Jersey's separation from France
How Jersey and the nearby French coast would change if the sea level fell 60 feet
Hundreds or thousands of years?
But when did this happen? Scientific opinion has always been that it happened several thousand years ago. This may be true for Guernsey, which lies much further off the coast of mainland France, but did Jersey actually remain linked to France until much more recently?
After all, sea levels have fluctuated dramatically over time, as the planet has passed in and out of ice ages, and there is evidence around the coast of Jersey that the island was much smaller at one stage in history, with the sea level reaching many feet higher than it does today. The prehistoric remains in the cave at La Cotte de St Brelade were at a level which was once a sandy beach.
A walk to France?
The sea has not been at that level for many thousands of years, but is it only a matter of several centuries since it rose to cut off a route which enabled people to walk between the island and the French coast? 
Historian A C Saunders, in his 1935 book Jersey, before and after the Norman Conquest of England suggests that a terrible storm and earthquake as recently as AD709 (perhaps one of the tsunamis which is known to have devastated Europe’s Atlantic coast in the past) was the cause of the final separation.
“Tradition tells us that in the early days of the Norman rule the Bishop of Coutances used to visit this part of his diocese by crossing a temporary bridge,” Saunders wrote.
Geologist and historian Dr John Renouf addressed this issue in St Martin, Story of an Island Parish, the parish's Millennium book.
- "One vexed question concerns the issue of vanished land and even buildings, for instance Le Manoir de La Brecquette in St Ouen, the Forest of Scissy between us and the Cotentin, and the story of the Bishop of Coutances and the plank. This has also been of considerable interest to the history of Les Ecréhous."
He wrote that there were no geological objections to the theory that the whole low tide area at the Ecréhouse was once dry land and that the presence of peat between low and high tide levels on Jersey's beaches proves that dry land once existed there.
- "However, it is not now possible to say when the inundation of the land represented by the peats took place. The most that can be stated geologically is that the encroachment of the sea occurred at some unknown time after the peat formed. But of course, geology is not the only source of information about the extent of land on Les Ecréhous, or between the islands and France. Human records have something to contribute, too. We do have legend, but the interpretation of it is fraught with uncertainties at all levels. Unquestionably there is a body of indirect historical evidence suggesting strongly that there was was a considerable extent of low land at both l'Etacq and off Le Hocq up to about the 12th or 13th centuries.
- "Similar lines of argument can be used to suggest that there were some forested lands extending off the coast of the Cotentin and further south to Mont St Michel, which may or may not correlate with the Forest of Scissy. However, there is no strong evidence to indicate that there was anything remotely resembling a causeway in historical times linking either La Rocque or Les Ecréhous to the Cotentin with the only hurdle to be crossed a stream or river. The archaeological and historical investigations carried out at Les Ecréhous recently demand a greater land area there than exists at present, but at its maximum this would never have extended beyond the present low-tide limits. When such of this land as existed was destroyed by the sea is likely to remain imponderable for ever."
A map published by Deschamps-Vadeville in France in 1714 purports to show Alderney connected to the Cherbourg end of the Cotentin peninsular by a strip of land, Guernsey linked to Sark and forming a single island several times its present-day size, Jersey linked to France, and surrounded by coastal plains on its north, west and south sides, the Minquiers forming an island about three times that of Jersey today, and the Chausey Islands also linked to France. This map is said to be based on an earlier chart of AD1404, found at Mont St Michel, which was in turn based on a 9th century manuscript.
Mont St Michel
The tide has ebbed and flowed around Mont St Michel over the centuries, as well as on a daily basis, and what is now permanently linked to the French coast by a causeway, was once an island at high tide, but centuries before that was surrounded by a large forest. Soon it will be an island again, because the causeway is being removed as part of a major project. Tradition says that the forest of Scissy or du Quoqueland disappeared in the great inundation of AD709. Saunders writes that there was another great storm in January 1735 when much sand off the coast of Jersey and France was shifted and tree trunks, ruins of houses and part of a church were revealed.
He continues:”Towards the end of the eighth century Charlemagne sent Gervold, Abbot of Fontenelle, to visit the Island of Augia (as Jersey was then known), then inhabited by Bretons, to enquire about the condition of the inhabitants and to condole with the people on the loss of so large a portion of their land by the inroads of the sea.” Unfortunately Saunders gives no source for this statement, as is common throughout the series of books he wrote on Jersey’s history in the 1930s. He says that the storm of 709 was the final straw at the end of a gradual process of erosion but quotes a “Pegot-Ogier” as writing that about the year 670 Jersey was part of the mainland of France but a small wooden bridge had to be used to cross a little river near Portbail.
The land was allegedly very marshy but Saunders states that records kept at Mont St Michel show that revenues were received from land gradually being submerged until the middle of the 14th Century. He also suggests that although Jersey had become isolated from France, the Ecréhous remained inhabited and connected to France until much later, citing a charter dated 1203, when the islets were handed to the Abbaye de Val Richer, by the Seigneur de Pretel, who had in turn been given them by King John, which called for a chapel to be built there que les habitants ne peuve plus venir entendre la masse de Port Bail en Cotentin (because the habitants can no longer come to hear mass at Portbail in Cotentin).
St Brelade's Church
The Parish church of St Brelade is built in a strange position, away from the centres of population which existed at the time of its construction. One suggestion as to why this should be was expounded by Alex Podger in an article in the Annual Bulletin of La Société Jersiaise. He wrote that at the time the church was built there was more land off Jersey’s south-west coast than there is now, and that the area of Les Mielles in the south of St Ouen’s Bay, also part of the parish of St Brelade, was rich farmland. He says that the parish church was, therefore, sited mid-way between the farming community here and the community in St Aubin.
He does not, however, indicate why the church was built in the bay where nobody lived, rather than at Les Quennevais, where people did live and which was also midway between St Aubin and St Ouen’s Bay via an overland route.
Perhaps a great storm, which Podger suggests washed away sections of coastline and covered other areas in sand, removed an easier route between inhabited areas and the church around the shoreline.
Podger suggests that it was a great storm on 23 November 1334, when major flooding occurred all along the south coast of England, which did much damage in Jersey, allowing subsequent storms to damage the west coast still further, leading to a massive sandstorm which covered Les Mielles a century later.
Where the truth lies will probably never be known, but there certainly seems to be evidence that Jersey’s insularity is a comparatively recent phenomenon.
- Jersey in old documents
- BBC news report on 'Doggerland' exhibition
- Lost land near the Channel Islands Added 2016
Notes and references
- ↑ It is now generally accepted that a document referred to by early historians which claimed that it was possible to cross from Jersey to France across a plank was probably a forgery. The document has been mentioned in many histories from the 17th century onwards, sometimes accepted as fact, often derided as fiction. The actual identity and source of the document has never been revealed, perhaps because it never existed. However, many historical documents of this nature in the collection of the monastery at Mont St Michel have been proved to be forgeries