 Turtle Mountain stands immediately south of Frank . It consists of an older limestone layer folded over on top of softer materials such as shale and sandstone . <unk> had left the mountain with a steep overhang of its limestone layer . It has long been unstable ; the Blackfoot and <unk> peoples called it " the mountain that moves " and refused to camp in its vicinity . In the weeks leading up to the disaster , miners occasionally felt <unk> from within the mountain , while the pressure created by the shifting rock sometimes caused the timbers supporting the mine shafts to crack and splinter . 
