A densely forested island measuring nearly 150 metres long and 75 metres wide has appeared and disappeared twice within weeks on Williston Lake, a large reservoir in British Columbia, Canada. The island’s sudden emergence and disappearance have puzzled locals and experts alike.
The phenomenon was first observed in August when a boater captured video footage showing approximately 100 trees swaying on the island’s surface amid the reservoir’s waves. Several days later, the island vanished, only to reappear on Monday roughly 20 miles from its initial location. The shifting land mass has drawn significant attention due to its size, composition, and unusual mobility.
Williston Lake, created by the flooding caused by the W.A.C. Bennett Dam in the early 1970s, spans about 1,700 square kilometers, making it the largest freshwater body in British Columbia. Bob Gammer, a spokesperson for BC Hydro—the Crown corporation responsible for operating the dam and reservoir—said the discovery was initially hard to believe. Verification through satellite imagery and eyewitness accounts confirmed the island's existence, floating on the main body of the lake approximately 60 miles west of the dam.
BC Hydro officials believe the island formed over several years as trees and vegetation grew on accumulated woody debris in sheltered areas along the reservoir’s shoreline. Similar floating islands have been documented elsewhere, such as the well-known Forty Acre Bog on Wisconsin’s Lake Chippewa, where peat, roots, and trees form a mobile landmass.
The island currently hosts a mix of coniferous and broadleaf trees, as well as birds and small animals. Observers speculate that the exposed root systems in the water might provide habitat for fish. Gammer compared the island’s growth environment to hydroponic conditions, with well-nourished trees thriving on decaying organic matter submerged in water. He noted that the reservoir’s water levels are the highest in 14 years following an abundant winter snowpack and steady summer rainfall, which may have contributed to the island’s buoyancy and displacement into open water.
Between sightings, it is possible the island drifted back toward the shoreline, which could explain its apparent disappearance. Gammer emphasized that the island has not sunk but may be temporarily anchored in more sheltered parts of the lake. The age of the trees remains uncertain, though local residents speculate some could be decades old.
While some residents, including Rocky Avery who initially shared footage on social media to warn others of a potential navigation hazard, expressed enthusiasm about the island, BC Hydro officials caution against attempting to walk on it. Gammer described the island’s structure as “very unstable,” consisting of a fragile layer of logs beneath the trees that sway with the waves, posing a safety risk.
The reappearance of the island has sparked local interest and social media commentary, with some users humorously referencing current political tensions between Canada and the United States. Nonetheless, the island remains an unusual natural occurrence in the region’s landscape, emblematic of the dynamic interplay between human-made reservoirs and natural ecosystems.