A major earthquake more than 2,500 years ago likely caused one of the world’s largest rivers to change its course, according to a study published today in the journal Nature Communications. The findings by a global research team suggest that a similar event could have the potential to alter the river’s course again in the future.
The modern Ganges River, spanning 2,500 kilometers, flows from the Himalayas southeastward into Bangladesh, where it is known as the Padma River. It then connects with the Brahmaputra and Meghna rivers. Currently, the Ganges-Padma is located around 50 kilometers south of Dhaka. However, satellite imagery has revealed evidence of its former course, approximately 100 kilometers from the city.
This discovery indicates that a major event, likely seismic activity, caused an ‘avulsion’—the sudden creation of a new river channel and the abandonment of the old one. “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 in the Netherlands.
Co-author Michael Steckler, a geophysicist at Columbia Climate School in the United States, added, “I don’t think we have ever seen such a big one anywhere.” The study suggests that a large earthquake caused a seismic shift in the river system’s trajectory. In a previous study, Steckler found that a similar event could directly impact 140 million people living in the region.
According to Steckler and his colleagues in a 2016 paper, stress is increasing in a subduction zone where the oceanic crust is being pushed below the landmass consisting of India, Bangladesh, and Myanmar, as well as in a splay fault in the Himalayas. This buildup of stress could potentially lead to another significant seismic event, with far-reaching consequences for the Ganges River and the millions of people who depend on it.