Environmental Anthropology

English Channel

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Beach at Normandy as it would appear to the German army prior to the Allied landing. @ C.Michael Hogan

The English Channel is that saline water body that connects the North Sea to the Celtic Sea. It is bounded on the north by England and on the south by France. This water body was first created several hundred thousand years ago when a ancient lake sufferred a cataclysmic lateral rupture that producued an immense and sudden flood that scoured and dissolved the isthmus connecting present day England with the European continent. Very early presence of Neanderthals is evident on one of the Channel Islands dating to one quarter of a million years before present.

caption English Channel. Source: University of Texas

The present English Channel took shape approximately 6000 BC, breaching all land bridging to the continent. The English coast is characterised by sandy bottoms and beaches, whereas the French coastline has many more rocky bottoms and hard outcrops, interspersed with some sandy beach shorelines.

Geologic origin

As early as the Pleistocene there was no sea present at the present day English Channel; in fact, the English Channel has only become a recognizable sea in more recent times: becoming inundated 450,000 and 180,000 years before present via two catastrophic glacial lake rupture events, in which a terrestrial ridge in the Doggerland region was broken through; this ridge, known as the Weald/Artois Anticline, had impounded a proglacial lake. One of the proofs of this flood event is the formation of east-west erosional grooves in the English Channel bedrock, a characteristic of extremely large prehistoric flood events. This phenomenology is also consistent with prevailing east west elongation of most of the islands within the English Channel. The flood events scoured away soft overburden of the surviving bedrock, which would have created a Pleistocene landform of an isthmus connecting present day England and continental Europe. It should be noted that the recent ice age would have produced such low sea levels that a smaller isthmus would have continued to connect England to continental Europe (at the eastern end of the English Channel) until about the start of the Holocene. These sequences also explain why the biological diversity is greater in present day England than on Ireland, where the sea separation occurred somewhat earlier, thus allowing time for fewer species to colonise Ireland after glacial retreat.

Geography

The western extent of the English Channel is generally accepted to be a straight line between Île Vierge in Brittany, France and Lands End, Cornwall, England. The eastern demarcation is a line running between Calais, France and Dover, England, which is also a virtual sill with a characteristic depth of only about 45 metres. An intermediate feature of note is the Bay of Seine, which is situated between Cherbourg and the mouth of the Seine at LeHavre in France. It is within this bay that the famed beaches of Normandy lie, where the Allied invasion in World War II turned the tide of war against the German aggression.

Hydrology and Circulation

caption Estuary along the fractal French coast.@ C.Michael Hogan

Mixing in the English Channel is driven by both tidal forces as well as winds. High tide occurs at Lands End approximately 6.5 hours earlier than at Dover, as an indication of tidal flow. The England side of the English Channel is more stratified compared to the French side which is considerably more efficently vertically mixed. These variations are influenced by coriolis forces which also cause tidal heights to be greater on the French side, with a peak spring tide in the Gulf of Saint Malo reaching an amplitude of eleven metres.

Tidal streams in the eastern English Channel and Channel Islands area is generally anti-clockwise, whilst the western entrance of the channel has clockwise tidal circulation wedded to the Celtic Sea. In terms of vertical distribution of tidal kinetic energy, the surface tidal current is typically about fifteen percent higher than than that of the Epipelagic zone water column; furthermore the benthic current measured at one metre above the channel bottom is generally about sixty percent of the surface current velocity.

There is a strong seasonality to English Channel temperatures and stratification. In May the heating cycle has begun and surface water temperatures are slightly above the winter lows, attaining a rather even distribution of ten to eleven degrees Celsius. By late August or early September, water temperatures have reached a maxium of about 16 degrees, and maxium stratification has been realised. By November, waters are strongly cooling and the vertical stratification has been almost entirely eroded.

Groundwater systems at the English periphery of the English Channel are dominated by characteristics of the Chalk formation; the Chalk is a layer of porous limestone laid down in the Upper Cretaceous period, which material is rich in fossils and calcium carbonate. The Chalk formations served as important groundwater recharge areas as early as the Late Pleistocene on the present day English Channel. Exposed areas of the Chalk continue to serve as chief recharge mechanisms in areas such as the South Downs. On the French side, there are significant Cenozoic formations punctuated by Jurassic outcrops.

Islands

caption Mont St. Michel island now connected by causeway. @ C.Michael Hogan

There are a number of islands within the English channel, including the Guernsey island complex and the Jersey island complex, both island groups not being part of the United Kingdom, but are possessions of the British Crown. The Jersey Island group consists of the main island of Jersey and smaller uninhabited islets and reefs such as Les Écréhous, Les Minquiers Les Pierres de Lecq and Les Dirouilles. The Guernsey island group includes Guernsey, Alderney, Herm, Sark and a number of lesser islands.

The Isle of Wight, associated with the English coast off of Hampshire, is part of the United Kingdom and England's largest island at 384 square kilometres; the Isle of Wight is England's only island which comprises an entire shire (or county).  The Isle of Wight is approximately three kilometres from England's mainland separated by a narrow strait known as the Solent. There are a few small islands immediately off the highly fractal French coastline, among which are Mont Saint Michel and Chausey; however, Mont Saint-Michel is arguably almost attached to the mainland and is only a true island at high tide. It should be noted that the the Isle of Man and Isles of Scilly near the southwest tip of Cornwall are actually in the Celtic Sea rather than the English Channel.

Ecology

In terms of primary productivity there are two algae blooms per year in the western English Channel: one in spring and another in August.

A remarkable transition occurred in the English Channel during the 1920s; the historically dominant Plymouth herring fishery of the western English Channel gave way to an expanded pilchard fishery for reasons not entirely understood. Possible attribution to the Plymouth herring fishery decline is given to overfishing, although alterations in algae blooms and phosphorus levels may also be drivers. There is a corresponding Downs herring fishery in the eastern English Channel.

More profound ecosystem changes followed the herring to pilchard transition. From 1930 until 1970 winter phosphorus levels in the English Channel declined, phytoplankton productivity sufferred a severe decline ant the dominant Arrow worm Sagitta elegans (usually associated with mixed Atlantic seawater) was replaced by Sagitta setosa, an Arrow worm associated historically with English Channel waters off of Plymouth. Macro-plankton declined by about a factor of four in this same period and many species disappeared entirely from the English Channel before 1970.

Other species historically fished in the English Channel include the European seabass (Dicentrarchus labrax), which may be in danger of being overfished.

Prehistory

caption Neolithic standing stones at Carnac, France. @ C.Michael Hogan

Since England was connected to continental Europe before the Holocene by a landbridge, the prehistory of England and the Channel Islands are intrinsically connected to that of the continent, particularly of present day France and the Low Countries, (since the most persistent landbridge was situated at northern coastal France). Neolithic peoples are evidenced in the archaeological records of the Channel Islands as well as southern England; specifically traces of human civilisation are found of humanoid presence in the Paleolithic era; as a specific notable example the caves at La Cotte de St Brelade are dated to have evidence of Neanderthal habitation circa 250,000 years before present.

As early as 3500 BC there is significant monumental architecture on Jersey in the form of Western Europe's largest passage grave complex at La Hougue Bie, which is an impressive drystone structure. There is further evidence of continuous habitation by early man on the Channel Islands continuing through the Iron Age and into Roman times.

Medieval to Modern History

While the English Channel posed a barrier to large scale military actions and migration, relatively little note occurred from Roman until Viking times, other than the couriering of missives and books; notable among the books transported were the ancient volumes saved from barbaric destruction removed from the continent to Ireland after the fall of the Roman Empire.

At 811 AD Charlemagne recognised the need to fortify the English Channel coastline of the Carolingian kingdom in order to defend against Viking invasions that had begun to plague England, Scotland and Ireland. These defences were partially successful, although Charlemagne's empire was militarily stretched thin, given the Arab invasions from the south occurring at the same time.

The year 1066 AD marked the last successful invasion of England. The Norman fleet, under leadership of William of Normandy, crossed the English Channel and landed at Pevensey, from which they advanced to meet the English army in the Battle of Hastings. The Norman victory led to installation of William as King of England, and the substantial influence of continental Europe upon the British Isles.

One of the most important naval battles in history was the English defeat of the Spanish Armada in 1588. The significant early battles of this naval conflict occurred in the English Channel as the Armada sought to execute an invasion of the English mainland by excorting a massive Spanish army accross from the Netherlands. Mainly through the strategic thinking of Vice Admiral Sir Francis Drake, the superior maneuverability of the English fleet was able to take advantage of the curious winds and tides of the English Channel and North Sea to deprive the Spanish of their rendezvous, and inflict damage on the Armada that would proove disabling on their continuing glight to Ireland.

The largest military event in the history of the English Channel was the Allied Invasion of Europe carried out across 80 kilometres of the Normandy coastline commencing June 6, 1944. The amphibious landings and coordinated aerial attacks were planned by General Frank Maxwell Andrews (Allied Commander in Europe until his death) and General Dwight D. Eisenhower. Enormous loss of life, the highest Allied casualties and troops being American, led to the turning point of World War II in Europe and the successful repulsion of the German army.

References

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  • D.H.Cushing. 1975. Marine ecology and fisheries. Cambridge University Press. 278 pages
  • W.M.Edmunds, C.J.Milne. 2001. Palaeowaters in coastal Europe: evolution of groundwater since the late Pleistocene. Geological Society of London. 332 pages
  • Sanjeev Gupta, Jenny S.Collier, Andy Palmer-Felgate & Graeme Potter. 2007. Catastrophic flooding origin of shelf valley systems in the English Channel. Nature 448 (7151)
  • Robert R.Marett. 1916. The Site, Fauna, and Industry of La Cotte de St. Brelade, Jersey.. Archaeologia. LXVII
  • Rosamond McKitterick. The New Cambridge medieval history, Volume 1. Cambridge University Press
  • G.H.Nash. 1997. Experiencing Space and Symmetry: The Use, Destruction and Abandonment of La Hougue Bie Neolithic Passage Grave, Jersey in G.H. Nash (ed.) Semiotics and Landscape: The Archaeology of Mind. Oxford: BAR International Series 661. 105-118.
  • John D.Reynolds. 2002. Handbook of fish biology and fisheries (Google eBook). Wiley-Blackwell. 432 pages
Glossary

Citation

Hogan, C. (2013). English Channel. Retrieved from http://www.eoearth.org/view/article/51cbedba7896bb431f693770

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