Another computer model

 

There is a new and rather spectacular computer generated interactive and animated "icemap" showing the expansion and contraction of the BIIS and the SIS during the Late Devensian. It's free for anybody to use, and it has been created by Henry Patton at Tromsø University in Norway.

https://icemap.rhewlif.xyz/?fbclid=IwZXh0bgNhZW0CMTAAAR3Q2Wsw4JAYdL_lyda1ajOdLQNbtwJ8iePNU34H-v__H4qAlL_yK383hTU_aem_ASWAPezhTzxON2vIelI668jcP7phW4y9poLVfj70C2jDTe9HnYeSPFfM1VL010AJ1AuLrKH2LHk726z2Byo50Qfa#

It's visually very attractive and seems to me to be pretty reliable for the most part. However, there is a major issue with dating, and the peak of the LGM is shown here as around 22,500 yrs BP as compared with around 26,000 yrs BP in the BRITICE reconstruction. Who is correct? This is a very substantial difference, no doubt explained by differences in the calibration of radiocarbon and marine isotope dating........

Also, Henry seems to have been using different databases for different parts of this computer programming exercise. On the ice extent map, the Devensian ice edge is shown hitting Salisbury Plain. That will cause quite a lot of discussion, since the BRITICE reconstruction is far different -- and with most researchers suggesting that the inner part of the Bristol Channel was not affected by glacier ice during the LGM, but that ice extent was greater during earlier glacial episodes.

Also, on the map showing actual LGM ice limits, the line used by Henry is very unreliable, being based on an acceptance of the "ice free corridor" in central and south Pembrokeshire -- which I demonstrated as being unreliable theoretically and in practice, in my 2023 QN article.

But all in all a very worthwhile and attractive teaching aid which will fascinate a new generation of budding glaciologists!

The LGM maximum line as shown on the new model.  The representation of the Bristol Channel as being effectively ice-free does not stand up to scrutiny.

The Lost Circle -- British Open Brass Band Challenge!!

You couldn't make this up. "The Lost Circle" has now been set to music by Belgian composer Jan Van Der Roost as a test piece for the British Open Brass Band competition.


https://www.4barsrest.com/news/60636/british-open-announces-2024-test-piece

This is hilarious on one sense. But it is also a stark reminder of the manner in which wild speculations and dodgy science can turn fantasies into myths and in turn into something seen by others (such as Belgian brass band composers) as established truth. The commissioning sponsors have clearly all been swept up in the media frenzy about Waun Mawn, and probably just loved that famous TV documentary fronted by Alice Roberts.  One cannot doubt that in good faith our friend Jan the Composer has accepted that the "Lost Circle" at Waun Mawn did actually exist -- before going on to explore musically what the "how and why" might have been.

So are MPP and his merry men feeling guilty about misleading gullible members of the public so comprehensively? I doubt that very much...........

===================

Here is the blurb:

British Open announces 2024 test-piece

'The Lost Circle' by Jan Van Der Roost will pose questioning musical challenges for bands wishing to construct a British Open winning performance at Symphony Hall this year.

The composer explored both why and how the Bluestones of Stonehenge came to their final resting place

A new commission by the critically acclaimed Belgian composer Jan Van Der Roost has been announced as the set-work for the 2024 British Open Championship.

'The Lost Circle' is his fifth major contest composition and has been commissioned through an international consortium of organisations, including the British Open alongside the national bodies of Belgium, The Netherlands, Norway, Switzerland, Germany and Austria.

It will receive its world premiere at the 170th British Open Championship at Symphony Hall, Birmingham on Saturday 7th September.

The work sees the composer return in inspiration to Stonehenge — the ancient site on Salisbury Plain in the UK that has held fascination to humans for millennia. It is, as the composer says, "a monument that has been the subject of questions, guesswork, doubts and speculations from time immemorial."

However, although 'The Lost Circle' is linked thematically in musical inspiration, it is not an "explicit successor" to his earlier 'Stonehenge' composition written in 1992.

Instead, as Jan Van Der Roost writes in his foreword to the 16-minute score, it is a work rich in thematic symbolism. It questions both how and why the inner circle of megalithic Bluestones were brought by ancient people on a 240-kilometre journey from deep in the Preseli hills in West Wales to their final resting place.

Speaking exclusively to 4BR he said: "I am honoured to write 'The Lost Circle' for the British Open and the national associations of Belgium, The Netherlands, Norway, Switzerland, Germany and Austria where it will subsequently be performed at their National Championships.

It follows 'Excalibur', 'Stonehenge', 'Albion' and 'From Ancient Times' in being used at major events, and I will be delighted to hear it performed at the magnificent Symphony Hall in Birmingham for its world premiere."

He added: "It is definitely a challenging and demanding work, but one I hope will be enjoyed by the conductors, performers and audiences alike in the months to come in the UK and Europe."

In making the initial contest announcement, British Open Championship Artistic Advisor, Dr Robert Childs told 4BR: "Jan Van der Roost is rightly regarded as one of the foremost composers writing for the brass band medium.

'The Lost Circle' is a magnificent work — and one which I am sure alongside our colleagues throughout Europe will provide a wonderful musical test for competing bands, and a thoroughly rewarding musical experience for listeners."

British Open Contest organisers Martin and Karyn Mortimer added: "It will be the first time Jan Van Der Roost has written a work to be used at the British Open Championship. We are thrilled to be able to provide the stage for its world premiere. Our thanks got to him and to our consortium friends for making this wonderful piece possible."

Feedback mechanisms and ice sheet behaviour

Two glacial episodes in Scandinavia -- but why was one more extensive than the other?

This is a very interesting paper on the behaviour of the Scandinavian Ice Sheet. For some time I have been interested in the manner in which feedback mechanisms operate within and on the edges of large ice masses. As readers of this blog will know, I have pondered occasionally on the role played by large troughs (such as Sognefjord in Norway and Nordvestfjord in East Greenland) in the efficient evacuation of ice and the dynamics of the ice mass. Assuming that in each successive glacial cycle these troughs are widened and especially deepened, we can also assume that the efficiency of ice transfer is improved -- but does that mean that ice sheets will get bigger and bigger in each successive glaciation? Not necessarily -- there might be ice edge advances at the trough outlets, but maybe ice edge retreat elsewhere because of ice capture in the trough catchments. In other words, there might be increased ice edge crenellation. This could all get very confusing -- and to their credit Henry Patten and others have already been thinking along these lines with respect to the BIIS.

The authors of the new Scandinavian paper concentrate on the role of gradual sediment filling of the low points in the landscape and the "capturing" of ice flow by spectacular features like the Norwegian Trough. With respect to the BIIS and the Celtic Sea arena, the BRITICE team have already been speculating on whether the Late Devensian Glaciation was the most extensive of all the Quaternary glaciations, partly because of the vast thickness of sea floor sediments across which the ice was flowing -- increased bed lubrication, sediment deformation, accelerated flow rates and a lower surface gradient are all interconnected.  Surging behaviour also comes to mind.  But what are the side effects of the "purges" that seem to have occurred in the Celtic Sea area?  Does a more extensive LGM mean that the glaciation was also more intensive?  Not necessarily.

Interesting questions so far, and not many answers......

==================

Gustav Jungdal-Olesen, Jane Lund Andersen, Andreas Born, and Vivi Kathrine Pedersen, 2024.
The influence of glacial landscape evolution on Scandinavian ice-sheet dynamics and dimensions
The Cryosphere, 18, 1517–1532, 2024

https://doi.org/10.5194/tc-18-1517-2024

Abstract. 
The Scandinavian topography and bathymetry have been shaped by ice through numerous glacial cycles in the Quaternary. In this study, we investigate how the changing morphology has influenced the Scandinavian ice sheet (SIS) in return. We use a higher-order ice-sheet model to simulate the SIS through a glacial period on three different topographies, representing different stages of glacial landscape evolution in the Quaternary. By forcing the three experiments with the same climate conditions, we isolate the effects of a changing landscape morphology on the evolution and dynamics of the ice sheet. We find that early Quaternary glaciations in Scandinavia were limited in extent and volume by the pre-glacial bathymetry until glacial deposits filled depressions in the North Sea and built out the Norwegian shelf. From middle–late Quaternary (   0:5 Ma) the bathymetry was sufficiently filled to allow for a faster southward expansion of the ice sheet causing a relative increase in ice-sheet volume and extent. Furthermore, we show that the formation of The Norwegian Channel during recent glacial periods restricted southward ice-sheet expansion, only allowing for the ice sheet to advance into the southern North Sea close to glacial maxima. Finally, our experiments indicate that different stretches of The Norwegian Channel may have formed in distinct stages during glacial periods since 0:5 Ma. These results highlight the importance of accounting for changes in landscape morphology through time when inferring ice-sheet history from ice-volume proxies and when interpreting climate variability from past ice-sheet extents.

The extraordinary Mr Croll -- the world's first glaciologist

 

James Croll, looking somewhat unhappy.  He didn't like fieldwork very much -- maybe he had just got wet out on the Scottish moors........

James Croll (1821-1890) was an extraordinary man with very little formal education who became a janitor at the museum of the Andersonian University in Glasgow in 1859 and who taught himself (because of his insatiable appetite for learning and his open access to the university library) physics, astronomy and geology.  He corresponded with Charles Lyell and disagreed with him about the origins of what were then called "drift" deposits, but he was greatly encouraged in his researches by Sir Archibald Geikie, and then obtained a position in the office of the Geological Survey of Scotland.

He is revered in Scotland as one of the country's great scientists and as one of the most original of thinkers, and he stood out from the other "glacialists" of the time, who were mostly geologists who happened to be interested ion the Ice Age. I think we should give him the accolade of being the first genuine glaciologist, because of the manner in which he combined the principles of physics, astronomy, climatology and geology in order to understand how glaciers work and how Ice Ages come and go through geological time. 

He saw the Earth as a single system within which events in one sphere (for example, changes in ocean circulation) had repercussions of knock-on effects in all other spheres. He built on the early work of Agassiz in 1840 to argue strongly against Lyell's "great flood" and for extensive landscape modification by expanded land ice. He developed an astronomical theory of oscillatory climate change 60 years before Milankovitch published a very similar theory. He developed a coherent theory of ice sheet growth and shrinkage, and (without any field measurements to work on) developed the idea of an equilibrium profile. He referred quite clearly to feedback mechanisms in glacier behaviour, and wrote about albedo effects. He considered the effects of ice sheet growth and shrinkage on global sea-level, and proposed considerable eustatic drops of sea-level coinciding with glacial maxima during the Ice age. He even started to explore the idea of isostatic loading and unloading, arising from his observations on Scottish raised beaches. He used bore hole records and used field observations on glacial stratigraphy to illustrate his ideas on glacier oscillations and glacial and interglacial episodes. Most extraordinary of all, he created a "model" of the Antarctic Ice Sheet even though, at that time, nobody had set foot on the Antarctic continent, let alone done any measurements on ice thickness, surface gradients and extent. His "model" incorporated innumerable parameters, most of which are still used in computer-based models today. What might he have achieved had there been computers in his day? Then, from his predictions on the nature of the Antarctic Ice Sheet, he had the temerity to use his "model" to suggest what the Great British Ice Sheet might have looked like at the time of maximum glaciation.......... his map was almost a century ahead of its time, and is reminiscent of the maps still in use around 1960, when I was a student.

He was, of course, in 1879  too radical and too far ahead of everybody else to have escaped unscathed -- and towards the end of his life there was a backlash from the more conservative members of the scientific establishment.  In spite of the fact that he was supported and encouraged by the Geikie brothers, and in spite of his copious and creative correspondence with all the great scientists of his day, he never was a full member of the science elite in Britain, and he was known in some quarters as a "controversialist".  The main criticism directed towards him was that his ideas were unsupported by hard evidence and that he strayed too far into the realm of theory  or speculation.  That was all very sad, because one by one his ideas have been accepted and moved into the mainstream -- and field evidence has supported most of his inspired speculations.  Yes, he made mistakes, but that is what happens on the frontiers of science, and the word "extraordinary" is one that will continue to be used for James Croll by those who examine the origins of the science of glaciology.

https://onlinelibrary.wiley.com/doi/full/10.1002/jqs.3420

‘The most remarkable man’: James Croll, Quaternary scientist
Kevin J. Edwards

Jnl of Quaternary Science
First published: 04 April 2022
https://doi.org/10.1002/jqs.3420

This is the abstract from Kevin Edwards's paper about this "most remarkable man":

ABSTRACT

The year 2021 marked the bicentenary of the birth of James Croll (1821–1890), the self-educated son of a crofter-stonemason, whose life was characterised by a dizzying range of occupations and homes, poor health and financial concerns, and yet he became a pioneer of orbital dynamics and ice age climate change with an impressive record of publication. Drawing upon archival information and recently published observations, this paper explores selected aspects of Croll's biography, his scientific connections and controversies, and that area of his life relevant to Quaternary science. He was a 19th century polymath whose multifaceted contributions have been a catalyst for subsequent systems-based climate science on the grand scale, including the foundations for the seminal work of Milutin Milankovitch on the rhythms of Quaternary environmental change.

See also:

Rose J. 2021. Lyell, the Geikies and Croll's observations on terrestrial glacial sediments and landforms. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 112: 261–274.

Sugden DE. 2014. James Croll (1821–1890): ice, ice ages and the Antarctic connection. Antarctic Science 26: 604–613.

Croll, J. 1879. On the thickness of the Antarctic ice, and its relations to that of the glacial epoch. Quarterly Journal of Science, January, 34 pp.

This is James Croll's map (1879), incorporating many components since proved to be correct. Compare with the more modern maps below. Croll was sure that the Scandinavian and British - Irish ice sheets were connected in the North Sea. Flowlines across Northern Scotland were largely correct. The Irish Sea ice stream is shown quite clearly. The ice edge is correctly located on the Celtic Shelf edge. However, Croll assumed that glaciers had a constant surface gradient from centre to periphery; the glacial equilibrium profile had not yet been discovered. So he greatly overestimated ice thickness in the centre of the accumulation area. Consequently, his image showing thick glacier ice flowing across southern England was somewhat overenthusiastic!! He has ice flowing down the Bristol Channel from east to west -- precisely the opposite of the ice flow pattern as understood today.

The most recent ice flow maps, mostly computer generated, are more correct that Croll's map -- but they are still faulty in some areas because of modelling mistakes and inadequate ground truthing.

==================

Also found on the web:
Achievements and Key Points

James Croll:

Was the foremost advocate in the 1800s of the idea that climate change is caused by the changing relationship between the earth and the sun.
Devised they theory that climate is controlled by solar insolation – the amount of energy reaching the earth from the sun.
Linked our planet’s ice ages to solar insolation variations caused by: Earth’s elliptical orbit around the sun (100,000-year cycle); precession of the equinoxes (23,000-year cycle); and axial tilt (41,000-year cycle).
Noted how the elliptical shape of Earth’s orbit around the sun varies with time – sometimes the ellipse is more eccentric (elongated).
Said ice ages happen when there is a combination of events: the earth’s elliptical orbit around the sun is at its most eccentric and mid-winter takes place when the earth’s orbit is at its farthest point from the sun. These conditions of reduced sunlight result in lower temperatures, leading to a build-up of ice and snow in the oceans and on the ground.
Said the build-up of ice redirects the trade winds and hence ocean currents. Warm currents like the Gulf Stream no longer bring heat from the tropics to the colder regions, enhancing the orbital cooling effect, leading to ice ages.
Advanced the theory of ice-albedo feedback. This says that if ice begins accumulating at a pole because of a decrease in winter sunlight, then the extra ice will reflect more of the sun’s heat back into space, leading to further cooling.
He (incorrectly) said ice ages alternate between the northern and southern hemispheres – the north and south taking it in turns to have moderate climates and ice climates in a cycle lasting 22,000 years in each hemisphere, with each ice age lasting about 10,000 years.
Although today we know Croll did not get all the details correct, his work provided a mechanism that explained the ice ages. It provided a basis for Milutin Milanković to go further the following century and generate the concept of Milankovitch cycles.

========================

This is an interesting programme from 2010, in which Iain Stewart talks at some length about the life and times of James Croll -- starting about 30 mins into the programme.

https://www.youtube.com/watch?v=vGnBz0VwXoE

Bluestone transport: Edgar Barclay was the originator of the human transport hypothesis -- not HH Thomas

Two of Barclay's Stonehenge paintings

Reference: 
Barclay, 1895. “Stonehenge and its Earth-works”. Nutt, London, 225 pp.

https://archive.org/details/stonehengeandit00barcgoog/page/n64/mode/2up?view=theater

https://www.sarsen.org/2014/05/barclay-edgar-stonehenge-and-its-earth.html

Thanks to Tim Daw for flagging up this little volume a few years ago. I have been looking at it again,  and while a lot of the contents of the book are naive and fanciful, it contains many astute observations and deductions. Barclay clearly had no contact with the "glacialists" of his day, and he makes no mention in his book of the possibility of glacial stone transport.  He was certainly not the first writer to refer to the "prodigious effort" involved in assembling the Stonehenge monoliths and the building of the monument, but (and here I stand to be corrected) he seems to have been the first person to propose the long-distance transport of the bluestones from their places of origin across the sea and overland. (We can safely ignore Merlin the Wizard and Geoffrey of Monmouth for the time being.....)

He was advised (somewhat prematurely) by the geologists of the day that the bluestones cannot have come from any British rock outcrops, and so he speculated that they might have come from Brittany, and that they were transported across the Channel by our ancient ancestors. He also suggests in his text that the bluestones must have been deemed as special or valuable -- in order to justify the "prodigious effort" involved in moving them. Barclay was also aware the the chippings and bluestone fragments scattered about across the Stonehenge landscape, and of a link with the abundant round barrows on the chalk downs.

I think the key passages in the text below justifies us in giving the credit -- or the blame --to Barclay for the invention of the human transport hypothesis in 1895.  What HHT did 28 years later was to correct the source area to West Wales and to add the petrological detail which permitted him to claim (again somewhat prematurely) that he knew pretty well exactly where the bluestones had come from. In 1858 Ramsey had suggested that Wales was the source for the bluestones.   It's worth remembering that neither Barclay nor Thomas believed that the bluestones had been quarried.  Both of them realised that the bluestones were simply weathered boulders collected up from what had been a scatter across the landscape.

================

Edgar Barclay (1842-1913)

The artist Edgar Barclay was born in 1842 and studied art in Italy and Germany. For several years as a working artist he divided his time between London and Italy, but he returned to England in the 1880s and began painting rural scenes of Wessex, especially of Stonehenge. He exhibited extensively and was known for his skill in handling light and big skies. He was also an accomplished historian, writing and speaking particularly on Stonehenge. He addressed the British Archaeological Association in 1893. He clearly had good contacts, and wrote "Stonehenge and Its Earth-Works” in 1895. He suggested -- because of the weathering crusts on many of the bluestones -- that they were simply collected as boulders rather than being quarried.

Extracts:

p 6
The inner circle and inner horse-shoe are composed of the foreign  "Blue-stones",  igneous rocks. The locality from which they were originally taken remains undetermined ; experts, after microscopic examination, have affirmed that in "no part of Great Britain is there any stone to be found of the same description." Of these some differ markedly in their nature from others.

p 77
The most arduous operation in connection with the erection of Stonehenge was the transportation of the Blue-stones ; we should, therefore, be forced to believe that although the builders lacked the energy to complete a gap in the Sarsen circle, they nevertheless had the opportunity and energy to fetch and set up the Bluestones. This is a contradiction ; we therefore conclude that stones are missing because the building has suffered from spoliation. Fortunately, ancient records which make mention of Stonehenge inform us how this probably came to pass.

pp 124-126
In conclusion, we take a retrospective glance at the results of our inquiry. To begin, there is the striking fact that Stonehenge consists of stones foreign to the neighbourhood, and belonging to geological formations widely apart ; proof that its construction was a far greater undertaking than the present appearance of the ruin would lead any one to suspect, and of the power of the founders to organize labour on a very considerable scale.

This is specially shown by the case of the Blue-stones, which, according to the judgment of experts, are foreign to this country, and which, so it has been concluded, from the weathered surfaces of some of their chippings, were, like the larger Sarsens, never quarried, but derived from boulders left on the surface, or, more probably, were brought from some sea-washed shore.

The labour of carrying these stones up from the coast was no mean one, and that they should have been transported across the sea is not merely a conspicuous proof of the resources of the founders, but indicates either that those who controlled the work were themselves moved by a strong sentimental motive, or that they played upon a strong sentimental feeling animating others, otherwise so laborious and unusual a course, and one so uncalled for by any utilitarian purpose, would never have been pursued.

The dictum of petrologists, that the Blue-stones are of foreign origin, is in harmony with the tradition that the stones have been transported hither by sea. The geological formation of Brittany points to that country as their probable source, a probability greatly strengthened by historical considerations. Geoffrey of Monmouth, when giving an account of additions effected by King Aurelius to the monastery at Amesbury, followed a tradition which stated that a stone circle was taken down and utilized for that purpose. We have no reason to believe that Geoffrey had knowledge of Stonehenge, situated a mile distant west of the monastery ; and mystified by another tradition which stated that the stones had been shipped, it appears that he in consequence concluded that the stone circle in question must have been situated in Ireland ; thus he kept to the right direction for their source, whilst considerably exceeding the real distance. It is incredible that Aurelius should have brought his building material from that country; he had not the power, supposing he had the crazy desire to do so ; he had no fleet, and the sea was commanded by piratical Saxons, his deadly enemies. In the introduction of the Irish incident we, therefore, recognize Geoffrey's embellishments ; we here see the old familiar artifice of making an incredible story appear veracious, by the introduction of circumstantial details, thus in the thick of the Irish embroglio he makes his characters orate in the time-honoured classical and biblical manner.

The Altar-stone belongs to a different geological formation to either the Wiltshire Sarsens or the foreign stones, and affords another proof of lavish expenditure of labour ; whilst the shaping of the rocks, and the manner in which the superimposed blocks are securely locked in their places by means of tenon and mortise, evidences the attainment of considerable skill.

Moreover, it is a striking fact that these rocks, collected with prodigal labour from sources so widely apart, should have been set up on a bare and desolate down, the surrounding land for the space of several miles being more thickly studded with barrows than any other district in this country, which produces a strong impression, the correctness of which is fully confirmed by closer scrutiny, that the ruin and the gravemounds are in some way connected. We noted the critical positions of the outlying stones, and that mysterious alignments proceed from the ruin and traverse the barrow-studded plain.

The design has manifestly not been dictated by utilitarian necessities, or by aesthetic sentiment, it shows the temple to have been dedicated to Sun-worship, the stones being so disposed as to form religious symbols ; the meaning of that symbolism we have endeavoured to explain, and in doing so we have followed ideas once current in Gaul.

The unity of the design was proved by the relative proportions of the parts, and that the different parts were raised at the same epoch is further attested, first, by the finding together of pieces of the different sorts of stone used in the construction within a gravemound, and, secondly, by chippings of all the rocks having been found in the concreted substance around the bases of the Bluestones. When thus proving the unity of the design, we proved also that the temple is not of prehistoric antiquity, for we have no reason to believe that the ancient Britons were capable of adjusting their buildings with a knowledge of geometry.

What did HH Thomas know about the extent of glaciation?

I have been digging up some more info about what HH Thomas knew or did not know when he presented his controversial views on the transport of the bluestones in 1923.  (And in 1921, actually......)  

Let's take 1910 as a reasonable date to look at.  The "state of play" was determined at the time by such senior geologists and "glacialists" as James Geikie (far more important than his older brother Sir Archibald), Carvill Lewis, Frederick Wright,  Thomas Jehu and John Wesley Judd. 

Henry Carvill Lewis (1853-1888) , an American who did much fieldwork in the British Isles.  He proposed that the edge of the great Ice Age glaciation in Britain  coincided with a line of prominent moraines and other features which could be traces across country.  At first he found it difficult to accept that traces (such as erratic boulders) south of his limit were genuinely related to the presence of glacier ice, and he initially assigned them to some great Ice Age Flood. But later in his all-too-short life he fell into line with Geikie and others and did accept that the maximum position of the ice edge in the Ice Age was well to the south of his hypothetical line. 

 

Prof James Geikie (1839-1915), a Scottish geologist who was convinced that there was very extensive glaciation in the Ice Age, and that the ice limit in SW England lay somewhere off the Cornish coast. he was also active in promoting the idea that there had been several glaciations, separated by warmer intervals or interglacials.

Frederick Wright’s map of 1895, showing a strange ice limit across South Wales, based in part on Carvill Lewis’s identification of assumed terminal moraines. Wright ignored the abundant records of far-travelled erratics to the south of this line.

Europe and the greatest extent of glaciation during the Ice Age. From “Prehistoric Europe - A Geological Sketch”, by James Geikie (Edward Stanford, London, 1881). Note that Geikie incorporates the whole of the Bristol Channel area into the glaciated area, with an ice edge on or near Salisbury Plain……..

In this map, also from Wright (1895) a highly generalised line, based on the work of James Geikie, is drawn well to the south of the “moraines” identified by Carvill Lewis. Geikie recognised that the abundance of glacial erratics around the Bristol Channel coasts indicated extensive glaciation, at least as far south as the Cornish coast.

Extract from Harmer’s “erratic map” of 1928, showing erratic boulders and ”drift” exposures in abundant locations including South Pembrokeshire, Gower, Glamorgan and the Ilfracombe district — all to the south of the “moraines” mapped by Carvill Lewis. The work on this map was done between 1902 and 1913, and it must have been known to HH Thomas.

Prof Thomas Jehu (1871-1943) was born in Wales and later spent most of his working career in Scotland. As a young man he studied the glacial deposits of North Pembrokeshire, and published his findings in a highly regarded article in 1904. He recognized a tripartite succession in the drift sequence of Pembrokeshire -- namely Lower boulder clay, Middle sands and gravels, and Upper boulder-clay.  He characterised the latter deposit as a "rubbly drift" -- this is now recognized as a mixed deposit of melt-out till, flowtill and ablation till, rearranged and redeposited in a chaotic ice wastage environment.  Jehu agreed with Hicks that the Irish Sea ice that affected North Pembrokeshire flowed across the county from NW towards SE -- thus contradicting Geikie who had earlier portrayed the ice as having travelled from NE towards SW,

 Prof John Wesley Judd (1940-1916) was a prominent geologist who specialised in petrology.  He was Professor of Geology in the Royal College of Science and at Imperial College, and also President of the Geological Society.  Because he was London-based, he was right at the centre of things, and knew all about what was going on in assorted disputes and areas of progress.  He participated actively in the Stonehenge bluestone debate, and provided comments or additional material to some of the prominent archaeologists includingGowland and Hawley.  In 1901, Judd suggested that the bluestones at Stonehenge were erratics of glacial origin. He argued that the debris at Stonehenge had come from North Pembrokeshire or North Wales. He also observed that in areas affected by very ancient glaciations, most of the till had been eroded away by natural processes, leaving only a thin scatter of erratics here and there. Further, he observed that hard stones (including bluestones) left behind on Salisbury Plain would have been targetted down through the centuries for building purposes simply because neither chalk nor flint makes good building material.  Intriguingly, Judd concentrated not on the 43 known bluestone monoliths or orthostats themselves, but on the Stonehenge debitage. He found an extraordinary assortment of soft or fragile stones.  He made the point specifically that this material did not seem to be very closely related to the remaining standing bluestones -- so he concluded that only the hardest stones had survived, with all the other material breaking down and becoming incorporated into the soil layer over many thousands of years.  Judd suggested the presence of a “Stonehenge moraine” incorporating an abundance of foreign stones which would have been readily available to the builders of Stonehenge. He also argued -- perfectly plausibly -- that “stone availability” (of both bluestones and the larger sarsens) might have actually determined the precise position of the monument. 

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All things considered, the accumulated evidence shows that by 1910 the broad outlines of glaciation in the Bristol Channel / Celtic Sea arena were already established, involving thick and active ice carrying erratics and other glacial materials from the NW across Pembrokeshire and up the Bristol Channel, affecting the coasts of South Wales and the South-West Peninsula. In making his claims about the impossibility of bluestone transport towards Stonehenge HH Thomas wilfully ignored a great amount of evidence in the printed literature, and wilfully misrepresented the opinions of senior "glacialists". It is quite extraordinary that he got away with it -- but that, maybe, was because he was a geologist talking to archaeologists or antiquarians. If he had been a geologist talking to other geologists, he would certainly not have got away with it.  They would have had his guts for garters. 

Interestingly enough, the great majority of the articles published by Ixer and Bevins in recent years have also been published in archaeological journals -- and presumably they have been refereed for the most part by archaeologists. What a strange coincidence........!!

HH Thomas knowingly misrepresented the glacial erratic transport evidence in the Bristol Channel

I have been looking again at the manner in which, in 1923, HH Thomas informed the world that the glacial transport of bluestones from west to east (up the Bristol Channel) would have been impossible.  Here is an earlier post of mine:

https://brian-mountainman.blogspot.com/2019/10/hh-thomas-and-his-glacial-blind-spot.html

Thomas was guilty of over-simplification and selective citation of his samples (there were very few anyway) and his rock identifications, in order to flag up the idea that there were just two main sources for the bluestones. It's interesting that in 2018 Bevins and Ixer attacked Thomas's slapdash methods, his sharp practices and his reputation pretty enthusiastically, but they restricted their scrutiny to his geological analyses, and criticised him for homing in on Carn Meini and Carn Alw as the main source locations for the Stonehenge bluestones.

https://brian-mountainman.blogspot.com/2018/06/herbert-thomas-scrutinized.html

https://brian-mountainman.blogspot.com/2011/03/more-on-hh-thomas.html

https://brian-mountainman.blogspot.com/2022/06/dale-judd-and-engleheart-versus-thomas.html

Retracing the footsteps of H.H. Thomas: a review of his Stonehenge bluestone provenancing study.
Richard Bevins and Rob Ixer
Antiquity, May 2018.
https://doi.org/10.15184/aqy.2018.10
Published online: 31 May 2018

Bevins and Ixer later (in the magazine called Liver Science) went off on a tangent and tried to demonstrate (without any evidence at at all)  that the bluestones were transported by land instead of by sea.  That was a serious waste of time and effort, especially since HHT did not try to promote the idea of sea transport either.  That came later, with the involvement of Atkinson and other archaeologists.

https://www.livescience.com/63003-sloppy-stonehenge-study.html 

Also, it's rather ironic that in attacking HHT for concentrating on the "wrong" two tors, they then concentrated on trying to convince the rest of us that two other tors or rock outcrops (Carn Goedog and Rhosyfelin) were key to the understanding of what went on  -- while admitting in other papers that the bluestone monoliths and fragments at Stonehenge have come from multiple locations.  Not for the first time, pots and kettles come to mind!

B and I  also declined to comment on the most influential part of the HHT paper -- namely the section dealing with the bluestone "mode of transport."  But the section in the 1923 paper on the "ice transport option" is truly awful, misrepresenting all sorts of things and including many statements that HHT must have known were untrue -- even allowing for the fact that he was writing a century ago. That section should have been scrutinized.   Below I reproduce the key part of the infamous paper, with some comments of my own.

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Extract from HH Thomas, 1923 Antiquaries Journal

MODE OF TRANSPORT

Having in a great measure solved the problem of the source of the Foreign Stones, we must consider carefully the possible and probable modes of transport of the stones from Pembrokeshire to Salisbury Plain. Two modes of transport have been suggested : one natural, by ice during the great Ice Age ; the other, by human agency at, of course, a later period.

The Hypothesis of Ice-transport. 

Professor Judd in 1901 put forward the hypothesis that the Foreign Stones of Stonehenge had been transported to the Plain by ice during the Pleistocene Glacial Period, and this view seems to have found favour and acceptance in many quarters.

We have, of late years, considerably advanced our knowledge of the distribution and extent of the British Ice-fields, and also accumulated much information concerning the directions and limits of dispersal of erratic boulders. The geological evidence is such that the idea of a glacial origin for the Foreign Stones will not bear investigation.

((Comment:  Perhaps not a good idea to get your conclusion in first, before considering the evidence.........))

Let us consider critically this hypothesis of glacial transport as suggested by Professor Judd. First, there is no evidence of glacial drift on Salisbury Plain such as would of necessity have been left by any ice-sheet capable of transporting the masses of rock in question. Isolated masses of rocks foreign to the district, other than those used in the fabric of Stonehenge are entirely wanting, as also are small pebbles of such rocks from the gravels of the neighbourhood. It has been claimed, without producing any evidence in support of the statement, that such masses did exist but that they have all been collected to make walls, gateposts, millstones, etc. But, as Mr. Stevens of Salisbury has cogently stated, no one can point to a single rock-mass like any of those used at Stonehenge having been put to any such purpose. Mr. Stevens says ' There are many millstones and gateposts in Wiltshire, but where is there one which corresponds in any way to the upright Foreign Stones of Stonehenge ? Unhappily this tangible evidence is wanting ; so, alluring as the Glacial Drift Theory may appear, it must reluctantly be set aside for want of convincing evidence.'

((Comment: It's disingenuous of Thomas to pretend that substantial "rock masses" of exactly the right type on Salisbury Plain are required in order to demonstrate that glacial entrainment and transport might have occurred. There are erratic stones in the records of work prior to 1923, and the Boles Barrow bluestone was already on the record following its discovery by Cunnington in 1801.  If you want to wear rose-tinted spectacles rather than dark sunglasses, you might wish to count the Stonehenge bluestone assemblage as quite valid evidence of glacial transport and dumping, and Thomas should have acknowledged this.))

To transport glacially a series of igneous boulders of great size from Pembrokeshire to Wiltshire postulates the existence of an ice-sheet of unbroken character occupying the whole of the intervening country ; and with the ice moving in a direction a little south of east. We have, fortunately, good evidence of the extent of glaciation of Pembrokeshire, and we find that this county was crossed in a south-easterly direction by an ice-sheet that moved down the Irish Sea. This ice-sheet carrying Scottish
boulders, crossed the low plateau of Anglesey and Carnarvon, gathering fresh material as it went, but was kept from passing far inland by the local Welsh ice-sheet that had its centre of dispersal in the highlands of Snowdon, The Arenigs and Cader Idris, and was pressing outwards towards the coast. On reaching the latitude of Pembrokeshire, far removed from the main centre of Welsh glaciation, the Irish Sea ice-sheet was allowed to spread fanwise and to override the plateau-regions of Pembrokeshire and Southern Ireland which offered relatively little opposition. In spite of this there is the clearest evidence, from the distribution of Pembrokeshire and Scottish boulders that the ice-front lay only just south 

of the present coast-line of Pembrokeshire, and that the ice as a solid mass neither crossed the Bristol Channel to Devon and Cornwall, nor passed in an easterly direction beyond the coastal regions of Pembrokeshire. 

((Comment: This is utter nonsense, and Thomas must have known it.  We are talking here of the maximum known glaciation in the region.  To claim that the glacier ice front lay just to the south of the Pembrokeshire coast, and to claim that the ice progressed no further up the Bristol Channel,  is to fly in the face of the evidence that had been in the public domain for more than 20 years.  Jehu and many other professional geologists must have been appalled by Thomas's claims.  Judd, who died in 1916, would have turned in his grave.  Glacial deposits were already known, and described in the literature, from the Bridgend - Pencoed area, from Fremington, Trebetherick and the Isles of Scilly -- all attesting to a very extensive glaciation  that could, even according to the thinking of geologists in 1923, have extended to Somerset and Salisbury Plain. Thomas must have known of the Pentre, Newton and St Athan erratic boulders in the Vale of Glamorgan, all three almost certainly from Pembrokeshire.  And far-travelled glacial erratics were already described from the coasts of Devon and Cornwall.))

No boulders of Pembrokeshire rocks, such as would of necessity be carried by any extension of this icesheet, have ever been found either on the north coast of Devon, Cornwall or Somerset, or on the south coast of Wales east of the estuary of the River Towy.

((Comment:  That is not correct. The Pembrokeshire erratics in the Storrie Collection, from the till at Pencoed in Glamorgan, were well known by 1923. Indeed, Thomas himself was one member of the Geological Survey team that described the erratics in the Bridgend GS Memoir of 1904.))

Scottish boulders, however, occur on the north coast of Devon and on the coast of Glamorganshire where their presence, unmixed with Pembrokeshire boulders, indicates that they were not carried by that portion of the ice-sheet which had crossed Pembrokeshire but had been borne by the portion that came down the central region of the Irish Sea. The ice-sheet would probably have a crescentic front and the medial portion would have the furthest southerly extension. It is to be noticed that all the occurrences of Scottish boulders outside Pembrokeshire and its adjacent islands lie at raised-beach level, as at Croyde Bay and in Glamorganshire. There is no evidence of the erratic material mounting the cliffs or extending inland. The inference is, therefore, that these Scottish boulders were deposited from icebergs that had broken away from the central portion of the main ice-front and were stranded on relatively distant shores. The geological evidence proves conclusively that although Pembrokeshire was crossed in a south-easterly direction by a lobe of the Irish Sea ice-sheet the front of this ice-sheet never reached across or far up the Bristol Channel.

((Comment:  Thomas gets himself into a frightful tangle over the shape, thickness and  movement of  "the ice sheet" -- and although he may be right to assume that Scottish erratic boulders were constrained within a segment of the ice stream, he must have known the evidence on the file that Pembrokeshire erratics were in fact transported much further east than the Towy estuary.))

Passing to the country intervening between Pembrokeshire and Wiltshire, we find nowhere along the line that an ice-sheet would have to traverse in order to transport Pembrokeshire boulders to Salisbury Plain, any evidence of glaciation of an intense character. 

((Comment:  This is a somewhat absurd statement, given that most of this territory is currently under water.  And what sort of glaciation is to be counted as "of an intense character" as distinct from one that is not intense?))

There are no trains of far-travelled boulders, no ice-scratching and polishing of outstanding rocks, and no thick accumulations of boulder-clay. As has been pointed out in a previous communication such a hypothetical ice-sheet, in order to account for the Foreign Stones of Stonehenge would have to gather from Pembrokeshire blocks all of about the same size and mainly of two rock-types. It would have to carry them all that distance without dropping any by the way. 

((Comment:  Here, Thomas raises the nonsensical idea that ice cannot possibly have delivered to Stonehenge exactly the right number of bluestones, of the right colour and lithology, to satisfy the designers and the builders of the monument.  This has, of course, been repeated many times since.  So many unsupported assumptions are built into that it is really not worth wasting time on them.))

Further, it would have to pass over all kinds of rocky obstacles without gathering to itself any of the various materials over which it was forced to ride. Such in itself, without the additional positive evidence that is forthcoming as to the extent of the glaciation of Pembrokeshire and adjoining counties, permanently disposes of the idea of glacial transport for the Foreign Stones of Stonehenge.

((Comment:  Thomas must have known, from his work with the Geological Survey including Cantrill, Strahan, Dixon and Jones, that glacial entrainment, transport and deposition are complex matters which are difficult to predict and which constantly throw up surprises in the field.  The apparent absence of erratics from all upglacier outcrops does not (and did not in 1923) demonstrate the absence of glaciation.))

Note: The rocks of the Western Isles, Ailsa Craig, and Galloway are fairly common as erratics. They occur on the Cardigan coast, on the plateau-region of Pembrokeshire and its outlying islands (Skomer, Skokholm, etc.), and on the Glamorganshire coastal regions of the Bristol Channel.

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I'm still staggered that Thomas was allowed to get away with all of this, and to make such definitive statements on the record.  We know that a few people -- including Engleheart and Dale -- were sceptical, but where were all the geologists who knew that he was talking nonsense?  Was he such a forceful character that nobody had the guts to challenge him?  Or was the establishment view already established -- namely that the human transport of the bluestones was a matter of national pride, meaning that anybody who challenged the idea could be charged with being unpatriotic?