What caused the Frank Slide?
The primary cause of the Frank slide was the unstable structure of Turtle Mountain. A thrust fault runs through it, and eroding sandstone and shale beneath older limestone plus deeply eroded cracks in the limestone on the top would have caused the rock to fall eventually. Secondary causes include coal mining inside the mountain and dramatic changes in weather conditions – a quick freeze – that night. Secondary causes were coal mining inside the mountain and dramatic changes in weather conditions – a quick freeze – that night.
