rockfall

noun

1. A quantity of rocks that has fallen from a cliff etc.

   “A 200-ton rockfall recently blocked the Machynlleth sidings, trapping several locomotives; a rock-slip on the approach embankment to Talerddig required expensive revetting last year; and on the coastal section to Barmouth an 80 foot-high stone revetment was completed some time ago at Friog; [...].”

   “Design work is now complete on the Parsons Tunnel North programme, which envisages a 209-metre rockfall shelter built from a jack-up barge as there is no road access.”