Hello barnacle_bill and thank you for your question.
There is no tectonic plate between England and France. The English
Channel (or La Manche as our French neighbours call it) was formed at
the end of the last ice age due to the melting ice.
Map of tectonic plates:
http://media.maps101.com/SUB/WORLD_THEMATIC/tectonic.gif
Formation of the Channel:
"Before the end of the last ice age, around 10 000 years ago, the
British Isles were part of mainland Europe. As the ice sheet melted, a
large freshwater lake formed in the southern part of what is now the
North Sea. The outflow channel from the lake entered the Atlantic
Ocean in the region of Dover and Calais.
At some point around 6500 BC, catastrophic erosion swept away the
chalk to create the English Channel, which has since been further
widened by wave action on the soft, chalk cliffs. The same mechanism
continues to widen the English Channel today."
http://en.wikipedia.org/wiki/English_Channel
Thank you for your question, and if you need any clarification of my
answer, do not hesitate to ask prior to rating my answer.
Very best regards
THX1138
Search strategy included:
"english channel" "ice age"
://www.google.com/search?hl=en&lr=&safe=off&as_qdr=all&q=+%22english+channel%22+%22ice+age%22 |
Request for Answer Clarification by
barnacle_bill-ga
on
24 Feb 2005 05:41 PST
Thanks for taking the time to look at this question.
I'm asking because I remember vaguely, when the chunnel was being
built, it was said that the british isles and france where moving away
from each other at a rate of 5cm every 100 years (or something like
that) and that there was a small fault between the two countries.
I apreciate that my original question was to do with 'tectonic plates'
but could a geographic fault do the same thing?
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Clarification of Answer by
thx1138-ga
on
24 Feb 2005 05:54 PST
Hello again barnacle_bill.
You are correct that the distance between Englan and France is
increasing, but this is due to erosion rather than any kind of
geological fault. If there were geological fault that increased the
distance 2?5 cm every year, the chunnel would probably never have been
built.
"On a geological scale the distance between Britain and France
continuous to increase as 2?5 cm of the chalk is eroded sideways every
year."
http://aviser.imaker.no/data/f/0/18/72/7_5301_0/GeoExpro_40-48.pdf
Very best regards
THX1138
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Request for Answer Clarification by
barnacle_bill-ga
on
24 Feb 2005 06:11 PST
just to add something, this site after a search of my own is more
informative of the actual geographical stucture of the channel.
http://www.geologyshop.co.uk/chtung.htm
Can you get back to me on this one, I'd like to hear your views.
thanks again for looking
BB
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Clarification of Answer by
thx1138-ga
on
24 Feb 2005 06:33 PST
Hello again barnacle_bill,
Yes that's an interesting article, particularly the part regarding
erosion. (pity the graphics don't load)
"Since then the cliffs have been subjected to marine erosion,
subaerial weathering and more recently the works of man. The attack by
the sea tends to have a destabilising effect whilst the process of
subaerial weathering would, given no further marine erosion,
ultimately result in a stable cliff the shape of which would resemble
the escarpment of the North Downs to the west of Folkestone.
The rate of erosion of the toe of the cliffs between Folkestone and
Dover has been measured as up to 0.75 m per year (May, 1966). However,
the rate and amount of erosion at any specific locality is dependent
on the protection of the cliff foot by shingle or debris from
recurrent cliff falls. Clearly the process of toe erosion is halted,
albeit temporarily, by sea defences with sufficient height to provide
protection from wave splash and spray or with sufficient width to keep
the shoreline remote from the cliff base."
Also see:
"During the very cold bits of the Ice Age, what is now the English
Channel would have been a wide river plain.
Sea levels began to rise, until they finally reached their current
levels. Just before the midway point of this process, some 6,000 years
ago, the sea levels divided us from what is now mainland Europe."
http://www.bbc.co.uk/devon/outdoors/walks/walk_through_time/07.shtml
Very best regards
THX1138
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Request for Answer Clarification by
barnacle_bill-ga
on
24 Feb 2005 06:54 PST
I dont mean to split hairs, but the same article states:
" The intensity of these movements, particularly the last extensional
phase, is not the same everywhere, and it should be noted that the
tunnel route is situated to the north and just outside of the most
highly tectonised zone. This explains why the route actually
intersects only a few major faults (with throws of a few metres) on
the French side, while on the UK side no fault with a throw greater
than 1m was recorded during tunnelling."
now to my untrained (geologically speaking) ears sounds like there is
tectonic movement here?
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Clarification of Answer by
thx1138-ga
on
24 Feb 2005 06:59 PST
Hello again barnacle_bill,
I didn't say there were no fault lines in the English chanell (there
are) I said there are no tectonic plate borders in the English
chanell, which is what you asked. As I understood your original
question, you wanted to know why there was water between England and
France. The reason is not due to any geological activity (tectonic
plates or other geological activity) but due to the fact that at the
end of the last ice age the sea level rose due to the ice melting.
For further information see:
http://www.theotherside.co.uk/tm-heritage/background/channelform.htm#join
Very best regards
THX1138
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Request for Answer Clarification by
barnacle_bill-ga
on
24 Feb 2005 07:14 PST
THX1138 thanks very much for your help clearing this one up.
BB
(and that last link is very useful)
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Clarification of Answer by
thx1138-ga
on
24 Feb 2005 07:23 PST
Hello again barnacle_bill,
Don't mention it, I'm glad I was able to help out.
Very best regards
THX1138
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