I've had a bad cold this week and so have watched quite a bit on telly. One of the programs I (re)watched was the BBC documentary Coast. It seems that by using underwater detection equipment in the North Sea off the coast of Norfolk, they can trace the path of an ancient river system that flowed south toward the English Channel.

They also took samples from the seabed and found peat deposits. Peat can only be formed on dry land, not saltmarsh.

A few years ago on holiday in Wales I went to a seaside village called Borth. An interesting place.

It's worth making the trip to Ynyslas at low tide in the hope of witnessing this amazing sight. Tree stumps of oak, pine, birch, willow and hazel can be found embedded in peat at one metre below the normal surface between high and low water marks. Even twigs and branches are uncovered.

This submerged forest proves that the coastline used to be further west and that the sea level has risen. Radio carbon dating suggests that these trees died around 3500 BC (but others to the south, near Borth, date from 1500BC). The tree stumps were preserved by the acid anaerobic conditions in the peat.

The forest remains also hark back to the legend of a lost land - the Lowland Hundred or Cantre'r Gwaelod as it's known in Welsh.

Ruled by Gwyddno Garanhir, the low-lying kingdom was protected from the sea by a series of dykes and sluice gates. One stormy night, the appointed watchman Seithennin - a heavy drinker - was at a party and left the water gates open. The land was flooded and disappeared under the waves. Perhaps there was an earthquake and a tidal wave or tsunami.

It is said that if you listen closely, you can hear the bells of the lost city ringing out from under the sea, especially on quiet Sunday mornings and particularly if you're in Ynyslas or Aberdyfi.
http://www.bbc.co.uk/wales/mid/sites.../pages/5.shtml

http://en.wikipedia.org/wiki/Cantref_Gwaelod