Amazing Cliff Collapse Caught on Camera
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Lowaicue
英語在香港
What absolute rubbish. This is entirely the fault of Cameron.
DamnYankee
Loyal to the end
Tom, where was that?
SmarterthanYou
rebel
where was the tsunami alert?
Lowaicue
英語在香港
It was at Dead Man's Cove near Hells Mouth on the north coast of Cornwall not far from the village of Portreath. It used to be a favourite spot for suicides, maybe still is. There have been cracks visible for many years, some quite substantial. When I used to holiday there many years ago you could crawl (or walk if you were courageous) to the cliff edge and peer down at the swirling breakers below.
how'd they know it was going to collapse? seems they were anticipating it.
cancel2 2022
Canceled
DamnYankee
Loyal to the end
I didn't ask you.
Wherever the ocean was hottest due to global warming. What do you mean where was that?
cancel2 2022
Canceled
Wherever the ocean was hottest due to global warming. What do you mean where was that?
I think geology and hydrology has something to do with it. Cornwall can really be imagined as a finger of 400 million year old Devonian slates along with Carboniferous sandstones and shales pointing across the Atlantic Ocean towards the USA, with a backbone of granite.
Stop it. St. Algore will call you a "denier" and it will make you cry.
cancel2 2022
Canceled
It's(sic) undeniable. Granite cliffs don't behave in that manner, sedimentary cliffs do. I can't speak for Algore maybe if he is subjected to constant battering with wind and tides he would collapse in similar fashion.
Lowaicue
英語在香港
Granite can and does decompose. Cornwall has huge areas of decomposed and semi decomposed granite. It is called kaolin.
DG can occur as great areas, as at St. Austell or in very small patches no more than a few inches wide but perhaps many tens of metres deep (or high, depending on ones location at the time). There is no reason to suppose that the granite cliffs around Hells Mouth do not have DG or SDG intrusions. (That is not to say that the cause of the cliff fall was due to DG.)
Lowaicue
英語在香港
Then you did not want a complete answer.
cancel2 2022
Canceled
Never said that granite doesn't erode, that would a stupid thing to say. Granite tends to erode steadily and not in the spectacular manner of those cliffs. Anyway what are DG and SDG intrusions?
DamnYankee
Loyal to the end
Except I did get a complete answer, without the superfluous bullshit about suicides and your holidays spent in the area.
Lowaicue
英語在香港
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.
DamnYankee
Loyal to the end
This explains why you're as dumb as a bag of rocks.