Context:-
Recently researchers from the Indian Institute of Science may have uncovered the cause of the mysterious ‘gravity hole’ in the Indian Ocean.
- Geoid – Scientists use the geoid, a model of global mean sea level, to measure precise surface elevations.
- Due to the uneven distribution of mass throughout the Earth, the geoid’s shape is smooth but irregular.
- The planet’s rotation, gravitational forces, and internal structure also affect the shape.
- In the absence of tides and currents on the oceans, all the water would settle onto a geoid, rising wherever there is high gravity, and sinking where gravity is low.
- The resulting unevenness in the ocean surface, known as geoid anomalies.
- Indian Ocean Geoid Low (IOGL) – One of the most pronounced geoid lows on Earth lies just southwest of the Indian peninsula, the Indian Ocean geoid low (IOGL).
- Dutch geophysicist Felix Andries Vening Meinesz discovered it in 1948 during a survey.
- Here gravity is lower than average, thus making the sea level 106 meters lower than the global average at the site.
- IOGL is a consequence of a mass deficit inside the Earth’s mantle beneath the Indian Ocean.
- Formation – Previous studies on the gravity anomaly focused solely on its present-day state, without delving into its origins.
- The Gravity Hole is estimated to have assumed its current form around 20 million years ago and is predicted to endure for millions more.
- The IOGL comprises slabs from the Tethys Ocean which separated the supercontinents of Gondwana and Laurasia.
- Researchers believe that the ocean’s agitation has caused the African Large Low Shear Velocity province (LLSVP), commonly referred to as the “African blob,” to generate plumes beneath the Indian Ocean.
- These plumes, along with the mantle structure in the vicinity of the geoid low, are responsible for the formation of this negative geoid anomaly.
Frequently Asked Questions About Indian Ocean Geoid Low (IOGL)
A: The geoid is a model of global mean sea level used to measure precise surface elevations. It accounts for the uneven distribution of mass and the effects of gravity, rotation, and internal structure to represent the shape of the Earth’s surface as if it were covered by the oceans.
A: Geoid anomalies refer to the unevenness in the ocean surface caused by variations in gravity. In areas where gravity is higher, water tends to rise, resulting in higher sea levels, while areas with lower gravity experience a sinking effect, leading to lower sea levels. These variations create irregularities in the geoid shape.
A: The Indian Ocean Geoid Low (IOGL) is one of the most prominent geoid lows on Earth. It is located southwest of the Indian peninsula in the Indian Ocean. The discovery of the IOGL occurred in 1948, and it is characterized by lower gravity, which results in the sea level being approximately 106 meters lower than the global average at that location.
A: The IOGL is primarily caused by a mass deficit within the Earth’s mantle beneath the Indian Ocean. It is believed to be associated with the movement of slabs from the Tethys Ocean, which separated the supercontinents of Gondwana and Laurasia. The interaction of these slabs with the African Large Low Shear Velocity province (LLSVP) and the mantle structure in the vicinity of the geoid low generates the negative geoid anomaly observed in the IOGL.
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