Mining Debris Buries Welsh Village Summary

  • Last updated on November 10, 2022

A heap of rock-debris tailings collapsed on the South Wales coal-mining village of Aberfan, killing more than 130 people and destroying an elementary school and several houses.

Summary of Event

At 9:15 a.m. on October 21, 1966, 117,000 cubic meters of colliery waste started into motion on the side of a tip heap 67 meters high in the mining village of Aberfan, near Merthyr Tydfil in South Wales. A flow-slide rapidly developed and traveled at 15 to 30 kilometers per hour about 500 meters down a 12.5-degree slope. About 75,000 cubic meters of debris came to rest on the lower slopes of the mound, but about 42,000 cubic meters traveled 100 meters farther into the adjacent village and came to rest in the streets as a wet deposit 7 to 9 meters deep. The slide was preceded by 6 meters of subsidence at about 9 to 12 meters from the crest of the mound. The sunken area promptly liquefied, and workers on the tip watched as a series of what they described as “dark, glistening waves” of supersaturated debris traveled downslope. Aberfan landslide (1966) Landslides Mining;accidents [kw]Mining Debris Buries Welsh Village (Oct. 21, 1966) [kw]Debris Buries Welsh Village, Mining (Oct. 21, 1966) [kw]Welsh Village, Mining Debris Buries (Oct. 21, 1966) Aberfan landslide (1966) Landslides Mining;accidents [g]Europe;Oct. 21, 1966: Mining Debris Buries Welsh Village[09000] [g]United Kingdom;Oct. 21, 1966: Mining Debris Buries Welsh Village[09000] [c]Disasters;Oct. 21, 1966: Mining Debris Buries Welsh Village[09000] [c]Manufacturing and industry;Oct. 21, 1966: Mining Debris Buries Welsh Village[09000] Davies, Sir Herbert Edmund Robens, Alfred

The flow-slide demolished two cottages, crushing their occupants. It went on to engulf and destroy a primary school (which was occupied at the time) and eighteen houses, and also damaged a second school and various other dwellings. None of the 144 people who were caught in the flow-slide survived: The dead included five teachers and 109 pupils of the Pantglas Junior School. Most of the children were between seven and ten years old. Seven other children died, and twenty-nine children and six adults were injured, some of them seriously. Sixty houses had to be evacuated, sixteen of them because they were damaged by mud from the flow, others because of the flood that ensued when water gushed across the site from a ruptured water main and from the base of the slide.

Aberfan had been founded in the 1870’s, when the Merthyr Vale Colliery Merthyr Vale Colliery was sunk in a picturesque valley draining the Brecon Beacons. The rows of small, terraced houses were home to about four thousand residents and constituted a village—not in the rural sense, but as an enclosed, self-sufficient community with a strong working-class identity and a common destiny bound up with the production of coal.

Because of the cost and technical difficulty of returning waste to the mine galleries (the “back-packing” technique), it was deemed expedient to dump it in conical mounds, or tips, around the shaft. Beginning in the 1920’s, seven of these tips were created at Aberfan. The last one, begun in 1958, caused the disaster. Despite their common origin, the tips were far from homogeneous. The fourth, for example, was created by a device called a Maclane Tipper, and the seventh was created by laying temporary railroad tracks for the trucks full of debris, which were then unloaded by crane. That was the procedure being followed on the day of the disaster. The first six tips were composed of mining debris, boiler ash, and coal debris, but tip 7 was made up of “tailings,” fine particles left after chemical processes and vacuum drying have extracted coal from a mined lode. At Aberfan, the tailings came from a coal filtration plant that had been in operation at Merthyr Vale Colliery since 1962, and they contained 39 percent ash and 6 to 8 percent moisture.

No geological or hydrological studies had been carried out before the tips were begun. Tips 1, 3, and 6 were situated on well-drained land, but tips 4, 5, and 7 were built over watercourses. Tip 7 was also situated on an outcrop of the Pennant Sandstone, from which water issued in a spring. The tailings that made up this tip were completely uncompacted and low in density, 4.5 kilograms per square meter. That meant that water could decrease the volume of the tailings by 16 to 18 percent and cause liquefaction, the physical transformation from a granular solid to a viscous liquid. Merthyr Mountain, situated behind Aberfan, has a comparatively high annual rainfall (about 150 centimeters); between 1952 and 1965, Aberfan was flooded eleven times to depths of 60 to 210 centimeters.

In 1966, the residents of the village were more worried about floods than about a possible spontaneous collapse of the tip. The National Coal Board had given its assurances that both problems were under control. At that time, engineers did not expect flow-slides to occur in material as coarse as mine tailings, yet in December, 1939, a rotational slide had occurred in loose, water-saturated tip material at Cilfinydd Common, a short way south of Aberfan. In two or three minutes, a huge slide of debris between 2.5 and 7.5 meters deep had traveled more than four hundred meters downslope and across a busy main road. No vehicles were caught in the flow-slide, but the weight of the debris crushed the road into small particles, which became saturated by the water that had accumulated at the base of the tip.





In the 1960’s, Britain produced 60 million tons of colliery waste per year, including 5 million tons of tailings and slurry (small particles of coal saturated with water). Few constraints and regulations governed the widespread practice of tipping such debris, and there was a high, though unrecognized, risk of collapse. Indeed, flow-slides occurred at Aberfan on tip 4 in October, 1944, and on tip 7 in the autumn of 1963. Between 1963 and the catastrophe in 1966, material continued to be tipped onto the scar of the slide on tip 7.


The disaster was followed by a massive reaction; supplies and assistance arrived at the site in unmanageable quantities. A trust fund set up in late 1966 accumulated about £1,750,000 in donations from more than forty countries; it was used to compensate victims for material losses, to construct a memorial to the disaster, and to finance the construction of a new community center. It could do little, however, to mitigate the intense and prolonged sense of loss and bereavement of a tight-knit community that had lost almost an entire generation of its children.

Initially, the Welsh Office Welsh Office, British of the British government was reluctant to do more than clean up the debris and seek compensation for the victims from the National Coal Board, National Coal Board, British which refused to admit liability until this had been clearly established by a tribunal. Under great pressure from the residents of Aberfan and their elected political representatives, the government eventually appropriated £3.5 million to remove all the tips from Aberfan. The tribunal eventually exonerated the Merthyr Tydfil Corporation but found nine officials of the National Coal Board guilty of gross negligence. It proved impossible under British law to prosecute them, and the chairman of the National Coal Board, Lord Alfred Robens, who bore ultimate responsibility for the disaster, did not resign.

The Aberfan disaster exposed the fact that there had been no plans or surveys of the seven tips and no control over the process of creating tips. As often happens, legislation was hastily introduced after the event, but the tribunal concluded that even without legal requirements concerning public safety, the National Coal Board had been at fault for allowing waste to be deposited without proper supervision and adequate monitoring. This conclusion was reached on the basis of data provided by Alan Bishop Bishop, Alan of Imperial College, London, who built a laboratory model of the Aberfan tip, in which he simulated the effect of over-steepened slopes, saturation by rainfall, and internal discontinuities resulting from the pattern of dumping; his study underlined the need for the formulation and application of regulations to govern the construction and maintenance of large, artificial landforms.

From the start the Aberfan landslide caught the imagination and stirred the consciousness of Britons and foreigners, all the more so as there was a prevailing feeling that miners pay a disproportionately high price for the wealth and comfort of the rest of society. Like mining communities everywhere, the residents of Aberfan were accustomed to living with the constant risk of tragedy, but they were unprepared for the expression of massive solidarity. Many did not react kindly to the limelight and the sensationalist news reporting, but the sense of community in Aberfan did not disappear even after the departure of the politicians, officials, and journalists. The bereaved families had been given £5,000 each to move away from Aberfan, but few did so. All who remained were bound by the tragedy.

Excavation, dumping, construction, and subsidence are widespread consequences of human use of the land surface and the earth’s resources. As long ago as 1912 a study revealed that the human species is a more active geomorphological worker than any other natural agent; the effects at this point are lesser only because people have been creating earthworks for but a fraction of the time that nature has. Much remains to be learned about the behavior and stability of constructed landforms and about the risks they pose to human settlement.

The landslide at Aberfan illustrated that disasters result as much from human vulnerability as they do from physical impacts. The Sherman landslide, for example, which was set in motion in the 1964 Alaskan earthquake, involved 270 times more debris than the Aberfan slide and moved four to seven times faster. It occurred in an uninhabited valley and caused no damage and no deaths, thus remaining no more than a geological curiosity. In contrast, in Aberfan a relatively minor physical impact led to a catastrophe because it coincided with a situation of vulnerability and a lack of preparedness. Aberfan landslide (1966) Landslides Mining;accidents

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Aberfan Tribunal. Report of the Tribunal Appointed to Inquire into the Disaster at Aberfan on October 21st, 1966. London: Her Majesty’s Stationery Office, 1967. The short but widely read account of the official inquiry into the disaster. It is frank and lucidly written, with carefully selected details and a strong moral stance.
  • citation-type="booksimple"

    xlink:type="simple">Austin, Tony. Aberfan: The Story of a Disaster. London: Hutchinson, 1967. A factual account of the disaster from the impact to the conclusion of the tribunal. Well reported and rich in detail.
  • citation-type="booksimple"

    xlink:type="simple">Bishop, Alan W. “The Stability of Tips and Spoil Heaps.” Quarterly Journal of Engineering Geology 6 (1973): 335-377. A general review of the problem of slope stability on artificial mounds, with examples from Britain (including Aberfan) and the United States. A very readable survey of the problem, with some technical details and photographs.
  • citation-type="booksimple"

    xlink:type="simple">England, Edward O. The Mountain That Moved. London: Hodder & Stoughton, 1967. Journalistic account of the disaster and its immediate aftermath; religious in tone, but without a consideration of the wider implications of the disaster.
  • citation-type="booksimple"

    xlink:type="simple">Miller, Joan. Aberfan: A Disaster and Its Aftermath. London: Constable, 1974. Chronicle of the event and of the social, economic, and political ramifications. Includes sensitive accounts of the lives of the survivors, their suffering, and the struggle for justice.
  • citation-type="booksimple"

    xlink:type="simple">Rapoport, I. C. Aberfan—the Days After: A Journey in Pictures. Cardigan: Parthian/National Library of Wales, 2005. Photographic study of the aftermath of the Aberfan disaster vividly documenting its effects upon the community. Bibliographic references.

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