Amazing Cliff Collapse Caught on Camera

Lowaicue said:
Erosion and decomposition are slightly different. Granite can decompose in very confined situations. If it is exposed it is not noticable because the powdered rock disperses, but in a confined area such as a vertical fault a 'seam' of DG (decomposed granite .... - sometimes referred to a DCG) can sit for millenia before some other movement allows it to collapse. [CLIFF /// CLIFF] In some areas the North Cornwall cliffs are honeycombed with old mine workings particularly on the St. Just peninsula and up at St. Agnes. The area of the collapse, as far as I know, was not in the tin mine area.
When excavating the underground railway in HK, in what was assumed to be solid granite, drillers hit a seam of DCG which started to run. It took many trucks of ready mix concrete to fill the resulting void.
The reasons for cliff collapses can be many, from excavation by the sea in the form caves formed by wave action or by minute land movements over many years. As I mentioned, cracks appear along those cliff tops fairly frequently (geologically) and, as is witnessed by the fragmented rocks below frequently lead to collapses. They tend not to 'go' when people are watching though.
(SDG is Semi-Decomposed Granite. This and DG or DCG are often refered to in the construction industry as 'pop' granite. No, I don't know why.)
Incidentally, on the subject of names, the silver grey granite aften used to face buildings is/was often used for gravestones and hence is known as tombstone granite in Cornwall .. and probably in the States too, since Cornish miners carried their trade there a hundred years ago.
Click to expand...

Those cliffs are composed of Devonian slate.

The expert explained: “The action of the wind, the sea, and the ice will break up a rock mass like that and you’re losing support for the cliff from below.
“The combined effects coalesce to cause the failure so that gravity exceeds the strength of the rock mass.”
“It’s an ongoing process around the coast but it’s very very unusual to catch a large event like that and especially film it.
“I think Geologists around the world will be interested to see it.”
Environment Agency spokesman Paul Gainey said: “Coastal rock falls like this are caused by a combination of factors.
“It’s wave and wind action: the waves erode the foot of the cliff and undermine it. Wind bufffets the cliff and erodes it away.
“Those effects can be compounded by weather conditions on a particular day to create a rockfall.”
“The rock in this cliff would be Devonian slate, which runs through North Cornwall.
“It’s very unusual to see a rock-fall, and more unusual to see a rock-fall of that size, on the North Coast in particular.”
Local photographer and Coastguard cliff rescue officer Colin Higgs said: “We can only warn people of the dangers of the cliffs in this state.
“There have been too many tragedies along this stretch of cliff. Heavy rain can take a long time to percolate through.
“That will make the cliffs unstable. We do have instances of people falling off cliffs in that area.”
Click to expand...

http://www.cornwallcommunitynews.co.uk/2011/10/07/north-cliff-collapses/
 
Aoxomoxoa said:
Those cliffs are composed of Devonian slate.



http://www.cornwallcommunitynews.co.uk/2011/10/07/north-cliff-collapses/
Click to expand...

I am indebted to you for this. Research is something I never do preferring to rely on my innate knowledge and experience, a practice that on this rare occasion failed me. Granite makes up a considerable area of that part of Cornwall and I had assumed that it stretched further than it did.
However my points about erosion and decomposition and the possibilities of such a fall occurring are still correct as are my points about the actions of the sea being one of several causes of a collapse.
Perhaps I should research in future but I always think that, on a forum like this, it and cutting and pasting are tantamount to cheating.
 
LOL LowIQ shows he's an idiot once again. For a minute there I thought that maybe you had some knowledge in at least something. :palm:
 
Aoxomoxoa said:
He has extensive knowledge of civil engineering having worked in that sector for many years.
Click to expand...
Apparently it's not that extensive, not knowing the difference between an igneous rock that is typically sound and a low-grade metamorphic rock that is typically layered and prone to weathering. :)
 
DamnYankee said:
Apparently it's not that extensive, not knowing the difference between an igneous rock that is typically sound and a low-grade metamorphic rock that is typically layered and prone to weathering. :)
Click to expand...

Much of Cornwall is granite and does decompose much more than ordinary granite due to the higher levels of feldspar.
 
The video is awesome. The total lack of belief in St. Algore of the Trees is disturbing though. You all KNOW it is due to the global warming trend that is obviously true because of consensus and stuffs... No denying it or we'll throw you to the faithful on MSNBC...
 
DamnYankee said:
So you have cheap rocks in the mother land.
Click to expand...

As Low rightly points out it is that fact which produces kaolin clay. Kaolin has many uses including porcelain, high grade paper and last but not least kaolin and morphine suspension which is indispensable for relieving Bangkok Belly. I have taken it with me many times but then somebody pointed out, on my last trip, that as I was going via Dubai to Thailand, I would get banged up if they found it in my luggage.
 
Damocles said:
The video is awesome. The total lack of belief in St. Algore of the Trees is disturbing though. You all KNOW it is due to the global warming trend that is obviously true because of consensus and stuffs... No denying it or we'll throw you to the faithful on MSNBC...
Click to expand...

The fact is that those cliffs face the full force of the Atlantic and the prevailing south westerly winds, which are the primary drivers of erosion in that area. The nearest land fall southwest of there is Florida so it gets all of your second hand hurricanes. I suppose we ought to be thankful that you don't charge for them.
 
They make morphine suspension for Bangkok Belly? (Whatever that is)...

Sounds like a great excuse to take drugs. Personally I take my prescriptions for my chronic kidney stones...
 
Aoxomoxoa said:
The fact is that those cliffs face the full force of the Atlantic and the prevailing south westerly winds, which are the primary drivers of erosion in that area. The nearest land fall southwest of there is Florida so it gets all of your second hand hurricanes. I suppose we ought to be thankful that you don't charge for them.
Click to expand...

It's really our final solution for GB.
We intend to continue to wear away at your little island, until there's nothing left but a memory. :)
 
Damocles said:
They make morphine suspension for Bangkok Belly? (Whatever that is)...

Sounds like a great excuse to take drugs. Personally I take my prescriptions for my chronic kidney stones...
Click to expand...

It's a tried and tested remedy for diarrhoea, the trouble is that places like Dubai are so restrictive that it is considered to be a serious offence to have it in your luggage. As for Bangkok Belly, I thought that was self explanatory.

http://www.dubaifaqs.com/drugs-dubai.php
 
DamnYankee said:
Apparently it's not that extensive, not knowing the difference between an igneous rock that is typically sound and a low-grade metamorphic rock that is typically layered and prone to weathering. :)
Click to expand...

Perhaps if you were to admit to the limits of your knowledge you presence here might be more welcome.
And, let me add, the granite of the cliffs in that part of the country is weathered and of the same or similar colour to the rocks shown in the video.

http://upload.wikimedia.org/wikiped...d.jpg/800px-Land's_End,_Cornwall,_England.jpg
 
Damocles said:
They make morphine suspension for Bangkok Belly? (Whatever that is)...

Sounds like a great excuse to take drugs. Personally I take my prescriptions for my chronic kidney stones...
Click to expand...

I imagine that if you took a hundred bottles, allowed the kaolin to settle and drank the liquid only you might get a hit!!
 
Lowaicue said:
Perhaps if you were to admit to the limits of your knowledge you presence here might be more welcome.
And, let me add, the granite of the cliffs in that part of the country is weathered and of the same or similar colour to the rocks shown in the video.

http://upload.wikimedia.org/wikiped...d.jpg/800px-Land's_End,_Cornwall,_England.jpg
Click to expand...

I wasn't aware that there were limits to my knowledge. Why don't you just admit that you fucked up here, and couldn't tell the difference between granite and slate? :)
 
You must log in or register to reply here.
Back
Top