Glacial and periglacial structures and landforms

Originally uploaded for the Guesswhere UK group. This is a view NNW across White Path Moss from Stanage Edge in the Peak District, at Nat Grid Ref. SK 244 836. Stanedge Pole, a wooden guide post mounted in a cluster of boulders is visible on the skyline towards the left side. White Path Moss is an extensive flat area of peat bogs and watery pools, very difficult to cross except on a very subtly elevated shallow ridge known as Friar's Ridge. It is generally accepted that this is a nivation platform, a.k.a. cryoturbation platform. These form where a permanent but relatively shallow snow-patch (as distinct from an ice-sheet) has existed for an extended period of time, perhaps thousands of years. They are well-known from periglacial environments, past and present-day. Beneath the more-or-less stagnant snow-patch, there can be considerable freeze-thaw action, breaking up the top surface of the underlying bedrock and causing it to flow slowly down even the shallowest of slopes. The effect is for this flow material to 'fill in' any pre-existing hollows and generally smooth out the existing landscape, ultimately tending to become a flat surface. In this locality the nivation platform is a broadly linear feature, parallel to the outcrop of Stanage Edge and set back from it by as much as 1.5 km. Whatever the reasons for the origin, I was really struck by the colours up here on this bright December day. Best viewed large....

An image from a photostudy of the Mother Cap Stone, an extraordinarily photogenic natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. In this photo it is caught in the golden light of the setting sun.

An image from a photostudy of the Mother Cap Stone, an extraordinarily photogenic natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. In this photo it is caught in the golden light of the setting sun. This is an uncropped version of the next photo. I like both; which do you prefer?

An image from a photostudy of the Mother Cap Stone, an extraordinarily photogenic natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. In this photo it is caught in the golden light of the setting sun.

An image from a photostudy of the Mother Cap Stone, an extraordinarily photogenic natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. In this photo I tried to capture another aspect of its profile, this time silhouetted against the dark clouds and golden light of the setting sun.

An image from a photostudy of the Mother Cap Stone, an extraordinarily photogenic natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. In this photo it is still illuminated by the bright western light a few minutes after sunset.

An image from a photostudy of the Mother Cap Stone, a natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. This was a rather cloudy and gloomy autumn day, but the late afternoon sun provided some low-angle brightness which emphasised the textures of the outcrop.

An image from a photostudy of the Mother Cap Stone, a natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. This was a rather cloudy and gloomy autumn day, but the late afternoon sun provided some low-angle brightness which emphasised the textures of the outcrop.

An image from a photostudy of the Mother Cap Stone, a natural rock tor of cross-bedded Chatsworth Grit (Namurian) high on the South Yorkshire Eastern Edges in the Peak District National Park. This was a rather cloudy and gloomy autumn day, but the late afternoon sun provided some low-angle brightness which emphasised the textures of the outcrop.

Only half an hour previously, the cloud had been down to ground level, enveloping the scene in a damp drizzly mist. Then within the space of 15 minutes or so, the cloud lifted and shafts of sunlight beamed down on to a golden autumnal landscape. Taken from Burbage Edge in the Peak District National Park. Higger Tor is on the right skyline and the Carl Wark hillfort just to the left of centre.

Only half an hour previously, the cloud had been down to ground level, enveloping the scene in a damp drizzly mist. Then within the space of 15 minutes or so, the cloud lifted and shafts of sunlight beamed down on to a golden autumnal landscape. Taken from Burbage Edge in the Peak District National Park. Higger Tor is on the right skyline and the Carl Wark hillfort just to the left of centre. Vertical scale exaggerated x2 in order to emphasise geological and geomorphological features, but it also makes for a nice effect! The v-shaped notch of the Burbage Brook is especially clear in this vertical exaggeration. This probably indicates renewed downcutting during post-glacial isostatic uplift of the area. (The 'cheese wire effect')

Only half an hour previously, the cloud had been down to ground level, enveloping the scene in a damp drizzly mist. Then within the space of 15 minutes or so, the cloud lifted and shafts of sunlight beamed down on to a golden autumnal landscape. View southwards from Burbage Edge in the Peak District National Park. The Burbage Brook flows through the prominent v-shaped channel; the Carl Wark hillfort is on the skyline just to the right of centre.

An image from a photostudy of the Mother Cap Stone, a natural rock tor of cross-bedded Chatsworth Grit (Namurian) high up on the South Yorkshire Eastern Edges, overlooking the Derbyshire Derwent valley in the Peak District National Park. A southerly view in the late afternoon on this autumn day.

The view down the Burbage valley from the north end of Burbage Edge. Higger Tor is the highest feature on the skyline, with the Carl Wark hill fort in the centre. The v-shaped notch of the Burbage Brook probably indicates renewed downcutting during post-glacial isostatic uplift of the area. (The 'cheese wire effect')

The view down the Burbage valley from the north end of Burbage Edge. Higger Tor is the highest feature on the skyline, with the Carl Wark hill fort in the centre. The v-shaped notch of the Burbage Brook is especially clear in this vertical exaggeration. This probably indicates renewed downcutting during post-glacial isostatic uplift of the area. (The 'cheese wire effect')

Halfway up the slab of Plattkofel, we were beset by short-lived snow showers, with sunshine in between. The high mountains (Marmolada group) to the south-east are caught in sunlight. There are small glaciers up there.

This photo shows part of the modern open quarrying for fluorite and barytes along the line of Dirtlow Rake near Castleton, on the site of the former Hollandtwine Mine. This is a rather special place. On the far north-west wall, the quarrying has cut a perfect cross section through a cave system. There are vertical vein cavities with horizontal fluting. These lead down to a meandering horizontal passage about 20 m below the original ground level. This passage must have been a phreatic tube at one time - entirely below the water table. The scalloping seen in the supplementary photos is a typical solution feature seen in these sort of tubes. Finally, there is a lot of fine yellow-ochrous loose sediment infilling some of the swallets and partially choking up the phreatic tube. I think this is a loess deposit - a fine wind-blown dust originating from rock 'flour' ground up by ice-age glaciers. In the last glacial period (the Devensian) the Peak District was largely free of ice, although it was under cold, permafrost conditions. Strong winds around the periphery of the ice sheets blew all the dust around which accumulated in pre-existing hollows and fissures on the formerly glaciated surface. So, this quarry has enabled us to see karst (solution) and periglacial features that would normally only be accesible to cavers. I would hope that some of this quarry face would be preserved, but my understanding is that the whole lot will be backfilled and grassed over, so we will end up with a tidy, bland, green grassy area which tells us nothing at all. :-( But I suppose it will keep the planning authorites happy.

This photo shows part of the modern open quarrying for fluorite and barytes along the line of Dirtlow Rake near Castleton, on the site of the former Hollandtwine Mine. This is a rather special place. On the far north-west wall, the quarrying has cut a perfect cross section through a cave system. There are vertical vein cavities with horizontal fluting. These lead down to a meandering horizontal passage about 20 m below the original ground level. This passage must have been a phreatic tube at one time - entirely below the water table. The scalloping seen in the supplementary photos is a typical solution feature seen in these sort of tubes. Finally, there is a lot of fine yellow-ochrous loose sediment infilling some of the swallets and partially choking up the phreatic tube. I think this is a loess deposit - a fine wind-blown dust originating from rock 'flour' ground up by ice-age glaciers. In the last glacial period (the Devensian) the Peak District was largely free of ice, although it was under cold, permafrost conditions. Strong winds around the periphery of the ice sheets blew all the dust around which accumulated in pre-existing hollows and fissures on the formerly glaciated surface. So, this quarry has enabled us to see karst (solution) and periglacial features that would normally only be accesible to cavers. I would hope that some of this quarry face would be preserved, but my understanding is that the whole lot will be backfilled and grassed over, so we will end up with a tidy, bland, green grassy area which tells us nothing at all. :-( But I suppose it will keep the planning authorites happy.