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

Saturday, 1 August 2015

Quarrying and entrainment beneath an advancing glacier


While looking at some material relating to the Wisconsin Glaciation of North America, I came across this interesting diagram in the Illinois State Geological Survey web site.

It's interesting because it portrays pretty well the exact scenario that I envisage for the quarrying and entrainment of blocks and other debris from the area around Craig Rhosyfelin in North Pembrokeshire.  What we have in this idealised scenario is an old valley transverse to the direction of advancing ice flow,  with plucking and entrainment along shear planes within the ice.  This enables blocks and other debris to be transported in an englacial situation.

Nothing new under the sun......

North American Ice Sheets


I found this interesting image of the North American Ice Sheets during the last (Wisconsin) glaciation, c 20,000 years ago.  The quality of the image is not very good, but you get the general idea.....

Note that there were four ice sheets, all joined together. (In Antarctica today we see the West Antarctic and East Antarctic Ice Sheets connected in a similar way.)  Note that this was a very extensive glaciation in which the ice edge in many areas progressed beyond the limits of earlier glaciations.  The exception is the area to the SW of the Great Lakes, where earlier glacial deposits are still exposed at the surface.

More detail here:



Map credit:
Dr. Judson L. Ahern
University of Oklahoma

Thursday, 30 July 2015

Franz Josef glacier flow film


This is amazing -- a time-lapse photography sequence showing how the ice of the Franz Josef Glacier in New Zealand flows over a period of 18 months.

bit.ly/1I7Fk20

Sea level 20,000 years ago


 I came across this very striking image which shows in red the area which is currently inundated but which was dry land at the peak of the Devensian glacial episode c 20,000 years ago.  In Britain, the North Sea, Scandinavia and the Baltic, large parts of this "dry" area were ice-covered, and because of the isostatic depression of the land surface under the weight of ice, the sea was actually able to penetrate across the boundary between the area shown in red and the area shown in light blue.  As ever, things in reality were a good deal more complex than they appear in nice simple illustrations like this one.......

Saturday, 18 July 2015

Science in the open -- or behind closed doors?




I've been looking at my past posts, and discovered that there are 218 posts mentioning Rhosyfelin between 2011 and now.  That's a lot of posts -- and, thanks to my faithful community of readers and contributors, a lot of open and friendly discussion, with a vast range of topics relating to this site, put under the microscope.  You can do the search for yourselves, and check out what we have discussed........

It's interesting to explore which posts have been most popular, in terms of page views and comments.  One of the most popular was the recent post about BigFoot!  That says something in itself about the state of science in the world........

The Rhosyfelin Fracture Pattern  has 511 page views;
The Incorrigible Quarry Hunters turn up at Carn Goedog has 596 views; 
 Big meltwater conduits beneath an ice stream has over 3,000 page views;
The Carn Meini "Bluestone Quarry" -- Oh no it isn't! Oh yes it is! has 811 views;
The Stonehenge rock types -- time for an update? has 749 views;
The Rhyolitic "debitage" around Stonehenge has 1242 views; 
The Neolithic Quarry Obsession has 632 viws;
Bronze Age use of mauls and hammerstones has 1163 views;
Stonehenge -- a breeding ground for pseudoarchaeology? has 1264 views;
The Craig Rhosyfelin dig has 1118 views;
and there are others which have had more than 400 page views.

All in all, there are 711,000 page views on the blog, from all over the world.  It's obvious that most of the views are from people interested in Stonehenge, but I suspect that there are a lot of views from geologists and geomorphologists as well, since my illustrations come up quite prominently when people search on Google for images.  I presume that Google researchers are often directed to the site -- although I am totally mystified about how tags and keywords work.  Sometimes I get messages from experts who say I should take "search engine optimisation" (SEO) more seriously, and that I should earn some dosh through allowing adverts on the site.  "No thank you" to both of those......

What I have tried to do on the blog is encourage "folk science" which invites an open exchange of information and an open testing of hypotheses, involving both specialists and those who just want to learn. 

Back to Rhosyfelin.  The other way of doing things is to obtain a large research grant, dig away on a site happily for several years, tolerate no dissent, publish nothing at all about the progress of the research, and invite no dicussion with people who might actually have something to contribute or some hard questions to ask.  The ruling hypothesis rules, and after a few celebrity PR lectures here and there to amiable and gullible audiences, to prepare the ground, everything is announced in a blaze of glory in conjunction with a big paper involving many members of the research team.  It may be good, and it may be rubbish.  We shall see.  If it's published in an archaeological journal, it's doubtful that any of the peer reviewers will have been earth scientists.

When said paper appears, accompanied no doubt by a TV spectacular (rumoured to be on Nat Geog Channel), let's hope that those responsible have read this blog and picked up some useful information from it about glacial and periglacial processes and about the events of the Ice Age.......

I'm not accusing Prof MPP and his colleagues of anything unusual here.  This "science behind closed doors" happens all the time, in many different fields.  There is huge competition for research grants, and reputations are at stake both for individuals and academic institutions.  Universities have their own publicity machines these days, and they employ professional publicists who write press releases about important  -- or unimportant -- research which are sent out to the global media.  Saturation coverage.  I have seen countless examples of crap research glorified in carefully crafted press releases which are then regurgitated almost unaltered in the press and on the telly.  Journalists these days don't investigate -- they regurgitate.  For the researchers, exposure is everything.

Now that commercial interests have become important, another factor comes in to play.  Research teams don't publicise their results too far ahead, even in their own peer groups, since they want to get things as right as possible before publishing and have a maximum impact.  But there is always SOME discussion with peers, for example through conference presentations or poster displays of key results.  So there are checks and balances, with the most radical ideas questioned and tested before they are submitted in the context of papers submitted to peer-reviewed journals.  But "commercial confidentiality" trumps all of that, and I have seen the insidious and dangerous effects of it in other fields.  Secrecy clauses come into play, and in medical science (for example) pharmaceutical commercial sponsors or biotech corporations reserve the right to vet research, insist on it being rewritten in a form which they approve of, or even veto publication altogether if the results are "inconvenient."  Very sinister indeed.  This is not the way science should be conducted, and I feel very strongly about it.  

So rumour has it that National Geographic has paid over rather a lot of money to the MPP research team with certain exclusive rights attached to the deal.  If that is true, shame on all concerned, since in that direction lies orthodox or establishment science, as once practiced in Stalinist Russia.........  Those who are obedient (and discover the things they are meant to find) are rewarded and flourish, while those who ask questions and come up with uncomfortable observations and results are packed off to the salt mines and are never heard of again.

There now.  That was a good gripe!  Feel better now.  Time for a cup of coffee and a chocolate biscuit.



Friday, 17 July 2015

Chatter marks and rock mechanics

Here are some more photos of the classic glacial erosional "micro features" on Rodloga Storskar in the Stockholm Archipelago.  Apart from the striae or striations which I have already described, these features are of interest in terms of rock mechanics, and they are all related to fractures on stressed rock surfaces.  We don't know how thick the ice was when these features were formed, but it might have been up to 2,000 m thick -- that means that the stresses on rock surfaces were enormous.


Nowadays these features are grouped together and are called "chatter marks", but as we can see from the photos below, there is a lot of variety in the forms.  The top photo shows a series of roughly parallel and regularly spaced linear fractures, approx perpendicular to the direction of ice movement:



 The next one shows many fractures in a small area, some of them crescentic gouges and others irregular and linear.  These were formed on a moulded surface across which the ice was rising so as to surmount a hill about 30m  high.  The theme of ice having its greatest effects on a rising land surface is a common one -- here there would have been compressive flow, as distinct from the extending flow accompanied by tension or dragging forces on the lee side of obstacles.


 Below we see a very large crescentic gouge -- almost 1 m wide, with many more smaller chatter marks in the vicinity.


 This rock face, again on a rising surface, has a high density of fractures of many different types.


And since large tools were required to create these gouges and fractures, here are a couple of photos of rocks seen littering the rock surface in the vicinity.  These are quite large enough to have been effectively pressed into the rock surface by the pressure of overlying ice.  The fractures are really brittle fractures -- and one contributing factor is the differential resistance of tool and bedrock.  It helps, of course, if the tool is harder than the bedrock, but tools under compression are more resistant to breakage than rock surfaces under tension -- so even if the tool rock type is the same as that of the bedrock, erosion and fracturing becomes possible.  But tools are of course also comminuted on the glacier bed.  The problem with all of this is that the actual processes involved are almost impossible to observe under present-day ice sheets.
  


Wednesday, 8 July 2015

The perfect crescentic gouge


I've seen a lot of crescentic gouges in my time, but this is probably the most perfect one I have ever encountered in the wild.  It's about 30 cm across, with the convex side facing up-glacier and the horns pointing down-glacier. It's got an almost perfect semi-circular or crescent shape, and looks like a new moon!  If you click to enlarge, you should be able see the slight colour difference between the smooth pink granite rock face affected by over-riding ice and the rougher texture left when part of the surface was crunched away by a large boulder forced downwards. 

This is just one of a series of photos taken on my recent visit to Rodloga Storskar in the Stockholm Archipelago.  More to come, with a discussion on rock mechanics......