A trip to photograph an ancient weakness in the earths surface

My interest in the science of geology is its endeavour to unravel the history of the earth from rocks and structures, a complex story that requires the mind to grapple with the depth and enormity of geological time and processes. It is also personally rewarding to make a landscape photograph that conveys the geological story of a landscape.

From: Carney, J.N., Horak, J.M., Pharaoh, T.C., Gibbons, W., Wilson, D., Barclay, W.J., Bevins, R.E., Cope, J.C.W. & Ford, T.D., (2000), Precambrian Rocks of England and Wales, Geological Conservation Review Series, No. 20, Joint Nature Conservation Committee, 

At some point in the deep geological time of the Precambrian, the Cymru and Wrekin terranes collided and the collision zone (suture) or terrane boundary, has created an inherent weakness in the earths crust and a nucleation point for subsequent dislocations from external tectonic forces. Geological mapping has revealed that the Cymru/Wrekin terrane boundary has a long history of movement in the Precambrian, during the Caledonian Orogeny and then the Variscan Orogeny. These movements along the terrane boundary generate faults and folds (disturbances) in the overlying rocks and these features have been exploited by erosional processes, notably the actions of freeze-thaw weathering, flowing water and glacial ice. Which is a good thing, as the scenery of the Brecon Beacons National Park would be otherwise a lot photogenically poorer.

Faults of the Fforest Fawr Geopark
http://www.fforestfawrgeopark.org.uk/understanding/rocks-and-geology-of-the-geopark/faults-and-folds/geological-faults-in-the-geopark/

The head of the Senni valley has; a classic glaciated cirque; a U shaped profile; a miss fit water course of the Blaen Senni and the upper valley is aligned with the Tawe (Swansea) Valley/Cribarth disturbance. The valley orientation is initially NE before abruptly swinging north, which coincidentally aligns with another major structural trend which is termed Malvernoid. To the east of where the Senni valley swings north is the Cwm-du valley, a hanging valley above the floor of the Senni valley, with a suite of moraines and steep headwall of Graig Cwm-du. Cwm-du also has a mis fit stream and coincidentally the head waters of the Nant Cwm-du also parallel the Tawe Valley disturbance. This is an area I've visited on numerous occasions to try and make an image that I'm happy with.

There are a number of approaches to reach the vantage point on the Fan Frynych ridge over the Senni valley, the most scenic approach being through the Craig Cerrig Gleisiad National Nature Reserve and at this time of year, there is the potential for low angled sunlight on the northerly facing scarps and valley sides, with patches of heather in bloom for floral interest.

The weather forecast
Credit - Met Office

The forecast was optimistic considering the picture of the visible satellite, rainfall radar and wind strength readings from online weather station, nonetheless there was potential for some atmospheric lighting.

The scenic Craig Cerrig gleisiad
Foreground - vegetated antiscarps of the landslide and western headwall
Middle  - Craig cerrig-gleisiad
Horizon left - Cadair Arthur and shower cloud

Surveying the landscape to the south west from Fan Frynych's summit and it doesn't take much imagination to visualise a continuous plateau surface to Fan Llia, before erosion processes exploited  weaknesses in the bedrock and the dissection of the plateau. Sadly on this trip, as with previous trips the weather dictated the view of the Senni Valley would again remain unphotographed, this time the winds strength was problematic, maybe next time?

Undulating plateau dissected by Cwm-du

Cwm-du and the north facing scarp of Craig Cwm-du with layer cake stratigraphy of the Lower Old Red Devonian Senni beds

Instead a tactical retreat was made to a headwater stream of the Nant Cwm-du, with a view down into the Cwm-du and Senni valleys and 'relative' shelter from the wind. A patient wait for a break in the shower clouds, was spent donning and doffing rain wear and pondering plateau glaciation, cold based ice, periglacial processes, the thickness of soliflucted till, oh and the delights of descending through the landslide debris of Craig Cerrig Glesiad in head torch light ...

My patience was rewarded with a fortuitous break in the clouds. It wasn't the landscape image I had hoped for, but a satisfying one with the atmospheric lighting and a view along and down an ancient weakness in the earths crust revealed by erosion processes.

Wild camping - two bites at the cherry

The met office and mountain weather information service respective forecasts converged to deliver the prospect of potentially a decent sunset AND following sunrise AND I was free of work commitments = wild camping trip. With the sun rising and setting near to the maximum azimuth of summer solstice, a north facing view would offer the best prospect.  The Carneddau in Snowdonia were long overdue a visit, but as so often, 24hrs out the weather forecast changed and not for the better. The plan was revised to further south in Wales, Fforest Fawr and the northern escarpment of Y Mynydd Du, with its scarp and suite of glacial and periglacial landforms. It's an area I know fairly well and a location although well photographed, hasn't quite yet made it onto the UK's landscape portfolio bucket list. Despite some valiant efforts, I've failed miserably to get a respectable sunset/sunrise image of the view and geomorphology.

The weight of the wild camping pack made for slow going up a very modest gradient across the moorland, giving me plenty of time to reflect on; my physical conditioning was sub prime; the ascent of the Carneddau would have been an interesting experience; George Monbiot's observations on the environmental destruction by sheep is pretty much on the money; the flowering bog cotton clearly demarcated areas of degrading peat and when stringers of cirrus cloud started streaming across the sky, I'll confess to wondering why I bother. I did stumble upon a delightful camping spot, a raised fairly level pitch on moss covered ground, a nearby stream and a pitch with a wonderful backdrop, things were looking up. With the tent pitched, dinner cooked and heartily eaten, it was time for a wander.

With wanderlust in overdrive a gulley was ascended on Fan Brycheiniog to see if there was anything of floral interest and on ledges inaccessible to sheep, there was a surprising diversity of flora, most of it past its photograph 'best by date' or inaccessible, a cushion of mossy saxifrage was the highlight.

The main viewpoint for sunset was the escarpment of Bannau Sir Gaer with its suite of geomorphological landforms and exposures of sedimentary geology. With a viewpoint found, there was plenty of time until sunset to stand back and contemplate Deep Time. The youngest features visible are the alluvial fans at the foot of gulleys and vivid active debris flows that scar the hill slopes, some geomorphologists speculate that the active debris flows have been initiated due to a change of grazing regime to predominantly sheep grazing around 1600AD. The next suite of landforms are the talus cones formed from freeze thaw weathering of mudstones/shales and undermining of overlying  sandstones'siltstones, and represent periglacial weathering at the end of the last Ice Age, with minor accumulations in the holocene. The scarp foot landforms and the cirque enclosing Llyn y Fan Fach indicate possible permanent snow beds and the presence of glacial ice of the late Devensian stadial. Though there are landforms that appear 'fresh' in appearance and other landforms with an older, less defined features, possibly demarcating landforms formed either side of an interstadial between the Older and Younger Dryas stadials. There's also some intriguing overprinting of landforms, that indicates an event chronology; alluvial fans 'gulleying' and burying the talus deposits; talus deposits infilling depressions and overriding scarp foot landforms and some of the scarp foot ramparts show successive crests or ridges implying retreat/advance of glacial ice/snow patches. Then it's into Deep Time proper, with a gap of some 280-300 million years to the end of the Variscan orogeny and the folding of bedrock into the South Wales syncline. Back another 70 million years to the end of the Devonian, conglomerates were uncomformably deposited onto a strata of the Lower Devonian. The lower Red Devonian sediments originated from a vast mountain chain eroding to the north. A few miles to the north, in the Myddfai Steep Belt, Silurian strata is almost vertical in attitude and striking SW to NE it represent an expression of the Caledonian orogeny and what is now believed to be a terrane boundary, that pushes the geological history back into Proterozoic.

With sun always setting into a blanket of cloud it was a case of making the most of the last rays of warm light for an image.

On the walk back to the tent some thought was given to what the Cirrus clouds heralded for dawn.

The resident Sky Lark population woke me before the alarm sounded about 03.00hrs, with the tent being buffeted and an ominous 'booming' noise to the west, suggested the weather wasn't going to play ball. A look outside and the NE horizon seemed promising, alas Y Mynydd Du was blanketed in hill fog, sigh. Plan A was abandoned and other options considered with a cunning photography plan B of an image of flowering bog cotton at sunrise formulated.

Eroding peat hags reveal a land surface that is probably representative of its appearance at the end of the last Ice age, when this area would have been tundra.

The weather then deteriorated rapidly and a damp hill fog blanketed everything, which made for an interesting bit of compass work to find the tent again.

The weather seemed set in, so I 'rested my eyes' for a while and opened them to find the hill fog lifting and cloud breaking up, the best of the light was long gone, but the tent pitch deserved a record shot before breaking camp and heading home.

Ice, snow, alpenglow and aspect ratio

The forecast was for light winds, temperature inversion, excellent visibility, hill fog lifting and clear skies, with snow still lying on the ground at high levels. I didn't fancy dawn, but a leisurely afternoon/evening wander somewhere in Fforest Fawr seemed promising. The forecast was that good, the wife was motivated to go for a walk too, I did suggest she take her camera gear as sunset/dusk could be good, she just wanted to stretch her legs.

View to the Black Mountain escarpment and upper reaches of the Tawe valley

Parking up in the Upper Tawe valley, it became evident that it was a 'sensational' winters day for walking on the hills, plenty of snow still lying, the sun shining and no wind.  In my eyes, there's a huge difference between sensational weather and conditions for hill walking and landscape photography. Powder blue sky, harsh sunlight and blue shadows are probably the most uninspiring combination for making images, however for hill walking these are probably as good as it gets and a scan around suggested plenty of walkers on the popular summits. Whilst getting 'suited n booted' the options were considered;  a trip up to Fan Hir/Fan Foel might involve some trail breaking on the ground under the escarpment and considering this was an excursion for views, only one of the party would be trail breaking and trail breaking for someone to follow with shorter legs, oh, and that other member of the party didn't like long descents under head torch. I suggested the summit of Cefn Cul. A hill with views, but rarely visited, so other hill walkers footprints wouldn't be an irritation or issue in any composition and the clincher, was sunshine all the way up Cefn Cul, whereas most of the walk in to the Black Mountain would be in shade. To the north and east, high pressure and a temperature inversion revealed itself with a band of haze obscuring the most distant views 20km+, but this band of haze could hold some potential, come sunset/dusk.

Moorland topography and 'texture'

It was an enjoyable walk up across the moorland, the ground frozen, only a few inches of virgin snow, a few spots with maybe a foot in depth and the warmth of the sun, meant layers were soon discarded down to base layers, fabulous. There was no urgency, so plenty of stopping and wandering around to soak up the views over the Tawe and Crai valleys, a look through the binoculars revealed just how many people were out and about on other hills, we came across a solitary set of footprints partially infilled with snow, testament to this hills solitude.

Fan Gyhirych

The prospect for dusk seemed good too, as a distinct yellowy/cyan band in the sky on the horizon became more prominent. A slight concern, from a photography perspective, was high cloud to the west. There's a couple of low knolls on Cefn Cul that vie for the highest points, both give views and it was great to just sit there in the sunshine and enjoy the moment.

Fan Gyhirych II

Instead of staying on the summit area for dusk, I thought there was an area lower down with potentially more interest and along the way the moorland grasses offered some compositional interest at dusk. It was also apparent the Fan Gyhirych would be prominent in most compositions and some high cloud might afford some interest in the sky if it caught the dusk colour too.

The wide view 

As the sun set the cyan/yellow band on the eastern horizon started to turn red and the last light of the setting sun catching the summits also was a crimson red, this lighting phenomena is called alpenglow. This dusk ticked almost all the boxes for perfect alpenglow, with reds turning to magenta as the sun sank lower below the western horizon and I did have a small pang of regret for not being on Fan Foel on the Black Mountain.

Ice, snow and alpenglow

The wife was just enjoying the spectacle of  watching dusk unfold, blue shadows turn magenta and the sky colour intensify slowing going through the warm spectrum. My Xmas present of a Down Jacket paid dividends, as there was no moaning about the, by now, fast dropping temperature over the snow fields and increasing windchill from a breeze. What the photos don't convey was the absence of noise, it was complete silence, no roar of engines or any bird calls and the hill summits had emptied of walkers. It was as if everything was stood still entranced, watching the magic of dusk unfold.

3:2 view composed for 5:2

On a more mundane note, above and below are a 3:2 image composed for a 5:2 image crop, I personally think there are many views in the uplands that suit this format and it is something the 5DS R will be evaluated on. A single image is far preferable for a panoramic crop, than stitching a number of images as the colour changes/light intensity can be fairly dynamic at dusk and dawn. In high winds making a series of images for panoramic stitching, becomes a lottery, ditto with squall/storm lighting too.

5:2 aspect ratio crop

The walk off was an uneventful  the colour fading from the sky and the car reached just as head torches were needed, it was one of the better excursions with a magical dusk in the hills.

Dusk/Twilight colour

Out with the old and in with the new

The festive season and fate dictated that the weather gods smiled broadly on the days I was committed to entertaining family, so no surprises there then.   I did manage two dawn trips to the southern slopes of Fforest Fawr. The 1st promised a scene of snow mantled hills, hoar frosted rocks and moorland, with cold clear air and the ethereal dawn colours of blue and magenta, with the proviso that cloud was moving in by noon as a warm weather front crossed the UK. At an unearthly hour the headtorch revealed much promise, a severe frost coating everything in the Forest of Dean, 2 kettles to clear the frost from the car windscreens. On the way the and full beam headlights revealed hoar frosted trees and grass. Sadly, the weather front c/w cloud, had other ideas, the twinkle of stars disappeared near Abergavenny. Maybe the cloud might break up or the distant horizon would be clear for sunrise?  Nope. 

It was interesting to witness the phenomena of verglas formation unfold, as the incoming warm air melted the hoar frost, which instantly froze, coating rock with ice. I'd always assumed rain falling on sub zero rock as the cause of verglas. 

Hope was sustained, with cloud breaking up to the south east. Alas, the snow/frost thawing on the hills generated a blanket of hill fog and my cunning plan utterly unravelled.  With the hill summits shrouded in fog, the cloud started to break up letting through some sunlight, sigh.

A small positive was the overhead cloud and diffuse light, which presented some photographic interest in the Limestone pavement.

Maidenhair Spleenwort

Lichen and limestone gryke

So, that was it for 2014. Might 2015 deliver a more obliging sunrise over Fforest Fawr?

A new year and a renewed optimism, the Met office mountain weather forecast again wrote of broken cloud, excellent visibility etc. Time to visit to Fforest Fawr again. Deja vu as the car windscreen was de-frosted at an unearthly hour of the night and the Forest of Dean was impressively sparkling in hoar frost. Parking up in Fforest Fawr, the frost had disappeared, whilst getting 'suited and booted' I was conscious of the cold and brisk wind, cloud was moving briskly across the sky and with head torch illuminating the way, I too moved briskly to get warm.

The cloud obscuring where the sun would rise  ...

The view to the SE

Ah well, the sun would clear the cloud eventually. Which it duly did and so the cloud in view cleared too, hmmm.

Suffusion doline, limestone pavement and fast disappearing cloud.

With the cloud absent from both the desired composition and overhead, my spirits dropped a tad. A blank sky, post sunrise, is a depressing sight as 1) it reveals the full misery of a cyan coloured horizon and b) the 'cool' colour imparted to shadows and neutral surfaces. The exposed limestone pavement is neutral grey in colour, great for warm light, not so great for shaded aspects and why overhead cloud is so welcome in colour photography.  

On the plus side, it was a great day for a wander, viewpoints explored and much to ponder on the landforms and topography. Thoughts turned to the afternoon light and a hill to the SE showed some potential. On the way back to the car I spotted this in the grass.

Cordyceps militaris

The Scarlet Caterpillarclub (Cordyceps militaris) a fungus that parasites moth larvae.

The new location demonstrated the stark difference in ease of traversing limestone and sandstone terrain.  I reacquainted myself with the tedium and effort of traversing Molinia dominant moorland on the quartzitic sandstones and from there on, kept to the bracken/nardus terrain instead. In comparison with other areas of the Brecon Beacons NP, the size of the sinkholes through the quartzite sandstone were notable.  Some viewpoints were also found and even some clouds put in an appearance too.

Fforest Fawr view

Where the quartzite bedrock is exposed there are fine examples of glacial striae, polished surfaces, chatter marks etc

Chatter marks and glacial polish, glacial ice movement from left to right.

Incoming sheet cloud from the SW was the sign that sunset would be a non event and time to go home, not a bad day on the hills though.