Author Topic: Britain's longest sea cave.  (Read 1994 times)

Offline alasdair neill

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Britain's longest sea cave.
« on: June 09, 2014, 09:56:40 am »
Currently this is quoted as Holl o Boadie on Papa Stour, Shetland, quoted as 300m or 400m long, the length probably originating from the 1878 6" OS map which shows a length of about 990 feet so 300m is likely to be correct. This has been copied onto even the most recent OS maps. A post on the web (which I have been unable to relocate unfortunately) states the OS mislocated one of the entrances so the length between entrances may be too long.
A list of the Worlds longest sea caves,
http://www.caverbob.com/seacave.html
gives Holl o Boadie as the 8th longest sea cave in the world.
Recently partly surveyed a cave in Cornwall with over 200m done so far and an estimated 100m left to do, which could prove to be the longest surveyed sea cave in Britain when this is complete (next weekend?).

Offline mrodoc

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Re: Britain's longest sea cave.
« Reply #1 on: June 09, 2014, 10:12:08 am »
I have read the article on the NZ caves. These run parallel to the cliffs and are enlarged on cross joints. Whereabouts is this Cornish cave - north or south?

Online Alex

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Re: Britain's longest sea cave.
« Reply #2 on: June 10, 2014, 12:41:29 pm »
When we say sea caves are these submerged caves, or caves in the cliff face above the water line?
Anything I say is represents my own opinion and not that of a any club/organisation that I am a member of (unless its good of course)

Offline alasdair neill

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Re: Britain's longest sea cave.
« Reply #3 on: June 10, 2014, 03:35:24 pm »
On north coast of Cornwall.
This cave can be explored with just some pools where you get wet feet at low water springs, and the entrances can be reached dry, but at other stages of the tide floods and can probably be swum or kayaked through but would be lethal in a big swell. Passages up to 20mx20m ish.

Offline irnbru

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Re: Britain's longest sea cave.
« Reply #4 on: June 10, 2014, 06:02:49 pm »
Stack O' Brough (or Scorries Island) South of Wick is about that length - nice easy dive and open to the surface

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Offline graham

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Re: Britain's longest sea cave.
« Reply #5 on: June 10, 2014, 06:26:02 pm »
Mr O'Doc: aren't there karst springs near Brixham, a bit like the Doolin Green Holes?

How long are they?
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Offline alasdair neill

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Re: Britain's longest sea cave.
« Reply #6 on: June 11, 2014, 09:53:28 am »
Judging from OS maps the length of the long axis of Stack o'Brough is about 170m.

Offline alasdair neill

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Re: Britain's longest sea cave.
« Reply #7 on: June 12, 2014, 09:28:42 am »
Found more stuff on Papa Stour caves, for anyone interested:
Scottish Natural Heritage Commissioned Report 102 Site Condition Monitoring Surveys..of Papa Stour cSAC (2003) which includes surveys of the caves. Available online.

Offline mrodoc

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Re: Britain's longest sea cave.
« Reply #8 on: June 12, 2014, 02:53:40 pm »
Mr O'Doc: aren't there karst springs near Brixham, a bit like the Doolin Green Holes?

How long are they?

Nothing found there yet except short tubes. The rumours of a blue hole at Plymouth reported 30 years ago were greatly exagerrated!

Offline alasdair neill

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Re: Britain's longest sea cave.
« Reply #9 on: June 16, 2014, 01:10:23 pm »
Survey yesterday showed a length of about 380m with a big opening up to the right of the western entrance which we didn't go into. Locally called the Hall and Parlour, a name referred to by Tonkin c. 1710, which seems to refer just to the two largest entrances at the eastern end of the cave. There may be a longer cave in the area which is much more difficult of access, I only did a brief visit many years ago by boat.