Judgement Cliff rock avalanche (JCRA) occurred during the latter part of 1692, during which 131-181 x 106m3 of faulted Miocene white limestone with chert nodules and minor sandstones and mudrocks, on a 38° overdip slope was detached on the eastern bank of the Yallahs River near Llandewey. The rock mass failed by a combination of sliding, free fall and toppling, impacted and disintegrated near the base of the original slope and flowed downslope subsequently damming the Yallahs River. Seismic loading followed by high water pressure in clefts are thought to be the main triggers for the event. The debris travelled horizontal and vertical distances of 1.763 km and 0.44 km respectively, accumulating over an area of 1.09 x 106m2. The height/length and depth/ length values, hummocky surface topography and highly disintegrated nature of the deposit suggests that it was emplacement by flow of relatively dry debris.