Sixty years after the Aberfan disaster, a reposted guide from AGU Eos recounts how a coal waste tip on a slope above the Welsh village failed on the morning of 21 October 1966. Workers at Tip Number 7 noticed the ground had shifted by about three metres, but had no telephone to raise the alarm quickly. Within hours, the spoil turned into a fast-moving wave of slurry that travelled roughly 500 metres and struck Pant Glas Junior School and nearby houses.
The landslide involved about 105,000 cubic metres of material moving at 17 to 34 km/h. It killed 116 children and 28 adults, and injured 35 more. The last survivor was recovered less than two hours after the slide, but survival chances in such debris were low. The source includes eyewitness accounts from the tipping crew, who described the ground rising and then turning into a wave of "muck, slush and water" rushing toward the village.
The official tribunal that investigated the disaster was deeply critical of the National Coal Board. It found that the Board had neglected the stability of its tips and bore overall responsibility for the failure. The report also regretted that the Board did not admit blame early, instead denying responsibility through much of the hearing before finally accepting it. The source notes that the post is a repost of older blog entries, with images not yet restored.