It was foggy on the morning of October 21, 1966.

Not that that was unusual for the small Welsh village of Aberfan. It had been raining for weeks, but that wasn’t unusual either for an area that received over 60 inches a year. It was dreary and misty, yes. But also full of excitement.

Because, for the pupils of Pantglas Junior School, it was the last day before their half-term holiday. It would begin at midday, if only they could make it through just a few more hours of school. Head teacher Ann Jennings knew her students were anxious; morning assembly was full of titters and restless bodies.

And, at 9:15 am, the sound of distant thunder.

Thunder turned out not to be thunder at all.

As the sound grew louder and louder, eight-year old Gayle Minett recalled that “all the school went dead. You could hear a pin drop. Everyone was petrified, afraid to move. Everyone just froze in their seats…the sound got louder and nearer, until I could see the black out of the window. I can’t remember any more but I woke up to find that a horrible nightmare had just begun in front of my eyes.” 

The distant rumble turned into roar as a tidal wave of coal waste 40 feet high slammed into the school, filling classrooms and burying those inside underneath 140,000 cubic yards of coal waste. Unbeknownst to those inside, the landslide had already taken out a farm and several houses on its way down the mountain.

Terrified parents and community members rushed to the scene. One journalist wrote:

“Men, women and children were tearing away the debris in an effort to reach the trapped children. As the men shovelled debris from spade to spade, children’s books appeared. An odd cap was seen. A broken doll. Mothers gathered around the school steps, some weeping, some silent, some shaking their heads in disbelief. Teams of men and boys worked in long rows from the school building, handing buckets of slurry from the classrooms. At regular intervals everything would come to a halt – the roar of heavy machinery, the shouts, the scraping of shovels. Not a murmur would be heard among the thousand workers. Time stood still. And rescuers listened tensely for the slightest sound from the wreckage – for a cry, a moan, a movement – anything which would give hope to the mothers and fathers.”

Of the 169 people inside Pantglas Junior School, just 25 survived. When all the bodies were finally recovered weeks later, the final death toll stood at 116 children and 28 adults.

Over half of the youth population of the village of Aberfan had perished in a single morning, the result of an incident that a tribunal later commissioned to investigate called a deadly accident that “could and should have been prevented.”

So what happened?

Mining had been a part of the landscape of South Wales for many years. During a time when coal was necessary for domestic heating, demand was high and the area around Aberfan was rich with resources. The Merthyr Vale Colliery was opened in 1869 near the village, providing a boon and much-needed employment to the town’s residents. By 1916, however, the operation had run out of space on the valley floor for “spoil tips,” or waste produced during the mining process. No matter; the company simply began piling it on the mountainside above the village instead. Within a few decades, there were seven large piles (called “tips”) containing 2.7m cubic yards of waste on the hills surrounding Aberfan.

One of these, Tip Number Seven, lay directly above Pantglas Junior School.

The pile had grown so large on a hill so steep that local residents began to worry. In both 1963 and 1964, the Aberfan Town Council raised concerns to the National Coal Board over the tip. “I regard it as extremely serious as the slurry is so fluid and the gradient so steep that it could not possibly stay in position in the winter time or during periods of heavy rain,” read a statement in the 1963 letter.

The National Coal Board ignored the plea. But, more than just taking no action, the Board attempted to bully the town into silence. “The threat was implicit,” reported the BBC later, “make a fuss and the mine would close.” For the over 8,000 miners and their families in and around Aberfan, it was a risk they couldn’t ignore.

The town council backed down from their appeals.

Tip Number Seven, the waste pile in question, had been started in 1958 and, by 1966, rose 111 feet in the air and contained 230,000 cubic meters of waste. It not only sat in a precarious position behind the school, it had also been built atop highly porous sandstone that rested atop an underground spring. Heavy rains in the weeks prior had swollen nearby mountain streams and, at 7:30 a.m. on October 21, workers assigned to the tip discovered that it had started to slide. Although the crew opted not to move forward with the day’s planned tip operation, they were unable to prevent further slippage, and at 9:15 a.m., an avalanche of slurry began hurtling toward the village below at over 80 miles per hour.

It was a disaster of epic and heartbreaking proportions.

A tribunal was tasked with investigating the Aberfan disaster. After interviewing 136 witnesses and examined 300 exhibits, the panel concluded the sole party responsible for the tragedy was the National Coal Board.

“The Aberfan disaster is a terrifying tale of bungling ineptitude by many men charged with tasks for which they were totally unfitted, of failure to heed clear warnings, and of total lack of direction from above,” the investigators wrote in their 1967 report. “Not villains but decent men, led astray by foolishness or by ignorance or by both in combination, are responsible for what happened at Aberfan.”

The Coal’s Board president, Lord Robens, denied all wrongdoing.