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For centuries the quarries in the slope of the "Tschingelberg" had provided valuable schist-plates and with the introduction of public school (and chalk boards) in the Swiss canton of Glarus the demand increased exponentially.
Between the years 1861 to 1878 the mining was done by few people, but to satisfy the demand the local administration of the nearby village of Elm took over the business. 200m above the village a semi-open tunnel, 180m long and 65m deep, was excavated into the mountain, destabilizing the slope it caused some minor rockfall events and some fissures opened. However in 1876 more than 300m above the quarry a larger fissure appeared and until summer 1881 the fissure continued to growth. Still the quarrying with explosives, causing strong vibrations in the entire mountain, continued.
The weather in August and September 1881 was very rainy and the water percolated into the open fissures. Everywhere around the quarry new fissures and rockfalls were noted. The local authorities closed the quarry and nearby houses were evacuated, however the situation was not regarded dangerous for the village of Elm.
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Then, September 11, 1881 a local teacher, Mister Wyss, observed a massive failure of the weakened slope of the Tschingelberg.
"At afternoon 4 o'clock I stood, with the pocket watch in my left hand, on the open window observing carefully the movements of the mountain. Continuously smaller portions felt from above, from the middle and from below, the uppermost firs of the forest began to move backwards, falling into the fissure.
The first greater rockfall occurred at exactly 5 o'clock and 15 minutes; the rock masses felt into the valley at the speed of a flash. They covered the quarry … and the schist filled the huts [...] and the hotel of the Martinsloch, evacuated by the inhabitants two days before. Also the rivers Tschingel and Ramin were buried.
The second, even larger rockfall occurred seventeen minutes later, at 5 o'clock and 32 minutes, rushing with high speed above the earlier deposits.
Again 4 minutes later the third rockfall occurred. The enormous mass flowed through the air. The earth surface trembled; I run out from the house and followed the street. After 20 passes the houses behind me felt down. I estimate, according with other credible eyewitnesses, that the rock masses in 2 to 3 minutes reached the end position, where it now lays."
Fig.1. The landslide of Elm, figure from Geographisches Lexikon der Schweiz (1902-1910), image in public domain.
The landslide of Elm is notable because of such reports, describing the movement like "a flow" of incredible speed, flowing above the ground and even upwards the slopes. This particular behavior of rock flows is still today poorly understood and one of the most intriguing features of the physics of mass movements.
Fig.2. Map of the landslide of Elm, figure from Geographisches Lexikon der Schweiz (1902-1910). Note the ridges on the landslide remembering flow structures (image in public domain).
The landslide of Elm killed 115 people. Almost no bodies were recovered and only 13 victims could be identified, based on the cloths they were wearing that day.
Bibliography:
HÖFLER, H. & WITT, G. (2010): Katastrophen am Berg - Tragödien der Alpingeschichte. Bruckmann Verlag: 144