Three things to watch for in this video. The first time you watch it, you’ll likely notice the boulder more than anything else. But if you watch it again, at the very beginning, look at the top of the image to see the boulder break off. And finally, just before the boulder hits, watch the lead car get violently jerked to the side.
Rock in the road
On the plus side, with all of the rain, no one would notice if the driver’s pants were already wet.
Erosion can be a nasty earthmover. Notice all the muddy water just before the boulder breaks free?
and before the event, look up at the volume of water in the waterfall.