THE BOOK
Some of the ideas discussed in this blog are published in my book called "The Bluestone Enigma" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
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Tuesday, 28 November 2017

BRITICE 2 -- the new map


Here is the new glacial map published by the BRITICE team.  Note that it is supposed to show only those features attributable to the Devensian glacial episode --  but many features are of course inherited from older glaciations and modified.  Hardly any erosional features can be assumed to belong to the Devensian glaciation alone.....

The map can be accessed here:

https://www.sheffield.ac.uk/polopoly_fs/1.706291!/file/Generalised_map.pdf

Sunday, 26 November 2017

BRITICE Glacial Map 2 -- a mixed blessing



I suppose we should welcome the publication of a big new paper, with multiple authors, describing the compilation of the latest version (No 2) of the BRITICE map of the British Isles.  The map is much more detailed than the first one, and that is to be welcomed, and the accompanying paper makes interesting reading.  The BRITICE project fieldwork is now wound up, but I dare say that there are many papers still to be published, from what has been a very large project involving large numbers of geomorphologists and other specialists.  They have done a vast amount of fieldwork, both on land and at sea..... or have they?

Here is a link to the paper:

http://onlinelibrary.wiley.com/doi/10.1111/bor.12273/full

Clark, C. D., Ely, J. C., Greenwood, S. L., Hughes, A. L. C., Meehan, R., Barr, I. D., Bateman, M. D., Bradwell, T., Doole, J., Evans, D. J. A., Jordan, C. J., Monteys, X., Pellicer, X. M. & Sheehy, M. 2017 : BRITICE Glacial Map, version 2: a map and GIS database of glacial landforms of the last British–Irish Ice Sheet. Boreas. https://doi.org/10.1111/bor.12273. ISSN 0300-9483.

Abstract



During the last glaciation, most of the British Isles and the surrounding continental shelf were covered by the British–Irish Ice Sheet (BIIS). An earlier compilation from the existing literature (BRITICE version 1) assembled the relevant glacial geomorphological evidence into a freely available GIS geodatabase and map (Clark et al. 2004: Boreas 33, 359). New high-resolution digital elevation models, of the land and seabed, have become available casting the glacial landform record of the British Isles in a new light and highlighting the shortcomings of the V.1 BRITICE compilation. Here we present a wholesale revision of the evidence, onshore and offshore, to produce BRITICE version 2, which now also includes Ireland. All published geomorphological evidence pertinent to the behaviour of the ice sheet is included, up to the census date of December 2015. The revised GIS database contains over 170 000 geospatially referenced and attributed elements – an eightfold increase in information from the previous version. The compiled data include: drumlins, ribbed moraine, crag-and-tails, mega-scale glacial lineations, glacially streamlined bedrock (grooves, roches moutonnĂ©es, whalebacks), glacial erratics, eskers, meltwater channels (subglacial, lateral, proglacial and tunnel valleys), moraines, trimlines, cirques, trough-mouth fans and evidence defining ice-dammed lakes. The increased volume of features necessitates different map/database products with varying levels of data generalization, namely: (i) an unfiltered GIS database containing all mapping; (ii) a filtered GIS database, resolving data conflicts and with edits to improve geo-locational accuracy (available as GIS data and PDF maps); and (iii) a cartographically generalized map to provide an overview of the distribution and types of features at the ice-sheet scale that can be printed at A0 paper size at a 1:1 250 000 scale. All GIS data, the maps (as PDFs) and a bibliography of all published sources are available for download from: https://www.sheffield.ac.uk/geography/staff/clark_chris/britice.

-------------------------



So is the new map reliable, and is it of any use to the rest of the world as a teaching and research aid? Yes, and yes again. But I have major reservations about the fact that the map is available as a "zoom in" version, rather like the BGS geology map available on their viewing facility. Clearly much of the data has been input on a very small scale, so that when we zoom in to look at a part of the countryside at a scale of 1:50,000 or maybe 1:10,000 the result becomes nonsensical, with straight edges to lakes and moraines (for example) that bear no relationship to the details of local topography.

We can only judge things on the basis of what we know, and so I have taken a long hard look at what the map tells us about that area around Preseli and Carningli (my home area). Even given that the map shows "last glaciation features" and nothing older, what we see makes no sense at all.

Glacial Lake Teifi and the surrounding area, from the BRITICE Glacial Map 2

Hypothetical "Glacial Lake Nevern" and other features in the Preseli - Carningli area, 


from BRITICE Glacial Map 2

The outlines of Glacial Lake Teifi more or less coincide with what we see in assorted published papers, but the other information shown on the map is very scanty indeed for the Cardigan - Moylgrove area. That must disappoint many of the authors who have published their research findings, with considerable local detail on the record. When we zoom in on Preseli and the hypothetical area of "Lake Nevern" we find even more problems.  Why is "Lake Nevern"  shown at all?  So far as I am aware, nobody since Charlesworth in 1929 has taken it at all seriously, and many papers by a variety of authors have shown that the "evidence" for it does not withstand scrutiny.  The paper authors site "George 1970"as their source of information, but George was simply citing (very uncritically) Charlesworth, and provided no evidence for this so-called lake.  Careless.   As readers of this blog will know, there are a few places where thin laminated (lake?) sediments appear to be present on the northern flank of Preseli, but they are better explained by short-lived ponding of meltwaters in complex terrain in a dead-ice environment.  I have called this "Lake Brynberian" -- a possible small lake of limited duration and extent.   There are other fluvioglacial landforms and moraines in this area which are in the literature.  They should have been mapped, but have not been.  And where did that impounded lake at Pontfaen come from?  I am aware of no evidence in support of it.

https://brian-mountainman.blogspot.co.uk/2015/05/lake-brynberian-further-thoughts.html

The impression is gained that this map has been produced by researchers accessing satellite and bibliographic data and sitting in front of computer screens, unlike the BGS bedrock and sedimentary map for the UK which has been based largely upon the field notes of surveyors working in the field. Black mark for BRITICE, and glowing praise for the BGS.  In the abstract to the paper, the authors state:  "All published geomorphological evidence pertinent to the behaviour of the ice sheet is included, up to the census date of December 2015."  That is patently not true.  There are abundant references in the literature (just a few of them by me, and many others as well) that have clearly not been consulted.

Then we come to the map showing the wider Late Devensian context, reproduced above from Figure 11 in the article text.  The authors still insist that there was a long "surge" lobe pushing far out into the south-western approaches.  I don't know of any sea-floor or sedimentary evidence that supports it,  and I do not know what glaciological theories have been summoned up in its creation, but it sure doesn't look like any other glacier ever seen on Planet Earth.  It was probably dreamed up by some guys as a way of explaining the short-lived advance onto the northern coast of the Isles of Scilly, but there cannot possibly have been an ice edge more or less at sea-level in western Pembrokeshire and simultaneously more or less at sea-level in the Isles of Scilly, more than 200 km to the south, with ice flow as shown on the map.  The ice must have come from the NW, not the NE, and in an unconstrained situation such as that of the outer Bristol Channel, the eastern ice edge must have been far to the east of that shown on the map.  The map also ignores published evidence of Devensian ice affecting the area around the mouth of Milford Haven.  You can do some searches on this blog for more information.



Overall, this new paper, and the map, are useful contributions from the BRITICE team.  But rubbish in, rubbish out.  Now we need some serious fieldwork, on the ground, involving people who know what they are looking at.  Apparently these days they call it "ground truthing" ---- and it is apparent that we all need more of it.



Friday, 24 November 2017

A week in the Azores




Just in case anybody wonders where we have been lately, we've enjoyed a week of walking in the Azores -- on the main island, Sao Miguel.  Thoroughly delightful.  Great walking territory, in spite of there being no glaciers or moraines to look at.  

Myris would have enjoyed it -- calderas, volcanic cones, ash beds, lava flows, volcanic bombs, fumaroles etc all over the place.  And a great orange-coloured swimming pool fed by geothermal springs, with a water temperature of 36 degrees C.  Now THAT was rather splendid.......

Apologies

Found the source of the problem -- some of the posts were going into junk and may have been deleted inadvertently.  Must be something to do with my screening settings -- will try and sort it out.  Meanwhile, if any important posts have been lost without trace, please try again........

UPDATE, Fri 24th Nov 2017

All sorted, I think.  My "mail rules" -- the settings that determine the mailboxes into which messages are sent -- had all been de-activated.  Goodness knows how that happened -- maybe there was a software update which I didn't notice.  So some messages were simply blocked, I think, and others went into the junk box.   And the sun is shining too........

Thursday, 23 November 2017

Stonehenge and the birds


I found this on the web the other day -- yet another illustration of the extraordinary use of the old ruin by birds, maybe particularly during the autumn flocking - roosting season.  Are they jackdaws or starlings? Whatever they are, the scale of droppings being dumped onto the stones is so vast that the actual damage to the stones has to be greater than the damage that might be done by allowing the geologists to take small cores from every one of the standing stones, recumbent stones and stumps.  We need to know what the provenances of all these stones are, and we need to know what the cosmogenic ages are for the exposed stone surfaces, in order to better understand how the stones got there and when they were erected.

Come on, Historic England -- you know it makes sense!  Let the geologists take their samples!

This is a great NASA image taken from the space station, showing Wales and Ireland, and showing too that the Earth is not flat.  That will come as a surprise to some people.

Because of a freakish cloud cover, we can see beautifully the Cheshire Plain - West Midlands depression along which the eastern branch of the Irish Sea Glacier penetrated to the neighbourhood of Birmingham on at least two or three occasions.

Is there a glitsch?




Just checking with faithful followers of this blog --  I have received a message from one person who has tried to post comments in the last few days, but I have received nothing through the normal Email channel. Sounds as if there is something wrong somewhere.

I'll appreciate it is one or two of you could post something so that we can do a clinical trial.......

Thanks!

Sunday, 19 November 2017

The Survival of Maiden Castle



Here is a great photo of Maiden Castle, a fragile tor exposing Pre-Cambrian (?) rhyolite adjacent to Trefgarn Gorge.  Thanks to Pete Storey and the Pembs Geology Group Facebook page.

As we have explained before, the prevailing view is that this tor is too delicate to have survived Devensian glaciation around 20,000 years ago, and so the maximum position of the ice edge has to be placed further north.  Trefgarn Gorge itself must have been a major meltwater route, carrying vast quantities of meltwater from north Pembrokeshire southwards towards Milford Haven.

Place names in the "Rocky Mountains"

The crags of Carn Meini / Caer Meini / the Ragged Rocks

Following my earlier post on "Caer Meini" and other place names in the eastern parts of Preseli, I have found another old book -- long since out or print --  by ET Lewis, called "Mynachlog-ddu -- a guide to its antiquities."  In it, he makes many interesting points, while displaying rather too much respect for the "expertise" of assorted "experts"......

Anyway, he says some very interesting things about place names. He refers to Carn Meini / Caer Meini as "the remarkable mountain called the Ragged Rocks" and also refers to the area as "the Rocky Mountains" --- maybe with tongue in cheek.  He cites a tourist called HP Wyndham (1774) as his source -- and maybe these labels were used informally by English-speaking visitors to the Preseli area.

Lewis speculates that the name "Caer Meini" arises from the fact that the summits "appear circular and like the stupendous ruins of a castle wall."  That's an imaginative interpretation, but it raises the issue of the AGE of some of these names.

Carn Goedog seen from the east.  A place of great slaughter?

In his text on the meanings of some of the other tor names, Lewis mentions that Carn Goedog means "the wooded carn" or "woodland carn" -- and I have no problem with that, since there is a copse of splendid mature trees not far away at Hafod Tydfil which suggests that without human interference / clearance and animal grazing, mature woodland would indeed be the climax vegetation here on the north flank of the mountain.  There is no reason why that should not also have applied in the Mesolithic and Neolithic, and right up to the time of the Celtic settlement and the naming of familiar places.  On the main ridge, and on the more exposed southern and western flanks of the uplands, the woodland might have been more scrubby.  There are bluebells growing in the Carn Goedog area, and as I have pointed out before, these plants are very good indicators of past wooded environments because they like heavy shade for the summer and autumn seasons.

The Welsh word for "forest" or "wood' is "coedwig" -- so "coedog" could simply be a mis-hearing, mis-spelling or corruption of that word.

More interesting by far is the suggestion by Lewis that "Goidog" or "Goidiog"may be related to an old Welsh word for "slaughter" or carnage. (The modern word is quite different.)  So, given the suggestion that the Battle of Mynydd Carn in 1081 might have occurred on the plateau of Talfynydd, less than a kilometre away from Carn Goedog, might this name have been given to the carn as a remembrance of that bloody conflict?  Indeed, might some phases of the battle have occurred around the carn itself?


Friday, 17 November 2017

Collapsing iceberg arch


I have been watching some of the videos on YouTube of collapsing ice fronts, rolling icebergs and iceberg arches giving way -- now that Arctic cruises are immensely popular, social media are full of snippets of film of "exciting" ice front events and of boats getting rather too close to the action.  There have been some close shaves -- members of the public (and even tour operators) seem to have little idea what natural forces are being unleashed when thousands of tonnes of ice fall into the water. The resultant displacement waves are quite high enough to wash people off rocks where they may be standing, or to turn boats over -- as I tried to demonstrate in my novel "Acts of God".

Anyway, people scream, shout and clap -- and gasp with relief when they manage to escape big waves that threaten to overtake their rapidly retreating boats. But one day there will be a big accident, because tidewater ice edges have become rather too popular with adrenalin junkies........

In principle, I don't have a problem with people getting close to glaciers and developing some understanding of how glaciers work.  And tour operators should certainly be informing as many people as possible about accelerating glacier retreat and the link with global warming.  Sadly, there is too much junk science around -- the fact that an iceberg rolls over, or an arch collapses, or a glacier front suffers a sudden catastrophic failure, does not in itself indicate that this is a "global warming event".   This is all perfectly normal glacier and iceberg behaviour -- and these things happen whether a glacier is advancing or retreating in a deep water situation.

The picture above is from one of the videos,  showing a big chunk of ice falling from an arch -- it would not have been a good idea to be beneath it in a kayak (or any other craft) at the time!  Over the next minute or two, after this photo was taken, the arch lost more and more of its mass in a welter of falls big and small, until it completely disappeared.  Then, of course, the remaining parts of the iceberg made major readjustments by rolling in the water, surrounded by a great apron of brash ice.

Monday, 6 November 2017

Stonehenge -- the authorised version (again)



Julian Richard's new book came out at the end of September.  It's called "Stonehenge -- the story so far", published by Historic England at £22.95 (or whatever), hardcover, 352 pp.

You can read bits of it if you look on the Amazon web site. It's very nicely packaged, with attractive photos and diagrams, and a modern page design.  But what about the text?  Well, from what one can see, we have the same old stuff as usual.  A friend very kindly sent me the text as it relates to the bluestones, in a section dealing with "sourcing and transporting the raw materials".  I am not impressed, since what we have --yet again -- is evidence of an author who is desperate not to rock the boat or to allow for any questioning of the fondly-held assumptions of decades.  Is this bland acceptance of the authorised version something that Historic England insists upon? Is it really true that it cannot admit to any disputes in an "official" publication? Does it really think that Joe Public cannot handle honest academic debate, in which there might be two (at least)  perfectly feasible explanations for one or another of the features at Stonehenge? I should have thought that honesty on this score would excite interest and enthusiasm for our historic heritage, rather then damping it down.........

So what does JR have to say?  Immediately we are into the ruling hypothesis, with confirmation bias flagged up for all to see. We are introduced to Carn Meini (Menyn) which is described as a place of "convenient slabs and pillars." JR continues excitedly: " In this showroom for monoliths tempting stones lie everywhere; some even look as if they have been propped up and are ready for loading onto a sledge for the start of their long journey - perhaps more stones intended for Stonehenge that never made it?" Oh dear. He forgets to tell us that there are at least a dozen other tors in the general area for which exactly the same words could be used.

He then goes on to talk of the geological provenancing, without any mention of the work of Ixer and Bevins, and he actually misrepresents their findings. They will surely not be amused.  Spotted dolerite does not just come from Carn Goedog and Cerrig Marchogion, as he implies. And the rhyolite at Rhosyfelin does NOT provide an "exact match" for bluestone fragments at Stonehenge. Quote: "At this outcrop excavations have shown where a pillar of stone was removed from the rock face, the quarrying dated by radiocarbon to c 3400 - 3300BC."  That weird "pillar" of stone and its "extraction point" pop up all the time, promoted by people who cannot be bothered to apply any scrutiny.  Has Julian Richards or any of the others who promote this nonsense ever been to the site and looked at the narrow natural fissure in the rock face that clearly has nothing whatsoever to do with monoliths or extraction points?  It was dreamed up by MPP in a moment of mad enthusiasm, simply because it was close to sampling point 8 used by Rob Ixer and Richard Bevins, and it has been re-imagined ever since by people who seem to have left their common sense behind.

And the radiocarbon evidence?  Most thoughtful human beings might think "It just doesn't fit.  Therefore, since there is no other evidence of quarrying anyway, we might as well give up on the quarrying thesis and think of something else instead."  But these archaeologists are made of sterner stuff.  "No, since we have already decided that this is a Neolithic quarry, we just have to shift the date back by a few centuries and work out what happened to all those nice bluestones before they were shifted to Stonehenge.  So we have to assume there was a convenient proto-Stonehenge somewhere in the vicinity....." Once these archaeologists have a nice ruling hypothesis to play with, there is no way they are going to abandon it.

And just as the geologists are going to be pretty angry about being ignored, we geomorphologists are also extremely displeased.  For Richards to trot out the quarrying story without question, in the full knowledge that there are two peer-reviewed papers in print which question every single bit of "evidence" presented by the archaeologists in one extremely dodgy "Antiquity" article, is not just careless but also disrespectful and deliberately misleading.  The author had two years to incorporate our findings into his text, and chose instead to ignore them.

Interestingly, having applied no scrutiny whatsoever to the quarrying hypothesis, Richards does devote considerable space to the glacial transport hypothesis.  So he does at least acknowledge that there are two competing theories.  But there is a complete lack of balance in the way he treats them.  He simply repeats the usual arguments about the Boles Barrow stone, the apparent lack of other erratics on Salisbury Plain, and the Christopher Green pebble counts. "Quite simply," says our intrepid author, "the theory of glacial transport does not stand up to scrutiny and should be dismissed."  And he concludes his section with a summary of the ideas of MPP, TD and others about highly prized or magic stones being brought to Stonehenge as a great sacred or symbolic gesture.

That's the authorised story, and Richards is sticking to it, come hell or high water.  If you are still tempted to buy this book, you will, I think, never find a better example of selective evidence citation and confirmation bias.






Friday, 3 November 2017

From the world-famous Rhosyfelin School of Archaeology.....



No comment needed........

Picton Point -- old glacial deposits?



Pembrokeshire geology map with the addition of a speculative flowline for the Irish Sea ice which might have affected the region around Picton Point

Picton Point is the south-facing headland that separates the western Cleddau and the Eastern Cleddau, in the tidal inner reaches of the Milford Haven waterway.  It's a delightful spot, with wide vistas to west, south and east.  My wife and I went over there for a walk the other day, and I was struck -- not for the first time -- by the frequency of erratic boulders and cobbles scattered along the shoreline.  These have not been carried here by longshore drift or by the tides -- there is very little wave action here.  So the erratics have dropped out of pre-existing glacial and fluvioglacial deposits as the low cliffs are nibbled away.

The main processes here (as at Mill Bay, the famous place from which the Altar Stone was supposed to have come) are biological and mechanical.  Tree roots are exposed as the Coal Measures sandstones and shales are sapped or undercut; then the trees tip over more and more until they fall down onto the beach; when that happens, loose rock debris on the cliffline ( already broken up to some degree by vast and expanding root systems) is dislodged and comes crashing down too, resulting in coastal retreat by a few more feet.  And so the process continues.  On the land surface above the cliffline there are glacial and fluvioglacial deposits, and these are dropping down onto the foreshore bit by bit as the coast retreats. The process is slow, but inexorable, and is essentially one of sudden or catastrophic cliff collapses in different locations as one big tree after another comes down-- usually during an extreme storm event like Storm Ophelia or Storm Brian in recent weeks.  A huge oak tree came down close to Picton Ferry during one or the other of those storms.

This tree will be down before too long, and when it falls a chunk of the 
cliff face will come with it.

(As it happens, similar processes have been at work at Craig Rhosyfelin, dislodging large blocks of rhyolite at irregular intervals and causing fallen and smashed-up rock debris to accumulate against the rock face.  There, however, the trees may have always been much smaller.)

Annotated image from the Geology of Britain Viewer (BGS).  Here we can see that glacial deposits are quite abundant in this area.


Erratics are scattered on the foreshore to the east of Picton Point, but they are far more numerous on the western side.  Most of them are less than 50 cms in diameter.  They are rather well rounded, and heavily stained.  This suggests two things to me -- one, that they have come from fluvioglacial sands and gravels rather than from till;  and two, that the deposits are old (Anglian or Wolstonian) rather than Devensian.

  
Two images from the foreshore to the west of Picton Point. Most of the rock fragments are quite angular, having come from recent rockfalls on the retreating cliffline; they are mostly Coal Measures sandstones.  But the rounded cobbles include rhyolite, dolerite, gabbro, volcanic ash, and Cambrian sandstones -- almost certainly from the St David's Peninsula

These are early days in my Picton Point investigations -- watch this space.....