Winter light and colour

This post covers two excursions to the Brecon Beacons National Park and locations avoiding the high winds and gusts to gale force intensity, the sheltered lee side of scarps/hill sides.

The first trip was an afternoon excursion to the eastern flank of Y Mynydd Du, to coincide with the departure of a weather front and the relative shelter of the Old Red Sandstone escarpment. Anomalously high Autumn temperatures - well into winter and grass was still holding a green tinge of growth - and an absence of frosts, hadn't brought the rich palette of colour to the upland sedges and grasses, the cold spell over the festive season might have rectified this.  This area also encapsulates the headwaters of the Afon Tawe and the lake Llyn y Fan Fawr, it is fair to suggest there's no shortage of moisture and recent heavy rainfall had left the ground saturated with surface water streaming down the hill, streams in torrential flow and below ground the natural soil pipes were revealed with water flowing into normally dry gulleys.

The moorland also has a number of eroding peat hags, an increasing UK wide phenomena that is causing some debate as to the cause, in environmental and earth science circles

Eroding Peat hag

The erosion of preat hags does reveal a ground surface covered in rock debris, much of it angular in nature and probably a relict land surface from the the end of the last glacial stadial 11,500+ years BP when this area would have resembled arctic tundra.

Rock debris revealed by eroding Peat.

On the theme of controversy and Ice age landforms, Llyn y Fan Fawr has prompted some discussion of its origin, an active glacier is the popular consensus, there are alternative views though.

View to Llyn Y Fan Fawr and present outlet stream (not visible)

I can't find any references, but the moorland does seem to have a suite of landforms arraigned normal to the down valley glacier ice flow.

There's also a scatter of erratics, that might be from winnowed moraine or till and on the western flank of Fan Gyhirych a series of lineations that are discordant to the southerly dipping bedrock, these have been postulated as glacial lineations.

Fan Gyhirych glacial(?) lineations

With the wind easing, I ventured up onto the escarpment for a look around. On the way up, the path  exposed these mudstone, siltstone and sandstone beds, that nicely sum up the composition of the Brownstones formation.

Sandstone, siltone and mudstone beds, of the Old Red Devonian, Brownstones formation.

The wind was still on the strong side, so only Fan Hir was visited for a view over to Fforest Fawr and with ominous cloud rolling in from the west it was back to the car.

View from Fan Hir

On the way down, a stop to record the infant Afon Tawe flowing through soliflucted sheets of glacial till.

Infant Afon Tawe

The 2nd trip was an afternoon excursion too, the morning wasn't the best and the Mountain Weather Forecast hinted strongly that even with a weather front clearing, walking at elevated and exposed routes would be challenging, so keeping the tripod steady seemed optimistic for dusk, more interesting was the forecast of sunshine and snow showers.  The car parks for popular low level walks would be full, so the National Nature Reserve of Craig Cerrig Gleisiad and Fan Frynach, seemed the best bet for quiet and some views. The National Nature reserve has a lot to offer from a geomorphology and flora perspective, I'll hope to cover these aspects in future posts/visits, as the images on this trip were of the views. I'll add that the Mountain weather forecast was spot on.

Cadair Arthur

I've always known the peaks of Corn Du and Pen y Fan as Cadair Arthur, but this name seems to have fallen from favour in recent times. A pity, as viewed from the NE the twin summits do appear arm chair like, the connection with Arthur I have no idea, but there's a thread of Arthurian folklore in the Brecon Beacons NP.

Breaks in the cloud were few and the showers were light in intensity, the final image, just caught some light before the sun dropped below the hills.

The National Nature Reserve makes for an interesting outing with plenty to see and varied routes at high and low levels.