In the early morning hours of April 29, 1903, a massive section of limestone broke away from the summit of Turtle Mountain in Alberta, Canada, and crashed into the valley below where approximately 600 people were sleeping in the community of Frank. The bustling coal mining town was founded just two years earlier, and was located at the base of Turtle Mountain. In less than 100 seconds, the rockslide obliterated the eastern section of the town killing close to a hundred people. The dimensions of the rock mass that fell was staggering — it was a kilometer long, nearly half a kilometer wide and 150 meters deep. It weighed an estimated 90 million tons. Because of the massive weight and depth of the rubble, no attempt was made to recover the bodies which still remain buried under 45 meters of rock.

Tourists get their pictures taken among the huge boulders at Frank, Canada. About 80 bodies are still buried under these rocks. Photo credit: Peter/Flickr

Turtle Mountain, which stands immediately south of Frank, consists of an older limestone layer over top of softer materials such as shale and sandstone. During the mountain building process the once horizontal layers of limestone had folded until they were almost vertical — a very unstable orientation. Furthermore, a major thrust fault runs through the mountain that had weakened the layers of rock within the mountain. Large surface cracks along the summit of the mountain allowed water to enter deep within Turtle Mountain. The water continued to eat away at the limestone and the repeated freezing and thawing action of water and ice caused the cracks to widen, creating even more instability. Finally, erosion by water and ice of the softer sandstone and shale layers on the lower half of the mountain beneath the older layers of limestone had created a significant overhang. Turtle Mountain was just waiting to fall. Somehow, the indigenous Blackfoot and Kutenai peoples knew about the mountain's instability and refused to camp in its vicinity. They called it "the mountain that moves".

When coal was discovered on Turtle Mountain, the Canadian-American Coal and Coke Company opened a mine and the town of Frank — named after the owner Henry Frank — was established for the miners and employees of the company to stay. The town had a gala opening on its foundation day September 10, 1901 featuring speeches from territorial leaders, sporting events, a dinner and tours of the mine and planned layout for the community. The Canadian Pacific Railway ran special trains that brought people from neighboring communities to celebrate the event.

View from the north shoulder of Turtle Mountain. The Frank townsite was where the old road leaves the slide on the left. Frank Lake was created by the slide. Photo credit: Keith McClary/Wikimedia

Turtle Mountain fell less than two years later. Immediately following the slide, people started blaming the coal mining company for the disaster, which might not entirely be untrue. While the primary cause of the rockslide was the unstable geological structure of the mountain, later studies suggested that the mountain had been at a point of "equilibrium", and even the smallest deformation such as that caused by mining would have triggered a slide.

The mine reopened within weeks of the disaster and Frank’s population not only recovered but grew. Although many people left the town fearing another massive rockslide, many stayed and Frank grew from 600 inhabitants at the time of the slide to a population of 1,178 by 1906. A new residential subdivision was developed just northwest of the original town across the railway tracks to accommodate the growing population. There was now a new zinc smelter, a new three-story hotel and a small zoo. But fears of a second slide continued to persist. Finally in 1911, the government ordered the people to move because it was too risky. Over the next several years the town was slowly dismantled. The mine itself closed in 1917.

Today, Frank is a quiet residential community of about 200 people. Rubble still covers about 300 hectares of the valley drawing roughly 100,000 tourists to the area every year. The Frank Slide site was designated a Provincial Historical Resource in 1977, and in 1985 an interpretive center was opened that explains to visitors the Frank Slide and the coal mining history of the region.

Photo credit: Paul Hansen/Flickr

Photo credit: Al/Flickr

Photo credit: Ken Eckert/Wikimedia

Photo credit: Library and Archives Canada/Flickr

Turtle Mountain before the slide. Photo credit: www.wambold.ca

Turtle Mountain after the slide. Photo credit: www.wambold.ca

Frank and Turtle Mountain after the 1903 landslide; photograph taken in 1911. Photo credit: Canadian Disasters

The devastation of Frank, taken from Turtle Mountain in 1911. Photo credit: Canadian Disasters

Aerial view of the 1903 Frank rockslide, taken in 1922. Photo credit: Canadian Disasters

View of part of the town of Frank, Alberta, and the east part of the slide, photograph taken in 1911. Photo credit: Canadian Disasters

Sources: Wikipedia / Alberta Culture and Tourism