A massive earthquake 2,500 years ago may have changed the course of the Ganges River

An international team of researchers studying the impact of earthquakes on networks of river channels has spotted in satellite images what appears to be the ancient channel of a river parallel to the Ganges in India.

After visiting the area located approximately 100 km south of Dhaka, the capital of Bangladesh, They concluded that a powerful earthquake 2,500 years ago may have suddenly changed the course of the Ganges River.

In the study recently published in the journal Nature Communications, the authors state that the magnitude of the earthquake, previously unknown to science, may have reached 7.5 or 8. The earthquake was so strong that it diverted the main course of the river, even though it was more than 180 kilometers away from the epicenter..

Why did the Ganges change its course?

Avulsions occur in rivers crossing large deltas such as the Ganges. sediments flowing from mountains and hills forming layers in their beds. As soon as the high bottom breaks through the surrounding plain, the water of the river breaks the banks and looks for an easier path.

The difference between this type of rupture and rupture caused by earthquakes is that the latter occurs instantly. While exploring a low-lying area about 1.5 kilometers parallel to the river’s current flow, researchers came across a new excavation that showed vertical trenches of light sand on its side cutting through horizontal layers of mud.

They are known as seismites, a type of sand volcano that can “erupt” at the surface. These structures are known features of earthquakes.

What could have caused the earthquake that shifted the Ganges?

The main conclusion of the study, based on the identified geological evidence, is that a sudden rupture of the Ganges River occurred, triggered by a large earthquake that occurred 2500 years ago. The event was powerful enough to displace the main channel belt in the Bengal delta, liquefying the soil and creating large sand dams.

One possible origin of the earthquake may be a subduction zone to the south and east, where a large tectonic plate on the ocean floor has wedged itself beneath the continental crust of Bangladesh, Myanmar and northeastern India.

Another source of this phenomenon may be the presence of giant fractures at the base of the Himalayan Range, north of the affected area, where the Indian tectonic plate is colliding with the rest of Asia. “Major earthquakes affect large areas and can have long-lasting economic, social and political impacts,” warns co-author Syed Humayun Akhter, vice-chancellor of the Open University of Bangladesh.

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