IN GEOLOGY, UNLIKE business, nothing is too big to fail. Mountains offer the most spectacular example. Pushed up by the crumpling of Earth’s crust following the collision of tectonic plates, they could in theory keep rising almost indefinitely. In practice, they do not. A suite of geological processes—including the grinding of glaciers, the gentle impact of rain, and forcible cracking by freezing and thawing of water—erode them down to size.

In a paper published in Nature Jérome Lavé, a geologist at the University of Lorraine, describes another, much more spectacular mechanism. Dr Lavé has collected evidence suggesting that, in around 1190, an enormous landslide slashed perhaps 500 metres from the height of Annapurna IV, a mountain in the Himalayas that stands about 7,500 metres high today. If he is right, it would be one of the biggest landslips ever recorded. The falling mountain top would have displaced up to 27 cubic kilometres of rock—roughly enough to bury the entirety of Manhattan to about the height of the Empire State Building.