The English Channel (French: la Manche, Breton: Mor Breizh, Cornish: Mor Bretannek), often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about 560 km (350 mi) long and varies in width from 240 km (150 mi) at its widest to 34 km (21 mi) in the Strait of Dover. It is the smallest of the shallow seas around the continental shelf of Europe, covering an area of some 75,000 km2 (29,000 sq mi). The IHO defines the southwestern limit of the North Sea as "a line joining the Walde Lighthouse (France, 1∞55'E) and Leathercoat Point (England, 51∞10'N)". The Walde Lighthouse is 6 km east of Calais (50∞59?06?N 1∞55?00?E), and Leathercoat Point is at the north end of St Margaret's Bay, Kent (51∞10?00?N 1∞24?00?E). The Strait of Dover (French: Pas de Calais), at the Channel's eastern end is its narrowest point, while its widest point lies between Lyme Bay and the Gulf of Saint Malo near its midpoint. It is relatively shallow, with an average depth of about 120 m (390 ft) at its widest part, reducing to a depth of about 45 m (148 ft) between Dover and Calais. From there eastwards the adjoining North Sea continues to shallow to about 26 m (85 ft) in the Broad Fourteens where it lies over the watershed of the former land bridge between East Anglia and the Low Countries. It reaches a maximum depth of 180 m (590 ft) in the submerged valley of Hurds Deep, 48 km (30 mi) west-northwest of Guernsey. The eastern region along the French coast between Cherbourg and the mouth of the Seine river at Le Havre is frequently referred to as the Bay of the Seine (French: Baie de Seine). There are sev
ral major islands in the Channel, the most notable being the Isle of Wight off the English coast, and the Channel Islands, British Crown Dependencies off the coast of France. The Isles of Scilly off the far southwest coast of England are not generally counted as being in the Channel. The coastline, particularly on the French shore, is deeply indented; several small islands close to the coastline, including Chausey and Mont Saint-Michel, are within French jurisdiction. The Cotentin Peninsula in France juts out into the Channel, and the Isle of Wight creates a small parallel channel known as the Solent in English waters. The Celtic Sea is to the west of the Channel. The Channel is of geologically recent origins, having been dry land for most of the Pleistocene period. It is thought to have been created between 450,000 and 180,000 years ago by two catastrophic glacial lake outburst floods caused by the breaching of the WealdЦArtois anticline, a ridge that held back a large proglacial lake in the Doggerland region, now submerged under the North Sea. The flood would have lasted for several months, releasing as much as one million cubic metres of water per second. The cause of the breach is not known but may have been an earthquake or the build-up of water pressure in the lake. The flood carved a large bedrock-floored valley down the length of the Channel, leaving behind streamlined islands and longitudinal erosional grooves characteristic of catastrophic megaflood events. It destroyed the isthmus that connected Britain to continental Europe, although a land bridge across the southern North Sea would have existed intermittently at later times after periods of glaciation resulted in lower sea levels.