If falling rocks are big enough and hit hard enough, they can create a blast so intense that the rocks are pulverised into powder. Such extreme rockfalls are followed by a shockwave that can snap trees hundreds of metres away.

“They’re extremely weird phenomena, which have been somehow overlooked,” says Fabio De Blasio of the University of Milano-Bicocca in Italy.

The first known example took place in Yosemite National Park, California on 10 July 1996. Two large masses of …