Porth yr Ogof

Infobox Cave
name = Porth yr Ogof
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location = near Ystradfellte
depth =
length = convert|2.25|km|mi|1|lk=on
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survey_electronic_format = (which cave software is it in)
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geology = limestone
number of entrances = 15
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hazards =
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translation = the mouth of the cave
language = Welsh
pronunciation =

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 measured over 2.25 km in length and among the cave's fifteen entrances is the largest cave entrance in Wales. Many of the entrances are only accessible to cave divers. The cave is not suitable for development into a show cave like its close neighbour Dan yr Ogof, and as a result the cave is often used to introduce people to the sport of caving.

Inside the cave

Entry to Porth yr Ogof is made via either a wide Main Entrance, a ledge on the left or through the knee-deep river flowing through the center. Cavers are presented many difficult 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 the width of a man's hand) and The Creek, home to Death Ledge on its nearside wall.

Porth yr Ogof may be small and uncommercialised, but it is invaluable as a learning resource for the sport of caving. Along with the other attractions in the cave, two short potholes are easily accessible by amateur potholers. That is not to say the cave is free of deep water; 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 many sumps (completely flooded passageways) can be pointed out, 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 [http://www.ukcaves.co.uk/cave-porthyrogof Porth yr Ogof - UK Caves database] ] cite book|last=Farr|first=Martyn|title=The Secret World of Porth Yr Ogof|id=ISBN 1-85902-559-5|year=1998|publisher=Gwasg Gomer] , 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 emerges again. It is not recommended that anyone attempts to cross this pool or exit this way unless they are properly equipped and have the training and experience to do so safely. [http://www.croydoncavingclub.org.uk/Archive/Pelobates/061/Porth.htm Porth yr Ogof: Cave of Death] by Chris Crowley of the Croydon Caving Club in "Pelobates" (issue 61), March 1993 (accessed July 12, 2006).]

Geological and human history

'Porth yr Ogof' means 'the mouth of the cave' in Welsh, 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 Fact|date=February 2007, as it is not easily overlooked once one is in the valley, but because of the passageway's susceptibility to severe flooding there has been no evidence found of any prehistoric human habitation. The cave and its many visible fossils was mentioned in the writings of Edward Lhuyd, and in the 19th century it was mentioned again by the first pioneers of the caving sport.

References