River Ganges changed its course after massive earthquake hit its shores 2500 years ago: Study

Can seismic activities change the course of rivers? Well, a study reveals that a major earthquake that occurred 2,500 years ago caused one of the biggest rivers on the planet to change its course abruptly. That river was none other than the Ganges.

This breakthrough discovery about changing courses of rivers is known as avulsions in scientific terminology. Rivers have always been changing their courses, but it was never confirmed that earthquakes could be the driving force behind them. Certainly, no study has ever linked seismic activity with the Ganges’ course before, which makes this study one-of-a-kind.

Today the Ganges flows for over 2,575 kilometres (1,600 miles) from the Himalayas down to the Bay of Bengal. It forms the world’s second-largest river system as it teams up with other rivers.

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It is hard to gather that such a massive water body system can change its course due to an earthquake. But course changes take decades and a lifetime. It is because sediments washed from upstream can change the lay of the land, raising the riverbed until the water finds a path of less resistance by flowing in a slightly different direction.

Earthquake changedthe course of the Ganges

Avulsions need not require time of decades or even years to make a change. As per the new study, earthquakes can lead to changes in rivers that happen almost instantaneously.

Looking at satellite imagery, the team discovered what appeared to be a former main channel for the Ganges running parallel to the river as it runs today for around 100 kilometres (62 miles).

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They were exploring the area in 2018 when they spotted something interesting along the retired river’s flank- sand volcanoes. Also known as seismites, they’re characterised by strips of sand emerging vertically through horizontal layers of mud and are a known side effect of earthquakes.

They also found seismites across a large expanse of land and all of them seemed to have similar patterns, indicating they were created at the same time.

The chemical analysis of the seismites revealed they date back 2,500 years, when, as per researchers, a magnitude 7 or 8 earthquake reshaped the landscape.

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The source of the Ganges-shifting earthquake could have originated from a subduction zone to the south and east where part of the oceanic crust is working its way underneath Bangladesh, Myanmar, and northeastern India.

Also, the large splay faults at the base of the Himalayas may have been the driving force, which is a concerning possibility as research suggests these zones could be due to another earthquake similar in magnitude to that which changed the course of the Ganges.

(With inputs from agencies)