Turtle Mountain Landslide – Alberta, Canada – April 29, 1903

Excessive amounts of coal were removed from the mountain without adequate protection from overlying layers of rock. As a result, seventy people in the small town of Frank were killed.

Early in the morning of April 29, 1903, a gigantic slab of limestone rock broke away from Turtle Mountain at the 3,000-foot level. It weighed about seventy-five million tons, was half a mile wide, and as it crashed down the side of the mountain it broke apart into huge boulders. With the momentum acquired in descent this mass of rocks cut across the valley of the Old Man River at the foot of the mountain, continued up the slopes on the other side of the valley, and destroyed most of the town of Frank. Seventy of the town’s residents were killed. Debris from the landslide can still be seen today. Turtle Mountain was built up in the ancient past with sedimentary rock, mainly limestone. Geological structures of this kind are a common setting for coal deposits.

Layers of coal seams are found alternating with layers of rock. In this location mining the coal was especially easy as the seams slanted downward toward the face where the mine entrance was. Gravity did most of the work, and very little blasting was needed. One thousand tons of coal was being extracted daily within the first year of operation but, despite some telltale signs, little thought was given to the effects of the work on the stability of the mountain. On any given shift seventeen miners extracted coal somewhere along a ten-foot-wide seam that, after a year, stretched back for 5,000 feet into the mountain. Early in 1903 miners noticed, as they came to work, that some of the supporting pillars were badly splintered, pillars that had been in good shape at the end of the previous day’s shift.

With today’s understanding of geology it is easy to explain what was happening, but that was not obvious in 1903. The sedimentary formations of rock that constituted Turtle Mountain form a series of horizontal strata. Some of these may be coal, some limestone. Any weakening in one of these layers can trigger a slide, allowing upper layers of rock to cascade downwards along the general slope. In Turtle Mountain this slope was quite steep so any movement would be accelerated by gravity. When the landslide occurred, the mine entrance was blocked, leaving seventeen men trapped inside. Three other men who had just left the work area to take loads of coal to the entrance escaped the trap that caught the seventeen men but they were overtaken by the cascading material of the landslide and were never seen again, buried forever under tons of rock. As the reality of the event became obvious to the seventeen men inside, they ran to the mine entrance, only to find that it was now a heap of shattered timbers and fallen rock. They were now cut off from the outside world at a point three hundred feet inside the mountain.

Before their lamps faded they examined their options. First they made their way to a lower level, hoping that the exit there was still open, only to find that the river had flooded that entrance and was rapidly backing up into the mine. They realized that closures of entrances together with widespread flooding might have already cut off their supplies of fresh air. They had to act fast before their small amounts of fresh air would soon be used up. Hoping that they were sufficiently close to the surface they decided to try to cut a tunnel upwards and outwards. To remove the mass of material at the entrance was impossible.

Over a period of twelve hours they worked steadily in shifts and finally came out on the face of the mountain to stare at the destruction below. The scene before their eyes was terrifying. Where their homes had been there was now a mass of white limestone rock. All but a part of the town’s center was gone. The falling rock had swept across a mile of intervening ground before landing on the town of Frank. A milelong section of double-track railway line, the main highway, and the coalmining plant had been destroyed. Old Man River began to back up and form a lake behind the mass of rock. A freight train entering Frank at the moment of the slide was lucky enough to escape. It arrived as the landslide began to move down the mountain and it was able to speed past the town before everything crashed around it.

The rock mass that constituted the landslide was shattered by impacts against the side of the mountain as it came down. Long before it reached the valley below it had been transformed into several large boulders plus a myriad of fragments of all sizes so, in one sense, it was no longer a landslide. It began as one but ended up as something else. The different pieces of rock traveled for one or two miles from the base of the mountain over uneven ground by a series of skips and jumps until it reached the 400-foot level on the other side of the Valley of the Old Man River. There was no way of escape for the residents of Frank before the rocks reached it. The total amount of time involved was less than a minute. The history of the landslide can be read today in the indentations made on rocky surfaces by bouncing boulders as they made their way across the valley.

As the mountain was examined after the event it became clear that the dislodged slab of rock had broken away along lines that were ancient fissures formed by successive faulting throughout the long history of the buildup of the mountain to its size in 1903. One man who kept a boarding house in Frank woke up when he heard the sound of the slide and rushed to the entrance of his house. He was just in time to see the masses of rock fragments sweep past him at a distance of a few feet. Another workman who lived in one of the cottages that was destroyed woke up and, before he could do anything, was aware that his cottage was rocking backwards and forwards. The only thing he remembered after that was that he was forty feet from the house with his bed lying twenty feet farther away. His leg was broken and he had been wounded in several places by small rocks.

The story was similar with many of the others who survived. In one home when a couple and their children were asleep there was no time to escape before their home was shattered and they somehow survived, albeit with numerous injuries. The first action of both the Mining Company and the government of Canada inspectors was the assessment of the cause of the disaster. Some accusations had already been made such as that the mining company had not provided adequate support of the higher strata, thus reducing pressure on them and so endangering their stability. The Mining Company insisted that the mine was in first class condition before the landslide and that the few instances of movements in the coal walls were normal for any mine.

A senior miner pointed out that new movements of walls were observed from time to time in the six months before the landslide, each one occurring between one and three in the morning, presumably when temperatures were at their lowest. This miner described the experience of these movements as being like a ship’s violent shaking when struck with a large wave and he added that they alarmed many of the workers. Some left the mine because of the shaking. Weather records were examined and it was established that the day before the landslide was warm and wet and the night that followed recorded temperatures far below anything experienced throughout the previous six months. The weather factor, it was agreed, was one causal factor. Water expands and contracts wherever there are places that allow water in.

These are all normal processes of nature that will be at work everywhere whether or not there is human intervention. Mining inevitably creates new spaces into which water can enter. In addition, even with the maximum number of supporting pillars, the removal of a thousand tons of coal daily changes the density or weight of one part of the mountain and, as was the case in the early weeks of April 1903, if there is a sudden increase in the amount of coal being removed every day, this change in the distribution of weight on he mountain accelerates the strain on its stability. The fact that the mountain was composed of a series of horizontal layers of rock and coal makes it particularly sensitive to any movement that would interfere with its stability.

Since the coal seams sloped parallel to the mountain’s layers there was a constant challenge facing the Mining Company to ensure that the supporting pillars were always doing their work. The government inspectors concluded that the landslide could not be explained by a single cause. A combination of factors, acting together, led to the disaster. Nevertheless, it is difficult to get away from the conviction that the coal mining operations were the main cause, especially when it was noted, after the event, that the location of the edges of the break where the mass of rock came away from the mountain coincided exactly with the upper limit of operations of the coal workings. The coal was being removed from within huge spaces measuring more than three hundred feet in height.

Loosened coal offers very little resistance to the enormous pressure from above, that is to say the pressure from the rest of the mountain, so inevitably there must have been some movement from time to time along the roof of the coal seams. The Mining Company was well aware of the reports brought back by the miners regarding the splintering of the wood pillars that supported the overhanging rock and this should have persuaded the company to install more and stronger timbers. When coal mining resumed at Frank years later, safety features that should have been there in 1903 were firmly in place. After 1903, some people began to move away from the mountain, fearing another slide. The town did expand over the years, but there was nowhere for it to grow eastward, so the town of New Frank took root just northwest of the original town.

In 1911, a Royal Commission study found the North Peak of Turtle Mountain to be structurally unstable. In reaction to this study, the government ordered everyone out of that section of Frank. People moved to other areas and many settled in New Frank, the present location of Frank. Today, the remains of the old town of Frank and the rocks that came down the mountain in 1903 form a tourist attraction. Limestone rocks in depths ranging from 5 to 100 feet litter the entire area. There is an information booth beside the highway and a number of displays that re-enact the events of more than a century earlier.

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