Indian Ocean Geoid Low

July 6, 2023

Researchers from IISc, Bengaluru have identified the cause of an over 3 million sq. km -wide ‘gravity hole’ – known as the Indian Ocean Geoid Low (IOGL)- in the Indian Ocean.
At IOGL, located just south of Sri Lanka, Earth’s gravitational pull is at its weakest.
- As a result, sea level is 106 metres lower than the global average.
According to scientists, the IOGL likely took its present shape about 20 million years ago and will likely last millions more.
Earth is not a true sphere — it’s flatter on both poles and bulges along the equator.
- As a result of this and other factors such as mass of its crust, gravitational pull varies making earth’s shape irregular.
These anomalies (due to irregularity in gravitational field) on Earth’s undulating map are known as
IOGL is called lowest geoid anomaly on Earth.
Researchers found that IOGL was caused by plumes of molten rock rising along the edges of Tethys Ocean bed.
- Tethys was a prehistoric ocean that separated the mega-continents of Gondwana and Laurasia.
Hot material from African superplume — a large section of Earth’s mantle that carries heat from near the core up to the crust — was being deflected eastwards.
This material then ended under IOGL.
The researchers found that ‘low density anomalies’ or the presence of lighter materials in the upper to mid-mantle (layer of Earth between the core and the crust ) below the IOGL, were responsible for the low gravity in this region.