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 ( cy, Bannau Brycheiniog, ) are a mountain range in South Wales. In a narrow sense, the name refers to the range of Old Red Sandstone peaks which lie to the south of Brecon. Sometimes referred to as "the central Beacons" t ...

in south

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

. 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.Nuttall, John & Anne (1999). The Mountains of ...

. The plateau reaches its highest point of 754m 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 Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language spoken in Wales * Welsh people People * Welsh (surname) * Sometimes used as a synonym for the ancient Britons (Celtic peop ...

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 The Old Red Sandstone 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 northeastern seaboard of North America. It also exte ...

laid down during the

Devonian period The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

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

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

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