An earthquake changed the course of the Ganges River 2.5 thousand years ago

An international team of geophysicists has discovered evidence that about 2.5 thousand years ago, an earthquake caused the Ganges River to shift sharply dozens of kilometers north.

The statement by the Columbia University Media Office indicates that the movement led to changes in the structure of sand and silt deposits in the river delta, which is considered one of the largest rivers in Asia.

“Rivers usually change their course gradually, but earthquakes can also cause more dramatic changes in course,” says Liz Chamberlain, an associate professor at Wageningen University in the Netherlands. “But we have never seen examples of how such disasters can alter the flow of the world’s largest rivers like the Ganges.

Scientists discovered this fact by studying and analyzing the structure of soil samples collected dozens of kilometers south of Dhaka, the capital of Bangladesh, while building a pit for a pond. Scientists discovered traces of earthquakes in the sediments of these soils, which are characteristic changes in the structure of soil layers caused by earthquakes.

The researchers point out that they later discovered similar seismic deposits 85 kilometers south of this point, which led them to believe that the Ganges Delta was subjected to a strong earthquake in the recent past. Scientists determined the age of both seismic sites and studied satellite images of the Ganges Delta.

The analysis showed that the effects of the earthquake in both sites occurred at the same time, about 2.5 thousand years ago. Scientists also discovered that the two sites are in a lowland, 1.5 kilometers wide and 100 kilometers long, and located parallel to the current course of the Ganges River. According to them, this valley represents an ancient riverbed that was blocked by sand and silt deposits, and its structure changed dramatically during a strong earthquake in the ancient era.

According to the researchers, this earthquake was strong and similar ones often occur in the Eurasia region, but they cannot determine its precise location, and they believe that its epicenter was either in the Himalayas or off the southeastern coast of Bangladesh. Scientists concluded that subsequent studies would help clarify the source of this earthquake and assess the possibility of such a disaster recurring.