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Saturday, 10 January 2015

Mount Hood moraine


 An interesting photo of the jumbled moraine exposed on Mount Hood in the United States, in the Sandy Glacier cave system.  Notice the wide range of rock types represented and the manner in which, even here high on the mountain in the "wasting glacier" zone, there is substantial rounding of the boulders.  Some of this might have been achieved by meltwater, but for the most part we are talking here of the effects of true GLACIAL processes.

15 comments:

Myris said...

very interesting photo.
I note the size of the pseudo-proto-orthostats plus the complete grain size variation.
What processes would you invoke to just leave the ppos on Salisbury Plain.
This is really my asking how do you overcome the reported absence of any glacial gravel/cobbles on said plain.
Wonderful starting point though.
I shall not accept the perfectly reasonable response 'I would not dstart from here'

BRIAN JOHN said...

This is a typical moraine found in close proximity to a glacier front -- one could take a similar photo at the ice edge of almost any warm-based glacier (but maybe not with such a nice variety of rock types). One of the interesting things about glaciated regions is that you do not get warm=based bed conditions everywhere -- if ice is cold-based it will be frozen onto the bed, and when the ice retreats you may find that there is virtually no debris left behind. Many areas (such as Buchan and Jameson Land in Greenland) have often been thought to have been unglaciated, because of the lack of glacial deposits on the land surface -- but then when you look more carefully you find that there ARE glacial traces -- albeit very subtle ones. use the search box to check out some previous posts.....

Absence of evidence is not evidence of absence. I don't accept Chris Green's river gravels evidence, as I have often said on this blog. And there ARE small foreign fragments and cobbles at Stonehenge -- packing stones, mauls, debitage galore. You might assume that the debitage all comes from broken up orthostats -- I might assume that a lot of it might come from broken up smaller stones and cobbles. Do you, or does anybody else, have any evidence to disprove the latter supposition? As I have often said before, the obsession with orthostats and proto-orthostats is something that suits the archaeologists very well indeed. They assume that heroic Neolithics would have carried big stones from A to B, but not smaller stones. It's not my role in life to pander to their dodgy assumptions!

Myris of Alexandria said...

Ah but the lack of lack of evidence is not evidence either.
There is a difference between not accepting Green,s data and providing contradictory proof. THAT is what is needed. Believe me I would be very happy to believe it and to have Green shown to be wrong but that has not happened.
M

Phil Morgan said...

Brian says ---- "And there ARE small foreign fragments and cobbles at Stonehenge -- packing stones, mauls, debitage galore. You might assume that the debitage all comes from broken up orthostats -- I might assume that a lot of it might come from broken up smaller stones and cobbles. Do you, or does anybody else, have any evidence to disprove the latter supposition?"

Phil says ---- "But no Blue Pennant Sandstone on Salisbury Plain, which there should be for the Pennant Sst travelled in/on the same ice as the bluestones"

BRIAN JOHN said...

Disagree with that, Myris. The default position of an earth scientist must be that there is an assemblage of glacial erratics at Stonehenge, introduced by glacier ice either to that locality or to somewhere quite close. The most convincing reason to move away from that default position is for somebody to show that glacial transport was impossible. That has not been done -- indeed the glaciologists accept it was perfectly possible. Chris Green's work was not at all convincing -- for reasons already enumerated. I doubt that anybody else is going to wander around the rivers of the Salisbury area counting 50,000 pebbles! Something else that might be convincing is a clear demonstration that Neolithic people carted large numbers of large stones around the country for one reason or another. As we all know, that hasn't been done either -- and all the evidence points to the Neolithics having a great tendency to use stones WHERE THEY FOUND THEM.

So the default positions remains where it is.

Myris of Alexandria said...

No Brian that is not the default position of most geoscientists.
Most would not accept glacial limits close to Salisbury Plain -I do agree the frost has grown closer in the last decade-or has been modelled so- but there is a lack of any field evidence. The range of rock types at SH that you use are mainly post-Darwinian in age and are lithic-spam. Search under the stone overlying the Altar Stone and you will find Brazilian amethyst and other New Age mineral rubbish. Note the cetre of SH has had gravel, clinker etc laid upon it.
The evidence for anthopogenic movement of the bluestones is also very sleight.
For my money if the proto-orthostat is an artefact then man triumph over nature.
But there is no single accepted rest position.
M

BRIAN JOHN said...

Actually most geoscientists have not even thought about Stonehenge. Of those who have gone into print, those preferring the "human" explanation include Herbert Thomas, James Scourse, Chris Green, Dai Bowen, and maybe Chris Clark who has advised MPP -- and then maybe you and Richard Bevins. Of those who have expressed the "glacial" view, we number Judd, Kellaway, Williams-Thorpe and her colleagues from the OU team, Alun Hubbard and his 7 colleagues including Henry Patton, and Lionel Jackson. I don't want to get into a numbers game here, but there is clearly no consensus. And remember that the "established wisdom" that glaciation on Salisbury Plain would have been "impossible" comes from two chapters in the big Stonehenge book, by Scourse and Green, neither of which was refereed. And then we can add literally scores of earth scientists who have argued for glaciation affecting SW England -- while not agreeing on where the actual ice limits were positioned.

As ever, we will agree to differ!

BRIAN JOHN said...

While I'm about it, I hate the word "orthostat" and I similarly dislike the term "proto-orthostat" -- both imply a human agency in setting a large stone upright in the ground. The debate is bedevilled by these terms which make rational discussion very difficult. Another example is the term "bluestone" which we all have to use as a shorthand term -- but which of course implies a particular desirable stone type. If the discussion could concentrate on assorted elongated or flattened or rounded stones which have not come from the immediate vicinity of Stonehenge, then we would all be much better off....

Myris of Alexandria said...

No in almost every paper by the pet rock boys they define bluestone as any non sarsen lithology used to make an orthostat.
Stick with that and you neatly confine both the erected smaller and Altar Stone uprights and their rock types.
Nothing else is bluestone and it is mendacious to suggest otherwise.
I agree numbers are meaningless and not all geologists are as you describe OWT for example is an Archie and it would be as true to call her a geologist as to call Dr Ixer an archaeologist.
I do fail to see the significance of most geologists have not thought about true so they have no bearing or relevance. It is those who have thought, have the correct expertise
and expressed an opinion that should be discussed.
My sense is that geological opinion is very decided, perhaps better than Archie opinion that is unanimous.
There seems to be no consensus by those who warrant being listened to.
If the proto orthostat is that, then
I must repeat the glacial theory is frozen out.
Still Dr Ixer has moved someway,20 years ago he predicted that if a quarry could be found then the game would be over. He is think says if the proto orthostat is that etc etc.
Perhaps he is having too much fun to want a definitive and definite answer.
M
M

Myris of Alexandria said...

The penultimate sentence prior to the auto-correct said
He is, I think, now saying, if the proto-orthostat is just that .....
M

BRIAN JOHN said...

Myris:

"Stick with that and you neatly confine both the erected smaller and Altar Stone uprights and their rock types. Nothing else is bluestone and it is mendacious to suggest otherwise."

That's a bit rich!! Why should I accept your definition of bluestone? I could equally well say it is mendacious to try and restrict the use of the term to "orthostats" and "proto-orthostats", just to suit the archaeologists and to divert attention away from all the other erratic material on the site......

I should have thought that any earth scientist would be interested in ALL the foreign material at Stonehenge. If some of it has come in as roadstone or hippy trinkets, fine, but there is plenty of stuff that isn't so easily explained away.

BRIAN JOHN said...

By the way, which "proto-orthostat" are you talking about?

Myris of Alexandria said...

You are being intentionally naughty, who said non bluestones(ss) are of no interest. I suspect that Dr Ixer has looked at as much adventitious material from the Stonehenge landscape as echte bluestones.
He has even looked at stones from molehills sent in by amateurs who could not get the postage right.
Almost none of it was brought to Stonehenge in early Times.
Some polished stone axes has potential but as some are West country in origin net even the most entrenched Artic hare will invoke glacial transport.
On a more interesting but ever related note have you read a bgs publication on the English Channel dropstones?
The pet rock boys are catholic in
their observations but like good Catholics draw the line at New Age heretics and all their works.
Rock crystal is rock crystal.
M

BRIAN JOHN said...

All good fun, Myris. Naughtiness is an essential part of life, and it is needed if the dead hand of orthodoxy is be be prevented from controlling the universe.

BRIAN JOHN said...

Phil -- SHOULD be Pennant Sandstone erratics at Stonehenge? Afraid not. That's not how glaciers work -- we still do not fully understand why entrainment of erratics happens in some places and not others. One could equally well say that there SHOULD be purple Cambrian sandstones, or Coal Measures sandstones, or Cambrian basal conglomerate boulders at or near Stonehenge, and yet none have been reported.....