Some of the ideas discussed in this blog are published in my book called "The Bluestone Enigma" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
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Sunday, 19 November 2017

The Survival of Maiden Castle

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

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

Place names in the "Rocky Mountains"

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

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

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

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

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

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

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

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

Friday, 17 November 2017

Collapsing iceberg arch

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

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

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

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

Monday, 6 November 2017

Stonehenge -- the authorised version (again)

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

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

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

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

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

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

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

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

Friday, 3 November 2017

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

No comment needed........

Picton Point -- old glacial deposits?

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

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

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

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

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

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

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

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

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