The town of Frank and Turtle Mountain on April 30, 1903, one day after the slide

The Frank Slide was a rockslide that buried part of the mining town of Frank, Northwest Territories, Canada, on the morning of April 29, 1903. It occurred at 4:10 AM, when over 82 million tonnes (90 million tons) of limestone rock slid down Turtle Mountain within 100 seconds, obliterating the eastern edge of Frank, the Canadian Pacific Railway line and the coal mine. It was one of the largest landslides in Canadian history and remains the deadliest, as between 70 and 90 of the town's residents were killed, most of whom remain buried. Multiple factors led to the slide. Turtle Mountain's unstable formation left it in a constant state of instability, leading area native tribes to call it "the mountain that moves". Coal mining operations may have weakened the mountain's internal structure, as did a wet winter and cold snap on the night of the slide.

• http://en.wikipedia.org/wiki/Frank Slide