Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click HERE
Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click HERE
Thursday, 30 August 2012
The arrows for Irish Sea Glacier movements are very generalised. Some of them refer to the Devensian glacial episode, and some to the Anglian. Almost all of the limits shown on this map are subject to further debate and correction. But we are getting there.....
The Devensian ice limit in Pembrokeshire is mine -- other published lines are demonstrably wrong, since they do not accord with the field evidence.
Click to enlarge.
Wednesday, 29 August 2012
In the meantime, just look at the extraordinary compression structures on all of the glacier snouts. Click to enlarge the image. There is also a lot of melting going on here. Where does the meltwater go to? Answers on a postcard please.....
Monday, 27 August 2012
This is an extraordinary "fluke" photo taken by satellite above Gaasefjord, one of the fjords running into Scoresby Sund, East Greenland. Sorry if the photo and the caption appear pornographic.........
These are two tidewater glaciers ejecting a constant supply of icebergs and brash ice into the fjord. We are probably looking at a six-month winter supply of glacier ice here which has simply piled up because it could not escape -- the photo was probably taken in May or June just as the sea ice was breaking up and "releasing" the accumulated iceberg debris so that it could be more easily dispersed into the fjord and onwards towards the outer coast.
You don't often see a dense accumulation of iceberg debris blocking up a fjord like this -- by comparison, the icebergs (and brash ice) falling off the glacier snout into the sea in the summer are all quite rapidly dispersed by tides, winds and currents.
Ice Sheet edge in Peary land, north Greenland. This might give a reasonable impression of what the ice sheet edge might have looked like in Somerset or Wiltshire during the Anglian glaciation. This is a summer photo -- the land is snow-free for maybe 3 or 4 months in the summer. Nevertheless, there is very thick permafrost.
A winter photo of an outlet glacier piedmont in Peary Land. It's almost too perfect to be true!! The ice in this glacier is very cold -- this would be classified as a "polar glacier" in which there is very little trace of meltwater action either in or beneath the glacier.
The other day I came across a very interesting study of glacial erratic distributions in Washington State, in the NW of the USA. Researchers have plotted the locations and types of thousands of erratic boulders on the flank of Rattlesnake Mountain. The erratics apparently became visible for the first time following very extensive forest fires which effectively cleaned off the vegetation cover, leaving a bare land surface. The interesting thing is that few of these erratics have been directly dumped by glacier ice coming from the Cordilleran Ice Sheet. Instead, they have been carried and emplaced by floating and grounded icebergs in periodic paleofloods and temporary lakes -- with water up to 800 feet deep at times.
The erratics appear to be of many different ages -- suggesting that many have been picked up, carried and dumped on several different occasions, each one coinciding with a new glacial episode.
There are many single erratics, erratic clusters and erratic trails -- but in this case the trails appear to be perpendicular or transverse to the main direction of iceberg movement or water flow. Erratics do indeed behave in a myriad of erratic ways......
The rocks were left after ice dams holding back a huge lake near Missoula, Mont., broke, re-formed and broke again from 1 million to 2 million years ago to as recently as 13,000 years ago. The floodwaters backed up at the downstream end of the Pasco Basin behind Wallula Gap, a narrow ridge opening through which the Columbia River flows today. The lake lapped the gentle slope of Rattlesnake Mountain, northwest of the gap and part of the Hanford Reach National Monument in south-central Washington Rattlesnake Mountain was the highest peak protruding from the 800-foot-deep temporary body of water, dubbed Lake Lewis. The rocks and boulders, so-called erratics, grounded as the waters of Lake Lewis receded after a few days like a slowly draining bathtub.
Bjornstad led a team that surveyed and analyzed the mostly-granite-strewn debris fields over 15 square miles of Rattlesnake Mountain. He said that the ice-rafted debris left deposits of three types: widely scattered rocks and boulders, distinct clusters and "bergmounds" – low, cone-shaped clumps of erratics that, like a moraine left by glaciers, alter the topography. Bjornstad's group discovered rafted rocks as long as 14 feet.
The erratics were concentrated along northeast-running gullies. Bjornstad suggests that the speed of the flowing water varied as it crossed an uneven surface, and that may have created eddies that forced an ice jam in the deeper, quieter waters at the back of these gullies. The erratics and bergmounds decreased as the surveyors worked up the mountainside. Bjornstad attributed the lower number to smaller successive floods.
Bjornstad and his colleagues found that most of the erratics were rounded, showing the effects of weathering and suggesting that they were carried in by older Ice Age floods.
Proposed glacial limits for the Anglian and Devensian Glaciations in Southern Britain
(BSJ, Aug 2012)
Here we are. This is my latest attempt at portraying the British Glacial Limits for the Devensian and Anglian glaciations -- along the southern margins of the British and Irish Ice Sheet. I think it accords pretty closely with the evidence on the ground and with the glacial modelling which I have covered quite extensively on this blog over the past couple of years. Current dating puts the Anglian at around 450,000 years ago, and the Devensian at about 20,000 years ago. There may well have been another glacial episode between these two -- currently referred to as either the Saalian or Wolstonian Glaciation. Many authors have attempted to map the limit of that glacial episode -- broadly, it seems to have been more extensive than the Devensian glaciation, and less extensive than the Anglian. However, the line drawn by Gibbard and Clark is so unsatisfactory, in so many ways, that I have left it off my reconstruction above. Let's just say for the moment that the events -- and the deposits -- of that episode are complicating factors, and that they will one day get sorted out........
Let's concentrate on South Wales and Southern England. Note that on the map I have shown the Anglian and Devensian ice edges in more or less the same position on the north coasts of Devon and Cornwall, assuming that the cliff barrier was sufficient to prevent any great ice incursion inland during either of the glacial episodes. In both glaciations the Irish Sea Glacier affected the Bristol Channel; in the earlier one the ice was so powerful that it pushed all the way eastwards into Somerset and maybe into Wiltshire, deeply inundating the whole of Pembrokeshire in the process; but in the Devensian the ice was more limited in extent, affecting Carmarthen Bay but maybe failing to penetrate further east than the Gower Peninsula.
Map showing the proposed extent of the Anglian Glaciation in Southern Britain, with approximate flowlines. On this map the small ice caps and perennially snow-covered terrain of SW England are shown as being incorporated into the glaciated area. In reality the margin between Irish Sea ice and locally generated ice caps would have been very difficult to discern. The ice caps over Exmoor, Bodmin Moor, Dartmoor, the Blackdown Hills, the Mendips and the Cotswolds are shown with the dotted symbol and identified by letters.
One or two points relating to the Anglian. The ice direction arrows are now pretty reliable, having been thoroughly established over many years by reference to striae, erratic transport, and glaciological modelling. That having been said, there must have been a very complex contact zone in the South Wales coastlands between Welsh ice streaming southwards from the Welsh Ice cap and Irish Sea ice pressing in with great force from the north-west and west. The evidence for pushing the glacier into Wiltshire? Well, glacial deposits on the Somerset coast, into the Somerset Levels and on the flanks of the Mendips, and glacial erratics on Salisbury Plain. This very extensive ice cover is also needed to provide a satisfactory explanation for the giant erratics (apparently ice rafted) on the English Channel coasts. It's all to do with isostatic depression. See many earlier blog entries on this. If anybody doesn't like this reconstruction, please give me a better explanation of these large coastal erratics......
One feature which is crucial to my reconstruction is the difference between the western and eastern pro-glacial zones -- ie the areas beyond the Irish Sea Glacier edge. I think that in the west, in the counties of Cornwall, Devon and Somerset, there was considerable snow and ice accumulation during each glacial episode, giving rise to many small local ice caps and perennial snowfields. David Evans, Stephan Harrison and colleagues have given us a good examination of one of these -- the Dartmoor Ice Cap. Further to the east, the air temperatures and ground temperatures were lower, and there was not so much precipitation -- so the landscape was essentially one affected by frozen ground or periglacial processes. The boundary between these two zones was probably in Wiltshire and Dorset.
A reconstruction of the Celtic Sea Piedmont Glacier during the Devensian maximum. The map excludes the complex contact zone between Welsh Ice and Irish Sea Ice in South and West Wales, and the ice cap / perennial snowfield zone of Devon and Cornwall.
One of the key features of my Devensian map is the ice margin in the outer part of the Bristol Channel. I think that the outer edges of the Pembrokeshire Peninsula were glaciated in the Devensian, since we find fresh glacial deposits near Dale, at West Angle Bay, and on the island of Caldey. On Caldey the ice was moving pretty well west to east. Maybe the ice margin was a little further eastwards, in Carmarthen Bay. There is still doubt about the events on Gower -- I would appreciate input from others on this. So was there effectively an ice dam across the Bristol Channel? As the ice started to melt, could there have been a great glacial lake here? There might have been -- and a reexamination of all of the submarine materials in the channel might give us some clues on this. The Devensian ice also reached the Scilly Isles -- as established by James Scourse and others, with the aid of radiocarbon dating evidence. However, we have to explain the very similar altitudes of the ice marginal deposits on all of these coasts, from St David's Head to the Scillies -- and if you reconstruct the surface contours of the Irish Sea / Celtic Sea ice mass, the contours must run broadly parallel with the ice edge. That means that the ice must have been moving predominantly from the NW towards the SE. I part company with most other geomorphologists on this -- they want ice in the Celtic Sea to be moving from NE towards SW, and they also want an ice surface gradient which is so low that it seems to me to defy the laws of physics.
So there we are, boys and girls. That's my current best explanation of the situation on the ground. Now let's test it to destruction........
Sunday, 26 August 2012
A computer-generated model of the area affected by the British-Irish Ice Sheet -- one of many models coming from the glaciology team at Aberystwyth university. Note that according to this model Stonehenge lies within the ice margin. But local ice caps are not shown -- and the modellers have not shown the Dartmoor Ice Cap....
In the light of the Dartmoor evidence which was recently published -- showing pretty unequivocally that Dartmoor and the other uplands of SW England were glaciated during the Devensian or LGM (Last Glacial Maximum) -- we have to do some serious revision relating to ice limits. Although the evidence for the Devensian is easier to pick up than the evidence for older glaciations (including the Anglian) things are complicated by the fact that ice edges have overlapped in quite complicated ways -- with the "greatest extent of ice" being of one age here, and of quite a different age over there. Each glacial episode and each growth of the British-Irish Ice Sheet has its own dynamics ...... and that makes life complicated for glacial geomorphologists.
That having been said, one must try to make some sense of the situation in the south-western counties of England. As I have pointed out many times on this blog, there is physical evidence on the ground for a glacial advance by the Irish Sea Glacier across the Somerset coast and into the Bristol area. There is further evidence of glacial material in the Bath - Bathampton Down area, and as far as the Greylake No 2 Quarry shown on this map:
Relief map showing main uplands and lowlands, rivers and key Quaternary sites in part of the SW quadrant of England. (Source: GCR tome on SW England)
Further inland, the evidence is more equivocal, and we still do not have clear evidence that the ice reached Street, Glastonbury, and the SE end of the Mendips. The glacial deposits so far recorded in this area appear to be very old -- they are conventionally interpreted as Anglian in age. On the other hand the Dartmoor evidence appears to be supported by the glacier modelling experiments done at Aberystwyth University, showing that (on the basis of glaciological principles) the Irish Sea Glacier COULD have covered the whole of the Somerset Lowlands and reached as far east as Stonehenge and Salisbury Plain. So where is the ground evidence to support that contention? Maybe a mottley collection of erratics at Stonehenge is the evidence we need -- but I quite accept that not everybody is inclined to accept that!
But there is a real dilemma here -- why are the glacial materials already described in the literature low down in the stratigraphic sequence, with no fresher deposits above them? But it defies logic to say that Devensian ice affected the SW uplands of Devon and Cornwall and reached the Scilly Isles, but did not extend as far as Salisbury Plain. Even if the ice sheet had an extremely low surface gradient when it pressed in from the W and NW, it must surely have pressed as far inland as Yeovil, Shepton Mallet and Frome? The laws of physics must apply -- although sometimes a simple law needs to be replaced by something more complex if explanations are to make sense.....
I still think it's probable that the Stonehenge erratics are genuine GLACIAL erratics, transported initially in the Anglian glacial episode. But I also think that in the Devensian the area shown in the lower map was affected by a very complex set of processes in which low temperatures, periglacial action, snowfields, icefields, small local ice caps and the glacier ice of the Irish Sea glacier all interacted with one another -- with an emphasis on landscape protection rather than alteration. Prof David Evans and his colleagues have pointed out that the ice on Dartmoor must have been thin, very cold, and very slow-moving -- so that there are very few traces of either erosional or depositional features in the landscape of today. Also, most of the "erratic" material carried by the ice was not very erratic at all, having been moved maybe no more than a few tens of metres from its source areas.
Ice thicknesses on the Dartmoor Ice cap at the time of its greatest Devensian extent. (After David Evans, Stephan Harrison and colleagues.) Note that in some places the ice was c 180m thick.
To synthesise. I think that during the Devensian maximum the whole of this landscape was covered by perennial snow and ice. Maybe for short periods in the warmer summers, the snow blanket was broken up, allowing solifluxion and some redistribution of materials to occur. How long did this snow cover last for? Centuries or millennia -- it's difficult to say, without hard evidence. Maybe it waxed and waned several times. Beneath most of the snow blanket, the ground must have been permanently frozen or locked into permafrost, but maybe some of the best-known periglacial processes (frost cracking, polygon formation etc) were inhibited because ground temperatures were not low enough. In hollows and valleys there must have been thick accumulations of snow, and there must have been many other snow-banks against escarpments and hillsides. The landscape might have looked like this from above:
Winter landscape, West Greenland, well beyond the ice sheet edge. Some of these snowbanks are perennial -- but most of them melt away every summer. The distance from the left edge of the photo to the right edge is less than 2 km.
Over the following uplands there were probably small, thin ice caps such as those I have often illustrated on this blog: Bodmin Moor, Exmoor, Dartmoor, the Blackdown and Brendon Hills, the Quantocks, the Polden Hills and the Mendips. As for the other smaller hill masses and upland plateau areas (including Salisbury Plain) -- they too might have supported thin ice caps at the same time as the Dartmoor Ice Cap was in existence. I also think that a lobe of ice from the Irish Sea Glacier must have pressed in from the Bristol Channel and Bridgwater Bay -- pressing inland for maybe 40 km or more. The ice also reached the Scilly Isles and pressed against the coasts of Devon and Cornwall, sometimes unable to push inland much beyond the cliffline and in other places making small incursions into old estuaries and embayments of lower land.
So what we have here is an extremely messy situation. If you had flown over or walked about in the area at the time, you would have been hard pressed to define the junctions between Irish Sea glacier ice, local ice created on the upland ice caps, and firn and snowfields which were quite independent and more liable to seasonal melting and regeneration. I will shortly post a map showing where I think the ice edge might have been.....
This is an interesting map (made by prof Fred Shotton in the 1960's) showing the distribution of Lower Palaeolithic artefacts in Southern Britain. The single dots represent sites where up to ten artefacts have been found -- and the larger dots indicate more than ten finds at a location. Shotton was very keen on showing the distribution of flint finds -- so most of these sites will show places where flint was used -- but he must also have included artefacts made with other stone types as well. There is obviously a relationship here with the limit of the Devensian glaciation, since the SE quadrant of the country is where the great majority of finds have been recorded. But cave finds are not shown on this map -- and there are plenty of those, including some in areas which were demonstrably glaciated during the Devensian.
My main interest here is in the counties of Somerset, Devon and Cornwall, where remarkably few of these Lower Palaeolithic finds are recorded. I wonder how this might relate to the nature and extent of the snow and ice cover during the Devensian glacial episode?
Saturday, 25 August 2012
The top one shows the plateau of Dranga and the bottom one shows the nearby plateau of Glama. Approx the same area is covered in both photos. They might look very similar, but note that in the top photo the edge of the snow-covered area is quite sharp, whereas in the bottom photo it is much more diffuse. To some degree this is because the top photo is a summer photo and the bottom one shows a springtime situation -- but the snowline and snow edge is certainly much sharper on Dranga. There is one further clue -- look carefully at the Dranga photo and you will see small projecting lobes running down into the radiating valleys. These are little outlet glaciers -- not very healthy ones, but they do at least still exist. In the case of Glama there is no ice cap at all -- there are no traces of glaciers flowing into the troughs -- everything white in the photo is seasonal snow which melts every summer and reforms again every winter.
Now then -- on the matter of Devon and Cornwall. I am pretty convinced that during the Devensian there were little ice caps like the Drangajokull on Exmoor, Dartmoor, Bodmin Moor and the Mendips, and maybe on other uplands as well. On some of the lower hills, and on Salisbury Plain, we will have had a situation analagous to that of the Glama Plateau -- a lot of permafrost, a lot of snow, but no actual glacier ice.
.... and on the coasts of Devon and Cornwall, and in the great inlet of the Somerset Levels? Almost certainly an ice edge of the Irish Sea Glacier, looking something like this:
This is a "fingered" ice sheet edge in West Greenland. Below is a more complex landscape, in Peary Land, North Greenland:
There are several types of "Ice Age" landscapes here. To the left is the edge of the Greenland Ice Sheet, fingering into the low-lying areas as ice lobes. There are several ice caps. One of them (top left) is connected to the ice sheet, but probably has its own dynamics. Just south of the centre of the photo is another small and almost circular ice cap -- maybe the Dartmoor Ice Cap looked rather like this. The higher land beyond the ice edge -- especially in the northern part of the photo -- is covered with ice patches, small glaciers, perennial and seasonal snowfields. Finally the lower lying areas are both ice free and snow-free in the summer -- but here there is very thick permafrost.
We have talked about this before. New development. This is an interesting map (made originally by Sparks and West, from many sources) showing the main occurrences of periglacial features in Great Britain. It's pretty rough, and many occurrences of single ice wedges (for example) are missing -- but you get the general idea. Again, the SE quadrant of the country, outside the Devensian glacial limit, is where we see the greatest concentrations of periglacial features associated with permafrost and surface movements in the active layer during the summer months. But there are quite a few features in Scotland, well within the Devensian limit, and also in Devon and Cornwall -- an area now subject to much scrutiny following the publication of the recent paper on the Dartmoor Ice Cap. One problem is that these features are difficult to date. When they occur close to the ground surface -- as in Pembrokeshire -- fossil ice wedges can reasonably be assigned to the Younger Dryas, since we know that it was very cold indeed, with permafrost widespread. We can probably assume that most of the periglacial features of Pembrokeshire, South Wales, Devon and Cornwall, are of approximately the same age. This still allows for the possibility of quite a heavy cover of glacial ice, firn and snowfields in SW England during the peak of the Devensian, around 20,000 years ago.
One question which has never -- to the best of my knowledge -- been satisfactorily answered is this: "Why are there prominent chalkland patterns on the chalklands of eastern England and Kent, but not on the chalklands of Wiltshire and Southern England?" It may be that this has something to do with the nature of the chalk itself, or with topography, but that explanation is not entirely satisfactory -- so we have to wonder whether there might have been a more extensive and thicker snow blanket in Wiltshire, for example, and a colder and more arid climate further east, permitting the development of much thicker permafrost and the formation of more prominent periglacial features in the landscape.
By the way, Ailsa Craig microgranite was (and still is?) the favoured rock used in the manufacture of curling stones........
Friday, 24 August 2012
One of my favourite photos from the old days --- a tabular berg, probably from Daugaard Jensens Gletscher -- the big outlet glacier at the head of Nordvestfjord. This photo was taken while we were kayaking on the fjord in August 1962. Tabular bergs of this size are not all that common in the East Greenland fjords, since the glacier front generally breaks up in smaller chunks rather than in big slabs.
This berg is quite badly degraded already -- maybe it has been moving about in the fjord for decades if not centuries. The sides are well worn, and there are many pinnacles and old meltwater tunnels exposed. Eventually, the current will take bergs like this out into Hall Bredning and Scoresby Sund -- some of them may even make it out into the open sea off the East Greenland coast.
Thursday, 23 August 2012
Sorry all -- our phone has been out of action for a week, and in spite of innumerable complaints from us and many of our family and friends it still isn't fixed. Broadband comes and goes for a few minutes at a time -- and when it does come on (as this afternoon) there is a flood of 50 or 60 messages! Please forgive me if I have missed any messages from anybody -- unintentional, I assure you.... also, I will try to pick up the threads and the arguments when things settle down again. A very nice young lady in India assures me that it will be fixed this very day. Hmmm......
Monday, 20 August 2012
Mauls and lumps of quarried or mined rock in the Bronze Age copper mine on
Parys Mountain (Phil Morgan)
Neolithic flint mine at Grimes Graves, Norfolk. The pit props and the
electric lights are modern......
Before coming to the question in the heading, let's take a look at this:
Bronze Age copper mining and "underground spaces"
Thanks to Rob Ixer for forwarding the reference mentioned below. For the moment, we'll have to be happy with Robert Johnson's abstract, since the article costs £25 or whatever for normal mortals to read. So those who are initiated into the mysteries of social archaeology (whatever that is) can read it, but the rest of us are mystified, and look on in awe........
Anyway, what the article seems to say is that when mining became an acceptable activity during the Bronze Age, caves were no longer used for rituals etc, so that deposits and the use of artefacts in caves ceased or at least diminished drastically. The author looks at data set A and data set B, finds that there is a correlation, and assumes a causal relationship. Very dodgy indeed. The author suggests that Bronze Age people "developed a different knowledge of how caves were formed" when they started mining, and ceased to look on underground spaces as magical or sacred places. Hmmm -- excuse me for saying so, but that sounds like a load of guff to me. Why dress this up in elaborate garments? Surely people moved out of caves and into the open landscape as communities became more sophisticated, as the population increased, and as the threat from large predatory animals diminished following the end of the last glacial episode? That was just one of many settlement shifts during the course of history -- others occurred when hunting and gathering gave way to permanent agriculture in preferred locations, so that migrational or seasonal settlement sites became permanent ones; and another shift occurred when agricultural surpluses and economic specialisation was associated with the growth of towns and then cities. I would suggest that ritual played no part in any of this.......... the driving forces were economic and social, not religious.
Moving swiftly on, the author seems to be suggesting that once mining was established (for example, on the Great Orme near Llandudno, and on Parys Mountain on Anglesey) people were no longer in awe with the mining and quarrying sites, and looked on them from that point on as strictly utilitarian places -- having an economic value bit not a spiritual or ritual value. If that's what Robert Johnson is saying, then I think I would agree with him!
So what about the attempts by TD, GW, MPP and the rest of them to flag up "quarrying sites" as places of huge spiritual or ritual significance? As I have said before, even if these quarries existed, I see no evidence anywhere that they were deemed to be specially significant. They would have been simply places where stone could be obtained -- and if the stones were special enough, maybe the locations would be given some economic or even strategic value by the communities that "owned" them.
As I have pointed out before, this is exactly what happens with coal mines in South Wales, copper mines in Cornwall, salt mines in the north of England, gold mines in South Africa and even mines and quarries extracting limestone for cement or Bath Stone for building. Are these places REVERED or WORSHIPPED? No way -- they are places invested with economic or resource value -- more likely to be associated with crimes and warfare than worship or ritual. I suggest that it was ever thus.......... even back in the Neolithic.
Can we get any guidance from flint mines like Grime's Graves, Cissbury, Blackpatch and Harrow Hill? As far as I can make out, no ritual or spiritual significance was attached to any of them. However, this might cause some confusion:
"The most memorable discovery at Grimes Graves is what appears to be a fertlity shrine set up in an abandoned shaft. The shaft is quite short - we can assume that the miners failed to hit the seam of flint they were after and gave up on further digging. But before they quit the gallery they carved out a ledge, or altar, upon which was found a godess figurine of chalk, either very obese or pregnant. Beside the female figure was a phallus of chalk. Surrounding both was a pile of antler picks. The accepted reading of this shrine is that the miners, disappointed at their failure to find the flint they needed, made a religious offering to the godess to ensure the continued "fertility" of the mine. As is usual in historical investigation, there is a second interpretation which considers the shrine to be a much later addition..........."
An impression of the "ritual" assumed to have been conducted in a "failed pit" at Grimes Graves. Was this a sign that the whole complex of excavated shafts and tunnels was sacred in some way? Probably not.
"Copper mining and the transformation of environmental knowledge in Bronze Age Britain"
Journal of Social Archaeology June 2008 vol. 8 no. 2 190-213
Department of Archaeology, University of Sheffield, UK,
The argument presented in this article is that copper mining during the Bronze Age in north Wales transformed the cultural landscape, specifically people's understandings of underground spaces — the mines themselves and nearby caves. The basis for the argument is a correlation between mining and a hiatus in the depositional history in the region's caves. The interpretation offered for this evidence is that through the creation and appropriation of underground spaces during mining people developed a different knowledge of how caves were formed. This new environmental knowledge denied the caves a status as mediatory or liminal places where rituals associated with other spheres of social life might be undertaken. Such knowledge was constituted by and served to structure the use and perception of the landscape by the communities who worked the mines.
Note from Phil Morgan, for which many thanks:
I've attached a photo of a Pennant Sandstone erratic with the Cynon (Aberdare) Valley, from whence it probably came, in the distance. This stone is one of three deposited in close proximity to one another on Senghenydd Common, they are clearly visible using satellite imaging (Where's the path = ST 11365 92419, 51.623593, -3.281783).
I don't know the location, and haven't checked the geology or the topography -- but it's a very nice photo of an erratic! If this is a sandstone, it's a very thin-bedded one -- looks more like a shale or mudstone to me -- but that would be typical of these rocks, which are among the youngest in South Wales -- equivalent of the Upper Coal Measures.
All that having been said, I do find it quite remarkable that if a cromlech or a recumbent stone setting has a large stone present on the site (normally termed a capstone) then it must have been quarried somewhere else, and transported to place where it is used. It's almost as if the archaeologists NEED to believe that large stones were moved rather than used in situ. Why is this? Do they NEED to demonstrate to themselves and the rest of society that our Neolithic ancestors were sophisticated civil engineers, simply so that we can have a heightened sense of awe and wonderment -- and in turn have a heightened sense of respect for those who make a living from excavating prehistoric sites?
It's all very strange. So we have the crazy hunt for quarries on and around Carn Meini in the Preseli area -- with an ongoing assumption by senior archaeologists that the "spotted dolerite quarry" which only they can see (the rest of us are probably not clever enough) must have been a rather sacred site in itself. Now we have the "quarry" at Rhosyfelin, another "quarry" at Carn Goedog, and now one at Garn Turne as well -- mentioned by MPP in his latest book.
It is a source of constant irritation that these places are simply called quarries without any evidence being presented of quarrying activity of any sort. Indeed, these "quarries" are simply not needed anyway, for as many archaeologists (including Steve Burrow) have pointed out, burial chambers were almost always built simply where suitable stones were to be found in the landscape. Pentre Ifan and Carreg Samson in Pembrokeshire are classic examples -- and many other sites have been mentioned on this blog over the past couple of years. But that explanation is less than satisfactory for other archaeologists, since they apparently need to believe that burial sites were chosen in order to be auspicious in some way, and located to the nearest metre (or Neolithic yard) on the ground -- and this meant that stones then had to be moved to the site from wherever they could be found and no matter how difficult that might have been. Those heroic civil engineers again -- and round and round goes the circular argument...........
Let's look at the Garn Turne recumbent stone, currently being excavated by Colin Richards and his colleagues.
Garn Turne rocky outcrops and "earthfast" cromlech with large (60 tonnes) recumbent capstone. The hill summit is where the largest cluster of bushes is seen, N of the centre of the photo. The capstone can be seen next to a single tree, SW of the centre of the photo. The whole area is one of typical glacial / periglacial litter -- like many other ruined tors and rocky outcrops in north Pembrokeshire.
An oblique aerial photo showing the capstone, the tree and the surrounding litter of boulders and rock outcrops.
Another photo, at ground level, taken at a time of much higher vegetation. In the background we can see the rocky outcrops at the top of the hill. Did the capstone come from that outcrop? It might have done, and the large stone could have moved downslope either as a result of glacial or periglacial processes.
I will be very interested indeed to see what evidence is adduced by Colin Richards in support of the idea that there was a "quarry" at the top of the hill at Garn Turne. Is the big stone different geologically from the bedrock on which it rests? If not, we might as well assume that it is a big rock more or less in situ. If it is different, and matches the geology of the rocky outcrops at the hill summit, then it is most likely to have moved downslope by natural processes.
Back to a point I have made over and again on this blog. So far as I can see, the builders of the Pembrokeshire cromlechs were pragmatic and utilitarian fellows, and opportunists to boot, who knew all about costs and benefits, and who built their burial chambers at locations where large stones were conveniently at hand. In exactly the same way, burial grounds today (and back into the Middle Ages) are preferentially located in areas of sandy and gravelly soil, for those are the locations in which it is easiest to dig large holes in the ground which are six feet deep. This rule is so well established in Pembrokeshire that when I was doing the fieldwork for my doctorate thesis, looking for fluvio-glacial sands and gravels, my first fieldwork locations were always the parish graveyards and even the nonconformist chapel burial grounds............
On the other point -- covered in one of our recent discussions -- about Neolithic quarries being sacred sites. Tosh. First, show me the evidence of quarrying activities. Second, show me that the site was revered in some way. Once you've done all of that, I might be prepared to think again.
Sunday, 19 August 2012
This is the Blogger Flipcard option as it appears on the screen.
Mosaic is a funny one too -- it simply gives you a very dense montage of all the illustrations used -- you can click on any illustration to read the full post associated with it. Snapshot mode does something similar.
Note -- this blog is now so big that unless you have lightning fast broadband, it will take some time for the whole history of the site to load onto your computer......
The quickest way of scanning through old posts is to use Flipcard, which gives you a large number of thumbnails per page. Again, if you click on any one of the images, the relevant page and entry will be displayed.
Friday, 17 August 2012
Thanks to Tony for alerting me to this little radio report:
Achill Henge is starting to get popular. Just over 12 minutes of wonderful radio......... and three cheers for Joe!
Another amazing image from Greenland -- at first sight, I thought this picture was a bit spooky, and even threatening -- made me think of triffids or strange white snow monsters extending their icy tentacles down from the freezing heights. But fear not -- these plateau ice caps and their little outlet glaciers are really quite harmless.......
You should be able to click on the photo and pick up some incredible detail on the glaciers, the fjords and the ice caps themselves.
Thursday, 16 August 2012
On browsing through some of the East Greenland climbing sites, I have come across many more images of extraordinary peaks in Renland and Milne Land. These are two of them. The wall in the top photo is, as far as I know, still unclimbed. The lower one is called Shark's Tooth, and was first climbed to two Russian climbers. The area is becoming something of a Mecca for climbers, because I suppose this is one of the last great climbing areas -- reasonably easy for access these days, with boat movement easier in Scoresbysund than it used to be, and with many of the peaks close to the shores of the fjords. This is where maximum downcutting occurred during the big glacial episodes, with glaciers with steep gradients being evacuated rapidly as the big fjord glaciers decanted into Scoresbysund.
Because access to some of these peaks is sometimes difficult in the summer on account of turbulent and wide meltwater streams, the latest fashion is for spring climbing expeditions, with access by snowmobile across Scoresbysund while the winter sea ice is still in place.
Sunday, 12 August 2012
Forget all this stuff about the Olympic Games originating in Greece. That's all nonsense, although out of deference to the Greek people (who have enough problems as it is) the media have kept rather quiet and have kept the truth under wraps. The evidence shows that the Olympic Games actually have their origins in the UK, and that Stonehenge is all that is left of the first Olympic Stadium. The Avenue was of course the first Olympic race track, and the Olympic Village, used to house all of the athletes, was at Durrington Walls. (One can still find traces in the Durrington Walls digs of the enormous feasts held at the end of each Olympic Games by the athletes, the volunteers, and the British Olympic Committee.)
In a typical understated British way, there are clues in the Olympic programme to the real origins of the Games. The whitewater bluestone transport time trial (shown above) is one example -- competitors are required to transport a 4-tonne lump of bluestone in a two-man dugout canoe through a raging torrent, without either drowning or incurring time penalties. The Olympic Showjumping is another example; there can be no further doubt about the function of the Sarsen Circle and the trilithons, and Zara Phillips (shown above) was obviously greatly moved during her competition by the cultural associations and the pressure of history driving her to great things.
Then we have the Amesbury Archer and all that sort of thing. Some archaeologists have gone to great lengths to prove that some of the archers whose remains are found in the Stonehenge area lived in the Alps, or France, or Scotland, or Wales. There is no problem with any of that. It is self-evident that they were all far-travelled competitors in one of the Olympic Archery finals of somewhere around 4,000 years ago. And they had nice teeth too, just like Mo Farah.