Travel to Florida three days ago we were following a semi on the highway.We were no more than two hundred feet behind the truck and we see a boulder break off a cliff and roll down. It was the size of a VW Beetle. As it rolled down a piece broke off about three feet square a hit the passenger side of the cab. Truck jack knifed right in front of us. Driver ok and we were grateful I didn’t hit our car. Wife was driving and controlled the car as tire smoke and truck parts were flying everywhere. No damage to our car just a two hour delay to remove the truck.