The Glamorgan Archive site (12) has a number of maps showing the distribution of coal types and collieries. ( Log Out / 
These sandstones have been much used in building construction (including the characteristic terraces of former miners' houses) and give rise to bleak uplands rising 300–600 metres above sea level between the steep-sided valleys in which most deep mines were developed. [7] As Cardiff and other ports in South Wales grew to meet the demands for exporting iron, steel and coal in the later part of the nineteenth century, valleys that had previously been sparsely inhabited suddenly increased in population. The 1:100 000 series maps are accompanied by comprehensive explanatory notes which can be viewed in the DIGS® online report system. NB: A guide to using the DIGS® online report system can be found here. The Rhondda valley grew from less than a thousand people in 1851 to more than 150,000 in 1911. When the United States entered the war in April 1917, the British instructed the United States Navy to send only coal-fired ships to assist them. New collieries, particularly in the western part of the coalfield where anthracite is found, were developed into the 1960s by the National Coal Board (for instance, Cynheidre Colliery No 1 shaft, at 798 yards (730 m) deep was sunk in 1954/6). The South Wales Coalfield (Welsh: Maes glo De Cymru) is a large region of south Wales that is rich in coal deposits, especially the South Wales Valleys. It supported a large part, but not all, of the coal industry in Wales. Later colliery shafts were sunk as deep as 800 yards (730 metres) in order to reach the thicker, better quality seams.

Initially running to Dingwall, they then were also shipped to Scrabster through Thurso. As the mines and other industries rapidly expanded throughout the coalfield, nearby towns also expanded to meet the demand for labour.
Hardship continued through the 1926 general strike, the great depression of the 1930s, World War II and thereafter. Iron ore was also extracted from the coal measures, principally from the north crop area (including Merthyr Tydfil and Blaenavon).

This work continues.

[17], Women in South Wales were often not economically active in the second half of the nineteenth century due to the Mines and Collieries Act 1842 which prohibited women from working underground. This was accompanied by a supplement, [1962], depicting the Five feet and Gellideg seams. To assist the Royal Navy, from the outset of the war the Government and railway companies ran what were termed "Jellicoe Specials", high-speed coal carrying freight trains that ran from South Wales to north-east Scotland, and then by ship to Scapa Flow. [13], On 15 September 2011, seven miners were working a narrow seam at the Gleision Colliery drift mine in the Tawe Valley, near Swansea, when a sudden ingress of water filled the passage in which they were working. Landslipping of the steep valley slopes, and subsidence caused by the coal extraction, have also posed problems.

Early activity was mainly by levels or adits driven into coal seams from outcrops in the valley sides.

A subsidiary of Western Coal (which mainly operates in the British Columbia and West Virginia coalfields), Energybuild plc, worked a drift mine near the old Tower Colliery, the Aberpergwm Colliery, until production was suspended in July 2015.

[14], Coal mining in the South Wales Coalfield was a dangerous occupation with lifelong health implications. [11], The Prince of Wales colliery in Abercarn exploded in 1878 causing 268 deaths. Change ).

with inset maps of the South Wales coast, Swansea harbour and docks, by Welsh Miners Museum, Afan Argoed Country Park, Cynonville, Port Talbot, Glamorgan; scale 1":2 miles; n.d. (20th c.) NAS XPL 12/1

Following the Aberfan disaster of 1966, when a coal-tip slurry flow buried a school, mine-waste tips, which had been piled precariously on hilltops in many cases, were extensively regraded and reclaimed. The Risca Black Vein colliery had many fatal accidents to the extent that it became known as the "death pit". When the United States entered the war in April 1917, the British instructed the United States Navy to send only coal-fired ships to assist them. By the end of WWI, the Royal Navy had 33 dreadnoughts and 9 battle cruisers, with 10 and 2 respectively entirely oil fuelled. Energybuild also operates the Nant y Mynydd opencast coal site nearby.

[8] By 1930 employment in the mines was half of that in 1920 as mechanisation increased leading to a net loss of 314,000 people between 1921 and 1935. In addition, old tips were reclaimed for their small coal content, which could be burned in power stations such as nearby Aberthaw. In 1966, 116 children and 28 adults were killed in Aberfan when a coal spoil tip collapsed onto them.