Beinn Alligin has a great cleft known as Eag Dubh na h-Eighe Achd caused by a rockslide in Britain around 3750 years ago.
One of the most prominent features of Beinn Alligin is a great cleft known as Eag Dhubh na h-Eigheachd (black gash of the wailing) or Leum na Caillich, which cuts into the ridge south of the summit. It occurred around 3750 years ago and is around 3.5 million cubic metres in volume. It is the scar of the most spectacular rockslide or rock avalanche in Britain, which runs out into the corrie of Toll a' Mhadaidh Mor. 
