Glacial and periglacial structures and landforms

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 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 this photo 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. This infill can be seen in the lower part of the photo. 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. The photo shows a portion of one of these. The vein cavities are associated with 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. 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. Best viewed large....

These are the Ox Stones on Burbage Moor, just south-west of Ringlinglow on the edge of Sheffield. The southern end of Stanage Edge is visible on the skyline on the left of the photo. The Ox Stones are comprised of the Rivelin (aka Chatsworth) Grit (Upper Carboniferous, Namurian age) and are a compact group of residual tors resulting from periglacial (permafrost/freeze-thaw) action during the last glacial period when the Peak District was largely free of ice but still under permafrost conditions. The mushroom shape of the tors is probably a result of wind erosion during this time in the cold, dry climate, with strong winds hurling sand against the tors in a low, ground-hugging sand-blast.

Originally uploaded for the Guesswhere UK Group. It was blowing very hard when I took this. This is a view from the summit of Suaineabhal (429m) in West Lewis, looking southwards over Loch Gruineabhat to the mountains of North Harris. Clisham (An Cliseam) is the left-most peak of the centre group which at 799m, is the highest mountain in the Western Isles. Suaineabhal is one of the lesser mountains of West Lewis, but a still a grand and rewarding climb, and its relative isolation from other hills makes for superb views all round from the summit. This is a starkly beautiful, remote landscape, little changed since the retreat of the last ice sheet 11,500 years ago. And now they want to cover it with wind turbines. Grrrrrrr!!!!! Suaineabhal is pronounced something like SWAIN-a-vahl

The doline pond at Patching, near Worthing, Sussex Taken with an early Kodak 1-megapixel digital camera.

Seaford Chalk with solution pipes, infilled with Palaeogene sands and gravels. Hope Gap, Seaford, Sussex. Taken with an early Kodak 1-megapixel digital camera.

Dry Valley in Chalk, near Ditchling Beacon, South Downs, Sussex. Taken with an early Kodak 1-megapixel digital camera.

Viewed from the Three Horseshoes pub on the Leek-Buxton road.

Hen Cloud is a spectacular outcrop of Roaches Grit ('Millstone Grit') at the southern end of the Roaches in the Staffordshire Moorlands area of the western Peak District.

Pleistocene river gravels of the proto-Thames form low cliffs on the south coast of Mersea Island, Essex. This is a site of regional geological importance and is a SSSI. Active erosion is taking place, with the cliffs receding northwards. Rising sea-levels associated with global warming will exascerbate this effect.

Pleistocene river gravels of the proto-Thames form low cliffs on the south coast of Mersea Island, Essex. This is a site of regional geological importance and is a SSSI. Active erosion is taking place, with the cliffs receding northwards. Rising sea-levels associated with global warming will exascerbate this effect.

Looking westerly from Silver How towards Lang How, Blea Rigg and the Langdale Pikes. This entire broad, ill-defined ridge between Great Langdale and Easedale is an absolute delight of miniature rocky peaks, grassy dells and little gems of tarns. A lovely place to spend a lazy, sunny, summer afternoon when the popular summits around about are thronged out with walkers. On this occasion, it was looking a bit grey and moody. I think Bill's mother must live somewhere over in the the distance. View large on black See where this picture was taken. [?]

Manstone Rock - a prominent quartzite tor on the Stiperstones ridge, Shropshire.

Originally posted for the Guesswhere UK group. The River Lathkill in full flood, surging through the tufa dam at Lathkill Lodge, Lathkill Dale, in the White Peak, Derbyshire. Uprising, carbonate-rich groundwater flowing into the river bed in certain places causes deposition and accumulations of calcareous tufa (a harder and more extensive version of a furred-up kettle), blocking the stream and enabling plants to colonise the river bed. Normally the water flows very slowly here and is sometimes completely dry in the summer. At high flow times, the river surges through the tufa dam, finding its way through a network of shallow channels, as in the picture.

The folds are superficial valley-bulge structures in the weak Namurian shales and do not extend more than a few metres into the subsurface. They have formed as a result of the differential loading of the valley sides and valley bottom - the weak valley floor sort of squidges up. This originates mainly from melting of permafrost conditions at the end of the last glacial period around 11,500 years ago. Continuing movement of the valley sides causes the landslides which periodically disrupt the A57 Snake Pass road nearby on the north flank of the valley.

Originally posted for the Guesswhere UK group. Splendid river terraces in Glen Catacol, on the north-west coast of the Isle of Arran, Scotland.

Gigjökull glacier, south Iceland, in September 1988. It's definitely much smaller now. Evidence of global warming? Scanned from Kodachrome 64 transparency film. Taken with a Zenit 'E'.