Ogof Ffynnon Ddu
Geology & landscape
Geological Feature: Cave / Cavern, Karst · Geological Period: Quaternary
Landscape processes: Glacial, Karst
Description
Description The site contains part of an extensive cave system which has at least 40 kilometres of passages, the largest length in any Welsh cave, situated within a vertical range of 300 metres, which is the greatest in any cave in Britain. In addition some other small, but related, caves are included in the site. The cave system is important not only for its sheer size, but also its spectacular morphological features, some extremely fine calcite deposits, and an historical record which may extend back to pre-Pleistocene times. Traversing the deepest exposed karst block in Britain, it offers an unparalleled record of successive rejuvenation in response to glacial excavations of an adjacent major valley. Biologically the cave has been better explored than almost any other cave in Britain. A number of rare crustacean species restricted to subterranean habitats are of particular note. Remarks: Part of the water catchment of the cave system is included in the SSSI in order to safeguard the invertebrate fauna and the active geomorphological processes requiring water. The site includes part of the Ogof Ffynnon Ddu National Nature Reserve. The site lies within the Brecon Beacons National Park.