Porth yr Ogof
Encyclopedia
Porth yr Ogof is a cave
located near the village of Ystradfellte
, near the southern boundary of the Brecon Beacons National Park
in Wales
. In 1998 the cave's passageways had been measured as over 2.25 km in length. Among the cave's fifteen entrances is the largest cave entrance in Wales (but many of those entrances are only accessible to cave divers
). The cave was used as a show cave
many years ago, but it does not have the attractions of more decorated caves such as Dan yr Ogof
, and so today the cave is more often used to introduce people to the enjoyment of the exploration of caves.
Porth yr Ogof is now uncommercialised
, and is also invaluable as a learning resource for caving. Along with the other attractions in the cave, two short pothole
s are easily accessible by amateur potholers. The cave is generally wet, however; White Horse Pool, named so because of the shape of the calcite deposit on the back wall, is several metres in depth despite the shallowness of the edges, and there are many sump
s (completely flooded passageways), the majority of which exist in the portions of the cave north of the Trademan's Entrance.
No one should attempt to cross this pool or leave the cave by this route unless they are properly equipped, are excellent swimmers, and have the training and experience to do so safely.
, most notably because of the gaping maw that is the Main Entrance. The cave lies on the Afon Mellte and is located in a comparatively narrow band of carboniferous limestone
. The river bed is dry from Ystradfellte onwards, the river only rising to the surface again just before the cave.
The cave has been known to humans for many centuries , as it is not easily overlooked once one is in the valley, but because of the passageway's susceptibility to severe flood
ing there has been no evidence found of any prehistoric human habitation. The cave and its many visible fossil
s was mentioned in the writings of Edward Lhuyd
, and in the 19th century it was mentioned again by the first pioneers of caving.
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
located near the village of Ystradfellte
Ystradfellte
Ystradfellte is a small village in Powys, Wales, in the Fforest Fawr area of the Brecon Beacons National Park.Because of the geography and topography of the area the village of Ystradfellte is not visible from the nearest main road, the A4059 Hirwaun to A470 stretch.Ystradfellte comes under...
, near the southern boundary of the Brecon Beacons National Park
Brecon Beacons
The Brecon Beacons is a mountain range in South Wales. In a narrow sense, the name refers to the range of popular peaks south of Brecon, including South Wales' highest mountain, Pen y Fan, and which together form the central section of the Brecon Beacons National Park...
in 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...
. In 1998 the cave's passageways had been measured as over 2.25 km in length. Among the cave's fifteen entrances is the largest cave entrance in Wales (but many of those entrances are only accessible to cave divers
Cave diving
Cave diving is a type of technical diving in which specialized equipment is used to enable the exploration of caves which are at least partially filled with water. In the United Kingdom it is an extension of the more common sport of caving, and in the United States an extension of the more common...
). The cave was used as a show cave
Show cave
Show caves — also called tourist caves, public caves, and in the United States, commercial caves — are caves that are managed by a government or commercial organization and made accessible to the general public, usually for an entrance fee...
many years ago, but it does not have the attractions of more decorated caves such as Dan yr Ogof
Dan yr Ogof
Dan yr Ogof is a long cave system in south Wales, five miles north of Ystradgynlais and fifteen miles south west of Brecon within the Brecon Beacons National Park. It is the main feature of a show cave complex which is claimed to be the largest in Europe and is one of the major tourist...
, and so today the cave is more often used to introduce people to the enjoyment of the exploration of caves.
Inside the cave
Entry to Porth yr Ogof is most often made through the wide Main Entrance, either using a dry ledge on the left or by wading through the knee-deep river to the centre and right. Cavers are presented various challenges inside, including The Wormhole (a curving crawl tube on the right wall of the Main Entrance), The Letterbox (a rectangular space in the passage) and The Creek, home to Death Ledge on its nearside wall. There are also two features named the Washing Machine - both feature large expanses of water.Porth yr Ogof is now uncommercialised
Show cave
Show caves — also called tourist caves, public caves, and in the United States, commercial caves — are caves that are managed by a government or commercial organization and made accessible to the general public, usually for an entrance fee...
, and is also invaluable as a learning resource for caving. Along with the other attractions in the cave, two short pothole
Pothole
A pothole is a type of disruption in the surface of a roadway where a portion of the road material has broken away, leaving a hole.- Formation :...
s are easily accessible by amateur potholers. The cave is generally wet, however; White Horse Pool, named so because of the shape of the calcite deposit on the back wall, is several metres in depth despite the shallowness of the edges, and there are many sump
Sump
A sump is a low space that collects any often-undesirable liquids such as water or chemicals. A sump can also be an infiltration basin used to manage surface runoff water and recharge underground aquifers....
s (completely flooded passageways), the majority of which exist in the portions of the cave north of the Trademan's Entrance.
Deaths
There have been eleven deaths at Porth yr Ogof since 1957, and all but one have lost their lives in the cold, fast-flowing and 4-5 metre deep Resurgence Pool at the far end of the cave, where the river Mellte resurges (emerges).No one should attempt to cross this pool or leave the cave by this route unless they are properly equipped, are excellent swimmers, and have the training and experience to do so safely.
Geological and human history
'Porth yr Ogof' means 'the mouth of the cave' in WelshWelsh language
Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...
, most notably because of the gaping maw that is the Main Entrance. The cave lies on the Afon Mellte and is located in a comparatively narrow band of 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...
. The river bed is dry from Ystradfellte onwards, the river only rising to the surface again just before the cave.
The cave has been known to humans for many centuries , as it is not easily overlooked once one is in the valley, but because of the passageway's susceptibility to severe flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ing there has been no evidence found of any prehistoric human habitation. The cave and its many visible fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s was mentioned in the writings of Edward Lhuyd
Edward Lhuyd
Edward Lhuyd was a Welsh naturalist, botanist, linguist, geographer and antiquary. He is also known by the Latinized form of his name, Eduardus Luidius....
, and in the 19th century it was mentioned again by the first pioneers of caving.