The Gravity Hole Enigma
Scientists Make Strides in Understanding the Unusual 'Gravity Hole' of the Indian Ocean
The existence of a massive “gravity hole” spanning over two million five hundred thousand square kilometers (one million square miles) deep beneath the Indian Ocean has puzzled scientists for years. While not a literal hole, geophysicists use this term to describe an area where Earth’s gravitational pull is significantly weaker than average. Now, researchers may have unraveled the mystery behind this extraordinary depression, shedding light on the ancient and intricate geological processes shaping our planet.
The Earth’s irregular shape, with flattened poles and bulges along the equator, results in variations in gravitational forces across different locations. To visualize these variations, scientists have created the Earth’s “geoid,” a potato-shaped representation highlighting gravitational highs and lows. One such low, known as the Indian Ocean geoid low (IOGL), has captivated researchers since its discovery in 1948.
In a recent study published in Geophysical Research Letters, scientists from the Indian Institute of Science in Bangalore, Attreyee Ghosh, and doctoral student Debanjan Pal, investigated the IOGL. They found that the sea level in the surrounding ocean is nearly 100 meters lower than the global average. By employing computer models to simulate changes over the past 140 million years, the team proposed that the IOGL might have formed due to the “African blob.” This enormous mass, located over 1000 km beneath Africa’s surface, was forced beneath the Indian Ocean.
Geologists believe the African blob originated from the remnants of the seafloor in the ancient Tethys Ocean, which existed more than 200 million years ago between the supercontinents Laurasia and Gondwana. Approximately 120 million years ago, as Gondwana migrated northward, the Indian Ocean was formed. Pal and Ghosh argue in their study that the IOGL assumed its present shape around 20 million years ago when plumes of hot, low-density magma surrounded the area as Tethys Ocean slabs submerged into the Earth’s mantle.
Despite these significant findings, many questions remain. Himangshu Paul from the National Geophysical Research Institute in India noted that other factors might also contribute to the existence of the IOGL. Simulations cannot perfectly replicate nature, leaving room for additional explanations. The study of this intriguing gravity hole continues to captivate scientists as they strive to uncover the complete story behind its enigmatic presence.