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Sunday, 5 June 2011

Streamlined hills on the Somerset Levels?

 I have just received this message from Alex Gee, for which many thanks!

I am writing to ask your opinion (as an expert in glacial geomorphology)  on the following observations.  For some years my friends and I have been digging a cave on the south flank of the Mendip Hills (above Wells).  After digging we often stop to admire the magnificent view across the Somerset levels. 


The Somerset Levels are marked in blue on this map

 Over time I have noticed that a lot of the small rounded hills on the levels, have a convex  asymmetric profile, their longitudinal axis being roughly east to west.  The westerly hill slope is gently graded (grass pasture used for cattle grazing), the easterly slope having a steep gradient (being unfarmed and wooded).  In plan form some are crudely tear drop shaped. Their length to height ratio is approximately  4 or 5:1,  the summits of the hills are generally at the eastern end, and 4/5 to  3/4 of the hills length to the east.   


 The more I look at them, the more the thought has grown that their assymetric shape (and orientation), could be due to easterly movement of glacial ice from the Bristol Channel?   Could the hills be a form of roche moutonnee?  There is no obvious structural explanation of their form. The hills are mainly composed of horizontally bedded Rhaetic and lower Jurassic strata, lying unconformably on Triassic  Mercia Mudstone (playa lake deposits) and Triassic Dolomitic Conglomerate. The slopes cut across the contact indiscriminately. This rules out the role of stratal dip.

Yesterday, I pointed out the morphology of the hills to my friend; who is a geologist and Mining engineer( ex-Cambourne school of mines).   His immediate comment was " If this was north of Watford then, I'd say it was due to glaciation".


This is an interesting observation, which I have never seen before -- and even Geoff Kellaway, who assembled much evidence for glaciation in Somerset, did not (as far as I know) mention possible streamlined hill shapes.  Some more work is obviously needed on this........

27 comments:

Anonymous said...

like this one in Sedgemoor? http://www.peteglastonbury.plus.com/Sedgemoor.jpg
PeteG

BRIAN JOHN said...

Thanks Pete -- but that one doesn't look very streamlined to me. A real streamlined form would be elongated, parallel with the direction of ice flow, and with a gentle slope on the up-glacier side and a steeper and shorter slope on the down-glacier side. If you look on Google Images there are bound to be many illustrations of roches moutonnees...

Constantinos Ragazas said...

Brian,

Could these 'streamlined hills' be a results of water flow? It seems that the side directly facing the water flow will be more eroded and steep while the side going with the flow will be more tapered.

I believe the description of these 'streamlined hills' of Sommerset Levels fits well such characteristics, including where the hill top would be relative to the length of the hill, the convex tear-like profile, etc.

Also, I remember reading somewhere that the 'inside' of the big sarsens at Stonehenge had an embankment of dirt buildup whereas the 'outside' of these sarsens there is none. I even remember seeing some pictures of this, but I just can't find them anymore. Know anything about that?

Kostas

BRIAN JOHN said...

Streamlined forms created by flowing water would be the other way round -- with the steep faces on the upstream side. I have seen such things in soft sediments -- caused by river flow or tidal streams in the sea.

Dirt buildup around the sarsens? Never heard of that -- but it's often said that the sarsens were placed with their smooth faces inwards and their rough faces outwards.

Tony Hinchliffe said...

Wonder if Bristol University's esteemed Department of Geography's geomorphologists have done any research into the physical formation of The Mendips? Surely someone academic has done some in-depth investigation? This is, after all, an important tourist destination, and, with increasingly educated visitors arriving in The Mendips, interpretation of the landscape for the curious visitors should be as essential a part of welcoming
them as good bed and breakfast facilities. Also, Bristol University has a very high number of "television" academics.It's easy enough to see this could be a case where Bristol University could have a beneficial effect on the regional economy of The West of England by stimulating tourism with the right academic research. After all, both Stonehenge and The Mendips are in that University's catchment area!

Alex Gee said...

Kostas, The situation is extremely complex and I have not made any claims either way. The morphology of the hills could quite obviously be the result of water flow (Frozen or otherwise); The levels are an estuarine flood plain surrounded by higher ground!. Given however the large amount of evidence for glaciation of the area gathered by Kellaway; and others since. The observation is still worth investigating.

Constantinos Ragazas said...

Alex,

The location of Somerset Levels, their geomorphology and that of the 'streamlined hills' you have described, and the proximity to Stonehenge make your observations, in my opinion, especially relevant. Clearly, given the orientation and shape of such hills, these could have been formed by water flow draining into Bristol Channel. This water flow could have been part of Robert Langston's Mesolithic inundation or meltwater from my 'local ice cover' theory. But it is hard to understand the kind of glacier advance or retreat that could have formed such hills. Of course Brian is the expert on this and I'll concede to his views on these hills.

But if the westerly side of these hills is not exposed bedrock but rather rich thick top soil, this would indicate to me alluvial processes that may have created these hills.

Another point worth considering. It is possible that such shaped hills (especially if these are rocky) be made by rapid water flow through on side of the hill (the steeper side). Then the orientation of such hills would be perpendicular to the water flow, and not parallel. I have seen such geomorphology in areas of the Aliakmon Basin in Western Macedonia, Greece, where I come from.

Kostas

Constantinos Ragazas said...

Alex Gee,

Any way that you can post some pictures of these 'streamlined hills', both individually and as a group? I am very interested in seeing what these could tell us. How big are they? And how these compare with the round and long barrows that are presumably man-made? You described these as 'rounded'.You say,

“The hills are mainly composed of horizontally bedded Rhaetic and lower Jurassic strata, lying unconformably on Triassic  Mercia Mudstone (playa lake deposits) and Triassic Dolomitic Conglomerate. The slopes cut across the contact indiscriminately. This rules out the role of stratal dip.”

If these lie “unconformably” on “playa lake deposits” would that indicate that prior to their formation there was a lake in that general area? Could these also be 'man-made'? Why and why not?

Kostas

Alex Gee said...

Kostas
The question of whether or not the hills were man made, is answered by the words Triassic and Jurassic?.
The phrase LAKE deposits would suggest that they were deposited at the bottom of a Lake.
The Website of the British Geological Survey is excellent and has plenty of information on the geology of the area.

Anonymous said...

Because these playa lakes dried up in the Triassic-- hundreds of millions of years ago- not too many humans then.
GCU In two minds.

BRIAN JOHN said...

Sorry Kostas -- you are clutching ay straws here. Every reason why not.

Constantinos Ragazas said...

Brian,

Never thought these 'streamlined hills' were man-made! Just as I don't think the rounded and long barrows are man-made either!

As you know, I believe Nature played a far greater role in making these 'prehistoric monuments' (including Stonehenge) than prehistoric men.

These 'streamlined hills', if they otherwise compare well with the round and long barrows in terms of size, shape, orientation, etc. may give us important clues as to what happened that can explain the landscape there.

If these 'streamlined hills' were formed by meltwater streams draining into Bristol Channel, perhaps also the barrows were made in similar ways. But with meltwater collecting in ice basins (along with dirt and other debris including bones etc.) and eventually draining into the sea once all the local ice had melted away down to the ground.

That is my hypothesis at any rate. I know you reject it. I am of an open mind... if not of 'two minds'.

Kostas

Anonymous said...

And he's not even from Barcelona, are you Kostas?

BRIAN JOHN said...

Kostas -- you are deliberately ignoring all the evidence that is inconvenient to you. The long barrows and round barrows are not just hummocks with characteristic shapes -- they have tunnels and chambers inside them, and some are immensely complex. Some even have inscribed stones. This is all quite apart from the bones, charcoal and artifacts found within them. Please get real here -- and please do some serious reading on these features. There is a HUGE literature out there -- and the idea that these barrows are natural features is simply unsustainable.

Constantinos Ragazas said...

Anon,

I would love to respond to your comment... if only I knew the reference your are making. Want to be more deliberate?

Kostas

Constantinos Ragazas said...

Brian,

You write,

“ the idea that these barrows are natural features is simply unsustainable”.

As you observed in your post to me, the formation of these barrows can be natural. But I do agree that there is more to these barrows than their formation. Certainly the soil and debris found in them is relevant. As is also I believe the circular ditch to most all of these; the flat and 'dimpled' tops (which Robert uses for his Mesolithic 'lighthouses' that guide his flotilla of reed boats to Stonehenge at night); the 'avenues', more prominent in some and most often oriented in the direction of the summer solstice sun; and most importantly, the chambers found inside many such round mounts.

Do we agree that of all of these the most important evidence that these barrows were constructed by men are the chambers themselves? Most everything else (including stone inscriptions and human remains found in them could have come later).

In my article, “The un-Henging of Stonehenge”, I argued that such chambers could have been build into the mounts afterwards -- as these provided convenient burial places. If there were caves conveniently located in the same area, prehistoric men would have used caves to bury their dead. But would we argue then that the caves were men-made?

But how do we explain such chambers deep inside the mounts and not at the perimeter? That would suggest that these chambers were men-made and covered by large mounts of soil.

I must confess! Your recent posts with photos of vaulted chambers found in Brittany has puzzled me greatly! Assuming that these could be definitively dated to the Neolithic or even earlier (and not Roman and even Medieval times), it's hard to understand how THESE could have been naturally formed!

Of course, I keep an open mind about all this and let the hard evidence determine what the Truth is. But I do scrutinize and consider all possibilities, including those that strike a discordant chord with many of your compatriots.

I do have an explanation and an experiment that can be easily performed which could help answer the question that has puzzled me: could these vaulted chambers found inside barrows be also formed by Nature?

I will make your Stonehenge Thoughts Blog historic by providing here and now a falsifiable theory of how such vaulted chambers could have been naturally formed!!! Please don't block it!

My theory, as you know, is that these barrows were naturally formed by vast amounts of soil and debris carried by local ice meltwater into retaining ice basins. Consider that in some such ice basins mounts of ice were carried there also in the same fashion. And consider that these ice mounts inside some retaining basins were later completely covered by broken up slate and rock and mud during certain geological episodes. Such ice mounts inside some retaining basins would be completely buried by a heavy cover of broken slate, rock and soil. (a little like pingos but not formed by frozen groundwater).
(continued in next post)

Constantinos Ragazas said...

(continued from previous post)

Now as the buried ice mount SLOWLY melts, and under the heavy weight and pressure of a cover of slate, stone and mud, the slate and stones would adjust and more tightly fit into a smaller surface area between the ice mount and the slate cover. Over time, the diminishing ice surface will squeeze tight and position in place the slate and stones and mud into what becomes a 'natural vault'. Once the ice completely melts, the vault will remain buried inside the barrow!

Brian, I know in the past you have made a great deal about 'falsifiability' of a theory. And I agree with you! We must not put forth theories that just cannot be tested! Like, for example, Robert's Mesolithic Lost Civilization! But the theory that I am proposing CAN BE TESTED! We can create in a parking lot and with scientific experimental controls these conditions to test this theory of how vaulted chambers can be naturally formed!

Something unique and important happened in the UK during the Mesolithic. And it wasn't Robert's Mesolithic boat people! Please help me uncover the Truth about Stonehenge for ALL of Mankind!

Kostas

BRIAN JOHN said...

Kostas -- OK, this is all good fun, and I know you are simply trying to wind us up here -- but for the purposes of serious study can I repeat that what we have here is a classic example of a hypothesis looking for some evidence. The processes you propose are not observable in nature, and indeed they go against many of the principles that are well understood for glacial, periglacial and fluvial processes.

I'm not going to publish any more on this unless you come up with some observations from the field which we can take seriously.

Alex Gee said...

Kostas, you're either a troll or an idiot. Until I've carried out a bit more investigation. This will be my last comment on the matter. Got better things to do with my time.

Constantinos Ragazas said...

Brian,

The question simply was “can vaulted chambers be formed by Nature?” I am putting forth a hypothesis and an experiment that CAN be done to test this. It is not in my style nor interest to 'wind up' anybody! Especially you, who I respect and appreciate as a serious seeker of truth.

You may chose to block this message. But I wanted you to at lease know my position.

Kostas

BRIAN JOHN said...

Kostas -- please go off and do that experiment of yours, and report back when you have the results. In the meantime, no more on your theory please...

Constantinos Ragazas said...

Alex Gee,

Responding to name calling is beneath my dignity, so I wont. But I am surprised at Brian for publishing your comment! And thankful that he has!

Much is revealed by such personal insults ...

Kostas

BRIAN JOHN said...

No more personal insults please, folks. Alex, your comment was a bit over the top, and I should have moderated it out! But Kostas, you don't exactly help yourself with your one-track pursuit of your theory and your apparent reluctance to read the abundant literature which is available to all of us on geology, geomorphology and glaciology -- not to mention archaeology. The great majority of your questions could be answered by yourself, just by doing a bit of web searching ... without bothering the rest of us.

Constantinos Ragazas said...

Brian,

You are right. I should be more considerate of the feelings of others. Sorry for being blasphemous. I was mislead by my intellectual demon that asks indiscriminately questions others find uncomfortable to ask.

But someone has to! You know that better than anyone. And your persistence in “your one-track pursuit of your theory” has now finally vindicated your intellectual integrity and honesty.

Congratulations. I take comfort from your example!

Kostas

Alex Gee said...

I apologise to Kostas for the insult, maybe it was a bit OTT.
The only thing it reveals about me though, is that I haven't got the patience of a saint, that Brian obviously has.

Constantinos Ragazas said...

Apologies accepted!

Can we now have the photos of the 'streamlined hills of Somerset Levels'? My ignorant but inquiring mind wants to see them!

Kostas

BRIAN JOHN said...

Kostas -- can I suggest you leave Alex in peace? he has already said he's working on this, and will post something when he is ready......

In the meantime, you can investigate for yourself by zooming in on Google Earth.