Bwlch y Ddwyallt is the name commonly applied to the high point of the plateau of Gwaun Cerrig Llwydion in the eastern part of the

Brecon Beacons The Brecon Beacons (; ) are a mountain range in Wales. The range includes South Wales's highest mountain, Pen y Fan (), its twin summit Corn Du (), and Craig Gwaun Taf (), which are the three highest peaks in the range. The Brecon Beacons ha ...

in south

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

. It is a top of

Waun Rydd Waun Rydd is a mountain in the Brecon Beacons National Park, in southern Powys, Wales. Its height is 769 m (2,523 ft) and it tops a large boggy plateau rising to the east of Pen y Fan Pen y Fan () is the highest peak in South ...

. The plateau reaches its highest point of above sea level on its northern rim overlooking the head of Cwm Cwareli. The name is an odd one to apply to a peak since the Welsh word 'bwlch' generally signifies a col or pass between mountains.

Geology

The plateau is formed from the hard-wearing sandstones of the Plateau Beds Formation of the

Old Red Sandstone Old Red Sandstone, abbreviated ORS, is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the eastern seaboard of North America. It ...

laid down during the

Devonian period The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding C ...

. These beds directly overlie the sandstones of the Brownstones Formation, also of

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

age, which form the bulk of the hill. The cliffs below Bwlch y Ddwyallt shows signs of having been glaciated during the ice ages as do those beneath Graig Fan Las on the eastern edge of the plateau.British Geological Survey 1:50,000 map sheet 231 'Merthyr Tydfil' & accompanying memoir

Access

The entire area is classed as open country. The

Beacons Way The Beacons Way (Welsh: Ffordd y Bannau) is a waymarked long distance footpath in the Brecon Beacons National Park, Wales. It is a linear route which runs for east to west through the National Park, and passes many of the most important landmar ...

runs along the southern edge of the plateau. Other footpaths skirt the remaining rims of the plateau and connect with neighbouring peaks.

External links

Images of Bwlch y Ddwyallt and surrounding area
on the Geograph website

References

{{Reflist Nuttalls Brecon Beacons Mountains and hills of Powys