Fan y Big (; ) is a subsidiary summit 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 ...

in the

Brecon Beacons National Park Brecon Beacons National Park, officially named Bannau Brycheiniog National Park (), is a National parks of the United Kingdom, national park in Wales. It is named after the Brecon Beacons (), the mountain range at its centre. The national park ...

, in southern

Powys Powys ( , ) is a Principal areas of Wales, county and Preserved counties of Wales, preserved county in Wales. It borders Gwynedd, Denbighshire, and Wrexham County Borough, Wrexham to the north; the English Ceremonial counties of England, ceremo ...

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 high and is often hiked as part of the Horseshoe Walk, a traverse of the four main peaks in the Brecon Beacons.

The hill

At , Fan y Big lies at the western tip of the Gwaun Cerrig Llwydion plateau. Its name translates as 'point of the peak' - perhaps in allusion to its striking pointed shape, as seen from some directions. The summit is smooth and grassy, but marked by a cairn, which stands on the edge of its precipitous western face. The view of this face from Cribyn is regarded as very striking. Fan y Big has since lost its status as a Hewitt.

Access

The peak is prominent on the north facing escarpment of the central 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 ...

and three footpaths meet at the summit. All the surrounding land is open access and so walkers can go where they wish. In poor weather however, the paths are the safest route for access. The peak is often crossed by hikers aiming for Cribyn,

Pen y Fan Pen y Fan () is the highest peak in South Wales, situated in Brecon Beacons National Park (Bannau Brycheiniog). At above sea-level, it is also the highest British peak south of Cadair Idris in Snowdonia. It is the highest point (List of countie ...

and Corn Du, and also forms part of the

Fan dance In the West, a fan dance (i.e., a dance performed with fans) may be an erotic dance performance, traditionally by a woman, but not exclusively. Beyond eroticism it is a form of musical interpretation. The performer, sometimes entirely nude ...

, or Horseshoe Walk, a circular route that traverses four peaks.

Geology

In common with other peaks of the Brecon Beacons, the upper slopes of Fan y Big are formed from

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s of the Brownstones 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 ...

. The lower slopes of the hill are formed from sandstones and

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

s of the underlying Senni Formation. The

rock strata In geology and related fields, a stratum (: strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ...

tilt gently southwards. The valleys to the northwest and east nurtured small glaciers during the last

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

. This

glacial erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

resulted in the very steep northern face which the mountain possesses.

References

{{reflist Brecon Beacons Mountains and hills of Powys Nuttalls