A team of scientists has found that a river in Canada has disappeared in just four days because of melting glaciers, The Guardian reported on Monday. The incident took place between May 26 and 29 last year, when the Kaskawulsh Glacier in Canada’s Yukon region suddenly diverted into another river. Led by the University of Washington Tacoma, the episode has been documented in a study that was published in the journal Nature on Monday.

The scientists described it as the first case of “river piracy” and said the incident illustrates how global warming can dramatically change the geography. “Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes. People had looked at the geological record—thousands or millions of years ago—not the 21st century, where it’s happening under our noses,” said lead author Dan Shugar, a geoscientist at the University of Washington Tacoma.

The Slims river has been carrying meltwater from the glacier into the Kluane river in the north, which flows into the Yukon river towards the Bering Sea. However, last year, after the glacier melted rapidly, its water drained southward into the Gulf of Alaska.

The team had been monitoring the retreat of the glacier for years now. “We went to the area intending to continue our measurements in the Slims river, but found the riverbed more or less dry,” said University of Illinois geologist James Best told The Guardian. He added that the delta top had become a dust storm. “In terms of landscape change it was incredibly dramatic,” said Best.

While the Slims has almost vanished, the Alsek river – a Unesco heritage site that is known for whitewater rafting – grew in size. Until 2015, both the rivers were more or less similar in size. But now the Alsek is 60 to 70 times larger than the Slims.