Staff writers
A major earthquake more than 2,500 years ago likely caused one of the world’s largest rivers to change course.
A global research team has made the finding in a study published today in the journal Nature Communications.
They warn a similar event has the potential to alter the course again.
The modern, 2500km long Ganges flows from the Himalayas southeast to cross into Bangladesh (where it is known as the Padma), connecting with the Brahmaputra and the Meghna rivers.
Today, the Ganges-Padma is located around 50km south of Dhaka, however using satellite imagery, the research group found evidence of its former course around 100km from the city.
It points to a major event causing ‘avulsion’ – the sudden creation of a new river channel and desertion of another – likely caused by seismic activity.
“It was not previously confirmed that earthquakes could drive avulsion in deltas, especially for an immense river like the Ganges,” says study lead Liz Chamberlin, a quaternary geochronologist at the University of Wageningen, Netherlands.
Co-author Michael Steckler, a geophysicist at Columbia Climate School, US, says “I don’t think we have ever seen such a big one anywhere.”
It’s likely that a large earthquake caused, quite literally, a seismic shift in the trajectory of the river system. In a previous study, Steckler found a similar event could directly impact 140 million people living in the region.
According to Steckler and colleagues in a 2016 paper, a subduction zone where the oceanic crust is being pushed below the landmass consisting of India, Bangladesh and Myanmar, and a splay fault in the Himalayas, are increasing in stress.