3RD SHIFT TRIED TO START THE BELTS AT APPROX. 5:30 AM AND THEY WOULDNT START. THEY BHOUGHT A BELT SWITCH MAY HAVE BEEN LEFT OFF SO THEY STARTED WALKING THE BELTS. AT APPROX. 7 AM THEY FOUND A ROCK FALL OCCURRED 57 BREAKS INBY THE #4 HEAD-DRIVE IN THE BELT ENTRY. THE FALL MEASURED APPROX. 80'X20'X10'.