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{{Short description|Gravity anomaly in the Indian Ocean}}
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.<ref name="HowFormed">{{cite journal |first1=Debanjan |last1=Pal |first2=Attreyee |last2=Ghosh |title=How the Indian Ocean Geoid Low Was Formed |journal=Geophysical Research Letters |volume=50 |issue=9 |publisher=American Geophysical Union/Wiley |date=16 May 2023 |article-number=e2022GL102694 |doi=10.1029/2022GL102694 |doi-access=free|bibcode=2023GeoRL..5002694P }}</ref><ref>{{cite web |url=https://iisc.ac.in/scientists-find-out-the-cause-for-geoid-low-in-the-indian-ocean/ |title=Scientists find out the cause for geoid low in the Indian Ocean |last=Raman |first=Spoorthy |date=2023 |publisher=Indian Institute of Science |access-date=15 January 2024}}</ref> It forms a depression in the sea level covering an area of about 3 million km<sup>2</sup> (1.2 million sq mi), almost the size of [[India]] itself. Discovered in 1948 by [[Dutch people|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.<ref name="HowFormed" />

==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.<ref>{{Cite journal |last1=Rao |first1=B. Padma |last2=Silpa |first2=S. |date=February 2023 |title=A review of geophysical research: Perspective into the Indian Ocean Geoid Low |journal=Earth-Science Reviews |volume=237 |article-number=104309 |doi=10.1016/j.earscirev.2022.104309|bibcode=2023ESRv..23704309R }}</ref><ref>{{cite web |last=Raman |first=Spoorthy |title=The missing mass – what is causing a geoid low in the Indian Ocean? |website=GeoSpace |date=16 October 2017 |url=https://blogs.agu.org/geospace/2017/10/16/missing-mass-causing-geoid-low-indian-ocean/ |access-date=2 May 2022}}</ref>

[[File:Earth Gravitational Model 1996.png|thumb|center|upright=2.5|Impact of gravity anomalies on local sea level]]

=== Results from numerical models ===

As the [[Indian plate]] moved northward after splitting from the [[Gondwana]] [[supercontinent]], the [[Tethys Ocean|Tethys]] oceanic [[lithosphere]] that existed between India and Eurasia sank inside [[Earth's mantle]]. As this cold dense Tethys [[Slab (geology)|slab]] reached the bottom of the mantle, it churned the African [[Large low-shear-velocity provinces|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.<ref name="HowFormed" /><ref name="CNN2023">{{cite news |url=https://www.cnn.com/2023/07/24/world/gravity-hole-geoid-low-indian-ocean-scn/ |title=There is a 'gravity hole' in the Indian Ocean, and scientists now think they know why |last=Prisco |first=Jacopo |date=24 July 2023 |publisher=CNN |access-date=15 January 2024}}</ref>

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%).<ref>{{cite web |url=https://earthobservatory.nasa.gov/features/GRACE/page3.php |title=Gravity Anomaly Maps and the Geoid |first=Alan |last=Ward |work=NASA Earth Observatory |date=30 March 2004 |access-date=15 January 2024}}</ref> The geoid low is believed to have formed around 20 million years ago.<ref name="HowFormed" /><ref name="CNN2023" />

[[File:IndiaMoving-revised 09-15.jpg|thumb|center|upright=2.2|Approximate collision of Indian Plate into Central Asia]]

==References==
{{reflist}}

==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}}.

{{Geography topics}}{{Coord|2|N|76|E|region:XI_dim:10000km|display=title}}

[[Category:Geology of the Indian Ocean]]
[[Category:Gravimetry]]
[[Category:Lowest points]]
[[Category:Sea level]]

Indian Ocean Geoid Low - Revision history

Wikindia777 at 13:51, 28 March 2026