If you ever wondered about ice's capacity for flowing like a viscous liquid, take a look at this photo -- of a piedmont glacier spilling out from the mountains in North Greenland. This glacier is sitting on a foreland of sediments -- probably mostly till. If the snout had been floating, there would have been a much steeper front and a much more jagged edge.
The ice is remarkably clean -- and this is often a sign that we are dealing with a polar glacier rather than a "temperate" one.
19 comments:
Brian,
Interesting photo! If you could be so kind to clarify the bluish foreground in the bottom of the photo? Is it sea water or is it ice?
Curious
what a beautiful photo!
PeteG
Open sea water with a lot of floating ice fragments on the left. Those fragments seem to be a mixture of sea ice and glacier ice from the ice front -- or maybe from other ice fronts off the photo.( Sea ice tends to look flat, and glacier ice afloat tends to look chunky!)
This phenomenon gets a mention - in a manner of speaking - at the end of the wiki entry on regelation - a copper wire and physics laboratory not being obligatory it would seem.
I know the blog is called "Stonehenge Thoughts. Folk here might be interested to know my thoughts on Silbury (posted just half an hour ago. One has to drum up custom somehow ;-)
They are somewhat unconventional thoughts. Indeed, some may find them unappetising, but when was science ever a branch of aesthetics?
Colin Berry aka sciencebod
Any eccentricity on my part, Chris, is as nothing compared with the thousands of Neolithic folk who we're asked to believe had nothing better to do with their time than trench and backfill, trench and backfill for a century, creating the largest manmade hill in Europe. Nobody has come up with an explanation, or even a testable hypothesis - nobody that is except yours truly. My hypothesis IS in principle testable, because the presence of intact plant tissue - still green, still recognizable as grass and moss - makes it likely that the soft organ tissue will also have left some chemical markers.- even if only fungal and bacterial cell wall chemicals, inorganic iron etc. Any hypothesis that is testable is a scientific hypothesis. Call it eccentric if you wish, but I have thought it through, including the fate of what was not consigned to the Hill, which will be the subject of my next posting.
I emailed Jim Leary today. Unfortunately, he's out of office, but I hope to find out what analyses if any have been done on the "dark" soil samples, the black mud, the "sticky" gravel etc in or close to what interestingly he describes as the "organic" mound at the heart of Silbury Hill.
Perhaps before you slip back into that harness - a sign if ever there was of someone with a singular lack of imagination - you might enlighten us as to your own thoughts on Silbury Hill... Was it maybe built by the Neolithic Chris Johnsons - who felt they had to do something - anything - to occupy the long hours between getting up in the morning and going to bed at night...
Er, what has this all got to do with polar ice and piedmont glacier lobes?
OK, so Chris and I got sidetracked. But I did introduce the term "regelation" into this thread. One could question whether it is instructive to refer to glaciers "moving like a viscous liquid", with the implication that solid ice can somehow deform like a plastic. According to the science of regelation, which only works with the atypical subset of liquids that expand on freezing, there is no deformation of solid. Instead there is transient melting under high pressure, with subsequent re-freezing - giving the appearance that solid ice has flowed, when in fact that is not the case. Irrespective of mechanism, it is still a very pretty picture Brian. No matter how old or jaded one gets, nature has an infinite capacity to ceases to spring surprises.
I suspect that real truth about Stonehnege, Woodhenge, Durrington Walls etc will also come as a surprise to many folk, brought up on ideas of sun worship, ritual human sacrifice etc. The crucial clue is, I believe, to be found in the official visitor guide to Stonehenge on page 24: Durrington ... has an avenue, a gravelled pathway, also with a solstice alignment... clusters of small rectangular neolithic houses... these date from about 2500BC. "The rubbish that had piled up against the fences that separated the houses included huge quantities of animal bone, mostly young pig(my italics)suggesting large scale feasting, particularly in mid-winter."
My Silbury post is the intro to a what I believe is an entirely new interpretation of Stonehenge and environs based on two components. The first is a transitional phase between the hunter-gather lifestyle and that of the settled Neolithic homesteader, relying on crops and domesticated animals, but needing initially an improvised winter-survival strategy. The second component, which flows from the first, is what I call (provisionally) - C-OSR, which is short for "cannibalism - one stage removed" (with pigs and perhaps chickens playing a key role. Yup, the deceased, by natural causes or otherwise, became too valuable to simply bury in the ground (with the risk of attracting scavengers). Stomach-churning idea perhaps - and you read it here first ;-)
But I need to accommodate the bluestone in this theory. We know that dolerite is harder than granite. Can anyone tell me anything about its fracture resistance and/or whether dolerite could be used for maintaining an edge on lowlier flints? Comminution of an unconventional source of protein for livestock winter-feeding may have made exceptional demands on flint, needing a flint-tool resharpening service (can flints be re-sharpened?). Was the original(?) bluestone circle used for flint-resharpening? Might that vertical groove in one of the bluestones have served as a angled guide for a particular mode of resharpening?
Apols for the typos. I keep forgetting there a "Preview" option on Blogger.
And I see you did a post in 2010 called Where are all the polishing stones?, with a reference to a rock with a groove...
OK, so it was not at Stonehenge. But this one is!
Brian,
What can you say about Lake Harrison? Quoting from Wikipedia,
Lake Harrison is the name given to a huge lake that in parts of the Ice Age covered much of the Midlands in England around Warwick and Birmingham and Leicester. It was formed when ice from Wales and the north blocked the drainage and trapped a lake between the ice front and the Cotswolds. Finally the lake made two overflow courses:
Southeast across the Fenny Compton Gap through the Cherwell valley into the Thames. This course has been abandoned.
Southwest. This course became permanent and is now the River Avon which flows into the Severn, whereas before the Ice Age the area drained northeastwards.
Ah -- glacial lakes -- they were everywhere. Or if nor everywhere, wherever a retreating ice margin allowed meltwater to be impounded against a backslope. Sometimes the water would overflow across a col, and sometimes a lake would drain suddenly if a lower route (eg an old river valley) suddenly became available. A lot has been written about Lake Harrison, and about Lake Pickering, Lake Teifi etc...
Brian,
Could the Irish Sea Glacier encrouching Somerset and Bristol Channel from the West formed an ice-dam restricting meltwater flow?
Yes, no reason why not. If the ice pressed against the slopes of Avon and Somerset, then one would expect that a lot of meltwater in the Severn estuary area might have been impounded.
Brian,
Could such impounded meltwater dammed by the Irish Sea Glacier pressing against the slopes of Avon and Somerset explain RJL's vast waterways?
Anon -- in a word, no.
@sciencebod. Look up!
The photo Brian shows reveals a natural wonder.
Our ancestors would have been aware of the wonders of the heavens, and the wonder of other natural phenonema. They were closer to nature than we are today. The astronomy at Stonehenge or Windmill Hill in those early days of the monuments would have been spectacular and story telling much better than East Enders as a way to while away the evening hours.
Scientific theories should be based on fact and observation. So while close examination of stones - elsewhere in this blog - might seem irrelevant, it will increase our store of knowledge even if does not invite a quick conclusion.
You ask for my theory about Silbury Hill. I confess I don't know - there are too few facts available. The closest interpretation I have seem that might be plausible is astronomic/astrological. You dismissed this approach a few days ago. I am not sure why.
Jon has a very practical interpretation of Stonehenge (final phase) when you delve more deeply and one that might complement your bizarre ideas about burial routines. I suggest you read more on his site - heavenshenge.
I deleted my earlier post because it was too personal and might be misinterpreted as discouraging retired people. Retirees have the luxury of time and experience to apply to this study, alongside the pros who need to earn a living, and hobbyists like myself. All of us can become eccentric but this is a much loved British tradition and I enjoy it so long as it is fact based.
Hello Chris. Yes, I noticed you had deleted that comment. Moving on, it is not clear whether or not you have read the post I put up yesterday, entitled A new unified theory for Stonehenge. Britain's first community recycling centre - designed for winter survival?
As a retired scientist I am accustomed to meeting resistance with new ideas. When I first proposed that enzyme-resistant starch (RS or RS3), recently called "the trendiest form of dietary fibre, was short chain linear alpha-glucan I had the in-house starch expert tell me I was crazy, and then, at the Kellogg's symposium, one of the country's leading starch experts said much the same thing. RS = short chain linear alpha glucan is now received wisdom, as well it should be, as my proposal was based on factual evidence, rather uncritical acceptance of textbook theory based an a faulty assumption that RS was one and the same as classically-retrograded starch.
Twenty five years on, I still use hard facts as the starting point for hypotheses. The facts I have accommodated in my "secondary cannibalism" model are several, to do with the evidence of feasting on pig at Durrington walls, the debitage of bluestone at the Stonehenge site, the evidence that something biodegradable was being systematically disposed of at Silbury that appears to have left dark strata in the backfilled clay and chalk, alignment of Stonehenge and other henges to identify the winter solstice as well as the summer one.
Yes, I will go and have a look at heavenhenge, but I have been reading astronomical theories re Stonehenge for well over 50 years, but none explain why the ancients went to all that trouble with the lintels, or even the supporting uprights. My model begins to provide an explanation, as briefly hinted at in the 10 point summary, possibly related to air-curing, smoking and other preservation techniques.
Brian will now give me a gentle admonition for straying off topic, as he well might, but I am simply responding to your oh so condescending dismissal of my thinking, Chris.
If it's geological relevance folk look for, then maybe someone can tell me if the bluestones could have been used for flint-sharpening, which might explain why they were so highly valued if an intensive operation using flint tools - any operation - was centred on the Woodhenge/Stonehenge sites.
@sciencebod Brian has said this is not an archaeology site so I will ask you like Brian did....I am a little confused,what has this to do with the glacier? Most of your posts are to do with Ancient history speculation. You have explained vaguely and then continues to post again about historical speculation....let me guess you'll explain again and then continue more speculation about Stonehenge etc. It doesn't matter if you tell us, the fact remains that this is is not the topic. Your ramblings would in fact be like talking about the physics of space flight as a commenter at a football game. No context to the current discussion at all. Maybe start a topic up and post your musings there. I am more interested in the fluid dynamics of ice. Which is what ice is. A Fluid. Despite your arguments ice is a fluid. You can delete this Brian, just my rambling as well.
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