Cefn Cil Sanws
Encyclopedia
Cefn Cil Sanws is a hill in the Brecon Beacons National Park within the county borough
of Merthyr Tydfil
in south Wales
. The summit at 460m above sea level is crowned by a trig point
. The steep cliffs of Darren Fawr and Darren Fach defend its western side which drops down into Cwm Taf. A major limestone quarry is worked on the southeastern side of the hill. An unexpected feature at this altitude is Merthyr Tydfil Golf Course which extends high onto the eastern and southern slopes of the hill.
age all tilted moderately to the south. The summit is formed from Carboniferous Limestone
whilst outcrops of Twrch Sandstone
(formerly known as the 'Basal Grit' of the Millstone Grit
Series) can be seen to the north and on its steep western flanks. There are sections of limestone pavement
on the tilted plateau surface and small crags and pavements of gritstone to their south. The latter show evidence of glacial striations
suggesting that the hill was over-ridden by ice moving southwards from the central Beacons during the ice ages.
as a nature reserve
. The steep cliffs of Darren Fach on the western side are the home to Britain's rarest tree - Ley's Whitebeam (Sorbus leyana) - the larger part of the country's population of these trees being found on this one cliff. Also of interest is the rare rigid buckler fern which clings to the scree slopes on this western flank.
and from Cefn-coed-y-cymmer
.
County borough
County borough is a term introduced in 1889 in the United Kingdom of Great Britain and Ireland , to refer to a borough or a city independent of county council control. They were abolished by the Local Government Act 1972 in England and Wales, but continue in use for lieutenancy and shrievalty in...
of Merthyr Tydfil
Merthyr Tydfil
Merthyr Tydfil is a town in Wales, with a population of about 30,000. Although once the largest town in Wales, it is now ranked as the 15th largest urban area in Wales. It also gives its name to a county borough, which has a population of around 55,000. It is located in the historic county of...
in south Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
. The summit at 460m above sea level is crowned by a trig point
Trig point
A triangulation station, also known as a triangulation pillar, trigonometrical station, trigonometrical point, trig station, trig beacon or trig point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity...
. The steep cliffs of Darren Fawr and Darren Fach defend its western side which drops down into Cwm Taf. A major limestone quarry is worked on the southeastern side of the hill. An unexpected feature at this altitude is Merthyr Tydfil Golf Course which extends high onto the eastern and southern slopes of the hill.
Geology
The hill is composed of a layer cake of rocks of CarboniferousCarboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
age all tilted moderately to the south. The summit is formed from Carboniferous Limestone
Carboniferous limestone
Carboniferous Limestone is a term used to describe a variety of different types of limestone occurring widely across Great Britain and Ireland which were deposited during the Dinantian epoch of the Carboniferous period. They were formed between 363 and 325 million years ago...
whilst outcrops of Twrch Sandstone
Marros Group
The Marros Group is the name given to a suite of rocks of Namurian age laid down during the Carboniferous period in South Wales. These rocks were formerly known as the Millstone Grit Series but are now distinguished from the similar but geographically separate rock sequences of the Pennines and...
(formerly known as the 'Basal Grit' of the Millstone Grit
Millstone Grit
Millstone Grit is the name given to any of a number of coarse-grained sandstones of Carboniferous age which occur in the Northern England. The name derives from its use in earlier times as a source of millstones for use principally in watermills...
Series) can be seen to the north and on its steep western flanks. There are sections of limestone pavement
Limestone pavement
A limestone pavement is a natural karst landform consisting of a flat, incised surface of exposed limestone that resembles an artificial pavement. The term is mainly used in the UK where many of these landforms have developed distinctive surface patterning resembling block of paving...
on the tilted plateau surface and small crags and pavements of gritstone to their south. The latter show evidence of glacial striations
Glacial striations
Glacial striations or glacial grooves are scratches or gouges cut into bedrock by process of glacial abrasion. Glacial striations usually occur as multiple straight, parallel grooves representing the movement of the sediment-loaded base of the glacier...
suggesting that the hill was over-ridden by ice moving southwards from the central Beacons during the ice ages.
Plants
Much of the hill is owned and managed by the Brecknock Wildlife TrustBrecknock Wildlife Trust
Brecknock Wildlife Trust is a wildlife trust covering the vice county of Brecknockshire in Wales. The offices of the Trust are located in Brecon. The Trust has 21 reserves, the majority of which are in the Brecon Beacons National Park. -External links:...
as a nature reserve
Nature reserve
A nature reserve is a protected area of importance for wildlife, flora, fauna or features of geological or other special interest, which is reserved and managed for conservation and to provide special opportunities for study or research...
. The steep cliffs of Darren Fach on the western side are the home to Britain's rarest tree - Ley's Whitebeam (Sorbus leyana) - the larger part of the country's population of these trees being found on this one cliff. Also of interest is the rare rigid buckler fern which clings to the scree slopes on this western flank.
Access
Most of the hill is open country. A public footpath and a bridleway at its southern end provide access from the A470 roadA470 road
The A470 is a major long-distance connective spine road in Wales, running from Cardiff on the south coast to Llandudno on the north coast. It covers approximately 186 miles , over a zig-zagging route through the entirety of the country's mountainous central region, including the Brecon Beacons and...
and from Cefn-coed-y-cymmer
Cefn-coed-y-cymmer
Cefn-coed-y-cymmer is a small community on the northwestern edge of Merthyr Tydfil in south Wales. It is situated in the neck of land between the rivers Taf Fawr and Taf Fechan at their confluence . The village lies within the community of Vaynor...
.