Canada's Deadliest Rockslide

On April 29, 1903, 30 million cubic metres of limestone crashed from the summit of Turtle Mountain and buried part of the sleeping town of Frank.

The rock mass that fell was 150 metres deep, 425 metres high  and one kilometre wide.

The bustling town of Frank was home to approximately 600 people in 1903. Most of the roughly 110 individuals who lived in the path of the slide were killed.

The primary cause of the Frank Slide was the mountain's unstable geological structure.

Underground coal mining, water action in summit cracks and unusual weather conditions also contributed to the disaster.

The rock likely moved as a dense, fast-flowing liquid, covering three square kilometres of the valley in 90 seconds.  The debris averages 14 metres in depth, but in some areas it is up to 45 metres deep.

The buried section of railway was rebuilt three weeks after the slide.  A road was completed through the slide in 1906 and later improved during the 1920s.  Before this road was finished, people had to travel over a rough road built around the north end of the debris.  This temporary route passed through what is now the Frank Slide Interpretive Centre parking lot.  The section of Highway 3 through the slide was constructed in the mid 1930's.

The elevation of the north peak of Turtle Mountain is 2,109 metres and the south peak is 2,200 metres high.  The coal seam was developed and mined between 1900  and 1918; it was about 4.5 metres thick and nearly vertical, pitching at approximately an 82 degree angle.