It occurs to me that there are so many new readers on this blog that some of you, at least, may have not penetrated as far back in the records as 2008. This is the article which I produced with Lionel Jackson for "Earth" magazine -- minus the illustrations.
http://www.earthmagazine.org/earth/article/1a1-7d8-c-1f
As you will see, there is a speculation (a very reasonable one, we think) relating to the movement of two parallel ice streams.
12 comments:
This is a very interesting summary.
I suppose what might throw the archaeologists off the track is all this talk of trails. The archaeologists seem to believe that such a trail would have left "bluestone" deposits on the route as implied by the article - there is no such evidence known. Equally, some stones on the trail might well have been used in other monuments between Stonehenge and Prescelly - which they were not as far as we can see. (The evidence around Boles Barrow is not watertight).
In the absence of confirmatory evidence along the trail, one might reasonably assume, on the basis of the article, that the most likely option is human transport.
Chris -- we have talked about this at great length already on the blog. Try doing some searches for "erratic clusters", "Darwin boulders" etc ...... see also my entries on entrainment and transport -- much about erratics there too.
The assumption that you have to have a trail of erratics from A to B is mistaken.
Remember that the Foothills Erratic Train is a very strange one -- supplied constantly by rockfalls onto the glacier surface, with supraglacial transport all the way from source to melting out area. In other words, the rocks were carried on the ice surface. That's VERY rare except in valley glaciers.
The reason why Lionel and I wrote about this was that there was a possible interesting parallel with South Wales and the Bristol Channel -- the idea is that there can be two ice streams running side by side, with erratics transported more or less along the junction zone.
Brian, I agree although it took me some time to get it and a lot of help from searches on "Stonehenge Thoughts". I was blocked for months by my mental picture of what a glacial trail might look like. Had I read this article earlier my prejudices would have been reinforced, although this was not your intention. Please bear in mind that many people like myself, fairly intelligent, academically inclined, and interested in the facts - we know next to nothing about glaciers. When I was at school history started with the Romans and before that people ran around in bear skins. Ice ages were cold.
Still trying to figure why some archeologists are on the wrong foot - Mike P. for example acknowledges the glaciation theory before dismissing it on the grounds that there is no trail of stones, no other "bluestones" in the Stonehenge area, and none yet found in other monuments. Maybe he is blocked like I was, on the other hand he is a smart guy and perhaps he understands it better. Neil Oliver may be not much of a scientist but I suspect as a media guy he is a good synthesizer, so I expect he reflects a widespread opinion among the archaeologists.
From what I think I understand now, all these non-effects, which I mentioned myself a while back as "objections", could actually be consistent with glaciation.
Sometimes "we" make things difficult for ourselves - as in the Aberdeen case. There will have been many glaciations since the rocks formed, coming from several directions and probably different streams as glaciers from North and East intersected (now I am guessing a bit). The Britice picture is never going to be definitive for this debate I think because it describes the most recent glaciation, and earlier glaciations are erased to a great extent by subsequent events and so no exact maps covering all the glaciations can be made without a lot more work than has been done.
My mental picture at the moment is that a few big erratics were picked up in the past and dumped near Stonehenge - extending the historic stream lines. The Altar Stone and the Dolerites and the Rhos-y-felin stones might not even have been dumped in the same glaciation. It is curious that it happened this way but definitely possible - the earth energy folk should be fascinated. Please tell me if I have still got it wrong from a geomorphological perspective.
Sorry if this is a bit garbled - I have to walk the dog and do a telco, so I am in too much of a hurry.
Brian,
The Foothills Erratic Train in Canada presents an interesting example. We have here,
1) “ rockfalls onto the glacier surface” in 'isolated episodes'
2) “with supraglacial transport all the way from source to melting out area.”
Hmm! Just like the mechanism I previously suggested for the transport of sarsens and bluestones to Stonehenge! See
http://brian-mountainman.blogspot.com/2011/11/altar-stone-where-glacier-left-it.html
comments 24 November 2011 16:08 and 25 November 2011 18:06
At that time (and other times as well) you ridiculed this idea as non-existing in Nature and as defying the Laws of Physics! Like to take those words back, Brian?
Speaking of Physics, just recently the book “Thermodynamics: Interaction Studies” containing my chapter “The Thermodynamics in Planck's Law” has been released online and can be downloaded for free at the following link:
http://www.intechopen.com/books/show/title/thermodynamics-interaction-studies-solids-liquids-and-gases
Kostas
Kostas -- I have never ridiculed the idea that rockfall material finds its way onto glacier surfaces. Many posts on this blog have shown the effects of just such a mechanism.
Please go off and look at a map -- the Rocky Mountains in North America are rather different from the Preseli Hills. There are NO cliff faces in Preseli which could provide rockfall material onto a glacier surface, other than a small cirque glacier in Cwm Cerwyn. End of story.
Brian,
Are you saying the landscape at Preseli has not changed for over 5000 years and possibly longer?
Since we do not know when these Preseli bluestones may have been entrained we also have no exact knowledge of how the landscape may have looked like back … whenever!
I really fail to see what you are objecting to!
Kostas
I'm saying that it has changed very little, maybe apart from the coast where the environment is much more dynamic. Please -- for the umpteenth time -- go off and read up about glacier profiles.
Kostas
A most interesting link http://www.intechopen.com/books/show/title/thermodynamics-interaction-studies-solids-liquids-and-gases.
Congratulations on having refuted the work of Einstein, Planck and most other eminent physicists. I have developed a model that predicts two possible outcomes for you and your fellow authors.
First: a visit to Stockholm to receive the plaudits of the Noble Committee and a large financial reward.
Second: a short trip to the tailors in the back of a van to be measured up for a back to front jacket. Followed by a lengthy stay in the secure wing of an appropriate health spa.
Rather than be accused of research bias. I leave it to my peer group of fellow contributors to decide the most likely outcome.
Alex Gee,
Always too generous with your opinion of me!
I have not refuted anyone! The math does that and the math is irrefutable! All I sought to do is to show there are other ways of viewing the physics consistent with our experience and not conflicting with it.
But since this is not about me, neither of the two outcomes in your comment are within my life-horizon!
You write, “I leave it to my peer group of fellow contributors to decide the most likely outcome”
Letting peer groups decide 'a day in a life' is and has been the problem! Don't you think? Ooh! You'll let the peer group decide that!
Kostas
????
Alex Gee,
Your many questions answer my ambivalence in your comment! Something was lost in this transatlantic flight of thought! Blame it on Brian! He always has me on the defensive!
I should just be pleased you found the link interesting! Thank you!
Kostas
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