When did Britain become an island? | Forum

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slumpystones Jul 19, 2007 18:36:16

Replying to Chris Collyer

Chris Collyer wrote:

From BBC News-
>>Britain became separated from mainland Europe after a catastrophic flood some time before 200,000 years ago, a sonar study of the English Channel confirms…

http://news.bbc.co.uk/1/hi/sci/tech/6904675.stm

Can anybody explain this one to me?
I always thought that the British Isles were joined to the rest of Europe until the end of the last ice age about 10-12000 years ago and that large areas of the north sea were grassland and populated by palaeolithic man (between ice ages) The article suggests that we were separated from Europe 200000 years ago instead, so did the sea level later fall again creating a vast valley between the southeast and France, and the areas of Doggerland further north, or am I missing something from this picture?

-Chris

The important bit is right towards the end:

"And even when water was locked up in giant ice sheets and sea levels plummeted, the Rhine and the Thames rivers would have dumped meltwater into a major river system that flowed along the Channel's floor."

The 30m of chalk that held back the lake were breached, and once the water had drained, it would have been a valley with rivers running through it.

I suppose ;)

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Pilgrim Jul 20, 2007 02:31:52

Replying to Chris Collyer

Chris Collyer wrote:

http://news.bbc.co.uk/1/hi/sci/tech/6904675.stm

Can anybody explain this one to me?
I always thought that the British Isles were joined to the rest of Europe until the end of the last ice age about 10-12000 years ago and that large areas of the north sea were grassland and populated by palaeolithic man (between ice ages) The article suggests that we were separated from Europe 200000 years ago instead, so did the sea level later fall again creating a vast valley between the southeast and France, and the areas of Doggerland further north, or am I missing something from this picture?

-Chris

Interesting. The way I understand it, this is the first erosional event that created what is now the English Channel.

After this event, one or more glacial ice ages occurred, and hoovered up what water was about, locking it into ice sheets that covered most of the top half of the British Isles. Then - with no water of consequence to worry about - the English Channel would have been easy to navigate, and Britain would been rejoined with "the Mainland" of Europe.

The end of the last Ice Age saw the release of this stored water into the pre-formed erosion channel, finally excising our Green and Pleasant from what is now the European continent. I figure that the marshy joint that stretched from the South East to Holland/Belgium finally gave in around 8000 BCE.

Peace

Pilgrim

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fitzcoraldo Jul 20, 2007 07:55:53

Replying to Chris Collyer

Howdo Chris
I can recommend the DTI Strategic Enviormental Assessment website as a excellent resource for information regarding offshore archaeology and geology.
http://www.offshore-sea.org.uk/site/scripts/category_info.php?categoryID=37
There's some crackin' down-loadable reports especially the latest SEA 7 stuff from Wessex Archaeology.

cheers
fitz

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Littlestone Jul 20, 2007 10:54:06

Replying to Chris Collyer

There's also this Chris -

http://www.guardian.co.uk/science/story/0,,2129662,00.html Part of the article reads -

"...a second massive flood completed the job of separating Britain from France around 180,000 years ago. Another vast glacial lake formed from rivers off the east coast of Britain and was temporarily contained to the south by an earth ridge spanning from north of the location of present-day Ipswich across to a point which is now The Hague. Water released into the Dover strait widened the channel to more than nine miles in some regions.
"Philip Gibbard, a geologist at Cambridge University, said the megafloods that created Britain were on a par with the largest known on Earth, including an event that created Lake Missoula in Washington state at the end of the last ice age.

"The second flood followed less severe glaciation and may have been witnessed by early humans..."

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Chris Collyer Jul 22, 2007 22:54:50

Replying to Chris Collyer

Thanks for the thoughts and links folks
I think Pilgrim summed up pretty much what has been bubbling around in my head, all I would add is that during warmer periods the sea level must have risen and cut Britain off from the mainland several times, to be rejoined again in succeeding Ice Ages as the Guardian article suggests - "Prior to this ridge being breached, Britain would have been a promontory with a very clear connection to France, but once this happened every time there were high sea levels Britain became an island," The Guardian are talking about an event 400000 years ago with the second lake and breach 180000 years ago (about the same time as the BBC are suggesting – give or take 20000 years). If this on/off island situation continued after the second event as well then the diagram at the bottom of the BBC report showing the various ‘incursions’ of early man makes a lot more sense to me now.

Fitz – I’ll have a look at those reports but they look a bit heavy going in places, here’s a few random gems from one -
‘global eustatic component of sea level rise’, ‘glacioisostatic
rebound in the western Highlands’, ‘Shoreline uplift isobases (in metres Ordnance Datum (OD)) for Main Lateglacial Shoreline of Younger Dryas age’, ‘Rheological models and glacio-hydro-isostatic rebound models’

Do they do a pop-up book version ;-)

-Chris

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The Eternal Jul 26, 2007 17:31:00

Replying to Chris Collyer

Chris,

Francis Pryor's book "Britain BC", which I'm part way through right now, gives a good account of the timeline, and prehistoric mans' parallel development. It's a good read so far.

Regards,
TE.