Aberfan: The Merthyr Vale colliery began to produce coal in 1875. Spoil from the mine workings was piled on the hills close to the village which grew nearby. Tipping went on until the 1960s. Although nationalised, the National Coal Board failed to appreciate the danger they had created. In October 1966, heavy rain made the giant coal tip unstable, resulting in the Aberfan disaster. The recent dumping of small particles of coal and ash known as 'tailings' seems to have been partly responsible. A black wave tore downhill across the Glamorganshire Canal and swept away houses on its path towards the village school. 114 children and 28 adults were killed.