According to a study in Nature Communications, an ancient earthquake, possibly magnitude 7.5 or 8, dramatically altered the course of the Ganga River 2,500 years ago, as evidenced by seismites near Dhaka, Bangladesh.
According to new research, the Ganga River’s course was dramatically altered by a massive earthquake that struck southern Asia 2,500 years ago.
Scientists had no prior knowledge of the earthquake until they discovered evidence of its tremendous power buried in the terrain close to Bangladesh’s capital, Dhaka. In a paper released on Monday, June 17, in the journal Nature Communications (pdf below), the team presented its findings. The Ganga main stem was rerouted by the magnitude 7.5 or 8 earthquake, which was so strong that it caused a displacement of more than 110 miles (180 kilometers) from the site of the quake.
Avulsions are sudden shifts in a river’s path. Researchers have previously documented avulsions brought on by seismic activity, but “I don’t think we have ever seen such a big one anywhere,” according to a statement from study co-author Michael Steckler, a geophysicist and research professor at the Lamont-Doherty Earth Observatory of the Columbia Climate School in New York.
One of the world’s biggest rivers, the Ganga flows for over 1,600 miles (2,500 km). It rises in the Himalayas, on the border between China and India. From there, it runs east through India to Bangladesh, where it empties into the Brahmaputra and the Meghna, two more significant rivers. The linked rivers spread out to create the world’s largest river delta, which empties into the Bay of Bengal.
The Ganga can alter its course on its own, without the assistance of an earthquake, by carrying sediments that progressively build up on the riverbed, just like other rivers that run through large deltas. The river eventually overflows and forges a new course for itself when enough silt accumulates in one area to make it higher than the surrounding terrain.
Although this process takes years or even decades, a river might be rerouted very instantly by an earthquake, according to Steckler.
“It was not previously confirmed that earthquakes could drive avulsion in deltas, especially for an immense river like the Ganges,” said Liz Chamberlain, the primary author of the study and an assistant professor at Wageningen University in the Netherlands.
The statement said that the first indications that the Ganga had been forcefully diverted in the past came from satellite images. About sixty-two miles (one hundred kilometers) south of Dhaka, Chamberlain and her colleagues saw what appeared to be an ancient river channel running parallel to the Ganga. In their further exploration of the area, the researchers discovered sand bands breaking through the muddy ground in multiple places. They determined that the bands were generated in a single event and recognized them as seismites, which are vertical layers of sand that “erupt” when an earthquake disturbs wet soils.
Chemical examinations of the sand and mud indicated that the event occurred 2,500 years ago, which the experts concluded must have been a massive earthquake.
The study suggests that the earthquake may have been caused by two distinct causes. The first is a region in northeastern India’s Shillong Massif mountains, where the Indian tectonic plate is flexing against the Eurasian plate and causing seismic activity. The second is the crust of the Indian Ocean subducting beneath northeastern India, Bangladesh, and Myanmar. According to the study, these processes are taking place more than 110 miles from the location of the seismites, indicating that the Ganga-rerouting earthquake had a minimum magnitude of 7.5 to 8.
Both the Indo-Burman subduction zone and the Shillong Massif have the potential to produce earthquakes with a similar magnitude, according to a 2016 study led by Steckler. The study estimated that 140 million people might be impacted by such an earthquake.
Last year, GreatGameIndia reported that a report submitted by the central government states that the melting Himalayan glaciers will lead to natural disasters.
You can read the study below:
s41467-024-47786-4