Throwback Thursday - The Frank Slide
- Feb 5
- 2 min read
On April 29, 1903, at 4:10 am, 110 million metric tonnes of limestone rock broke off and slid down Turtle Mountain in south-west Alberta. It obliterated part of the town of Frank. The mass that fell was 3300ft wide, 1390ft high, and 490ft deep. It is estimated the rock was travelling 120 km/hr. The sound was heard over 200 km away.
Frank was founded in 1901 as a coal-mining town. By 1903 the permanent population had reached 600, and appx 110 people lived in the path of the slide. The death toll is uncertain but is believed to be about 90 people, possibly higher as a large number of transient workers were last seen camping at the base of the mountain. The bodies of most of the victims were never recovered and remain there to this day.
The railway line was repaired within weeks, and the mine reopened shortly after. In 1910 Frank reached a peak population of 1000 people. The remaining section of the town was relocated in 1911 amid fears of another slide. The closure of the mine in 1917 caused a large depopulation, and Frank ceased to be an independent community in 1979 when it was amalgamated into the Municipality of Crowsnest Pass. There are now about 200 residents of Frank.
The cause of the slide is unknown, but several theories were developed. Coal mining in the area may have weakened the mountain, and weather may have contributed. Local Indigenous populations stated that the mountain was always unstable; they referred to it as “the mountain that moves” and refused to camp in the area. In the weeks leading up to the slide miners reported rumblings within the mountain, coal breaking from its seams, and mine support timbers shifting and cracking. Turtle Mountain consists of a hard limestone layer on top of softer sandstone and shale. At the time, erosion had left the mountain with a steep overhang of its limestone layer.
Two new peaks were created on the mountain – a south peak and a north peak. Geologists believe another slide will occur, likely from the south peak. Turtle Mountain continues to move a few millimetres per year. The mountain is now thoroughly monitored; over 80 monitoring stations have been placed on the mountain.
The Frank Slide remains the deadliest landslide in Canadian history and was the largest until the Hope Slide in 1965. It was never removed; with clearances for roads and the rail line the rubble remains in place. It is now a designated provincial historic site and houses a comprehensive interpretive centre.
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