Here’s an excellent blog about the history and transformation of the landscapes in the Brecon Beacons National Park. Alan Bowring, the Fforest Fawr Geopark Development OfficerDiscover tells us about the full force of what the ancient glaciers did to the area.
A blanket of snow has fallen across the park; its presence briefly transforming the landscape and the lives of those who live here. The myriad crystals sit one upon another forming an open lattice which absorbs all sound. An eerie silence follows. The usual day to day sounds of birds, streams and traffic all subside. But through this silence I hear echoes, echoes from a deep past when winter snows fell heavily. Today’s snows will linger awhile and then, over a few days, will likely vanish. But the snows of a thousand yesterdays lingered much longer – they did melt however their span was measured not in days but in millennia.
These echoes I hear are those of the last ice age when successive cold summers failed to rid these hills of winter’s white gift. Year on year the drifts accumulated until compressed under their own weight, the snowbeds turned to hard ice. Tongues of ice began to creep from the hills, edging forwards, merging with others until great glaciers filled the wide expanses of our valleys. Surging forwards the Usk valley glacier reached as far as the spot where thousands of years later our ancestors would establish the town of Usk itself, that lobe in the Towy valley reached to the future Carmarthen whilst to the south great ice rivers scraped their way down Cwm Tawe to Swansea and Cwm Taf to Cardiff’s northern edge. High in the deep northern hollows of the hills, the gouging and grinding carried on incessantly –nobody was around to witness it but the beautiful mountain cirques to which we now make pilgrimages – those at Llyn y Fan Fach and Llyn y Fan Fawr beneath the Black Mountain, that at Cwm Llwch beneath Pen y Fan – they were being rough-hewn in those times.
Echoes of that time are encountered in unexpected places too – the mounds which stretch across the Usk valley beneath Llanfoist and the grounds of Nevil Hall – ground-up dumps of mountain debris left as the glacier tarried awhile during its long retreat – geologists, with their fondness for such terms, call them ‘recessional moraines’. Similar scenes are encountered at Craig-y-nos, Sennybridge, Buckland Hall and Clyro.
Had we stood some years later at the pass at Bwlch and looked along where the A40 would one day run to the future Brecon we’d have witnessed a deluge pouring from the direction of Llangors Lake across the low ground and rushing down through the grounds of Buckland Hall bound for the Usk. A great lake, of which the present one is but a shadow, built up where its exit was barred by the huge Wye valley glacier, overtopping and spilling southwards instead of to the north. One event in this year’s Talgarth Walking Festival will explore that particular drama.
Even as the glaciers made their final disappearance, their effects were still felt. They had widened and deepened their valleys, shearing off the lower reaches of some of the mountain spurs round which they flowed. One by one these steep cliffs, once buttressed by ice, collapsed valleywards – look up at any one of the cliffs known as Darren around the park – above Crickhowell and near Cwmyoy for example and you are looking at the wreckage of these mighty landslides, the thunderous sounds of which would have provided some of the last resounding echoes of these extraordinary times.
Some of these and other chilling tales from our long winter of long ago are told during the various walking festivals in Talgarth, Crickhowell and Hay-on-Wye and during the geopark Festival in early summer.
Alan Bowring, Fforest Fawr Geopark Development Officer