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....
To order, click
HERE

Monday, 18 October 2021

More on Bronze Age boats




I just thought I should draw attention to this article, from Current Archaeology -- originally published in 2014 and re-published with revisions this year (June 30th):

 https://the-past.com/feature/building-morgawr-seafaring-bronze-age-style/?fbclid=IwAR2yTjHa26uKOgkTL4FUVGt8JNgJzPMRqtqwbQWc7asUenl77SO-Alr4OXk

Building Morgawr: seafaring Bronze Age-style

What did the fragmentary Bronze Age boats found around Britain look like when complete, and what were they like to handle? The best way to find out, Robert Van de Noort told Current Archaeology's Carly Hilts, is to build one yourself.

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

It's a nice article, but bear in mind that it has no bearing on the "Stonehenge bluestones" debate, because the creation of a craft like "Morgawr", big enough to carry a bluestone monolith, would have been totally dependent upon the use of metal tools.  So this is a Bronze Age topic, and not a Neolithic one.

A slate glacial erratic on Salisbury Plain?

 

The little state "worked point" found in the Mesolithic dig at Vespasian's Camp.  From a glacial erratic found in the vicinity?  North Pembrokeshire slate?

I read this article on Vespasian's Camp and Blick Mead years ago, and had more or less forgotten about it. I did posts about it in 2013 and 2014.  A lot of water has gone under the bridge.   Let's look at it again, with a very interesting paragraph:

https://archaeology.co.uk/articles/features/vespasians-camp-cradle-of-stonehenge.htm


Vespasian’s Camp: Cradle of Stonehenge
Current Archaeology, April 19, 2013
David Jacques, Tom Phillips, and Tom Lyons

Extract:


Does anybody know anything more about this flake?  Barry Bishop was obviously studying it.  It may well have been more carefully examined by now, by Rob Ixer and others.  It looks like dark grey or black slate to me.  If this was the parent material, of course the possibility of a slate erratic on Salisbury Plain comes into the frame.  It might of course be made of North Wales slate, but it is much more likely to have come from a dark-coloured Pembrokeshire slate, which is found in abundance both to the north and south of Mynydd Preseli.  This would be my preferred suggested provenance; after all, there are 43 other erratic monoliths -- or bits of them -- at Stonehenge, as well as innumerable lumps of rock and smaller fragments  in the wider Stonehenge landscape, mostly from the Mynydd Preseli area:




Fig 4.12 from "Stonehenge for the Ancestors"  --- courtesy Sidestone Press, who have made the book available for free via the internet.   Bluestone erratic fragments all over the place.........

"Slate" has been mentioned before in the context of Salisbury Plain erratic material, but it is a rather vague term, covering a multitude of sins.  In a comment following one of the earlier posts, Rob Ixer said:  "We do not know if it is slate. The macroscopical description has not been verified by a competent authority. The closest 'slates' may be Devonian or even the killas. (??)  The latter are both Cornish and Devonian/Carboniferous."

(Note:  Killas is a Cornish mining term for metamorphic rock strata of sedimentary origin which were altered by heat from the intruded granites in the English counties of Devon and Cornwall. The term is used in both counties.)

This is intriguing, from a 2017 article:


"........a microlith type from the Sussex Weald, though made from slate that could have been brought from as far west as Wales....."    Let's ignore the ruling hypothesis -- but the "Sussex Weald" connection is new to me...........

And this from 2014:  "The presence of Horsham-type points is unusual in Wiltshire, suggesting that people travelled here. A slate point from context (59) is particularly illuminating in this regard. Slate is exotic for the area and this piece appears to have been closely fashioned in the Horsham Point style (Figure 5, 1 and 2). An exceptionally large amount of burnt flint indicates nearby hearths and possibly large fires (Bishop below and forthcoming)."

WANHM vol 107, 2014, pp 7-27
Mesolithic settlement near Stonehenge: excavations at Blick Mead, Vespasian’s Camp, Amesbury
by David Jacques1 and Tom Phillips

https://www.buckingham.ac.uk/wp-content/uploads/2014/12/Blick-Mead.pdf

Contribution from Barry Bishop (p 17): 
" One of the most intriguing finds from the excavations is a small piece of light greenish slate, 42mm long, 13mm wide, 4mm thick and weighing 2g, formed into a basally retouched Horsham Point from Trench 19, context (59) (Figure 5: 1). Slate does not fracture conchoidally, thus it is difficult if not impossible to determine whether this piece was deliberately shaped. Several factors, however, suggest that it may have been consciously formed. Its shape is typical for this type of microlith, with the right side gently curved from base to tip. The left side continues flaring from the point to about half way down where it turns inwards, forming a slight shoulder. The base is slightly curved and at a slight oblique angle to the main axis of the piece. A small part of its edge is broken following natural cleavage planes, but mostly the edges are formed by steep snapping from the ventral side, although snapping at the base is bifacial, initially from the ventral face and then also inversely from the dorsal face, resulting in a concave bevelled edge. All edges are fresh with little evidence of rolling or abrasion. If this object is indeed a slate microlith it is, as far as this author can establish, unique in Britain."


This is an illustration of what appears to be the same piece of slate -- but here referred to not as black or grey, but as light green...........  that again would be perfectly feasible for something which has come from the Preseli area, where slates of many colours occur in assorted well-known slate quarries.

And this from David Jacques, in 2017:

"Of particular interest is a slate point which appears to have been fashioned in the Horsham Point style typical of the Sussex weald in the middle Mesolithic. The slate has been subjected to XRF analysis and is likely to have come from Wales or the Welsh borders. As such the object points to an ‘east meets west’ transmission of knowledge at Blick Mead and hints at gatherings of dispersed groups of people there. Other exotics include a sandstone tool, a unique find in Great Britain, which probably came from the West Midlands and a worked sarsen found in the residential area which is likely to have come from the Marlborough Downs area. The sense is of people from elsewhere meeting locals at the site and exchanging ideas, things and maybe genes."

You have to forgive David Jacques for the mental blockage about the possibility of glacial erratics on Salisbury Plain -- but a key point for me is that the "slate point" is not alone.  There are other erratic pieces too. in a Mesolithic context........

Stonehenge research -- a useful resource

 


https://infrastructure.planninginspectorate.gov.uk/wp-content/ipc/uploads/projects/TR010025/TR010025-000358-6-3_ES-Appendix_6.1_HIA_Annex%204_PreviousArchaeologicalInvestigations_StonehengeWHS.pdf

I came across this -- some may not be familiar with it.  A very comprehensive and yet concise summary of all the Stonehenge research down through the years, with a full bibliography.......

Friday, 15 October 2021

Glacial erratic transport -- 'tis indeed a wondrous thing

Erratic cluster of boulders from Pre-Cambrian basement rocks on the rocky shore of Rödlöga 
Storskär in the Stockholm Archipelago.  How is it that boulders like these, from different 
distances up-glacier and from many different geological outcrops, end up being dumped 
together in one small area?

I have written endlessly on this blog about glacial entrainment and the transport of blocks and debris beneath, within and on top of a glacier -- but whenever I think about the processes involved I am reminded that we know hardly anything.  All we can do is speculate, since direct observation is almost impossible, given the physical problems associated with working within or under a glacier, and the time scale involved.  The time taken for an erratic to travel from its entrainment point to its "final destination" can be measured in centuries if not millennia........... or maybe in some cases, just a few years.

There is remarkably little in the standard glacial geomorphology text-books (including mine!) but some authors suggest that erratics are thrown together as in the photo above in a somewhat random fashion.   But to call something "random" is the easy way out, and of course there are physical laws here which have determined why boulders from a dozen or so different locations have all ended up in the same place.  Note that some boulders are more angular than others; this means that they are made of harder rock, or else that they have not been carried as far as those that are rounded.  The size of the boulders is to some degree dependent upon the fracture pattern in the bedrock exposures from which they are derived;  the more massive and unfractured a rock is, the bigger will be the entrained blocks, slabs or pillars.

The two most-cited articles about erratic entrainment, transport and deposition are by Geoff Boulton:

Boulder shapes and grain-size distributions of debris as indicators of transport paths through a glacier and till genesis
G. S. BOULTON,
Sedimentology, December 1978, Volume 25, Issue 6
Pages 773-799
https://doi.org/10.1111/j.1365-3091.1978.tb00329

G.S. Boulton
Theory of glacial erosion, transport and deposition as a consequence of subglacial sediment deformation
J. Glaciol., 42 (1996), pp. 43-62

Useful as these articles are, they are more concerned with till than with erratics, placing much stress on deforming bed conditions.  So they do not approach a comprehensive erratic-related theory...........

According to Darvill et al (2015):  "No single model for the formation of erratic boulder trains exists, and it is possible that they can be formed in a variety of ways. This is not surprising given the reported variety in boulder size, train length, number of boulders, transport distance, and lithology. Two hypotheses prevail: (i) subglacial entrainment and (ii) supraglacial debris."  Only two?  Come along now, chaps. Things are much more complex than that...........

Geomorphology, Volume 228, 1 January 2015, Pages 382-397

Geomorphology and weathering characteristics of erratic boulder trains on Tierra del Fuego, southernmost South America: Implications for dating of glacial deposits

Christopher M. Darvill, Michael J. Bentley and Chris R. Stokes
https://www.sciencedirect.com/science/article/pii/S0169555X14004929

Anyway, we already have three parameters to fit into our erratic transport algorithm:  rock "hardness",  fracture pattern and distance travelled. If we were to try and design a computer programme to model what happens during transport, I would hazard a guess that we need scores more parameters to be built into it.

We read a lot in the literature about erratic trails, or trains, or fans.  There are many posts on these on this blog.  Just search for them.  We all like to look for lines or patterns in the landscape, and we like to think that landforms created by a single set of processes will have recognizeable characteristics;  think of drumlin fields, or streamlined erosional landscapes, or Rogen moraine patterns, or anastomosing / braided patterns on fluvioglacial outwash plains.  Looking back on it, David Sugden and myself, when we were writing our text called "Glaciers and Landscape", were looking for patterns all the time.  But just to give one example, when we were looking at bedrock variables affecting the efficacy of glacial erosion (and hence the entrainment of lumps of bedrock) we identified (a) the type and quantity of basal debris in the glacier sole, (b) the susceptibility of the bed to erosion - because of hardness, fracturing etc, ( c) the roughness of the bed, and (d) the permeability of the bed.

 A classic erratic "pattern" map -- the Foothills Erratic Train in North America:  erratic blocks and debris from a single identifiable source, carried along for most of the journey on a contact zone between two ice sheets, the Cordilleran to the west and the Laurentide to the east..
 

Another pattern, which we might call a train or a fan -- erratics carried in a contact zone between two ice streams, with "spreading" as a result of the expansion and contraction of one ice 
stream as compared to the other.

During a single glacial episode it is quite possible for a single erratic block to be moved in all four compass directions, carried downwards and then upwards, and on a convoluted or zig-zag route.  Maybe it will even be carried west to east in one phase and then east to west in another.  In other words, a block can maybe travel twenty miles and then end up more or less where it started out from.  If this sounds absurd, just bear in mind that in many glaciated terrains there have been early and late phases in each glaciation where local ice-caps dominated.  In North Wales, it is quite possible for erratic blocks from Snowdonia to have been carried northwards towards the Irish Sea in small local glaciers, then southwards at the time of peak glaciation by the Irish Sea Glacier, and then northwards again by late-glacial expansions of the local ice caps after the retreat of the Irish Sea Glacier.  There must have been similar erratic behaviour in the Brecon Beacons, in the Lake District, in some of the upland areas of Ireland, and even on Mynydd Preseli.

Then when we extend the story of erratic perambulations and zig-zag routes from one glaciation to three or four glaciations, all with different glaciological histories and time-spans, things start to get complicated.........

And it's also clear that erratics do not all travel along at the same rate when they are under, within or on top of a glacier or ice stream.  Some erratics "leapfrog" other erratics, and it seems that while some occasionally get stuck or trapped, others may be carried past them.  What exactly are the processes involved?  Again the timescale may be measured in hundreds of thousands of years.

How many parameters do we have now?  I am already beginning to lose count, and we haven't even started to talk glaciology.  On a glacier bed, we know that as a glacier advances and as its snout retreats, and as it thickens and thins, over and again during a single glaciation, the transition between cold-based ice and warm-based ice migrates sometimes up-glacier and sometimes down-glacier.  This means that the zone of optimal erosion and entrainment migrates too, with complex (but not random) consequences.  An upstanding tor, which we might expect to be eroded by overriding ice, may be protected and may remain more or less intact, whereas an area or exposed rock in a "sheltered" position such as a lowland depression may be intensely eroded, providing innumerable blocks to be transported away by the moving ice.  

I have tried to reconstruct possible scenarios on this basis to explain why bedrock blocks were entrained from the north flank or Mynydd Preseli but not apparently from the south flank.  Sure, we are in the realms of theory, but it is a theory that makes sense, and which is capable of ground truthing.

Some day somebody will model all these parameters into a single coherent scheme, so that what appears right now to be an almost random picking up and dropping off of stones by overriding ice begins to make sense.  We will understand perfectly why big boulders and little ones, black ones, white ones and red ones, rounded ones and angular ones, from a variety of unknown sources, all end up in one small patch about 3m x 3m in extent.  Or maybe even in one small patch at a place we call Stonehenge.

For the time being, let us just be satisfied that glacial erratic transport is indeed a wondrous thing



Thursday, 14 October 2021

John Wesley Judd -- the forgotten prophet



In the long-standing debate about the origins and transport of the bluestones, HH Thomas hogs the limelight.  But the real star of the show was John Wesley Judd, an English geologist who was a Fellow of the Royal Society in 1877 and President of the Geological Society between 1886 and 1888.  He wrote mostly on volcanism, but he had a wide range of geological interests -- and twenty years before HH Thomas, he was on the ball regarding the Stonehenge bluestones.

In 1901, one hundred and twenty years ago, Judd suggested that the bluestones at Stonehenge were erratics of glacial origin. He argued that the assemblage of 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 after hundreds of thousands of years, 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. This was a point also made quite forcefully by Thorpe et al (1991) following a large bluestone research project under the auspices of the Open University. Intriguingly, Judd concentrated not on the 43 known bluestone monoliths or orthostats themselves, but on the debitage or debris in the Stonehenge soil layer. He found an extraordinary assortment of soft or fragile stones including fissile sandstones, micaceous sandstones, greywackes (argillaceous and easily broken down), flagstones, slates and "clay-slates", and fine-grained glauconitic sandstones. 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 to the present day, 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 that “stone availability” (of both bluestones and the larger sarsens) might have actually determined the precise position of the monument -- an idea which has subsequently been largely forgotten.

A very smart old fellow...........  and here are some of the extracts (pp 58-61) from the work that he did for Prof William Gowland, prior to the publication of the famous 1903 article in Archaeologia in 1901 and in The Wiltshire Magazine in 1903.  Click to enlarge.



There are some very knowledgeable interpretations in there, and some simple yet profound points, urging a sensible scientific approach (rather than one involving fantasies and myths)  to the problems of bluestone origins and transport.  I particularly like the stress placed by Judd on this point:  if the builders of Stonehenge wanted to fetch big bluestone monoliths from West Wales and struggle mightily to get them to Stonehenge, why would they have carried the shaped bluestones (mostly those in the bluestone horseshoe) in their rough state and then whittled them down and shaped them on site at Stonehenge, rather than at their places of origin?  Old Judd knew all about Occam's Razor.

See also:









Tuesday, 12 October 2021

The bluestone arrival myth



When did the bluestones arrive?  Or were they there all the time, unused at first, and then 
used, over and again........??

Over and again, in books and articles, and in exhibits galore, we are told that there was a "bluestone arrival date" at Stonehenge.  That date varies a bit from one source to another, but the essence is that before 4,600 yrs BP the stones were not there, and then the bluestones were fetched from Wales specifically for use in the monument.  Suddenly (or maybe over a few decades) they were there, available to be incorporated into one bluestone setting after another.  The most common view is that the first setting of the bluestones was in the Q and R holes, in Stage 2 of the monument's history -- but Parker Pearson (2012) subscribes to the view that the bluestones arrived on site earlier, around 5,000 yrs BP, and were first used in the Aubrey Holes. he thinks this partly because og the frequency of bluestone fragments in the holes, and partly because of the presence of "compacted sediments" deemed to have carried the weight of standing stones.

These statements are typical:

Source: 
https://evanevanstours.com/blog/how-was-stonehenge-built/
The Bluestones Arrive (2,600 – 2,500 B.C.)
With the exception of evidence of human burials, Stonehenge remained largely untouched from its initial stages of construction for around 500 years. Then suddenly, around 2,500 B.C., the smaller ‘bluestones’ started to arrive.  Around 82 bluestones arrived from the Preseli Hills in Pembrokeshire, Wales – around 140 miles (225km) away.

Source:
When the newly discovered circle’s stones were removed by Neolithic tribes, they may, according to the team, have been dragged to Stonehenge, to be incorporated within its major rebuilding around 2500 BC.

Source:
.......it was the arrival of the bluestones that made Stonehenge special, so that understanding the meaning and purpose of these stones meant looking not only at Stonehenge but also the source area in the Preseli Hills.

Source:
The Aubrey Holes are a circle of Late Neolithic pits inside the circuit of Stonehenge's outer bank, associated with its stage 1 construction (Darvill et al. 2012a; Parker Pearson 2012: 181–86). Our recent reassessment of these 56 pits interprets them as being sockets for the bluestones on their arrival at Stonehenge (Parker Pearson et al. 2009: 32; Darvill et al. 2012a: 1029)

Castleden, 1993, p 95, says unequivocally that the bluestones arrived at Stonehenge in 2150 BC, and explores a number of romantic and fantastical notions as to how and why they were brought there.  Chippindale, 1983, p 267, refers to the "first appearance on the site" in Stonehenge Phase II, c 2150-2000 BC.  Johnson, 2008, p 164, refers to the arrival of "the original batch of bluestones from Wales."  Pareker4 Parker Pearson has written many times about the arrival of the bluestones, while revising the actual dates on which this great event is supposed to have occurred.

And so it goes on.  The human transport hypothesis is so pervasive that it is simply assumed to be true.  It seems to have occurred to nobody that the "bluestone arrival date" has nothing to do with an arrival (or series of arrivals or deliveries) at all.  It is simply the date at which bluestones started to be used (or modified for use)  in stone settings.  The boulders, slabs and pillars could simply have been lying around in the Stonehenge landscape for many thousands of years as glacial erratics before people started to pick them up and arrange them in clusters and patterns, in the process transforming an old earthwork monument into a new stone structure.

So what about the hard evidence on the ground, at Stonehenge?  The most accessible and detailed source is the weighty 1995 tome called "Stonehenge in its Landscape" edited by Ros Cleal and others.  It contains scores of diagrams, cross sections from excavations, tables and lists of finds -- all adding up to a detailed (and often confusing) portrait of the visible Stonehenge and that part of it which is buried beneath the ground surface.  The "arrival date" for the bluestones is mentioned frequently, and indeed even when it is not being mentioned it powerfully influences the interpretations of buried features and sediments.  Where bluestone fragments are observed in exposed sections the lowest bluestone is used as a "dating proxy" over and again.  Below the lowest bluestone fragments, it is assumed that the sediments pre-date the "bluestone arrival date",  and above them it is assumed that the sediments must be younger.  Radiocarbon and pollen evidence is handy to have, but where there are no organic remains the lowest bluestone fragments do the dating job very nicely............

Cart before horse?  Yes, I think so, in some cases at least.  There are many analysed sections in which things do not quite work out as they are supposed to -- so we have the introduction of the idea of bluestone fragments being in "secondary" and even "tertiary" positions.  In a previous post I remarked upon the presence of a rhyolite fragment in a Mesolithic context at Stonehenge -- in the discussion of which Mike Allen got into a bit of a tangle.





When your interpretations are driven by powerful assumptions, even your "accurate recording" of exposures can be influenced.  In your diagrams, where you encounter complex and subtle stratigraphy, it is tempting to locate your "bluestone-rich layers" and to draw a line beneath them.  This line then becomes the dividing line between a "pre-bluestone" layer below and a "post-bluestone layer" above, always interpreted as a secondary or tertiary fill of some sort.  So the graphic representation is falsified or corrupted, not because of scientific malpractice but because of unconscious bias.  I think this has happened time and again, and can be seen in many of the diagrams in the pages of the Cleal et al volume.

Now and then things get even more seriously convoluted, especially with respect to bluestone fragments found in contexts that pre-date the stone settings phases.  Cleal et al refer to this as Phase 1 or "the first monument".  Over and again in the records for the excavations of the ditch and its fills, there are records of bluestone fragments.  See for example pp 83, 85, and 132.  There are bluestone chips in many of the investigated Aubrey Holes.   Atkinson and Evans were confused by the presence of bluestone fragments in places where "they should not have been" --  see for example around pp139 and 140 of the text, in which John Evans does a series of intellectual somersaults in trying to explain why certain bluestone fragments are found in places where they are not supposed to be.  There is more discussion about the problematic occurrence of bluestones in the North Barrow bank and the South Barrow ditch, deemed as dated to Phase 3b by Cleal et al -- ie in one of the stone monument phases.  On the other hand David Field and others think that the North Barrow is OLDER than the Stonehenge embankment and the stone monument -- making it almost impossible to explain the presence of bluestone fragments there, if one adheres to the establishment view of "the arrival of the bluestones."

On and around p 376 of the large tome by Cleal et al, it is explained that the collection and recording of bluestone fragments by Hawley and most of the other excavators has been haphazard and even slapdash at times -- and it is also clear that we cannot make definitive judgments about either the presence or absence of bluestones, or their frequency or stratigraphy,  in the greater Stonehenge monument, when only about 50% of the surface area has been investigated.  On p 398 it is stated that the distribution of bluestone pieces, as far as it is known, does not demonstrate concentrations close to the bluestones themselves.  This might be a significant point.  Further, the distribution of bluestone fragments in the wider Stonehenge landscape suggests that many of them had nothing whatsoever to do with Stonehenge.

So this is my suggestion.  Nothing in the Stonehenge stratigraphy, or in the history of excavations, negates the idea that the bluestones and abundant sarsens were in the Stonehenge landscape long before Stonehenge was ever dreamed of.  When the earthwork phase of the monument was started, the stones that littered the landscape were simply ignored; but suddenly the local tribes began to use stone here, as they did everywhere else.  With that cultural shift, Stonehenge became a very special place, simply because of the abundance of available stone -- and then there was no stopping the builders, who became very ambitious.  First, they used the smaller boulders and slabs (both bluestones and sarsens)  in their settings; and then they started to differentiate between the sarsens on the one hand and everything else on the other. They also started to shape the stones they wanted to use, fabricating pillars and lintels in the process.  The first appearance of "bluestone fragments" in the Stonehenge sediments does not date the ARRIVAL of the stones, but does date the ONSET OF STONE WORKING.

And I still think that Stonehenge was never finished.  The presence of multiple sockets in the centre of the monument speaks to me of experimentation, changing design concepts and -- above all else -- of lack of stones. Certainly there was ambition.  The builders initially used whatever was immediately to hand -- but then they had to range further and further afield, until they eventually ran out of stones or decided that the effort of getting them was not worthwhile.

All perfectly simple.  If there is anybody out there who thinks I am wrong, they will no doubt be in touch......

See also:












































Follow the science -- up to a point

 


There is a big push at the moment by senior scientists like Sir Paul Nurse and Sir Patrick Vallance for science to be taken seriously, and for politicians to "follow the science."  It's all over the media.......

The presidents of the Royal Society (who tend to be eminent scientists) say the same thing, all the time.  To a point, I can see where they are coming from.  They feel undervalued, and wish that politicians would pay more attention to them.  But as I have said frequently on this blog, there is no such thing as "the science".  There is good science and there is bad science.  Sometimes there is some sort of consensus, but heaven help those who pretend that the "consensus" tells us what the truth may be.  Scientists are no better than anybody else at being objective, and eliminating bias from their work and their recommendations.  I spend a lot of time on this blog attacking the unscientific approach of the archaeologists, who seem to be preoccupied with ignoring evidence and proving the correctness of their ruling hypotheses. The more untestable their hypotheses are, the better they seem to like them, and the idea of actually seeking to falsify their hypotheses  seems to them to be more than a little ludicrous.  Karl Popper must be turning in his grave as he looks up (or down?) at the attempts to validate the myth of human bluestone transport / bluestone quarrying / lost circle construction and dismantling.  So yes, a plea to archaeologists to "follow the science" sounds like a good idea.......

But I have been just as critical, over the years, about pseudo-science and science that is inadequate in that interpretations and conclusions do not adequately relate to, or explain, the hard facts or the evidence on the ground.  I have spent a good deal of my time criticising Ixer and Bevins for "over-interpreting" their findings or demonstrating bias in their fieldwork or in their presentations of evidence. The "inconvenient" evidence that you may choose not to present may actually be far more important than the convenient evidence that you do include in your text.  But Dr I and Dr B are not the only ones that have deserved careful scrutiny.   I have had many jolly spats on this blog -- and in learned journals -- with fellow geomorphologists over such matters as sarsen stones, ice limits in the Scilly Isles, glacial deposits on Caldey Island and so forth.  

Back to Sir Paul Nurse.  He gave a recorded "essay" a few years ago on the influence of the philosopher Karl Popper on his own work:

https://www.bbc.co.uk/sounds/play/b04yb7nl

This is very interesting listening, and he is a very senior and much respected scientist, but he has his biases and his conflicts of interest just like everybody else.  The other day, in a newspaper article, he went on about "those who are anti--science and deny its findings", maintaining the absurd pretence that there is such a thing as THE science which has findings that are by definition correct.  Nothing could be further from the truth.  You do not become ant-science if you deny or question some of the science coming from some of the scientists -- and indeed this is exactly what Popper proposes as the fundamantal principle of sound science.  Nurse can't be sceptical about scientific findings in theory, when on the radio, and then slag off those who are being sceptical in the real world, when faced with scientific "findings" that may or may not be reliable.........

In the newspaper article, Nurse quotes, as another example of those who are anti-science, "those who attack gene editing as being unsafe - despite it being a highly precise way to improve agricultural crops. These people tend to cherry-pick data, are inattentive to reproducibility, lack scepticism about their own ideas, and are often discourteous and strident in their opinions."  That's hilarious and rather pathetic.  Nurse should know that gene editing is not "highly precise" and has been deemed by the European Court of Justice as "genetic modification" -- sharing the same risks and uncertainties.  GE does not "improve agricultural crops" -- it may, in the future, if it is allowed, change crops, but will it improve them?  How do you define "improvement" anyway?  And the sins that he lays at the door of the "anti-science" opponents of GE are exactly the same sins that can be laid at the door of the labs and the research groups whose interests he is so blatantly promoting.

Pots and kettles.  OK -- follow the science, or some of the science, some of the time.  And above all else, SCRUTINIZE the science, and if it is dodgy, just don't accept it.  You have Karl Popper on your side.

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

Karl Popper:  Conjectures and Refutations.  See this:

McLeod, S. A. (2020, May 01). Karl Popper - theory of falsification. Simply Psychology. 

Monday, 4 October 2021

A nice little erratic boulder

 


On looking through my East Greenland slide collection from 1962 I came across this one. It's in Kjove Land, on a vast expanse of moraine-covered tundra -- a nice little erratic, probably dumped in the last glacier advance around 12,000 years ago.

Three thousand posts

 



I have just realised that we have gone through the 3,000 posts barrier on this blog, since it started in May 2009.  There are 1.8 million hits on the site, and 31,900 comments so far.  Keep them coming!  I hadn't realised that I have been quite busy!!  Most of the posts have something to do with Stonehenge, although I cannot resist putting up posts now and then which are designed to share my knowledge of (and my enthusiasm for) glaciers, glaciated landforms and glacial sediments.  I like a good debate, and I enjoy teaching, even though I am no longer a teacher.  After all, I have to do something to keep the old grey matter in reasonable shape.........

Anyway, it's good to know that the blog contents are being archived by the National Library of Wales -- so that when something happens to me (as it surely will) all that effort will not have been wasted!

Oxford Gletscher -- the surface thermal regime of a surging glacier


Surface chaos on the Oxford Gletscher, associated with two surges -- a big surge related to 
the eastern branch of the main glacier, and a smaller one associated with a tributary 
glacier on the west flank of the valley.  Note the very prominent looped moraine ridges and 
the heavily pitted glacier surface.

In previous posts on this blog, I have drawn attention to the surging behaviour of some glaciers in the Staunings Alps / Scoresbysund region.  This post relates to Oxford Gletscher:

https://brian-mountainman.blogspot.com/2021/09/oxford-gletscher-and-discovery-of-surges.html

This is my account of the behaviour of Løberen, the "galloping glacier" in Nordvestfjord, Greenland, which has retreated some 7 km since the peak of its last surge:

https://www.theguardian.com/travel/2021/oct/03/my-love-affair-with-wales-megaliths-pentre-ifan-in-pembrokeshire

In the next big valley glacier trough to the east, occupied by Oxford Gletscher, something very similar has gone on.
  
Two modern satellite images of Oxford Gletscher -- slightly different scales.  
They show a snout retreat of c 4 km since the peak of the last surge.  The surge seems to have 
been initiated by two glacier tributaries high up in the valley, and then transmitted all the way 
to the snout as a rapid advance.

This is a study of some of the surge-type glaciers of East Greenland:

Surge potential and drainage-basin characteristics in East Greenland
Cambridge University Press: 14 September 2017
Hester Jiskoot,Tavi Murray andAdrian Luckman
Annals of Glaciology , Volume 36 , 2003 , pp. 142 - 148
DOI: https://doi.org/10.3189/172756403781816220


This is another useful summary:
Surging glaciers in Greenland - a status Anker Weidick

https://scholar.google.com/scholar_lookup?title=Surging+glaciers+in+Greenland%3A+a+status&author=Weidick+A.&publication+year=1988&journal=GrøNl.+Geol.+UndersøGelse%2C+Rapp.&volume=140&pages=106-110

Quote:  The first observation of surges in East Greenland was made during GGU field work in the Scoresby Sund region, where descriptions of the glacier Løberen were given by Henriksen & Watt (1968) and Olesen & Reeh (1969), and of Bjørnbo Gletscher by Rutishauscr (1971). Both glaciers are situated in the Stauning Alper, a mountainous area of Caledonian migmatites and granites (Henriksen & Higgins, 1976, especially map fig. 198, p. 218). The length of the quiescent phase has not been determined in the case of Løberen where the documented surge took place in the early 1960s, but a preceding quiescent phase must have covered several decades or even a century of downwasting of a 7 km lang glacier lobe with a maximum thickness of at least 300 m. As far as Bjørnbo Gletscher is concerned, Rutishauser (1971, p. 236) suggests an interval of 100 years between a surge around 1890 and an expected one at around 1990.  (Note:  the postulated 1990 surge has not happened.....)


Annotated satellite image of three small surging glaciers on the north shore of Scoresbysund.  The black lines show the trimlines associated with each surge.   Løberen glacier reached the sea around 1960 and has subsequently retreated c 7 km.  Oxford Glacier had (around 1950?) a splayed snout at the end of the wider Holger Danskes Briller diffluent trough, and has subsequently retreated c 4 km.  The unnamed glacier to the east had a simple snout and did not spill over into the trough, and has retreated about 2 km since its last surge.


In 1962 four members of the OU expedition to East Greenland spent nine days on Oxford Gletscher mapping its surface features and undertaking glaciological work on what we assumed was a "polar glacier".   Dave Sugden and I planned and conducted the research, helped by Svend Wurm and Sandy Hall. Two temporary camps were established on the surface of the glacier.  The intention was to use a hand-operated drill in key locations and to use a thermocouple ice temperature monitor (designed and made by our friend Brian Hughes) to take as many readings as possible, so as to obtain information on the glacier's thermal characteristics. In the event, it was impossible to drill deeper than 15 ft in any of the 17 drilled holes on the glacier surface -- and so the readings taken were not of any use for interpretations of glacier movement or deep internal characteristics.  But they were of interest for analyses of surface melting characteristics at the height of the melt season.  The glacier snout was located in 1962 at an altitude of c 800 ft, near the southern trough exit.   The firn line was located at c 3850 ft asl.


A plot in my notebook showing freezing point depths.  We expected a gradient down-glacier, but did not find it.  It looks as if the "norm" for exposed and ablating ice surfaces is c 1m, everywhere beneath the firn line.  However, the five anomalies, with freezing point depths of 5ft, 6ft and 8ft are all within a surge morainic loop that was not apparent to us when we were working on the glacier.  

Only two sites were investigated above the firn line, but at every single site the ice surface temperature was slightly above freezing point -- ie mostly a fraction of one degree above zero centigrade. This may be related to the fact that during our fieldwork it was snowing more or less continuously, and melting fast, with very wet surface conditions during daylight hours.  David thinks that there may well have been meltwater penetration between ice crystals because the ice was effectively dead of inactive.

Temperatures dropped with every successive reading in every drilled hole.  No holes were drilled below 15 ft, possibly because of encounters with morainic debris or because of freezing on the drill shaft in contact with the sides of each hole.   The lowest temperature recorded was -3.2 deg C at site K in the middle section of the glacier, and in a number of holes the lowest temperature recorded was below -2.5 deg C.  We assumed that in all locations the temperature would have continued to fall with increasing depth beneath the surface.

We encountered no dramatic temperature inversions, but there was one anomaly at site A, near the firn line where there was slushy surface snow.  Here freezing point was encountered at a depth of 8 ft, after which the temperature fell and then returned to zero at a depth of 11.5 ft.  This was possibly related to a meltwater conduit.  

Our main interest initially was to assess the depth of the "summer melting wave" into the ice, and to assess the thickness of the "winter freezing wave" -- sadly, because our drilled holes were so shallow, we could not assess the latter, but it is of interest that the summer melting wave penetrated on all parts of the glacier to a depth of approximately 1m, except for sites A, D, C, H and E, where zero deg C was encountered  much deeper, at around 2m. We were mystified by this at the time, and blamed errors in our ice temperature device, but it is now possible to see from modern satellite images that these "anomalous"sites were all within the loop of ice pushed westwards by the eastern tributary glacier in the surge that probably occurred about a decade before our visit.  


From the above annotated map, we can see that the temperature readings at sites F, A, D, C, H and E might well have been strongly influenced by the surge from the eastern tributary, since they are all within the loop of moraine.  However this might have happened, the zero C depth in the glacier is around 2m within this loop -- but I have no idea what the explanation may be! Perhaps this "slab"of ice is anomalously warm, or more susceptible to meltwater penetration, which may explain why it is apparently more mobile than the in situ ice beneath it?

David (who knows much more about glaciology than I do) has given some recent thought to our findings.  He says that on a true polar glacier, above the firn line (in the accumulation zone) the ice temperature at a depth of c 10 m (33 ft) should theoretically be the same as the mean annual air temperature.  We never had the opportunity to check that.  Around the firn line, theory has it that summer melting of snow and firn refreezes on contact with the ice, and this freezing process raises the temperature to zero.  Near the glacier snout on a polar glacier, where the surface gradient is steeper, in theory meltwater runs off, allowing the ice beneath the surface to remain below zero. 

Having now plotted the drilling locations on a reliable satellite image of the glacier, we can see just how much debris there was, although we did not see it because of a heavy snowfall while we were at our highest camp site, near drilling site C.   There must have been so much debris in the ice in this upper section of the glacier that it was a miracle that our drill holes actually managed to penetrate more than a metre into the ice.  

All in all, an interesting little piece of research, of no great importance, but a cause for some modest satisfaction for Dave and myself, 60 years later........


Trekking on the glacier, with the icefall in the middle distance.  Our colleague Svend was very disappointed that he did not get to film a genuine crevasses rescue.......

Highest camp site on the glacier, after a heavy snowfall. No wonder we did not know about 
all those morainic loops.........

The chaotic ice surface on the lower part of the glacier -- a legacy of a surge maybe 
a decade before our arrival.


Friday, 1 October 2021

Raised beach ridges in Bathurst Inlet, Arctic Canada


 Now this is the sort of thing that brings great joy to an old codger like me, having spent to much of my research life pondering on the wonders of raised marine features on coasts subject to isostatic recovery.........