Produced by: Tarun Mishra Designed by: Manoj Kumar
New evidence suggests that the Ganges River abruptly shifted its course approximately 2,500 years ago due to a distant yet massive earthquake.
Unlike gradual shifts observed upstream, this historic event occurred in the Ganges Delta, about 200 kilometres from its mouth at the Bay of Bengal.
Similar river shifts today could endanger millions living in delta cities worldwide, where infrastructure is vulnerable to flooding from sudden channel changes.
Rivers in flat deltas naturally meander due to sediment deposition, but seismic activity can rapidly alter their courses in days or weeks, unlike gradual changes over centuries.
Satellite images identified a crescent-shaped depression, likely an old Ganges channel, prompting fieldwork in the region.
Excavations revealed seismites—frozen-in-time sand volcanoes formed by seismic waves—which confirmed a significant earthquake as the cause of the river's shift.
The earthquake, estimated between magnitude 7 and 8, occurred about 2,500 years ago based on sand blow widths and sediment depths.
Today, up to 170 million people in India and Bangladesh face flood risks from similar seismic events, highlighting the vulnerability of densely populated delta regions.
With climate change raising sea levels and seismic risks continuing, preparing for unforeseen natural events remains a critical challenge for infrastructure and community resilience.
This study, published in Nature Communications, underscores the complex interaction between geological processes and human settlement in delta regions prone to natural hazards.