Several factors led to the Frank Slide . A study conducted by the GSC immediately following the slide concluded that the primary cause was the mountain 's unstable anticline formation ; a layer of limestone rested on top of softer materials that , after years of erosion , resulted in a top @-@ heavy , steep cliff . Cracks laced the eastern face of the mountain while underground fissures allowed water to flow into the mountain 's core . Local Indigenous peoples of the area , the Blackfoot and Ktunaxa , had oral traditions referring to the peak as " the mountain that move . " Miners noticed the mountain had become increasingly unstable in the months preceding the slide ; they felt small tremors and the superintendent reported a " general squeeze " in the mountain at depths between 1 @,@ 100 metres ( 3 @,@ 600 ft ) and 1 @,@ 500 metres ( 4 @,@ 900 ft ) . They found that coal broke from its seam ; it was said to have practically mined itself .