The force of gravity is not constant throughout the Earth. Especially in the Indian Ocean
The Earth is not a perfect sphere and is not composed homogeneously of the same materials. This means that the force that gravity exerts on us (or on any other object on its surface) can vary from one geographic point to another. That’s the theory, because the practice is a bit more complicated.
New interpretation. Although we learned in school that the Earth’s gravitational force causes an acceleration of 9.81 meters per square second on the Earth’s surface, this measurement Not homogeneous. This is thanks to a study conducted by researchers from the Indian Institute of Science We have a better idea What modifies these changes.
Exploration of the Indian Ocean. The work focuses on the so-called geoid minimum of the Indian Ocean (A geoid depression in the Indian Oceanor IOGL), is a region in the Indian Ocean where this force is exerted by gravitational interaction Particularly weak. The team of researchers investigated the causes and formulated a hypothesis about the cause of this gravity anomaly, which is one of the most noticeable anomalies on our planet.
Tethys Ocean. The key will be the movements of tectonic plates that have occurred over the past 30 million years. More specifically, in a movement that would have buried the crust on which the now-disappeared Tethys Ocean lies beneath what is now the African continent.
Large columns of molten rock. According to this hypothesis, this gravitational “gap” occurred after the Indian subcontinent separated from the ancient continent of Gondwana and began its journey along the Tethys Sea towards what is now known as the Eurasian continent. During this journey, the plate that served as the bottom of the Tethys Sea had descended into the Earth’s mantle.
India’s crossing north would have created the present-day Indian Ocean, but it would also have allowed the emergence of magma plumes, a relatively low-density rock that would have risen into the upper layers of the Earth thanks to this low density. According to the models, these feathers have begun to appear 20 million years agoIt spread out for some time and made the minimum gravity more intense.
Surveys and simulations. the studypublished in the magazine Geophysical Research Letters, is based on various simulations conducted by the research team. They start from a job similar Published in 2017 It was supplemented by data collected in ocean surveys conducted in 2018. The mission placed an array of seismometers across hundreds of kilometers of the Indian Ocean floor.
From this data, those responsible for this latest study simulated sub-tectonic movements over the past 140 million years.
A hypothesis that must be tested. The team’s models have helped provide a plausible explanation, but verifying that magma plumes are where the models predict will be a very complex task. The interior of our planet is one of the things that is very close and difficult to observe. Any effort to verify with our own eyes what lies beneath our feet has important limitations. No matter how deep we dig.
That’s why seismic analysis is our best tool, but collecting data this way is also a daunting task that requires seismic and tectonic movements. Surveys in the region will likely provide us with new data that will allow us to test the new hypothesis.
Image | Pal & Ghosh, 2023 / a pot
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*An earlier version of this article was published in July 2023
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