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A huge temblor that stir southern Asia 2,500 years ago abruptly changed the course of the Ganges River , new enquiry suggests .
The earthquake was antecedently unknown to scientific discipline , but researchers spotted clues of its Brobdingnagian force buried in the landscape near Dhaka , the working capital of Bangladesh . The squad revealed its finding in a study published Monday ( June 17 ) in the journalNature Communications . The quake likely strain order of magnitude 7.5 or 8 and was so powerful it rerouted the main base of the Ganges River — despite the displaced section of river being more than 110 miles ( 180 kilometers ) forth from the seism ’s epicenter .
The Ganges River merges with other major rivers in Bangladesh and empties into the Bay of Bengal.
Rapid river - course modification are call avulsions . Researchers havepreviously documentedavulsions have by seismic activity , but " I do n’t think we have ever get a line such a boastful one anywhere , " bailiwick co - authorMichael Steckler , a geophysicist and enquiry prof at the Lamont - Doherty Earth Observatory of the Columbia Climate School in New York , said in astatement .
The Ganges is one of the heavy rivers in the world , flow for about 1,600 mile ( 2,500 km ) . It starts in the Himalayas , on the boundary line between India andChina , and then flows east through India to Bangladesh , where it merges with other major rivers , including the Brahmaputra and the Meghna . The combined waterways fan out to form the largest river delta on Earth and empty out into the Bay of Bengal .
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The Ganges Delta (pictured from satellite) is the largest river delta in the world. The dark part of the delta is the Sundarbans, a vast wildlife preserve and mangrove swamp.
Like other river that flow through fully grown delta , the Ganges can modify its own row — without help from an earthquake — by carry sediments that step by step roll up on the riverbed . finally , enough sediment construct up in one spot to arise taller than the surround landscape painting , at which power point the river slop over and carve out a new path for itself .
While this process pass over several years or decade , an earthquake could potentially reroute a river more or less instantaneously , Steckler say .
" It was not previously confirmed that earthquake could force back avulsion in deltas , especially for an immense river like the Ganges , " field of study lead authorLiz Chamberlain , a geochronologist and adjunct prof at Wageningen University in the Netherlands , said in the statement .
Satellite mental imagery gave scientist the first clue that the Ganges had been violently rerouted in the past , according to the command . Neville Chamberlain and her colleagues recognise what looked like an previous river channel running parallel to the Ganges roughly 62 miles ( 100 km ) south of Dhaka . The research worker then explored the neighborhood to pull together more evidence and found bands of moxie cut through the mucky ground in several locations . They identified the band as seismites — erect layers of sand that " catch fire " when an quake shakes watery soils — and concluded that they had shape in a single event .
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Chemical analysis of the sand and mud revealed that the event , which the scientists deduct must have been a huge earthquake , took place 2,500 days ago .
Two separate mechanisms could have trigger off the temblor , harmonize to the study . The first is a seismically participating zone around the Shillong Massif mountains in northeastern India , where the Amerindic tectonic shell isscrunching up against the Eurasian photographic plate . The second is the subduction of the Indian Ocean crust beneath Bangladesh , Myanmar and northeast India . Both processes are occurring more than 110 miles from where the investigator encounter the seismites , which suggests the Ganges River - rerouting seism had a minimal magnitude of 7.5 to 8 , according to the study .
A2016 studyled by Steckler showed that both the Shillong Massif and the Indo - Burman subduction zona could trigger earthquakes of a similar magnitude again . Such a quake could impress around 140 million people , the study found .
