Earthquake 2,500 years ago could have changed Ganga’s course abruptly: Study

New Delhi: An earthquake around 2,500 years ago could have caused the Ganga river to abruptly change course, according to a new study published.

Researchers said the “undocumented” quake, possibly of magnitude 7-8, rerouted the main channel of the river in present day Bangladesh, a country vulnerable to big seismic shocks.

“I don’t think we have ever seen such a big one (earthquake) anywhere,” said study co-author Michael Steckler, a geophysicist at Lamont-Doherty Earth Observatory, Columbia Climate School, US.

“It could have easily inundated anyone and anything in the wrong place at the wrong time,” Steckler said. The study was published in the journal Nature Communications.

Originating in the Himalayas, the river Ganga eventually combines with other major rivers, including the Brahmaputra and the Meghna, before culminating in the Bay of Bengal. The rivers form the world’s second-largest system, the Amazon being the largest.

Many river-course changes, called ‘avulsions’, including some that happened in response to earthquakes have been documented by scientists around the world.

Similar to other rivers running through major deltas, the Ganga too is known to regularly change its course. Rivers can take years or decades to change their course, but an earthquake can cause an avulsion almost instantaneously, said Steckler.

This study is the “first confirmed instance” of an earthquake driving avulsion in deltas, especially for an immense river such as the Ganga, according to lead author Elizabeth L Chamberlain, an assistant professor at The Netherlands’ Wageningen University.

Using satellite images, the research team spotted what they said was likely the former main channel of the river, about 100 kilometres south of Dhaka, the capital city of Bangladesh.

This is a low-lying area about 1.5 kilometres wide that can be found intermittently for some 100 kilometres almost parallel to the current

river course.