India (Commonwealth Union)_ The Earth is generally portrayed as a perfect sphere. However, the planet’s actual form is uneven, similar to that of a potato. This unevenness is attributed to the non-uniform distribution of gravity across the globe, leading to the formation of geoids, which are irregularities on Earth’s undulating surface. One of these distinctive geoids lies beneath the Indian Ocean, where gravity weakens to an extreme low, creating what is referred to as a “gravity hole.”
As reported by Science Alert, this region, spanning approximately 2 million square kilometers, is known as the Indian Ocean Geoid Low (IOGL). The IOGL has long intrigued geologists who have sought to unravel its origins. However, a recent study claims to have discovered the answer. The study, published in the journal Geophysical Research Letters and conducted by Indian researchers Debanjan Pal and Attreyee Ghosh from the Indian Institute of Science (IISc), suggests that the IOGL is a remnant of Tethys, an ancient sea that existed millions of years ago.
Professor Ghosh, an Assistant Professor at the Center for Earth Science, explained that the IOGL poses one of the most intriguing problems in Earth Sciences, being the lowest geoid/gravity anomaly on the planet, with no consensus regarding its source. He said, “The existence of the Indian Ocean Geoid Low is one of the most outstanding problems in the Earth Sciences. It is the lowest geoid/gravity anomaly on Earth, and so far, no consensus exists regarding its source”. According to Professor Pal, the current shape of the “gravity hole” likely formed around 20 million years ago and is expected to persist for millions more.
Further, the researchers identified that the presence of “low density anomalies” or lighter materials in the upper to mid-mantle, the layer between the Earth’s core and crust, beneath the IOGL, contributes to the gravity low observed in this area. The findings are based on extensive computer models and simulations. Tethys, the ancient ocean responsible for the IOGL, served as a separation between the supercontinents of Gondwana and Laurasia. Further, the study’s findings shed light on the geological history of the region and provide valuable insights into the intriguing phenomena of gravity anomalies on Earth.
