Bangalore, India – Scientists have long been puzzled by a remarkable gravitational anomaly hidden beneath the Indian Ocean. Known as the Indian Ocean Geoid Low (IOGL), this region stands out due to its ocean surface dipping a staggering 106 meters lower than surrounding areas. This unusual phenomenon creates weaker gravitational forces, making the IOGL a unique subject of study for geophysicists seeking to unravel its origins.
For years, the source of this low-gravity area remained unclear, prompting various hypotheses among researchers. Some proposed that a subducted tectonic plate might sink into the mantle beneath the region, while others suggested complex interactions in the mantle itself as a possible explanation. Until now, no single theory fully accounted for the scale and implications of the anomaly.
Recent findings published in Geophysical Research Letters have brought new clarity to this geological mystery. A collaborative research team utilized advanced computer simulations alongside seismic data to investigate the anomaly’s origins, tracing it back approximately 140 million years. Their research points to low-density materials in the upper to mid-mantle beneath the IOGL as a significant contributor to the region’s gravitational peculiarity.
The study reveals that natural processes, specifically mantle convection, play a critical role in shaping the IOGL. These processes involve the upward movement of hot, low-density material from deep inside the Earth, likely linked to what is known as the African superplume, a column of molten rock that extends from the Earth’s core toward the surface.
Prof. Attreyee Ghosh from the Centre for Earth Sciences at the Indian Institute of Science highlighted that the geological history of the Indian tectonic plate has drastically influenced the formation of this anomaly. Over millions of years, the Indian plate has drifted northward, closing a sizable oceanic gap between it and the Asian plate. As the oceanic crust beneath the Indian plate was subducted, mantle dynamics shifted, leading to the rise of lighter materials and the resultant gravity low.
The findings suggest that this anomaly has persisted in its current form for roughly 20 million years, yet questions remain regarding its long-term future. According to Ghosh, while it may persist for an extended period, shifting plate tectonics could eventually alter its state. “The dynamics of the plates may lead to its disappearance in the coming hundreds of millions of years,” she noted.
Despite the advancements made in understanding the IOGL, not all researchers are convinced that the new study delivers a complete explanation. Dr. Alessandro Forte, a geologist at the University of Florida, raises concerns regarding the model’s ability to fully account for the mantle plume responsible for volcanic activity on Réunion Island, which forms part of the Deccan Traps, one of the world’s most significant volcanic structures. Discrepancies between model predictions and actual geological observations in various regions, including the Pacific Ocean and parts of Africa and Eurasia, underscore ongoing debates within the scientific community.
As research into the Indian Ocean Geoid Low continues, the quest for understanding this enigmatic feature highlights the dynamic and complex nature of Earth’s geology. The findings not only provide insights into the IOGL itself but also shed light on the broader processes that shape our planet over geological timescales.