaly, or "gravity hole", is centered southwest of Sri Lanka and Kanyakumari, the southernmost tip of mainland India, and east of the Horn of Africa. Due to weaker local gravity, the sea level in the IOGL would be up to 106 m (348 ft) lower than the global mean sea level (reference ellipsoid), if not for minor effects such as tides and currents in the Indian Ocean.[3][4]

Results from numerical models

As the Indian plate moved northward after splitting from the Gondwana supercontinent, the Tethys oceanic lithosphere that existed between India and Eurasia sank inside Earth's mantle. As this cold dense Tethys slab reached the bottom of the mantle, it churned the African LLVP (Large Low-Velocity Province), giving rise to mantle plumes of hot low-density material. These buoyant plumes rose to the upper mantle and the low-density material spread underneath the Indian Ocean region, forming the geoid low, according to research published in May 2023.[1][5]

Because of this lower density, the gravitational pull in the IOGL region, the largest gravity anomaly on Earth, is currently measured to be weaker than normal by about 50 mgal (0.005%).[6] The geoid low is believed to have formed around 20 million years ago.[1][5]

See also

References

  1. ^ a b c d Pal, Debanjan; Ghosh, Attreyee (16 May 2023). "How the Indian Ocean Geoid Low Was Formed". Geophysical Research Letters. 50 (9) e2022GL102694. American Geophysical Union/Wiley. Bibcode:2023GeoRL..5002694P. doi:10.1029/2022GL102694.
  2. ^ Raman, Spoorthy (2023). "Scientists find out the cause for geoid low in the Indian Ocean". Indian Institute of Science. Retrieved 15 January 2024.
  3. ^ Rao, B. Padma; Silpa, S. (February 2023). "A review of geophysical research: Perspective into the Indian Ocean Geoid Low". Earth-Science Reviews. 237 104309. Bibcode:2023ESRv..23704309R. doi:10.1016/j.earscirev.2022.104309.
  4. ^ Raman, Spoorthy (16 October 2017). "The missing mass – what is causing a geoid low in the Indian Ocean?". GeoSpace. Retrieved 2 May 2022.
  5. ^ a b Prisco, Jacopo (24 July 2023). "There is a 'gravity hole' in the Indian Ocean, and scientists now think they know why". CNN. Retrieved 15 January 2024.
  6. ^ Ward, Alan (30 March 2004). "Gravity Anomaly Maps and the Geoid". NASA Earth Observatory. Retrieved 15 January 2024.

Further reading

  • Ghosh, A., Holt, W. E. (17 February 2012). "Plate Motions and Stresses from Global Dynamic Models". Science, 335 (6070): 839–843. doi:10.1126/science.1214209.
  • Ghosh, A., Thyagarajulu, G., Steinberger, B. (16 October 2017). "The Importance of Upper Mantle Heterogeneity in Generating the Indian Ocean Geoid Low". Geophysical Research Letters, 44 (19): 9707–9715. doi:10.1002/2017GL075392.
  • Singh, S., Agrawal, S., Ghosh, A. (10 April 2017). "Understanding Deep Earth Dynamics: A Numerical Modelling Approach". Current Science (Invited Review), 112 (7): 1463–1473. JSTOR 24912692.

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