The Arches at Baileys Barn

Talybont-On-Usk, Brecon Beacons. Tel: 07875 453927

The Brecon Beacons - in the beginning...

The Brecon Beacons National Park is a playground for tourists and outdoor enthusiasts alike, but you don't have to run up mountains before breakfast to enjoy what it has to offer.

The National Park was established in 1957 and covers an area of 519sq miles, but it has taken over 450 million years of history to become what it is today:-

The oldest rocks in the Brecon Beacons National Park date from the Ordovician Period, between 495 and 443 million years ago and can be found in the west of the Park, around the Llandovery area. The rocks of the following Silurian period, from 443 to 417 million years ago, are similar, being fine sediments such as sandstone, mudstone and siltstone, and are also found in the western area of the Park. (Interestingly, both the Ordovician and Silurian periods were named after early Welsh tribes, the Ordovices who ranged over central and north Wales, and the Silures, who inhabited South Wales.)

Scwd Gwladys

Picture: Scwd Gwladys, Ystradfellte

During the Devonian period, from 417 to 354 million years ago, the rocks change significantly, becoming the predominantly red sandstone which makes up about two thirds of the National Park, and forms all the main ranges of hills – the Black Mountains, the Brecon Beacons and the Black Mountain.

In the following, Carboniferous period, between 354 million years and 290 million years ago the limestone which now dominates the southern part of the Park was formed, and later, from sources of abundant vegetation, the rocks of the rich coal seams of the South Wales coalfield formed.

Horseshoe Falls, Ystradfellte

Picture: Horseshoe Falls, Ystradfellte

Millstone Grit, a tough, pebbly rock (once used to make the famous circular millstones of Derbyshire) forms hard layers separating the limestone from the coal measures. It is this hard rock over which the rivers of the south of the Park flow to create the spectacular waterfalls in the Ystradfellte area.

With the exception of more recent deposits from rivers and glaciers, this is where the geological record of the Brecon Beacons National Park ends. Its international geological significance was recognised in October 2005 when the western, Fforest Fawr, area of the Park was given international Geopark status, sharing importance with other areas of the UK, Europe and beyond.

Llyn y Fan Fach and the Black Mountain

Picture: Llyn y Fan Fach and The Black Mountain

With the onset of the first ice ages, around 2.4 million years ago, the finishing touches began to be put to the landscape of the area. When the last glaciers finally retreated around 14,000 years ago, the shape of the landscape would have looked broadly how it does today. As the climate warmed rivers cut their valleys deeper, lakes formed in hollows, such as Llangorse Lake, and in glacial hollows below steep mountain faces, such as Llyn y Fan Fach, Llyn y Fan Fawr in the Black Mountain and Llyn Cwm Llwch in the Brecon Beacons.

Rivers and underground water cut caves and underground passages in the limestone of the south of the park, leaving extensive cave systems at Llangattock, Porth-yr-Ogof and the majestic caverns at Dan-yr-Ogof; sometimes spectacular shake holes were left on the surface where the roof of an underground cavern collapsed, and these can be seen on Mynydd Llangynidr, in the hills above Craig-y-Nos and further west in the hills above Llangadog. Thick bands of millstone grit prevented rivers from easily deepening valleys, and spectacular waterfalls were produced where the rivers tumbled over these bands of hard rock, such as on the rivers Hepste, Mellte and Nedd Fechan in the waterfall country in the south of the Park.

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