The Somerset Coalfield in northern Somerset, England is an area where coal was mined from the 15th century until 1973. It is part of a larger coalfield which stretched into southern Gloucestershire. The Somerset coalfield stretched from Cromhall (Gloucestershire) in the north to the Mendip Hills in the south, and from Bath in the east to Nailsea in the west – a total area of about . Most of the pits on the coalfield were concentrated in the Cam Brook, Wellow Brook and Nettlebridge Valleys and around Radstock and Farrington Gurney. The pits were grouped geographically, with clusters of pits close together working the same coal seams often under the same ownership. Many pits shared the trackways and tramways which connected them to the Somerset Coal Canal or railways for distribution.
The early pits were adits where coal outcropped or bell pits where coal was close to the surface. These methods were abandoned when deep seams were mined. The deepest shaft on the coalfield was at the Strap mine at Nettlebridge which reached . Flooding and coal dust explosions in some mines required improved ventilation and pumping engines. Several pits closed in the 19th century as the coal was worked out. Those that survived until 1947 became part of the National Coal Board, but the expense of improving equipment and working conditions meant that these became uneconomical and the last pit closed in 1973. There is still evidence of the mine workings, with the remains of buildings, spoil heaps and tramways in the area.
Geology
Structure The Somerset Coalfield covers a total area of about . It consists of three synclines, informally referred to as 'coal basins'. The Pensford Syncline in the north and the Radstock Syncline in the south are separated by the east–west trending Farmborough Fault Belt. Further to the west is the smaller Nailsea Syncline. The Radstock Syncline in particular is cut by a series of east–west thrust faults and north–south trending normal faults.Green, page 48
Stratigraphy
The Coal Measures are divided into a Lower, Middle and Upper with coal seams found within each of these divisions. Lower and Middle Coal Measures are found at depths between . Together the Lower and Middle Coal Measures are thick with the Middle Coal Measures averaging about 500 and 5,000 feet and the Lower Coal Measures about .Green pages 55–59
Only in the southern part of the Radstock Syncline have coals of the Lower and Middle Coal Measures been worked, mainly at the Newbury and Vobster collieries in the southeast and in the New Rock and Moorewood pits to the southwest. Whilst in the eastern part of Pensford Syncline coals of the Lower and Middle Coal Measures have been worked, at the Globe Pit in the Newton St Loe area in the 19th century.Green page 58 The Variscan orogeny (also responsible for the emplacement of the granitic batholiths in Cornwall, and associated tin and copper mineralisation) involved lateral compression of the rock sequence resulting in the tight folding, fracturing and faulting of the sandstone and mudstone strata, and the associated Coal Measures. Along the Radstock Slide Fault the distance between the broken ends of a coal seam can be as much as .Collier page 18 The complex geology and thin seams gained the field notoriety and three underground explosions, in 1893, 1895 and 1908 were amongst the first attributable solely to airborne coal dust.Down page 13
William Smith Exploratory surveys of the local geology were carried out by William Smith, who became known as the "father of English geology", building on work by John Strachey. Smith worked for the Stracheys who owned Sutton Court, at one of their older mines, the Mearns Pit at High Littleton. As he observed the rock strata at the pit, he realised that they were arranged in a predictable pattern that the various strata could always be found in the same relative positions and each particular stratum could be identified by the fossils it contained and the same succession of fossil groups from older to younger rocks could be found in other parts of England. Smith noticed an easterly dip in the beds of rock—small near the surface (about three degrees) then greater after the Triassic rocks which led to him a testable hypothesis, which he termed the principle of faunal succession, and he began to determine if the relationships between the strata and their characteristics were consistent throughout the country. During work as a surveyor (appointed by engineer John Rennie) for the Somerset Coal Canal Company and subsequently, he mapped the locations of geomorphological features, rock strata, and their vertical extent, and drew cross-sections and tables of what he saw and earned the name "Strata Smith".
Coal seams The following coal seams are recognised within the coalfield. They are listed stratigraphically i.e. uppermost/youngest first. Note that not all seams are continuous across the coalfield and that correlation of some seams from one basin to another is uncertain.British Geological Survey 1:50,000 scale geological map sheets 280, Wells, 281 Frome & Special sheet 1:63,360 scale Bristol District
Coal measures Coal seamsUpper Coal Measures within the Pennant Sandstones Forty Yard Coal (Pensford), Withy Mills Coal, Great Coal, Middle Coal, ?Pensford No 2 Coal, Slyving Coal, Bull Coal, Bottom Little Coal, Rock Coal, Farrington Top Coal, Top Coal, ?Streak Coal, Peacock Coal, Middle Coal, No 5 Coal, ?Bromley No 4 Coal, New Coal, No 7 Coal, No 9 Coal, Big Coal, Brights Coal, No 10 Coal (splitting into Nos 8 & 9 Coals), No 11 Coal, Rudge Coal, Temple Cloud Coal, Newbury No 2 Coal, Newbury No 1 Coal, Globe Coal, Warkey CoalMiddle Coal MeasuresGarden Course Coal, Great Course Coal, Firestone Coal, Little Course Coal, Dungy Drift Coal, Coking CoalLower Coal MeasuresStanding Coal, Main Coal, Perrink Coal, White Axen Coal
History It is believed that coal was mined in the area during Roman times and there is documentary evidence of coal being dug on the Mendips in 1305Coysh page 208Collier page 21 and at Kilmersdon in 1437. By the time of Henry VIII there were coal pits at Clutton, High Littleton and Stratton-on-the-Fosse.
During the early 17th century coal was largely obtained by excavating the outcrops and driving drifts which followed the seam into the ground. Only small amounts of coal could be obtained by these methods and bell pits were also dug.Collier page 22-23 These were vertical pits, with a shaft up to deep, which were opened out at the bottom. When all the coal that could safely be extracted from the pit had been recovered, another pit was sunk close by to intersect the seam and the waste from the second pit thrown into the first.
At the beginning of the 19th century there were about 4,000 people employed on the coalfield.Collier page 29 The Somerset Miners' Association was founded in 1872, later becoming an area of the National Union of Mineworkers.University of the West of England, "Bristol Historical Resource: Trade unions "
The uses of coal were varied. Coal was used in limekilns to produce lime for mortar used in building and by farmers to improve the soil. From 1820 coal was used to produce gas for lighting the production, smelting of iron ore at Westbury and Mells and to power steam driven woollen mills in the area. Coke was used to dry malt for the brewing industry.Down page 19
Transport
The coalfield had a relatively low population density and did not have a major coal-consuming industry nearby. In the pre-turnpike era, the roads serving the coalfield were unsuited to moving coal. Bulley notes "The problem ... was rendered far worse by the state of the roads in Somerset, which were notorious down to the middle of the 18th century. Parishes in the area sometimes neglected or refused to repair those roads which were heavily used by coal carts. Thus in 1617 the inhabitants of Stoke St Michael ... complained that "of late by reason of many coalmines ... the highways there are much in decay and grown very founderous".Bulley, J. To Mendip for Coal, Proc. of the Somerset Archaeology and Natural History Society 97 1952 pages 46-78
In Somerset, turnpike roads began in 1707 with the establishment of the Bath Trust, but turnpikes did not reach the coalfield until the mid-1700s. The Bristol Trust, which passed close to the western boundary of the coalfield, established in 1727 was of little importance, as Bristol was never a significant market, having its own coalfield. Turnpikes facilitated the movement of coal, and John BillingsleyBillingsley page 307 enthused "Nothing so much contributes to the improvement of a county as good roads. Before the establishment of turnpikes, many parts of the county were scarcely accessible. ... coal was carried on horses' backs to the distance of fifteen or twenty miles from the colliery; each horse carried about two hundred and half weight. Now one horse with a light cart will draw four hundred weight or four times more than a horse could carry. Can an insignificant toll be put in competition with this saving?"
Not all roads were improved, and in 1819 John Skinner observed roads "rendered bad" by the passage of coal wagons.Coombs Expansion of production was limited by access to market. Such a need implied a canal project, following Lord Middleton's dictum "Water transport is what all coal owners must aim at". There were large gains from being connected to a canal system, as stated by the Coal Commission: "At about this period (1800) the system of coal navigation was being rapidly extended, and the result was that coals were gradually finding their way into districts that could not be reached unless at great cost, by road".Report of the Coal Commission 1871, 3, pii
A scheme for an extension of the Avon Navigation was proposed in 1766, but canals did not reach the coalfield for almost another 50 years.Clew page 10 In 1794 coal proprietors formed a committee to construct the Somerset Coal CanalHalse pages 6–10 with two branches into the Cam Brook and Wellow Brook valleys, and from a junction at Midford, to join the proposed Kennet and Avon Canal at the Dundas Aqueduct near Bath. Coal was transported by the Somerset Coal Canal and later by the Bristol and North Somerset Railway and Somerset and Dorset Joint Railway, which were accessed from the pits by a series of tramways. After 1854, when the first railway line was opened, the tonnage carried by the coal canal declined rapidly.
Decline and closure The total tonnage of coal produced by the coalfield increased throughout the 19th century, reaching a peak around 1901, when there were 79 separate collieries and production was 1.25 million tons per annum. The peak years for production were 1900 to 1920. However, decline took hold and the number of pits reduced from 30 at the beginning of the 20th century to 14 by the mid-1930s, twelve at nationalisation when the National Coal Board was created on 1 January 1947, under the Coal Industry Nationalisation Act 1946, five in 1959 and none after 1973. Despite some investment in new infrastructure, particularly at Norton Hill, thin seams made production expensive, limiting profit and investment. The conversion of Portishead power station from coal to oil and reduced national demand together with competition from more economical coalfields led to the closure of the last two pits, Kilmersdon and Writhlington, in September 1973.
Area today Although there are still the remains of mines, disused or redeveloped buildings and a few spoil tips, most have been removed or landscaped and the area has returned to a largely rural nature. The towns and villages have some light industry, but are often commuter towns for Bath and Bristol. There are several limestone quarries, particularly in the Mendips.