 In the early morning hours of April 29 , 1903 , a freight train pulled out of the mine and was slowly making its way towards the <unk> when the crew heard a <unk> <unk> behind them . The engineer instinctively set the <unk> to full speed ahead and <unk> his train to safety across the bridge over the Crowsnest River . At 4 : 10 am , 30 million cubic metres ( 82 million tonnes ) of limestone rock broke off the peak of Turtle Mountain . The section that broke was 1 @,@ 000 metres ( 3 @,@ 300 ft ) wide , 425 metres ( 1 @,@ 394 ft ) high and 150 metres ( 490 ft ) deep . Witnesses to the disaster claimed it took about 100 seconds for the slide to reach up the opposing hills , indicating the mass of rock traveled at a speed of about 112 kilometres per hour ( 70 mph ) . The sound was heard as far away as <unk> , over 200 kilometres ( 120 mi ) north of Frank . 
