LANDSLIDES AND ROCK AVALANCHES 



287 



important coal-mining center. The moun- 

 tain itself is an exceedingly precipitate 

 series of cliffs of limestone, sandstone, 

 and shale rising over 3,000 feet above the 

 river. 



At dawn on April 29, 1903, a huge 

 rock-mass nearly half a mile square, and 

 from 400 to 500 feet thick in the center, 

 suddenly broke loose from the mountain 

 and crashed with terrific violence into 

 the valley beneath, overwhelming every- 

 thing in its course. The great mass, 

 broken into innumerable fragments by 

 the fall, plowed through the river bed, 

 crossed the valley and hurled itself up 

 the opposite slopes to a height of 400 feet. 

 Within a minute or a minute and a half 

 over a square mile of pleasant valley was 

 covered with a rock-flow from 3 to 150 

 feet deep. Most providentially the 

 greater portion of the town lay outside 

 the course of the slide ; nevertheless, 70 

 people were killed. 



One man, hearing the noise of the 

 rock-fall, rushed to the door of his house 

 in time to see the slide flash by, only a 

 few feet in front of him. Its passage 

 seemed practically instantaneous. An- 

 other man, hearing a great noise, looked 

 in time to see the fall of the mountain 

 and almost instantly the spread of the 

 material over the valley like a viscous 

 fluid. Yet some of the rock pieces con- 

 stituting the "flow" are 40 feet square. 

 A gang of coal miners was entombed in 

 the coal mine by the stoppage of the en- 

 trance by the debris, but they dug them- 

 selves out through the roof. 



Two and a half miles were traversed 

 by the slide, from the top of the creek on 

 the mountain to the foot, while the ma- 

 terial dislodged is estimated at 40,000,000 

 cubic yards. This is over three times 

 the size of the Elm slide. While it is 

 believed that the coal mining in the val- 



ley may have hastened the slide, the pri- 

 mary cause was undoubtedly the struc- 

 ture of Turtle Mountain. The huge 

 mass was in a state of unstable equi- 

 librium, and possessed a weak base. 



Although this great slide was a suffi- 

 cient catastrophe to make men gasp 

 throughout the land, especially those liv- 

 ing with overshadowing mountains as 

 their daily companions, it might have 

 been far worse. But one peak of Turtle 

 Mountain slipped. The steep shoulder 

 of the mountain which looks directly 

 down upon the town of Frank stood 

 firm. Had this, too, gone, the entire 

 community would have been smashed to 

 atoms in the twinkling of an eye, and 

 none left to tell the tale. 



Moreover, there is likelihood that such 

 a catastrophe may happen at almost any 

 time. The town of Frank, according to 

 the Canadian Geological Survey,* might 

 exist on its present site uninjured for 

 ages, but there will always be a possibil- 

 ity of a second destructive slide. The 

 fact that the north shoulder withstood 

 the shock of the first slide is no proof 

 that it is too solid to fall. Almost the 

 same conditions exist on the north peak 

 and shoulder today that obtained in the 

 central peak before it broke away. Unu- 

 sually heavy rains, rapid changes of tem- 

 perature, a slight earthquake, or falls in 

 the coal mine at the base of the mountain 

 following the closing of the chambers, 

 perhaps long after the people have lost 

 all dread of the mountain, may snap the 

 supports which retain this huge mass in 

 place and precipitate it upon a career of 

 destruction compared to which that of 

 the recent slide would be child's play. 

 The suggestion seems a wise one that 

 the people of Frank move a short dis- 

 tance up the valley to a point of safety. 



* Report great landslide at Frank, Alberta. 



