Researcher Jean Thie said he used satellite imagery and Google Earth software to locate the dam, which is about 850 metres (2,800 feet) long on the southern edge of Wood Buffalo National Park.
Average beaver dams in Canada are 10 to 100 metres long, and only rarely do they reach 500 metres.
First discovered in October 2007, the gigantic dam is located in a virtually inaccessible part of the park south of Lac Claire, about 190 kilometres (120 miles) northeast of Fort McMurray.
Construction of the dam likely started in the mid-1970s, said Thie, who made his discovery quite by accident while tracking melting permafrost in Canada’s far north.
“Several generations of beavers worked on it and it’s still growing,” he told AFP in Ottawa.
North American beavers build dams to create deep, still pools of water to protect against predators, and to float food and building materials.
Filed Under: Animal & Plant Life