South Wales Coalfield
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The South Wales Coalfield is a region of Wales that is rich with coal. It lies in parts of the districts/counties of Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taff, Vale of Glamorgan, Merthyr Tydfil, Cardiff, Caerphilly, Blaenau Gwent, Torfaen and Powys. It comprises a fully exposed synclinorium with a varying thickness of "Coal Measures" (Upper Carboniferous / Pennsylvanian) deposits with thick, workable seams in the lower parts and generally thinner and sparser seams in the upper parts, together with a development of sandstones ("Pennant Sandstone").Geology of South Wales. These sandstones have been much used in building construction (including the characteristic terraces of former miners' houses) and give rise to bleak uplands rising to 300-600 metres above sea level between the steep-sided valleys in which most deep mines were developed.
The coal generally increases in grade or "rank" from east to west, with bituminous coals in the east, and anthracite in the west. The Rhondda valley was particularly known for steam coals which fuelled ships of the 19th and early 20th centuries.
Communication along the valleys provided the main routeways for exporting coal. Early activity was mainly by levels or adits driven into coal seams from outcrop in the valley sides. Development of the coalfield was slow until the early- to mid-19th century; for instance, deep mining in the previously entirely rural Rhondda valleys did not become significant until about 1850. Tramway-fed canals such as the Swansea Canal and Glamorganshire Canal were supplemented, and then superseded, by the development of numerous competing railway branches which fed docks principally at Swansea, Cardiff, Newport, Llanelli and Barry. These towns grew dramatically as a result. Later colliery shafts were sunk as deep as 800 metres (760 yards) in order to reach the thicker, better quality seams.
Iron ore was also extracted from the coal measures, principally from the north crop area (including Merthyr Tydfil and Blaenavon. The availability of coal and nearby limestone (as a flux) gave rise to a substantial local iron and steel industry which was perpetuated in the twentieth century by the location of modern steelworks at Ebbw Vale and Cardiff (both now closed)and Port Talbot. These used imported iron ore.
Economic hardship struck the coalfield after the First World War and continued irregularly thereafter. The 1939 novel How Green Was My Valley by Richard Llewelyn (later filmed, with a risibly inaccurate "colliery village") typefies such hardship.
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 deep (729 metres) was sunk in 1954/6). Following the general collapse of the UK coal industry most pits closed during the 1980s and only one deep mine now remains in operation (Tower Colliery, on the north crop). However, a few small licensed mines work seams, mostly from outcrop, on the hillsides. Although some areas of the coalfield are effectively worked out, considerable reserves remain. However, geological difficulties make the cost of significant further extraction high. The coalfield experienced a late-stage development when opencast mining was commenced on a large scale, mostly on the gently-dipping north crop. Most of these sites have been filled and landscaped.
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. This work continues. Landslipping of the steep valley slopes, and subsidence caused by the coal extraction, have also posed problems.
In the later 20th century, coal mining was gradually replaced by other economic activities, such as electronics factories, and the evidence of the coal extractive industry has become less obvious.
