The summit of Sgùrr na Ciste Duibhe is remarkable in having slipped down by 5-10 metres from the Glen Shiel Fault, which runs just behind it on the north-east. The fault trace cuts the east ridge at the awkward 'bad step' and crosses the north shoulder at the 'Red Top', these outcrops being linked by a fretted crest. Route-finding along the Five Sisters ridge can thus be difficult in mist and snow. The slippage has also created dangerous fissures up to 10 metres deep on the upper south face, including the eponymous 'black chest'. Part of the slippage collapsed, probably 10.000 years ago, leaving a long cavity scar, creating the knoll for the 1719 battle, and temporarily damming the river which has cut through it at the defile of the Pass of Glen Shiel