THE BOOK
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....
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HERE

Tuesday, 28 January 2020

The Spectre, Antarctica





In the news today -- another of those extraordinary peaks in remote locations which has been climbed for just the third time (first climb by a British adventurer).  I'm endlessly intrigued by the manner in which these steep-sided and even vertical pinnacles are formed, and then survive.......

Highly entertaining was one press writeup which reported that the Spectre peak was located "470 kms south of the South Pole."  So there we are then.......

Wikipedia:
The Spectre (86°3′S 150°10′W) is a prominent rock spire, 2,020 metres (6,630 ft) high, near the center of Organ Pipe Peaks, Gothic Mountains, in Queen Maud Mountains in Antarctica. It was discovered in December 1934 by the Byrd Antarctic Expedition geological party under Quin Blackburn. The allusive name was suggested by Edmund Stump, leader of the United States Antarctic Research Program (USARP)-Arizona State University geological party in the Gothic Mountains, 1980-81.

Monday, 27 January 2020

The Hurlers stone circles, Bodmin Moor



I have been getting quite intrigued by The Hurlers -- a group of three stone circles on Bodmin Moor.  They have -- or had -- diameters of c 35m, 42m and 33m  most of the stones are gone.  There used to be 29 stones in each circle.  The central circle still has 14 stones in it, although there seems to be some doubt about how many were actually standing when a big excavation and reconstruction took place in 1935-36.     All in all, it appears that at least 50 stones have gone missing from the stone settings -- if they were there in the first place.  I have't followed up to see how many empty sockets have actually been identified, and with what degree of conviction....... 

In the same area there are other standing stones and Bronze Age features in the landscape -- so there seem to be strong similarities with the situation at Waun Mawn.  Does anybody have any observations on this site?  And any insights?


https://www.english-heritage.org.uk/visit/places/hurlers-stone-circles/history/


Quote:

Although not set out in a straight line, the centres of the circles trend towards the ridge to the north, with the still impressive bulk of Rillaton Barrow on the near horizon and the summit of Stowe’s Hill with it’s Neolithic tor enclosure and the striking natural granite formation known as the Cheesewring on the skyline. Dating to the early Bronze Age, the Hurlers lie in a remarkable ‘ceremonial landscape’ of stone circles, stone rows, standing stones, cists and cairns. A particular feature of the monuments in this area is their tendency to ‘refer to’ significant tors and horizon features, especially the tor enclosure on Stowes Hill and the group of large barrows on Caradon Hill. The numerous alignments apparent in this area suggest that the Hurlers may have been part of an important processional route.

The area has been extensively disturbed by mining and only the central circle has a large proportion of its stones in-situ, but this is because they were reset after the site was excavated by Raleigh-Radford in 1935-6. Fourteen stone uprights survive in the central circle, with fourteen markers for missing stones, placed in empty stone sockets during restoration works. Originally all the circles are said to have contained twenty nine stones (though the central circle is considerably larger than the other two) and it was Carew who noted the “...strange observation that a re-doubled numbering never eveneth with the first”. The inner faces of the stones are smooth and regular and most of the stones are flat topped and graded so that the tallest stones are to the south, which may support the idea of a processional route through the circles leading towards the north. This is also the case with the north circle and possibly also the south circle - though this is now in a very poor and incomplete condition. It has been noted that flat lozenge shaped stones tend to alternate with more slender uprights and it has been proposed that the former represent the feminine principle whilst the latter represent the masculine. Excavations revealed a quartz crystal ‘floor’ within the central circle and the small granite block currently sited within the circle may originally have marked the true centre.

Two standing stones known as the Pipers lie to the south-west of the Hurlers flanking a modern boundary bank. ‘Outliers’ such as these are a common feature of stone circles in Cornwall and further afield and they are likely to be prehistoric in origin, re-used as a prominent landmark when the boundary was first established. Interestingly, both the Pipers and the Hurlers fall on an approximate alignment between the ‘embanked avenue’ and stone circle on Craddock Moor and the prominent barrow group on Caradon Hill. The Pipers may thus represent a ‘portal’ giving access to the Hurlers from the west.

Wednesday, 22 January 2020

Icefall Zero: Free Offer for Kindle Ebook readers


More about Greenland, which is much in the news these days as a result of the climate crisis.......

When I published "Acts of God" five years ago, little did I realise that in no time at all there would be  at least 8 other books with the same title jockeying for position in the marketplace.  Not a good scenario.  In any case, the book sounded more like a theological treatise than a brutal conspiracy thriller with a lot of swearing and gruesome detail in it;  so I am saddened by the thought that there might have been various clerics and philosophers who bought it in the expectation that they would be reading something profound.  Not that I have had any complaints, but people are in general very polite......

Anyway, the book had to be rebranded, and if I have been a bit quiet lately on the blogging front it's partly because I have been unable to shake off a horrible persistent chesty cold, and partly because I have been doing a tight edit on the book, including a reformatting and cover design exercise.  There were lots of mistakes and inconsistencies in the old text -- now hopefully sorted out.

The Kindle version of "Acts of God" has been withdrawn (it is still available as a paperback) and it has been replaced by "Icefall Zero."

I'm currently doing a Midwinter Free Kindle Promotion on the rebranded book, so for the next five days it can be downloaded from the Amazon website at zero cost.  After 26 January, you will have to pay for the privilege of downloading it and reading it.

Here is the link:

Icefall Zero

Please feel free to share this info with friends, and if anybody feels like sticking a review (even a one-liner!) onto the Amazon web site, that would be appreciated.

Tuesday, 21 January 2020

Stanton Drew Moggalithic Monument


Thanks to Helen for drawing this to my attention on Twitter -- I had not seen it before, although it was posted around the time of the General Election.

https://almostarchaeology.com/post/189644783963/moggalithic

Obviously the content of this rather rambling post is relevant to our earlier discussions on the "hijacking" of prehistoric monuments -- and the learned studies related to them -- for the boosting of the Brexit cause.  I hadn't realised that Rees-Mogg had done an electioneering broadcast from Stanton Drew, and that people had actually looked at it.  He obviously did lots of tweeting as well.  Serious, or just a bit of frothy fun?

Quote:     "Was it just an innocent bit of eccentric electioneering fun that just happened to take place with a megalithic backdrop? Or perhaps the film was an appeal to a certain kind of voter who craves the nostalgic fantasies of the English countryside, windswept standing stones, comical ‘scrumpy and western’ bands like The Wurzels, and Brexit?   Or was this short film altogether something more sinister?"

Quote:  "The film is a particularly egregious example of what I have come to call #BrexitPrehistory (for it was not really about the election, it was about ‘getting Brexit done’) and it indicates the increasingly casual ways that prehistory is being used to make arguments for Brexit by leavers. However, the video also became a focal point for a lot of anti-Brexit (‘remainer’) sentiment, something I would also like to unpick here.  My contention is that we should not be using a prehistoric stone circle to make any kind of points about contemporary political and social challenges although it can be tempting to do so.   Stone circles like Stanton Drew, the one chosen by JRM as his backdrop, are neither leave or remain monuments. Yet, problematically, social media reaction to Rees-Mogg’s piece to camera suggests it might be both."

Quote:  "Alice Roberts tweeted: ‘How extraordinary that Rees-Mogg chooses to stand in front of a megalithic monument – which speaks so strongly of connections across prehistoric Europe – to make an isolationist statement!’ "

Quote:  "........stone circles can and should be kept out of our Brexit battles. They are no more an indicator of what Jonathan Last, in another great response to far-right use of prehistoric monuments, has called, ‘a conservative, nostalgic narrative of a lost rural England’, than they are surviving traces of an ancient utopia of free movement and European cultural cohesion.   Stone circles should be testament to the sophistication of Neolithic people. Stone circles should continue to be a source of wonder, mystery, the otherness of the past......"

Sunday, 12 January 2020

The Welsh ice shed

The ice shed area -- around the Teifi Lakes


Further to my posts about the position and the characteristics of the Welsh ice-shed during the Late Devensian glacial episode, I have been thinking about ice-flow characteristics on its flanks.  We can assume that on the western flank there will have been greater accumulation, greater ablation and higher ice turnover -- in other words, conditions were more dynamic, with glaciers flowing in all the main outlet troughs down towards Cardigan Bay and into a "conflict zone" with the ice of the Irish Sea Glacier.  This shows up quite nicely in the BGS map which we have looked at many times before.  It also shows up well on the computer simulation reproduced above, by Henry Patton and others in which the areas coloured black are those of most sluggish ice-flow (in this "episode"in the sequence the ice cap is of quite limited extent.).


The biggest glaciers by far were the Teifi Glacier and the Tywi Glacier, each more than 70 km long, while the other western outlet routes were shorter and steeper.

On the eastern flank of the ice shed accumulation rates were lower and ice movement was more sluggish.  On the other hand there was no "conflict" with Irish Sea Ice, at least to the south of Ludlow.  There appears to have been no identifiable "Severn Glacier" but the main ice steams were in the Wye and Usk Valleys.  The glaciers were quite complex, and geomorphologists and geologists have not found it easy to unravel either the sequence of events or the ice movement directions.  The ice which accumulated in the Teifi Lakes area, between Tregaron and Rhyader, seems to have flowed SE in a coherent stream towards Builth Wells, where it split into two, with one stream flowing towards the Black Mountain and the other broadly eastwards south of Radnor Forest.  The southern stream was diverted northwards around the northern face of the Black Mountain before decanting eastwards towards Hereford.  The Usk Glacier was even more complicated, since it incorporated ice flowing southwards from mid Wales and ice flowing northwards from the Brecon Beacons.  The ice initially flowed eastwards, and then the ice stream also split into two because of the topographic barrier of the Black Mountain.  

We should bear in mind that this was the Late Devensian scenario.  During earlier glaciations the ice from the southern part of the mid-Wales ice shed would have been thicker and more powerful, eliminating many of the local twists and turns and flowing broadly SE across the whole of the landscape of SE Wales towards the Severn Estuary and the Cotswold Hills.

It's this latter scenario that interests us when we try to work out what went on during the very extensive Anglian Glaciation.  According to this old map -- which I think is still pretty accurate -- it should be possible to find erratics from virtually anywhere in the SE quadrant of Wales in the Somerset Levels - Salisbury Plain landscape.


Friday, 10 January 2020

Strandflats, skerries, archipelagos and areal scouring

Breidafjordur, west Iceland.  Here there is an extensive archipelago of 2,700 islands.  Click to see this image at higher definition.

Lochmaddy, North Uist, Outer Hebrides, Scotland.  A classic example of a "skerries landscape" linked to a local strandflat

In recent posts I have examined some of the places where areal scouring, dead-ice conditions and maybe cold-based glaciers have combined to create undulating terrain and occasional areas of "knock and lochan" terrain.  The main feature is always sluggish and diffuse ice flow without any concentration of flow into streams, troughs or channels.  These rather beautiful wilderness areas are usually at high altitude, on plateau surfaces where ice cap generation takes place and where -- after ice cap growth -- the highest and most remote ice domes or ice-shed axes are located.  The Glama and Dranga plateaux in Iceland are examples, as are the Teifi Pools area in mid Wales and the Hardangervidda in Norway.  So these are essentially "ice source" areas where very specific glaciological conditions have applied, over and again during the Quaternary as one glaciation has followed another.

There are obvious similarities between these plateau landscapes and the coastal landscapes that fringe some areas of intensive glaciation where fjords have been created.  These are some of the most spectacular landscapes on earth -- for example the fjord landscapes of western Norway, East Greenland and parts of Arctic Canada.  The general principle that seems to apply is that when ice-flow is concentrated within outlet troughs on the fringes of an ice sheet or an ice cap, erosion will make each trough deeper and deeper as long as there are supplements to discharge -- but as soon as the possibility of diffluence occurs (ie when the glaciers reach a pre-existing mountain front) ice-flow will spread sideways and erosive capacity will be suddenly diminished. Then instead of troughs and channels created by streaming ice, we will see the development of wide open plains of undulating bedrock under the influence of areal scouring processes.  This is one of the most spectacular "process transformations" in nature, and when David Sugden and I were writing "Glaciers and Landscape" back in the stone age, we were very fascinated by it!  I have done a number of related posts on this blog......

The Sognefjord long profile, showing how the trough has been deepened steadily so long as there have been supplements to glacier discharge.  But as soon as diffluence became possible, close to the outer coast of Norway, erosive power was lost, and the fjord bed rises to the trough "threshold".  The skerries occur off the left edge of the diagram, where concentrated ice flow and erosion were replaced by areal scouring.


At the end of each glacial episode, when sea-level returns eustatically to more or less its interglacial level, these low-relief undulating rock platforms are flooded by the sea and are transformed into skerries and archipalagos with a  myriad of small islands, straits and channels with rocks and shoals all over the place.  Because there are no big glacial exit routes across these areas, the water is nowhere very deep, and fractures and other structural controls can generally be picked out in aerial photographs and satellite imagery.  There's a big debate about whether these extensive undulating platforms located at or around present sea-level are really cut by ice, or by other processes including marine erosion or by the cutting of ancient platforms by river erosion in pre-Quaternary times.  Some authors suggest that the Norwegian strandflat is a very ancient feature that has been covered by sediments which were stripped away in pre-glacial times -- suggesting that glacier ice has simply "occupied" an ancient feature without necessarily altering its appearance very much at all.  There is a good discussion here:

https://en.wikipedia.org/wiki/Strandflat

The archipelagos around the coasts of the Baltic, in Sweden and Finland, are different again, since here we have one of the world's great Pre-Cambrian peneplains.  There are abundant traces of ice scouring on a large scale across that part of the Stockholm Archipelago which I am familiar with, but there is no doubt that the essentials of the landscape are pre-glacial.  Some archipelagos, like the Bear Islands in Hall Bredning, just beyond the threshold of Nordvestfjord in East Greenland, might be referred to as the products of local rather than regional glaciological conditions, and the same may be said of Lochmaddy in North Uist -- see the photo at the head of this post.

This is an intriguing topic, worthy of greatly extended treatment -- and of course this is another question worth asking:  "Why is it that some glacier troughs that carried vast volumes of ice during the Quaternary glaciations have extensive skerries beyond their exit thresholds, and others do not?"

Another photo of the skerries in Breidafjordur, western Iceland.

Bing satellite image of part of the Stockholm Archipelago -- an area of modest surface relief underlain by the rocks of the Scandinavian PreCambrian Shield.  The area was covered by thick ice flowing directly southwards, but there are no clear troughs or other discharge routes.  Areal scouring affected this whole area. The details of coastal configuration are determined above all else by fracture patterns and lithologoical variations in the PreCambrian basement rocks.

Belcher Islands in Hudson Bay.  One of the strangest archipelagos in the world..........  made of PreCambrian sedimentary rocks which have been heavily eroded by overriding ice across several glaciations of North America.  The rocks are tightly folded and deformed -- if we look carefully we can see several pitching synclines and anticlines.

Archipelago of heavily abraded Shield rocks near Nain, on the east coast of Labrador.

These prominent peaks on one of the Bear Islands, in Hall Bredning, Scoresby Sund, East Greenland, lie within an unusual small archipelago around the outlets of Nordvestfjord and Ofjord.  This area has been affected by laterally spreading ice from these two huge outlet glacier routes, but strictly the Bear Islands should be interpreted as the seriously damaged right flank of the Ofjord glacier trough outlet.    Substantial glacial erosion has damaged and even whittled away most of the trough wall, leaving a few spectacular ridge remnants.

Thursday, 9 January 2020

Ok is no more........





Seasonal snowpatches on the Ok plateau -- a winter photo.  The small crater in the centre of the plateau is the most obvious feature in this image.  This is all snow -- not glacier ice.

There have been a number of media stories over the past six months about the disappearance of Okjokull, a small plateau glacier sitting on top of an old volcanic cone not far from Reyjkjavik in Iceland.  It sure has gone, and there are records of ice over 50m thick here, just a few decades ago........  It was unusual in that it was completely circular, resting atop a symmetrical cone which had lost its tip.

https://www.bbc.co.uk/news/world-europe-49345912

https://www.bbc.co.uk/news/av/world-europe-49844050/a-memorial-to-iceland-s-disappearing-glaciers?SThisFB&fbclid=IwAR1sbAb6UOFhFPI5t9asXOmxM3a3quUcF_CzqUtdn2VJmISGPlRHVhi9CGg



However, the claim made on the BBC Travel Show that this was the first Icelandic glacier to entirely disappear because of global warming was not correct.  A number of small glaciers in Iceland were apparently thriving for a few centuries during the Little Ice Age -- a cold snap that lasted from approx 1550 to around 1890.  The dates and duration varied from one place to another -- and some believe that the Little Ice Age did not properly end until around 1947.




However, as pointed out on this blog,  Glamajokull, the southernmost of the two ice caps on the plateau of NW Iceland, was quite extensive around 1850, at the local culmination of the Little Ice Age -- and it had entirely melted away by the time of the great Danish mapping exercise in 1913-14.  In contrast, Drangajokull, a little further north, covered an area in 1850 that was almost three times as large as its present size.  It had shrunk dramatically by 1913-14, and has shrunk dramatically since then.  How much longer will it last?  Maybe thirty years, if we are lucky.........

The Ok plateau as it is today, close to the core of the old ice cap.

I'm rather interested in the appearance and characteristics of these ex-ice cap plateaux.  They are usually devoid of any morainic features and they may have no definable till either -- just a scatter of boulders that may or may not be erratic or far-travelled, and a patchwork of exposed rock surfaces and areas covered with rock rubble or breccia.  There may or may not be traces of rock smoothing or streamlining -- for in general, ice movement may have been sluggish at best and non-existent at worst.  That is what happens beneath ice sheds or ice cap summits;  the further you are from an ice cap summit, the greater the likelihood of ice moulding and other erosive activity.  For much of the history of an ice cap, the ice beneath the summit may actually be frozen to the bed, and there may not be much activity within the ice mass either.

  
Satellite image of part of the Glama Plateau, showing typical "knock and lochan" terrain