A Lake in Canada Got a Mysterious New Island. Then, It Disappeared—and Now It's Back

In late July, a boater on the West Coast of Canada noticed something strange. A huge, forested island was floating in British Columbia’s Williston Lake, one of the largest human-made reservoirs in the world. The mass—full of trees, birds and other animals—puzzled locals, who had never come across it before, and it was not on any maps.

In August, he posted photos and a video of the island on social media to notify people of its presence ahead of an upcoming fishing derby. Bob Gammer, a spokesperson for B.C. Hydro, the government-owned power utility that runs the reservoir, initially thought the photos and video were a hoax created with generative artificial intelligence.

The picture shows a green mass about 150 yards long and 75 yards wide—nearly the size of two football fields—floating in the water. The island then disappeared in mid-August. But just days ago, on August 31, B.C.

Hydro found it floating nearly 20 miles northwest of its original location. Update: we found the island.After briefly becoming one of Canada's most famous islands and making international headlines, the floating island on Williston Reservoir has been found.Turns out it wasn't missing. All told, it travelled about 30 km in 15 days… pic.twitter.com/h1GSvEcV25 So, what exactly is this vanishing island?

Gammer tells Adeel Hassan at the New York Times that the island may have formed from logs and woody debris that accumulated over many years along the shoreline. As the materials gradually decomposed, plants and trees took root and created a habitat. The mass of plant and animal life may have moved away from the shore because the reservoir is at its highest in 14 years, due to high winter snowpack and heavy summer rain, Gammer tells the Guardian.

Geologist John Joseph Clague of Canada’s Simon Fraser University tells the Canadian Press’ Nono Shen that “there is erosion occurring, and trees do collapse into the lake, but they don’t kind of form this very large mat of forested material.” For now, he remains perplexed by the mysterious mass. Whatever its origins, it’s “a phenomenal sighting,” says Rebecca Helm, a marine ecologist at Georgetown University, to Rebecca Dzombak at National Geographic. Similar floating islands have been spotted elsewhere in recent years, including a well-known one called the Forty Acre Bog in Wisconsin’s Lake Chippewa.