Ar fore Gwener 21 Hydref 1966, fe lithrodd ton o wastraff glo lawr y Dyffryn yn Aberfan Tomen rhif 7 o Lofa Merthyr Vale, uwchben y pentre, oedd tarddiad y don hon. Am tua 9.15yb fe wnaeth y gwastraff glo hwn daro Ysgol Gynradd Pantglas ym mhentref Aberfan a dinistro nifer o dai gerllaw. O fewn pum munud cafodd 116 o blant a 27 o oedolion eu lladd yn y gyflafan- y mwyafrif o fewn muriau’r ysgol gynradd.
Roedd y plant wedi dychwelyd i’r dosbarth yn dilyn gwasanaeth y bore- yr olaf cyn gwyliau hanner tymor. Fe wnaeth y gwastraff glo daro’r dosbarthiadau yng nghefn yr ysgol gan ladd y brifathrawes, pedwar o athrawon a bron bob un disgybl yn y rhan hon o’r adeilad. Yng ngheiriau rhai o’r athrawon wnaeth fyw, oedd yn dysgu mewn rhan arall o’r adeilad, “we heard a tremendous rushing as thought a whirlwind had struck and then came absolute silence”. (FFynhonell: Aberfan and the Teachers).
Yn dilyn y gyflafan fe ruthrodd glowyr, rhieni a phobl lleol i’r ysgol i gloddio er mwyn ceisio cael y plant allan. I ddechrau dim ond rhawiau a bwcedi oedd ar gael, gyda rhai yn defnyddio llaw. Er gwaethaf yr holl gloddio ni ddarganfyddwyd neb yn fyw ar ôl 11:00 y bore hwnnw allan o’r domen. Yn ystod yr oriau a ddilynodd fe ddaeth pobl o bell ac agos i Aberfan i gynnig cymorth a chefnogaeth i’r gymuned. Cymrwyd bron i wythnos i ddarganfod yr holl gyrff.
Ar y dydd Iau yn dilyn y gyflafan cafodd llawer o’r cyrff eu claddu mewn angladd torfol, cafodd y gweddill eu claddu mewn angladdau preifat. Fe wnaeth negeseuon o gydymdeimlad ddod o bedwar ban byd yn y dyddiau ar wythnosau â ganlyn, ac fe wnaeth cronfa’r drychineb gasglu dros £1.75
miliwn. Mae cymoedd diwydiannol y De wedi profi sawl trychineb fawr yn y dau can mlynedd diwethaf, ond beth sydd mor enbyd am drychineb Aberfan yw fod mwyafrif y meirw yn blant bychain- heb gael cyfle i fyw bron dim o’u bywydau.
 

silence”. (Source: Aberfan and the Teachers)
Following the disaster colliers, parents and local people rushed to the school to dig, in an attempt to get the children out. To start, only spades and buckets were used to dig- with some using their hands. Despite all the digging nobody was dug out of the coal waste alive after 11:00am that morning. During the hours that followed people from near and far came to Aberfan to offer support and help. It took nearly a week for all the bodies to be recovered from the school.
On the following Thursday after the disaster many of the bodies were buried in a mass funeral, the rest were buried in private funerals. Messages of condolence came from all corners of the world in the days and weeks that followed, and the disaster fund raised over £1.75 million. The South Wales Valleys have suffered a number of terrible disasters in the last 200 years, but what makes the Aberfan disaster worst is the fact that most of those killed were children- who didn’t have the opportunity to live their lives.

The saddest day in the history of the Borough of Merthyr Tydfil was Friday 21^st October 1966, the Aberfan Disaster. In the previous 10 years there had been a good deal of correspondence between Merthyr Council and the National Coal Board concerning the tip. One Council official even wrote, ‘ You are no doubt aware that tips in Merthyr Vale tower above the Pantglas area and if they were to move a very serious situation would occur’. Over a week of heavy rainfall caused a mountain of slag to move incredibly quickly, engulfing Moy Road and Pantglas School just as junior school children were inside. The tragedy caused the sad death of  28 adults  and 116 young children. It is a day that few would ever forget. The tribunal that was held afterwards concluded that ‘ Blame for the disaster rests upon the National Coal Board’.