Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your North Sea shopping experience:

1. Compare - without doubt the biggest advantage that the North Sea offers shoppers today is the ability to compare thousands of North Sea at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a North Sea? Wrong! If the North Sea is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about North Sea then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling North Sea? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about North Sea and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your North Sea wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your North Sea then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the North Sea site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about North Sea, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your North Sea, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

{{Infobox Ocean| Ocean_name = North Sea| image_Ocean = North_Sea.jpg| caption_Ocean =| image_bathymetry =| caption_bathymetry=| location = Atlantic Ocean, [Ythan Estuary, Elbe, Weser, Ems (river), Rhine/Waal (river), Meuse River, Scheldt, River Spey, River Tay, Thames, Humber, River Tees, the River Wear and the River Tyne, [Denmark, Scotland, England, Germany, Netherlands, Belgium and France| length = 600 mi (970 km) {{Citation | last =Royal Belgian Institute of Natural Sciences | first = | author-link = | last2 = | first2 = | author2-link = | title =MUMM North Sea facts | date = | year =2002-2007 | url =http://www.mumm.ac.be/EN/NorthSea/facts.php | accessdate = July 19, 2007-->

| width = 350 mi (560 km)| area = 222,000 mi2 (575,000 km2)| depth = 308 ft (94 m){{Citation | last =OSPAR Commission, for the protection of the marine environment of the North-East Atlantic. | first = | author-link = | last2 = | first2 = | author2-link = | title =Geography, hydrography and climate | date = | year =2007 | url =http://www.ospar.org/eng/doc/pdfs | accessdate = July 19, 2007--> | max-depth = c.2,165 ft/660 m{{Citation | last =Answers Corporation | first = | author-link = | last2 = | first2 = | author2-link = | title =North Sea: Definition and Much More from Answers.com | date = | year =2007 | url =http://www.answers.com/topic/north-sea?cat=travel | accessdate = July 19, 2007-->

| volume = 94 000 km| residence_time =| salinity =| temperature_high =| temperature_low =| salinity =| shore =| islands =| cities =| trenches =| benches =| frozen =-->

The North Sea is marginal sea, epeiric sea of the Atlantic Ocean on the European continental shelf between Norway and Denmark in the east, Scotland and England in the west, and Germany, the Netherlands, Belgium and France in the south. The North Sea is over 600 miles long and 350 miles wide, and has an area of around 222,000 square miles. Many of the important rivers of Europe drain into the North Sea and it serves as the only drainage for the Baltic Sea as well, through the Skagerrak and the Kattegat, between Denmark, Norway, and Sweden. In the south, the North Sea connects with the rest of the Atlantic through the Strait of Dover into the English Channel and in the north through the Norwegian Sea. The North Sea has long been one of the important commercial highways of the world, as well as a source for valuable resources for border countries, but also a source of concern about the environmental effects of this economic bounty.

The North Sea averages about 100 m (325 ft) deep, but reaches down as deep as 700 m (2300 ft) and in some areas shallows can be a mere 15 m deep. The North Sea lies above the junction of three tectonic plates which can cause earthquakes and small tsunamis. However, the sea's coastal features are the result of glacier movements rather than tectonics. Deep fjords and sheer cliffs mark the coastline of the northern part of the North Sea whereas the southern coasts consist of sandy beaches and mudflats. These flatter areas are particularly susceptible to flooding especially as a result of storm tides. Elaborate systems of Dike (construction) have been constructed to protect coastal areas.

The development of European civilization have been heavily affected by the maritime traffic on the North Sea. The Roman Empires and the Vikings sought to extend their territory across the sea. Both the Hanseatic League and the Netherlands sought to dominate commerce on the North Sea and through it to access the markets of the world. Britain's development as a sea power depended heavily upon its dominance in the North Sea, where some of its rivals sought power, first the Netherlands and finally Germany and to a lesser extent Russia and the Scandinavian nations at various points along the way. Commercial enterprises, growing populations, and limited resources gave all the nations on the North Sea the desire to control or access it for their own commercial, military, and colonial ends.

Its importance has turned from the military to the economic. Traditional economic activity, such as fishing and shipping have continued to grow and other resources, such as fossil fuels and wind energy have been discovered and developed.

Naming The name of the North Sea originates from its relationship to the land of the Frisians. Frisia lies directly to the south of the North Sea, to the west of the Baltic Sea (Oostzee, the Baltic Sea), to the north of the former Zuiderzee (Zuiderzee, today's IJsselmeer) and the today reclaimed Middelzee (Middelzee). The name “North Sea” is attested in Middle High German and probably harks back to the name given by the Frisians, who settled on its south coast. Even the early Spanish name was Mar del Norte.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Common-place: Naming the Pacific | date = | year = | url =http://www.common-place.org/vol-05/no-02/peterson/index.shtml | accessdate = July 19, 2007-->

From the point of view of the German Hanseatic League of the Middle Ages, the sea to the east was the “East Sea” (Baltic Sea in German is literally the Ostsee), and the sea to the north, the North Sea. The spread of maps used by Hanseatic merchants, popularized this name throughout Europe. Other common names in use for long periods were Mare Frisia, and “Mare Frisicum“, “Oceanum“ or “Mare Germanicum“ as well as their English equivalents, Frisian Sea and German Ocean or Sea.

"German Sea" "The North Sea was known as the German Ocean until the early 20th C., when hostilities with Germany meant this name became politically unacceptable in Britain." (from the Latin Mare Germanicum) was commonly used in English language and other languages along with North Sea, until the early eighteenth century. By the late nineteenth century, Germanic Sea was a rare, scholarly usage.

Location For the most part, the sea lies on the European continental shelf. The only exception is a narrow area of the northern North Sea off Norway. The North Sea is bounded by Great Britain to the west and the northern and central European mainland to the east and south, including Norway, Denmark, Germany, the Netherlands, Belgium, and France.

In the south-west, the North Sea becomes the English Channel beyond the Straits of Dover. In the east it connects to the Baltic Sea via the Skagerrak and Kattegat. In the north it opens in a widening funnel shape to the Norwegian Sea, which lies in the very north-eastern part of the Atlantic.

Apart from the obvious boundaries formed by the coasts of the countries which border it, the North Sea is bounded by an imaginary line from Lindesnes, Norway to Hanstholm, Denmark running towards the Skagerrak. The northern limit towards the Atlantic is less well-defined. Traditionally, an imaginary line is taken to run from northern Scotland, by way of Shetland, to Ålesund in Norway. According to the Convention for the Protection of the Marine Environment of the North-East Atlantic{{Citation| last = OSPAR Commission | first = | author-link = | last2 = | first2 = | author2-link = | title =OSPAR / The OSPAR Convention | date =2004 - | year = | url =http://www.ospar.org/eng/html/1992-ospar-convention.htm | accessdate =July 24, 2007 -->of it runs further to the west and north from longitude 5° West and latitude 62° North, at the latitude of [Geirangerfjord in Norway.

The surface area of the North Sea is approx. 575,000 km2 (222,000 sq mi), with a volume of around 54,000 cubic meter (13,000 cu mi). This places the North Sea at the 13th largest sea.

Geology Geological history The Seabed of the North Sea forms two Sedimentary basin. The main northern one lies to the north of a ridge between Norfolk and Frisia, and had its origin in the Devonian. The southern basin, if not flooded, would drain towards the Strait of Dover and thence to the English Channel. This basin dates from the Carboniferous.

During the Devensian glacial, the most recent glaciation, much of the northern basin was covered by the ice sheet, and the remainder, including the southern basin, was tundra. However, during the Cromerian interglacial, there was a natural dam of chalk, the Weald-Artois Anticline."{{Citation| last =Invicta Media | first = | author-link = | last2 = | first2 = | author2-link = | title =Forming the Channel | date =30 March 2002; | year =1999-2002 | url =http://www.theotherside.co.uk/tm-heritage/background/channelform.htm | accessdate = July 25, 2007 --> Although the ridge probably collapsed during the [Kansan glaciation it still formed the highest part of the land bridge between continental Europe and Great Britain.{{cite news |first=Ian |last=Sample |authorlink= |coauthors= |title=Breach of ice age lake made Britain an island |url=http://www.guardian.co.uk/science/story/0,,2129662,00.html |work=The Guardian |publisher= |date= 19 July 2007|accessdate=2007-07-21 -->

The Storegga Slides were a series of underwater landslides, in which a piece of the Norwegian continental shelf slid into the Norwegian Sea. The immense landslips occurred between 8150 BC and 6000 BC, and caused a tsunami up to 20 m (65 ft) high that swept through the North Sea, having the greatest effect on Scotland and the Faeroe Islands.{{Cite web| author= Axel Bojanowski, | publisher= Spiegel Online | title =Tidal Waves in Europe? Study Sees North Sea Tsunami Risk | date = October 11, 2006 | year = | url =http://www.spiegel.de/international/0,1518,441819,00.html | accessdate = 2007-07-24-->

Plate tectonics The fault lines along the English Channel cause occasional earthquakes, which can result in damage to structures on land. The Central Grabens of the North Sea is an active area, as well as northwestern Europe's continental slope which is subject to landslides from earthquakes.{{Citation| last = Geology Shop | title =UK Earthquakes | date = | year = | url =http://www.geologyshop.co.uk/ukequakes.htm | accessdate = July 24, 2007--> Although not a site of major earthquakes or tsunamis, there are intraplate earthquakes which result in the uplifting of the continental crust causing landslides. The Dover Straits earthquake of 1580 is among the first recorded in the North Sea and caused extensive damage in both France and England both through its tremors and a tsunami. The largest earthquake ever recorded in the UK was the 1931 Dogger Bank earthquake, which measured 6.1 on the Richter Scale and caused a tsunami that flooded parts of the British coast. A more recent event along this fault caused the 2007 Kent earthquake

The North Sea is located at a triple junction of three continental plates formed during the Palaeozoic: Avalonia, Laurentia and Baltica.{{Cite journal| last = Lyngsie, S B | coauthors = Rasmussen, T M; Thybo, H | journal = Tectonophysics | volume = 413 | pages = 147–170 | title = Regional geological and tectonic structures of the North Sea area from potential field modelling | date = October 11, 2006 | year = 2006 | url = http://www.lyngsie.nu/Artikel-1.pdf | accessdate = 2007-07-24--> Baltica is now the eastern coastline and the Scandinavian countries; Avalonia consists of the southern and western North Sea coast along England, North Germany and France; and Laurentia marks the northern perimeter of the North Sea with the Atlantic Ocean.

Geological features The Norwegian trench is an oceanic trench in the North Sea off the southern coast of Norway. The trench marks the position of the subduction North Sea Plate descending beneath the Lithosphere Scandinavian Plate. The trench reaches from the Stad (peninsula) peninsula in Sogn og Fjordane to the Oslofjord. The trench is between 50 and 95 km (30-60 mi) wide and several hundred meters deep. Off the Rogaland coast it is 250 - 300 m (820-980 ft) deep, and at its deepest point, off Arendal, it reaches 700 m (2300 ft) deep as compared to the average depth of the North Sea, about 100 m (325 ft).{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Maptech : Topo Maps Charts Navigation Software GPS and Online MapServer | date = | year = | url =http://64.233.179.104/translate_c?hl=en&langpair=fr%7Cen&u=http://mapserver.maptech.com/homepage/index.cfm%3Flat%3D58.011403248490396%26lon%3D9.430819575677283%26scale%3D1500000%26zoom%3D50%26type%3D0%26icon%3D0%26width%3D498%26height%3D498%26searchscope%3Ddom%26CFID%3D1719760%26CFTOKEN%3D33728793%26scriptfile%3Dhttp://mapserver.maptech.com/homepage/index.cfm%26latlontype%3DDMS | accessdate = July 20, 2007 -->

To the East of Great Britain, the vast moraine plate of the Dogger Bank rises up to 15 to 30 m deep{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Maptech : Topo Maps Charts Navigation Software GPS and Online MapServer | date = | year = | url =http://mapserver.maptech.com/homepage/index.cfm?lat=54.74456315454079&lon=2.3527509224287115&scale=1500000&zoom=50&type=0&icon=0&width=498&height=498&searchscope=dom&CFID=1719760&CFTOKEN=33728793&scriptfile=http://mapserver.maptech.com/homepage/index.cfm&latlontype=DMS | accessdate = July 20, 2007 -->

The Silver Pit is a valley-like depression 45 km (27 mi) east of Spurn Head in England that has been recognized for hundreds of years by fishermen. Nearby is the Silverpit crater, a controversial structure, which may be a geological structure or may be an impact crater.

"The Long Forties" denotes an area of the northern North Sea that is fairly consistently forty fathoms (73 m) deep (thus, on a nautical chart with depth shown in fathoms, a long area with many "40" notations). It is located between the northeast coast of Scotland and the southwest coast of Norway, centered about 57°N 0°30′E.

The Broad Fourteens are an area of the southern North Sea that is fairly consistently fourteen fathoms (26 m) deep (thus a broad area with many "14" notations). It is located off the coast of the Netherlands and south of the Dogger Bank, roughly between longitude 3°E and 4°30′E and latitude 52°30′N and 53°30′N.

The North Sea is home to a number of sizable islands and archipelagos, including the Shetland, Orkney, and Frisian Islands islands.

See more: List of the largest islands of the North Sea

Hydrology Basic data The salinity of the water is dependent on place and time of year but is generally in the range of 15 to 25 parts-per notation (ppt) around river mouths and up to 32 to 35 ppt in the northern North Sea, still generally lower than North Atlantic salinity, which averages around 35 ppt.

The water temperature varies depending on the influence of the Atlantic currents, water depth, and time of year, reaching 25 °C (77 °F) in summer and 10 °C (50 °F) in winter, though Arctic currents can be colder. In the deeper northern North Sea the water remains a nearly constant 10 °C (50 °F) year round because of water exchange with the Atlantic. The greatest temperature variations are found on the very shallow Wadden Sea coast, where ice can form in very cold winters.

The exchange of salt water between the North Sea and Atlantic occurs through the English Channel, as well as in the northern North Sea along the Scottish coast and through the Norwegian Sea. The North Sea receives fresh water not only from its influent rivers but also from the Baltic rivers which are connected to the North Sea via the Skagerrak. The North Sea rivers drain a land area of 841,500 km² (324,905 sq mi) and supply 296-354 km³ (71-85 cu mi) of fresh water annually. The Baltic rivers drain almost twice as large an area (1,650,000 km², 637,068 sq mi) and contribute 470 km³ (113 cu mi) of fresh water annually.

Around 160 million people live in the catchment area of the rivers that flow into the North Sea. These rivers drain a large part of Western Europe: a quarter of France, three quarters of Germany, nearly all of Switzerland and Great Britain, half of Jutland, the entirety of the Netherlands and Belgium, the southern part of Norway, and a small part of Austria. This area contains the world's greatest concentration of industry: 15% of the planet's industrial production takes place in the catchment area of the North Sea.

Water circulation Along the Danish and Norwegian coasts the water flows back into the Atlantic via the Norwegian Current. This moves at a depth of some 50 to 100 m (165-330 ft). This current has a relatively low salinity due to the brackish water of the Baltic and the fresh water contributed by the rivers and the fjords. A part of the warmer water flowing in from the Atlantic turns northwards again along the Current and results in a warmer stream through the colder waters. In winter the Norwegian Current has a temperature of 2 to 5 °C (36°-41 °F) and the salinity is below 34.8 ppt. The Atlantic water in the North Sea, divided from the Current by a front, is generally over 6 °C (43 °F) with a salinity of 35 ppt.

The water in the North Sea is completely exchanged in between one and two years. Within the Sea, fronts based on temperature, salinity, nutrients and pollution can be clearly identified; they are more clearly defined in summer than in winter. Large fronts are the Frisian Front, which divides water coming from the Atlantic from water originating in the English Channel, and the Danish Front, which divides coastal waters from water in the central North Sea. The inflow of water from large rivers mixes very slowly with North Sea water. Water from the Rhine and Elbe, for example, can still be clearly differentiated from sea water off the northwest coast of Denmark.

{] / Meuse River || Netherlands || 2,524 || 89,134|-|Elbe ] || Norway || 603 || 21,295|-|IJsselmeer ] || Germany || 358 || 12,643|-|Skjern Å ] (includes River Tay and River Earn) ] (includes River Spey and River Ness) ] || Belgium/Netherlands || 126 || 4450|-|Humber ] || Scotland || 112 || 3955|-|Ems (river) || Germany || 88 || 3108|-|River Tweed || England || 85 || 3002|-|Thames || England || 76 || 2684|-|}

Tides The tides are caused by the tide wave from the North Atlantic, as the North Sea itself is too small and too flat to have its own tides. Ebb and flow alternate in a cycle of 12.5 hours. The tide wave, owing to the Coriolis effect, flows around Scotland and then in counter-clockwise direction along the English coast and reaches the German Bight some 12 hours after arriving in Scotland. In so doing, it runs around three amphidromic points: a central point lies shortly before the Straits of Dover. It is formed by the tide wave which is transported across the English Channel. It influences the tides in the narrow area of De Hoofden in the Southern Bight between southern England and the Netherlands. The other amphidromic system consists of two points close to each other which form a tide wave. The two other points just off the coast of southern Norway and lying on a line between southern Denmark and the West Frisian Islands form one single area around which the tides flow. Its central point lies on the Jutland Bank at 55° 25' N, 5° 15' E.

As a result, the tidal range in southern Norway is less than half a metre (1.5 ft), but increases the further any given coast lies from the amphidromic point. Shallow coasts and the funnel effect of narrow straits increase the tidal range. The tidal range is at its greatest at The Wash on the English coast, where it reaches 6.80 m (22 ft). In shallow water areas the real tidal range is strongly influenced by other factors such as the position of the coast and the wind at any given moment or the action of storms. In river estuaries, high water levels can considerably amplify the effect of high tide.

Coasts The western coasts of the North Sea are jagged, as they were stripped by glaciers during the ice ages. The coastlines along the southernmost part are soft, covered with the remains of deposited glacials which were left directly by the ice or have been redeposited by the sea. The Norwegian mountains plunge into the sea, giving birth, north of Stavanger, to deep fjords and archipelagoes. South of Stavanger, the coast softens, the islands become fewer. The Eastern Scottish coast is similar, though less marked than Norway. Starting from Flamborough Head in the northeast of England, the cliffs become lower and are composed of less resistant moraine, which erodes more easily, so that the coasts have more rounded contours. In Holland, Belgium and in the East of England (East Anglia) the littoral is low and marshy. The East coast and south-east of the North Sea (Wadden Sea) have coastlines that are mainly sandy and straight owing to longshore currents, in particular in Belgium and in Denmark.:fr:Mer du Nord

Northern fjords, skerries, and cliffs , NorwayThe northern North Sea coasts bear the impression of the enormous glaciers which covered them during the Ice Ages and created a split, craggy coastal landscape. Fjords arose by the action of glaciers, which dragged their way through them from the highlands, cutting and scraping deep trenches in the land. During the subsequent rise in sea level, they filled with water. They very often display steep coastlines and are extremely deep for the North Sea. Fjords are particularly common on the coast of Norway.{{Citation| last =EMECS International Center for the Environmental Management of Enclosed Coastal Seas | first =Guidebook | author-link = | last2 = | first2 = | author2-link = | title =5 North Sea | date = | year = | url =http://www.emecs.or.jp/guidebook/eng/pdf/05north.pdf | accessdate = July 24, 2007-->

Firths are similar to fjords, but are generally shallower with broader bays in which small islands may be found. The glaciers that formed them influenced the land over a wider area and scraped away larger areas. Firths are to be found mostly on the Scottish and northern English coasts. Individual islands in the firths, or islands and the coast, are often joined up by sandbars or spits made up of sand deposits known as “tombolos”.{{Citation| last =Home > Earth Heritage > Geological Conservation Review (GCR) > GCR Database | first = | author-link = | last2 = | first2 = | author2-link = | title =Coastal Geomorphology of Wales - GCR block | date = | year = | url =http://www.jncc.gov.uk/earthheritage/gcrdb/gcrblock.asp?block=24 | accessdate = July 24, 2007-->

Towards the south the firths give way to a cliff coast, which were formed above all from the moraines of Ice Age glaciers.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title = Development of the coastline | date = | year = | url =http://www.eastriding.gov.uk/aspirelinks/coastal/1development.pdf | accessdate = July 24, 2007-->The horizontal impact of waves on the North Sea coast gives rise to eroded coasts; the eroded material is an important source of sediment for the mudflats on the other side of the North Sea.{{Citation | last =CE3A8SMJGeologyforEngineers | first = | author-link = | last2 = | first2 = | author2-link = | title = Coasts: Geomorphology and Management | date = | year = | url =http://www.tcd.ie/Geology/MAIN-PAGE/CE3A8/coast.pdf | accessdate = July 24, 2007--> The cliff landscape is interrupted by large estuary with their corresponding mud and marshy flats disrupt, notably the Humber and the Thames, in southern England.

In southern Norway, as well as on the Swedish Skagerrak coast, skerry are to be found.{{Citation| last = Drömresan | first =Micke W | author-link = | last2 = | first2 = | author2-link = | title =Sailing in Sweden and the Baltic | date = | year =1997-2005 | url =http://www.dromresan.com/english/index.shtml | accessdate = July 24, 2007 --> Formed by similar action to that which created the fjords and firths, the glaciers in these places affected the land to an even greater extent, so that large areas were carried away. The coastal brim (''Strandflaten''), which is found especially in southern Norway, is a gently sloping lowland area between the sea and the mountains. It consists of plates of [bedrock, and often extends for kilometers, reaching under the sea, at a depth of only a few meters.

Southern shoals and mudflats The shallow-water coasts of the southern and eastern coast up to Denmark were formed by Ice Age activity, but their particular shape is determined for the most part by the sea and sediment deposits.{{Cite web| publisher= Natural England | title =Bridlington to Skegness: Habitat: Earth heritage | date = | year = | url =http://www.english-nature.org.uk/science/natural/NA_HAbDetails.asp?Name=Bridlington+to+Skegness&N=101&H=65 | accessdate = 2007-07-24--> The whole of the coastal zone is shallow; the tides flood large areas and uncover them again, constantly depositing sediments. In the micro tidal area (a tidal range of up to 1.35 m (4.43 ft)), such as on the Dutch or Danish coasts,{{Citation| last = Drs. Teunis Louters | title =Impact of Sea Level Rise on Dutch Wetlands: Morphological and ecological consequences over the next 50 -100 years | date = | year =1996 | url =http://www.netcoast.nl/publications/sealevel.doc | accessdate = July 24, 2007 --> barrier beaches with dunes are formed. In the mesotidal area (a tidal range of between 1.35 and 2.90 m (4.43-9.5 ft)), barrier islands are formed; in the macrotidal area (above 2.90 m (9.5 ft) tidal range), such as at the mouth of the Elbe, underwater sandbanks form.

The Dutch West Frisian Islands and the German East Frisian Islands are barrier islands. They arose along the breakers’ edge where the water surge piled up sediment, and behind which sediment was carried away by the breaking waves. Over time, sandplates arose, which finally were only covered by infrequent storm floods. Once plants began to colonize the sandbanks the land began to stabilise.{{Cite web| publisher= WorldAtlas.com | title =North Frisian Islands | date = | year =2007 | url =http://worldatlas.com/webimage/countrys/europe/denorthfrisian.htm | accessdate = 2007-07-24-->

Even though today they are established islands, some of them continue to be in motion. On the East Frisian Island of Juist for example, since the year 1650 there are five different proven sites for the church, as the spot for rebuilding the church had to keep pace with the ever-moving island. At times, Juist even consisted of two islands, which eventually grew back together. The neighboring island of Wangerooge in the last 300 years has moved a distance equivalent to its own length to the east, its church tower, destroyed at the outbreak of WW1 apparently moving from east to west.{{Cite web], on the other hand, arose from the remains of old Geestland islands, where the land was partially removed by storm floods and water action and then separated from the mainland. They are therefore often higher and their cores are less exposed to changes than the islands to the south. Beyond the core, however, the same processes are at work, particularly evident on Sylt, where in the south of the island, a break threatens, whilst the harbor at List (village) silts up.{{Citation| last = Ahrendt | first =Kai | author-link = | last2 = | first2 = | author2-link = | title =Expected Effects of Climatic Change on a Barrier Island - Case Study Sylt Island/German Bight | date = | year = | url =http://www.iczm.de/sylt.pdf | accessdate = July 24, 2007 --> The Danish Wadden Sea Islands, the next in the chain to the north, arose from sandbanks. Right up into the twentieth century, the silting up of the islands was a serious problem. To protect the islands, small woods were planted.On the southeastern coast there are several broad estuaries, such as the Meuse, Rhine, Weser, Elbe and Eider.

The Southern Bight has been especially changed by land reclamation, as the Dutch have been especially active. The largest project of this type was the diking and reclamation of the IJsselmeer.The Wadden Sea stretches between Esbjerg, Denmark in the north and Den Helder, Netherlands in the west. This landscape is heavily influenced by the tides and important sections of it have been declared a National Park. The island of Helgoland is an exception, as it was not formed by sediment deposition; in fact it is considerably older and is composed of Early Triassic sandstone.

Storm tides , LondonStorm tides threaten in particular the coasts of the Netherlands, Belgium, Germany, and Denmark. These coasts are quite flat, so even a relatively small increase in the water levels is sufficient to put large stretches of land under water. Storms from the west are especially strong, so the most dangerous places are on the south-east coast. Over the years, floods caused by storm tides have cost hundreds of thousands of lives and have significantly helped to shape the coast. Until early modern times, the number of victims from a single storm tide could be in the tens of thousands, even exceeding a hundred thousand, though to what extent these historically-reported casualties are accurate can only be estimated with difficulty.

The first recorded storm tide flood was the Julianenflut, on February 17, 1164. In its wake the Jadebusen began to form. Ancient records tell also of the First Marcellus Flood, which struck West Friesland (region) 1219. A storm tide in 1228 is recorded to have killed more than 100,000 people. The Second Marcellus Flood also known as the Grote Mandrenke in 1362 hit the entire southern coast of the North Sea. Chronicles of the time again record more than 100,000 deaths as large parts of the coast were lost permanently to the sea, including the now legendary town of Rungholt (see Lost city). The Strand (island) emerged from the remainders. During the Burchardi flood in 1634 the Strand was destroyed. Limfjord was first connected with the North Sea on February 3, 1825 when a flood pierced an opening. In 1862, another flood pierced another opening, the Thyborøn Channel, through the remainder of Agger Tange.

In the twentieth century the North Sea flood of 1953 flooded several nations' coasts and cost more than 2000 lives.{{Citation| last =Investigating Rivers | title =Coastal Flooding: The great flood of 1953 - A case study | date = | year = | url =http://www.naturegrid.org.uk/rivers/gt%20stour%20case%20study-pages/fld-cstl.html | accessdate = July 24, 2007 --> 315 citizens of Hamburg died in the North Sea flood of 1962. The "Century Flood" of 1976 and the "North Frisian Flood" of 1981 brought the highest water levels measured to date on the North Sea coast, but because of the dike (construction) built and improved after the flood of 1962, these led only to property damage.{{Cite web| author =home weather-uk | title = press pack Ready-prepared articles on rainstorms, deluges, and floods | date = | year = | url =http://www.weather-uk.com/press/flood.html | accessdate = 2007-07-24-->

Coastal preservation (Closure-dike) is a major dam in the Netherlands., North Sea Protection Works or Delta Works.The southern coastal areas were originally amphibious. The land included countless islands and islets which had been divided by rivers, streams, and wetlands and areas of dry land were regularly flooded. In areas especially vulnerable to storm tides, people settled first on natural areas of high ground such as Spit (landform) and Geestland. As early as 500 BC people were constructing artificial dwelling hills several meters high. It was only around the beginning of the High Middle Ages in 1200 that inhabitants began to connect single ring dikes into a dike line along the entire coast, thereby turning amphibious regions between the land and the sea into permanent solid ground.

The modern form of the dikes began to take form in the 17th and 18th centuries, built by private enterprises in the Netherlands. The Dutch dike builders exported their designs to other North Sea regions. The North Sea Floods of 1953 and 1962 were impetus for further raising of the dikes as well as the shortening of the dike line through land reclamation and river weirs so as to present as little surface area as possible to the punishment of the sea and the storms.{{Citation| last = Compare Infobase Limited. | first = | author-link = | last2 = | first2 = | author2-link = | title =North Sea Protection Works - Seven Modern Wonders of World | date =2006-2007 | year = | url =http://www.allwondersoftheworld.com/seven-modern-wonders/north-sea-protection-works.html | accessdate = July 24, 2007 --> Currently, 27% of the Netherlands is below sea level protected by dikes, dunes, and beach flats.{{Citation | last =About, Inc., A part of The New York Times Company. | first = | author-link = | last2 = | first2 = | author2-link = | title =Dykes of the Netherlands | date = January 30 | year = ©2007 | url =http://geography.about.com/od/specificplacesofinterest/a/dykes.htm | accessdate =July 19, 2007 -->

Coastal preservation today consists of several levels. The dike slope reduces the energy of the incoming sea, so that the dike itself does not receive the full impact. Dikes that lie directly on the sea are especially reinforced. The dikes have, over the years, been repeatedly raised, sometimes up to 10 m (32 feet) and have become flatter in order to better reduce the erosion of the waves. Modern dikes are up to 100 m (328 ft) across. Behind the dike there runs an access road and generally a thinly inhabited area. In many places another dike follows after several kilometers.

Where the dunes are sufficient to protect the land behind them from the sea, these dunes are planted with beach grass to protect them from erosion by wind, water, and foot traffic.{{Citation| last =Pat Gowen NSAG | first =NSAG | author-link = | last2 = | first2 = | author2-link = | title =The North Sea Action Group on Britains new EA Flood Plain Maps | date =31 December | year = 2000 | url =http://members.aol.com/ruraleye/fpmap.htm | accessdate = July 24, 2007 --> See also:

• Flood control in the Netherlands
• Zuiderzee Works
• Delta Works
• Thames barrier
• Afsluitdijk

History Roman occupation The Romans started exploring the North Sea starting 12 BC, with expeditions led by Nero Claudius Drusus and Tiberius. They conquered indigenous tribes and by 5 BC progressed to the river Elbe. Pliny the Elder describes Roman sailors going through Helgoland and as far as the northeast coast of Denmark.{{Citation| last = By Redbad | first = | author-link = | last2 = | first2 = | author2-link = | title =HISTORY OF THE FRISIAN FOLK Permission granted for publication on Boudicca's Bard - Part One - (1750 B.C. - 785 A.D.) Origins of the Frisians (1750 B.C. - 700 B.C.) | date = | year = | url =http://www.boudicca.de/frisian1.htm | accessdate = July 24, 2007 --> Following preliminary military actions by Julius Caesar in 55 and 54 BC and [Aulus Plautius, Britain was formally invaded and occupied starting in 43 AD, establishing trade across the Channel. The [Classis Britannica sailed right round mainland Britain before Roman rule ended in [.

In the power vacuum left by the retreating Romans, the Germanic Angles, Saxons, and Jutes began the next great migration across the North Sea. They had been used as mercenaries in Britain by the Romans. Many people from these tribes migrated across the North Sea during the Migration Period, conquering and perhaps displacing the native Celtic populations.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Germany The migration period | date = | year = | url =http://www.britannica.com/eb/article-58084/Germany | accessdate = July 24, 2007-->

Around the seventh century a wave of Frisian migrants moved to several islands in the North Sea, and a second wave moved to what is now Nordfriesland in northern Germany and South Jutland in southern Denmark in the 11th century.

Viking expansion The attack on Lindisfarne in 793 is generally considered the beginning of the Viking Age. For the next 250 years the Scandinavian raiders of Norway, Sweden, and Denmark dominated the North Sea with their superior longships, raiding monasteries, towns and fortresses along the coast and along the rivers that ran inland. According to the Anglo-Saxon Chronicle they began to settle in Britain in 851. They continued to settle in the British Isles and the continent until around 1050.{{Citation| last =Nick Attwood MA | first = | author-link = | last2 = | first2 = | author2-link = | title =The Holy Island of Lindisfarne - The Viking Attack | date = | year = | url =http://www.lindisfarne.org.uk/793/index.htm | accessdate = July 24, 2007-->

Alfred the Great, who is counted as the first English king, was the first to mount significant opposition to the Vikings eventually relegating them to the Danelaw and carving out his own kingdom. Harthacanute of Denmark and England was the last Viking king to rule over a territory spanning the North Sea as after his death the kingdom broke apart.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =British Kings and Queens - Historical Timeline | date = | year = | url =http://www.britroyals.com/timeline.asp | accessdate = July 24, 2007-->

With the rise of William the Conqueror the North Sea began to lose some of its importance. The new order oriented most of England and Scandinavia's trade south, toward the Mediterranean and the Orient. The Baltic Sea became increasingly important for northern Germany and Scandinavia as well as the powerful Hanseatic League began to rise.

Hanseatic League Though the Hanseatic League was centered in the Baltic, it also had important Kontors on the North Sea, including Bergen, the Steelyard in London, and Bruges.{{Citation| last =David K. Schreur. | first = | author-link = | last2 = | first2 = | author2-link = | title =The Hanseatic League | date = | year = | url =http://members.bellatlantic.net/~baronfum/hansa.html | accessdate = July 24, 2007-->

The rise of Bruges as a center of trade and a corresponding revival of the North Sea economic importance began in 1134 when a storm tide created a deeper waterway to the city allowing the entry of large ships to port. A lively trade sprang up between Bruges and London, mostly in textiles. Bruges became the end point of the Hanseatic East-West trade line that began in Novgorod and was very important for maritime connections between France, Spain, Italy, and the Netherlands and the Hanseatic regions of Northern Europe.

in 1441 the Hanseatic League was forced to recognize the equality of the Netherlands as Antwerp had risen as an economic power and tied itself to Denmark. After the so-called Count's Feud, a war of succession in Denmark, the Dutch were able to encroach upon the League's monopoly on Baltic trade and the reign of the Hanseatic League was at an end as the Netherlands became the center of the Northern European economy.

The Netherlands as a world economic power

In the 16th century, the Netherlands became the preeminent economic power in the world. For the Dutch merchant marine the North Sea served more as a starting point for their oceanic voyages. It had become the gateway and crucial outlet allowing Dutch merchants direct access to world markets.{{Citation| last =Donald J. Harreld, Brigham Young University | first = | author-link = | last2 = | first2 = | author2-link = | title =EH.Net Encyclopedia: Dutch Economy in the "Golden Age" (16th-17th Centuries) | date = | year = | url =http://eh.net/encyclopedia/article/Harreld.Dutch | accessdate = July 24, 2007-->

During the Eighty Years War, the Dutch began a heavily invested worldwide trade - hunting whales around Svalbard, trading spices from India and Indonesia, founding colonies in Brazil, South Africa, North America (New Netherlands), and the Caribbean. The empire, which they accumulated through trade, led to the Dutch Golden Age in the 17th century.

In 1651 England passed the Navigation Acts, which damaged Dutch trade interests. The disagreements concerning the Acts led to the First Anglo–Dutch War, which lasted from 1652-1654 and ended in the Treaty of Westminster (1654), whereby the Dutch were forced to recognize the acts. of 1666 by Willem vand de VeldeIn 1665 the English declared war on the Dutch once again, beginning the Second Anglo-Dutch War. With the support of the French, who, between the war, had marched into the Spanish Netherlands--present day Belgium, the Dutch gained the upper hand. In 1667, the English and the Dutch signed a peace treaty, the Treaty of Breda (1667) after the Dutch Admiral Michiel de Ruyter destroyed a large part of the British fleet in the Raid on the Medway. The peace dictated that the English would take over administration of Dutch possessions in North America (present day New York City) while the Dutch would get Suriname from the English and got to adjust the Navigation Acts to their benefit.

1672 is known in the Netherlands as "Rampjaar," the year of disaster. England declared war on the Netherlands once again, beginning the Third Anglo-Dutch War, and were quickly followed by France, the Prince-Bishopric of Münster, and the Archbishopric of Cologne in an alliance against the Dutch. The three continental allies marched into the Netherlands while the landing of English troops along the coast could only be briefly held up.{{Citation| last =David Ormrod, University of Kent | first = | author-link = | last2 = | first2 = | author2-link = | title =The North Sea as a core region in the early modern world: the shift from Amsterdam to London | date = | year = | url =http://www.helsinki.fi/iehc2006/papers1/Ormrod.pdf | accessdate = July 24, 2007-->

Britain: naval superpower England's climb to the pre-eminent sea power of the world began in 1588 as the attempted invasion of the Spanish Armada was defeated by the combination of outstanding naval tactics by the English under command of Sir Francis Drake and the breaking of the bad weather. The strengthened English Navy waged several wars with their neighbors across the North Sea and by the end of the 17th century had erased the Dutch's previously world-spanning empire.{{Citation| last =britishbattles.com | first = | author-link = | last2 = | first2 = | author2-link = | title =The Spanish Armada : Sir Francis Drake | date = | year =2007 | url =http://www.britishbattles.com/spanish-war/spanish-armada.htm | accessdate = July 24, 2007-->

The building of the British Empire as a domain on which the sun never set was possible only because the British navy exercised unquestioned control over the seas around Europe, especially the North Sea. The only significant challenge to British domination of the seas came during the Napoleonic wars. The Battle of Copenhagen took place in the Kattegat and ended the League of Armed Neutrality, a union of lesser naval powers including Denmark-Norway, Russia, and Prussia, which had united to protect neutral shipping against the British. The Battle of Trafalgar took place off the coast of Spain against a combined French and Spanish fleet and was won by Admiral Horatio Nelson, ending Napoleon plans to invade Britain and securing British dominance of the seas for more than another century.

The Dogger Bank incident in 1904 during the Russo-Japanese War was an attack by Russian naval vessels on British fishing boats mistaken for ships of the Japanese navy. The Russian sailors, on edge due to false reports of Japanese torpedo boats, also fired upon each other in the confusion. The incident resulted in the deaths of 3 British fishermen, a Russian sailor, and a priest aboard one of the Russian ships. The incident, also called "The Russian Outrage," caused a diplomatic crisis between Great Britain--which had an Anglo-Japanese Alliance with Japan at the time--and Russia. The crisis was defused after the Russian fleet was crushed by the Japanese and the Russian government paid compensation to the fishermen.

First World War sinks in the Battle of Dogger Bank on 25 January 1915. During the First World War, Great Britain's Grand Fleet and Germany's Kaiserliche Marine faced each other on North Sea.

The North Sea was the main theater of the war for surface action. The British Grand Fleet took position against the German High Seas Fleet. Britain's larger fleet could maintain a blockade of Germany, cutting it off from overseas trade and resources. Germany's fleet remained mostly in harbor behind their screen of mines, occasionally attempting to lure the British fleet into battle in the hopes of weakening them enough to break the blockade or allow the High Seas Fleet to attack British shipping and trade. Britain strove to maintain the blockade and, if possible, to damage the German fleet enough that British ships could be used elsewhere.

In general, Britain, though not always tactically successful, was able to maintain the blockade and keep the High Seas Fleet in port, although the High Seas Fleet remained a threat that kept the vast majority of Britain's capital ships in the North Sea.

The set-piece battles and maneuvering have drawn historians' attention but it was the blockade of German commerce through the North Sea, which ultimately starved the German people and industries into seeking the Armistice with Germany (Compiègne).

See also: Naval warfare of World War I#Theaters

Second World War The Second World War was, in terms of naval warfare, again mostly a submarine war on the German side. However, this time the main action was not in the North Sea but rather the Atlantic. Also different from the first war, the North Sea was no longer the exclusive territory of the Allies. Rather, it was, above all in the first years of the war, the stage for an intensive coastal war, featuring mainly small vessels like submarines, Minesweeper (ship), and Fast Attack Craft.{{Citation| last = Campaigns of World War II | first = Naval History Homepage | author-link = | last2 = | first2 = | author2-link = | title =Atlantic, WW2, U-boats, convoys, OA, OB, SL, HX, HG, Halifax, RCN ... | date = | year = | url =http://www.naval-history.net/WW2CampaignsStartEurope.htm | accessdate = July 24, 2007--> However, despite early successes, which brought about a supply crisis in Britain, the Germans did not succeed in breaking the British resistance. Like in the first war, the allies soon controlled the seas, {{Infobox Ocean| Ocean_name = North Sea| image_Ocean = North_Sea.jpg| caption_Ocean =| image_bathymetry =| caption_bathymetry=| location = Atlantic Ocean, [Ythan Estuary, Elbe, Weser, Ems (river), Rhine/Waal (river), Meuse River, Scheldt, River Spey, River Tay, Thames, Humber, River Tees, the River Wear and the River Tyne, [Denmark, Scotland, England, Germany, Netherlands, Belgium and France| length = 600 mi (970 km) {{Citation | last =Royal Belgian Institute of Natural Sciences | first = | author-link = | last2 = | first2 = | author2-link = | title =MUMM North Sea facts | date = | year =2002-2007 | url =http://www.mumm.ac.be/EN/NorthSea/facts.php | accessdate = July 19, 2007-->

| width = 350 mi (560 km)| area = 222,000 mi2 (575,000 km2)| depth = 308 ft (94 m){{Citation | last =OSPAR Commission, for the protection of the marine environment of the North-East Atlantic. | first = | author-link = | last2 = | first2 = | author2-link = | title =Geography, hydrography and climate | date = | year =2007 | url =http://www.ospar.org/eng/doc/pdfs | accessdate = July 19, 2007--> | max-depth = c.2,165 ft/660 m{{Citation | last =Answers Corporation | first = | author-link = | last2 = | first2 = | author2-link = | title =North Sea: Definition and Much More from Answers.com | date = | year =2007 | url =http://www.answers.com/topic/north-sea?cat=travel | accessdate = July 19, 2007-->

| volume = 94 000 km| residence_time =| salinity =| temperature_high =| temperature_low =| salinity =| shore =| islands =| cities =| trenches =| benches =| frozen =-->

The North Sea is marginal sea, epeiric sea of the Atlantic Ocean on the European continental shelf between Norway and Denmark in the east, Scotland and England in the west, and Germany, the Netherlands, Belgium and France in the south. The North Sea is over 600 miles long and 350 miles wide, and has an area of around 222,000 square miles. Many of the important rivers of Europe drain into the North Sea and it serves as the only drainage for the Baltic Sea as well, through the Skagerrak and the Kattegat, between Denmark, Norway, and Sweden. In the south, the North Sea connects with the rest of the Atlantic through the Strait of Dover into the English Channel and in the north through the Norwegian Sea. The North Sea has long been one of the important commercial highways of the world, as well as a source for valuable resources for border countries, but also a source of concern about the environmental effects of this economic bounty.

The North Sea averages about 100 m (325 ft) deep, but reaches down as deep as 700 m (2300 ft) and in some areas shallows can be a mere 15 m deep. The North Sea lies above the junction of three tectonic plates which can cause earthquakes and small tsunamis. However, the sea's coastal features are the result of glacier movements rather than tectonics. Deep fjords and sheer cliffs mark the coastline of the northern part of the North Sea whereas the southern coasts consist of sandy beaches and mudflats. These flatter areas are particularly susceptible to flooding especially as a result of storm tides. Elaborate systems of Dike (construction) have been constructed to protect coastal areas.

The development of European civilization have been heavily affected by the maritime traffic on the North Sea. The Roman Empires and the Vikings sought to extend their territory across the sea. Both the Hanseatic League and the Netherlands sought to dominate commerce on the North Sea and through it to access the markets of the world. Britain's development as a sea power depended heavily upon its dominance in the North Sea, where some of its rivals sought power, first the Netherlands and finally Germany and to a lesser extent Russia and the Scandinavian nations at various points along the way. Commercial enterprises, growing populations, and limited resources gave all the nations on the North Sea the desire to control or access it for their own commercial, military, and colonial ends.

Its importance has turned from the military to the economic. Traditional economic activity, such as fishing and shipping have continued to grow and other resources, such as fossil fuels and wind energy have been discovered and developed.

Naming The name of the North Sea originates from its relationship to the land of the Frisians. Frisia lies directly to the south of the North Sea, to the west of the Baltic Sea (Oostzee, the Baltic Sea), to the north of the former Zuiderzee (Zuiderzee, today's IJsselmeer) and the today reclaimed Middelzee (Middelzee). The name “North Sea” is attested in Middle High German and probably harks back to the name given by the Frisians, who settled on its south coast. Even the early Spanish name was Mar del Norte.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Common-place: Naming the Pacific | date = | year = | url =http://www.common-place.org/vol-05/no-02/peterson/index.shtml | accessdate = July 19, 2007-->

From the point of view of the German Hanseatic League of the Middle Ages, the sea to the east was the “East Sea” (Baltic Sea in German is literally the Ostsee), and the sea to the north, the North Sea. The spread of maps used by Hanseatic merchants, popularized this name throughout Europe. Other common names in use for long periods were Mare Frisia, and “Mare Frisicum“, “Oceanum“ or “Mare Germanicum“ as well as their English equivalents, Frisian Sea and German Ocean or Sea.

"German Sea" "The North Sea was known as the German Ocean until the early 20th C., when hostilities with Germany meant this name became politically unacceptable in Britain." (from the Latin Mare Germanicum) was commonly used in English language and other languages along with North Sea, until the early eighteenth century. By the late nineteenth century, Germanic Sea was a rare, scholarly usage.

Location For the most part, the sea lies on the European continental shelf. The only exception is a narrow area of the northern North Sea off Norway. The North Sea is bounded by Great Britain to the west and the northern and central European mainland to the east and south, including Norway, Denmark, Germany, the Netherlands, Belgium, and France.

In the south-west, the North Sea becomes the English Channel beyond the Straits of Dover. In the east it connects to the Baltic Sea via the Skagerrak and Kattegat. In the north it opens in a widening funnel shape to the Norwegian Sea, which lies in the very north-eastern part of the Atlantic.

Apart from the obvious boundaries formed by the coasts of the countries which border it, the North Sea is bounded by an imaginary line from Lindesnes, Norway to Hanstholm, Denmark running towards the Skagerrak. The northern limit towards the Atlantic is less well-defined. Traditionally, an imaginary line is taken to run from northern Scotland, by way of Shetland, to Ålesund in Norway. According to the Convention for the Protection of the Marine Environment of the North-East Atlantic{{Citation| last = OSPAR Commission | first = | author-link = | last2 = | first2 = | author2-link = | title =OSPAR / The OSPAR Convention | date =2004 - | year = | url =http://www.ospar.org/eng/html/1992-ospar-convention.htm | accessdate =July 24, 2007 -->of it runs further to the west and north from longitude 5° West and latitude 62° North, at the latitude of [Geirangerfjord in Norway.

The surface area of the North Sea is approx. 575,000 km2 (222,000 sq mi), with a volume of around 54,000 cubic meter (13,000 cu mi). This places the North Sea at the 13th largest sea.

Geology Geological history The Seabed of the North Sea forms two Sedimentary basin. The main northern one lies to the north of a ridge between Norfolk and Frisia, and had its origin in the Devonian. The southern basin, if not flooded, would drain towards the Strait of Dover and thence to the English Channel. This basin dates from the Carboniferous.

During the Devensian glacial, the most recent glaciation, much of the northern basin was covered by the ice sheet, and the remainder, including the southern basin, was tundra. However, during the Cromerian interglacial, there was a natural dam of chalk, the Weald-Artois Anticline."{{Citation| last =Invicta Media | first = | author-link = | last2 = | first2 = | author2-link = | title =Forming the Channel | date =30 March 2002; | year =1999-2002 | url =http://www.theotherside.co.uk/tm-heritage/background/channelform.htm | accessdate = July 25, 2007 --> Although the ridge probably collapsed during the [Kansan glaciation it still formed the highest part of the land bridge between continental Europe and Great Britain.{{cite news |first=Ian |last=Sample |authorlink= |coauthors= |title=Breach of ice age lake made Britain an island |url=http://www.guardian.co.uk/science/story/0,,2129662,00.html |work=The Guardian |publisher= |date= 19 July 2007|accessdate=2007-07-21 -->

The Storegga Slides were a series of underwater landslides, in which a piece of the Norwegian continental shelf slid into the Norwegian Sea. The immense landslips occurred between 8150 BC and 6000 BC, and caused a tsunami up to 20 m (65 ft) high that swept through the North Sea, having the greatest effect on Scotland and the Faeroe Islands.{{Cite web| author= Axel Bojanowski, | publisher= Spiegel Online | title =Tidal Waves in Europe? Study Sees North Sea Tsunami Risk | date = October 11, 2006 | year = | url =http://www.spiegel.de/international/0,1518,441819,00.html | accessdate = 2007-07-24-->

Plate tectonics The fault lines along the English Channel cause occasional earthquakes, which can result in damage to structures on land. The Central Grabens of the North Sea is an active area, as well as northwestern Europe's continental slope which is subject to landslides from earthquakes.{{Citation| last = Geology Shop | title =UK Earthquakes | date = | year = | url =http://www.geologyshop.co.uk/ukequakes.htm | accessdate = July 24, 2007--> Although not a site of major earthquakes or tsunamis, there are intraplate earthquakes which result in the uplifting of the continental crust causing landslides. The Dover Straits earthquake of 1580 is among the first recorded in the North Sea and caused extensive damage in both France and England both through its tremors and a tsunami. The largest earthquake ever recorded in the UK was the 1931 Dogger Bank earthquake, which measured 6.1 on the Richter Scale and caused a tsunami that flooded parts of the British coast. A more recent event along this fault caused the 2007 Kent earthquake

The North Sea is located at a triple junction of three continental plates formed during the Palaeozoic: Avalonia, Laurentia and Baltica.{{Cite journal| last = Lyngsie, S B | coauthors = Rasmussen, T M; Thybo, H | journal = Tectonophysics | volume = 413 | pages = 147–170 | title = Regional geological and tectonic structures of the North Sea area from potential field modelling | date = October 11, 2006 | year = 2006 | url = http://www.lyngsie.nu/Artikel-1.pdf | accessdate = 2007-07-24--> Baltica is now the eastern coastline and the Scandinavian countries; Avalonia consists of the southern and western North Sea coast along England, North Germany and France; and Laurentia marks the northern perimeter of the North Sea with the Atlantic Ocean.

Geological features The Norwegian trench is an oceanic trench in the North Sea off the southern coast of Norway. The trench marks the position of the subduction North Sea Plate descending beneath the Lithosphere Scandinavian Plate. The trench reaches from the Stad (peninsula) peninsula in Sogn og Fjordane to the Oslofjord. The trench is between 50 and 95 km (30-60 mi) wide and several hundred meters deep. Off the Rogaland coast it is 250 - 300 m (820-980 ft) deep, and at its deepest point, off Arendal, it reaches 700 m (2300 ft) deep as compared to the average depth of the North Sea, about 100 m (325 ft).{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Maptech : Topo Maps Charts Navigation Software GPS and Online MapServer | date = | year = | url =http://64.233.179.104/translate_c?hl=en&langpair=fr%7Cen&u=http://mapserver.maptech.com/homepage/index.cfm%3Flat%3D58.011403248490396%26lon%3D9.430819575677283%26scale%3D1500000%26zoom%3D50%26type%3D0%26icon%3D0%26width%3D498%26height%3D498%26searchscope%3Ddom%26CFID%3D1719760%26CFTOKEN%3D33728793%26scriptfile%3Dhttp://mapserver.maptech.com/homepage/index.cfm%26latlontype%3DDMS | accessdate = July 20, 2007 -->

To the East of Great Britain, the vast moraine plate of the Dogger Bank rises up to 15 to 30 m deep{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Maptech : Topo Maps Charts Navigation Software GPS and Online MapServer | date = | year = | url =http://mapserver.maptech.com/homepage/index.cfm?lat=54.74456315454079&lon=2.3527509224287115&scale=1500000&zoom=50&type=0&icon=0&width=498&height=498&searchscope=dom&CFID=1719760&CFTOKEN=33728793&scriptfile=http://mapserver.maptech.com/homepage/index.cfm&latlontype=DMS | accessdate = July 20, 2007 -->

The Silver Pit is a valley-like depression 45 km (27 mi) east of Spurn Head in England that has been recognized for hundreds of years by fishermen. Nearby is the Silverpit crater, a controversial structure, which may be a geological structure or may be an impact crater.

"The Long Forties" denotes an area of the northern North Sea that is fairly consistently forty fathoms (73 m) deep (thus, on a nautical chart with depth shown in fathoms, a long area with many "40" notations). It is located between the northeast coast of Scotland and the southwest coast of Norway, centered about 57°N 0°30′E.

The Broad Fourteens are an area of the southern North Sea that is fairly consistently fourteen fathoms (26 m) deep (thus a broad area with many "14" notations). It is located off the coast of the Netherlands and south of the Dogger Bank, roughly between longitude 3°E and 4°30′E and latitude 52°30′N and 53°30′N.

The North Sea is home to a number of sizable islands and archipelagos, including the Shetland, Orkney, and Frisian Islands islands.

See more: List of the largest islands of the North Sea

Hydrology Basic data The salinity of the water is dependent on place and time of year but is generally in the range of 15 to 25 parts-per notation (ppt) around river mouths and up to 32 to 35 ppt in the northern North Sea, still generally lower than North Atlantic salinity, which averages around 35 ppt.

The water temperature varies depending on the influence of the Atlantic currents, water depth, and time of year, reaching 25 °C (77 °F) in summer and 10 °C (50 °F) in winter, though Arctic currents can be colder. In the deeper northern North Sea the water remains a nearly constant 10 °C (50 °F) year round because of water exchange with the Atlantic. The greatest temperature variations are found on the very shallow Wadden Sea coast, where ice can form in very cold winters.

The exchange of salt water between the North Sea and Atlantic occurs through the English Channel, as well as in the northern North Sea along the Scottish coast and through the Norwegian Sea. The North Sea receives fresh water not only from its influent rivers but also from the Baltic rivers which are connected to the North Sea via the Skagerrak. The North Sea rivers drain a land area of 841,500 km² (324,905 sq mi) and supply 296-354 km³ (71-85 cu mi) of fresh water annually. The Baltic rivers drain almost twice as large an area (1,650,000 km², 637,068 sq mi) and contribute 470 km³ (113 cu mi) of fresh water annually.

Around 160 million people live in the catchment area of the rivers that flow into the North Sea. These rivers drain a large part of Western Europe: a quarter of France, three quarters of Germany, nearly all of Switzerland and Great Britain, half of Jutland, the entirety of the Netherlands and Belgium, the southern part of Norway, and a small part of Austria. This area contains the world's greatest concentration of industry: 15% of the planet's industrial production takes place in the catchment area of the North Sea.

Water circulation Along the Danish and Norwegian coasts the water flows back into the Atlantic via the Norwegian Current. This moves at a depth of some 50 to 100 m (165-330 ft). This current has a relatively low salinity due to the brackish water of the Baltic and the fresh water contributed by the rivers and the fjords. A part of the warmer water flowing in from the Atlantic turns northwards again along the Current and results in a warmer stream through the colder waters. In winter the Norwegian Current has a temperature of 2 to 5 °C (36°-41 °F) and the salinity is below 34.8 ppt. The Atlantic water in the North Sea, divided from the Current by a front, is generally over 6 °C (43 °F) with a salinity of 35 ppt.

The water in the North Sea is completely exchanged in between one and two years. Within the Sea, fronts based on temperature, salinity, nutrients and pollution can be clearly identified; they are more clearly defined in summer than in winter. Large fronts are the Frisian Front, which divides water coming from the Atlantic from water originating in the English Channel, and the Danish Front, which divides coastal waters from water in the central North Sea. The inflow of water from large rivers mixes very slowly with North Sea water. Water from the Rhine and Elbe, for example, can still be clearly differentiated from sea water off the northwest coast of Denmark.

{] / Meuse River || Netherlands || 2,524 || 89,134|-|Elbe ] || Norway || 603 || 21,295|-|IJsselmeer ] || Germany || 358 || 12,643|-|Skjern Å ] (includes River Tay and River Earn) ] (includes River Spey and River Ness) ] || Belgium/Netherlands || 126 || 4450|-|Humber ] || Scotland || 112 || 3955|-|Ems (river) || Germany || 88 || 3108|-|River Tweed || England || 85 || 3002|-|Thames || England || 76 || 2684|-|}

Tides The tides are caused by the tide wave from the North Atlantic, as the North Sea itself is too small and too flat to have its own tides. Ebb and flow alternate in a cycle of 12.5 hours. The tide wave, owing to the Coriolis effect, flows around Scotland and then in counter-clockwise direction along the English coast and reaches the German Bight some 12 hours after arriving in Scotland. In so doing, it runs around three amphidromic points: a central point lies shortly before the Straits of Dover. It is formed by the tide wave which is transported across the English Channel. It influences the tides in the narrow area of De Hoofden in the Southern Bight between southern England and the Netherlands. The other amphidromic system consists of two points close to each other which form a tide wave. The two other points just off the coast of southern Norway and lying on a line between southern Denmark and the West Frisian Islands form one single area around which the tides flow. Its central point lies on the Jutland Bank at 55° 25' N, 5° 15' E.

As a result, the tidal range in southern Norway is less than half a metre (1.5 ft), but increases the further any given coast lies from the amphidromic point. Shallow coasts and the funnel effect of narrow straits increase the tidal range. The tidal range is at its greatest at The Wash on the English coast, where it reaches 6.80 m (22 ft). In shallow water areas the real tidal range is strongly influenced by other factors such as the position of the coast and the wind at any given moment or the action of storms. In river estuaries, high water levels can considerably amplify the effect of high tide.

Coasts The western coasts of the North Sea are jagged, as they were stripped by glaciers during the ice ages. The coastlines along the southernmost part are soft, covered with the remains of deposited glacials which were left directly by the ice or have been redeposited by the sea. The Norwegian mountains plunge into the sea, giving birth, north of Stavanger, to deep fjords and archipelagoes. South of Stavanger, the coast softens, the islands become fewer. The Eastern Scottish coast is similar, though less marked than Norway. Starting from Flamborough Head in the northeast of England, the cliffs become lower and are composed of less resistant moraine, which erodes more easily, so that the coasts have more rounded contours. In Holland, Belgium and in the East of England (East Anglia) the littoral is low and marshy. The East coast and south-east of the North Sea (Wadden Sea) have coastlines that are mainly sandy and straight owing to longshore currents, in particular in Belgium and in Denmark.:fr:Mer du Nord

Northern fjords, skerries, and cliffs , NorwayThe northern North Sea coasts bear the impression of the enormous glaciers which covered them during the Ice Ages and created a split, craggy coastal landscape. Fjords arose by the action of glaciers, which dragged their way through them from the highlands, cutting and scraping deep trenches in the land. During the subsequent rise in sea level, they filled with water. They very often display steep coastlines and are extremely deep for the North Sea. Fjords are particularly common on the coast of Norway.{{Citation| last =EMECS International Center for the Environmental Management of Enclosed Coastal Seas | first =Guidebook | author-link = | last2 = | first2 = | author2-link = | title =5 North Sea | date = | year = | url =http://www.emecs.or.jp/guidebook/eng/pdf/05north.pdf | accessdate = July 24, 2007-->

Firths are similar to fjords, but are generally shallower with broader bays in which small islands may be found. The glaciers that formed them influenced the land over a wider area and scraped away larger areas. Firths are to be found mostly on the Scottish and northern English coasts. Individual islands in the firths, or islands and the coast, are often joined up by sandbars or spits made up of sand deposits known as “tombolos”.{{Citation| last =Home > Earth Heritage > Geological Conservation Review (GCR) > GCR Database | first = | author-link = | last2 = | first2 = | author2-link = | title =Coastal Geomorphology of Wales - GCR block | date = | year = | url =http://www.jncc.gov.uk/earthheritage/gcrdb/gcrblock.asp?block=24 | accessdate = July 24, 2007-->

Towards the south the firths give way to a cliff coast, which were formed above all from the moraines of Ice Age glaciers.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title = Development of the coastline | date = | year = | url =http://www.eastriding.gov.uk/aspirelinks/coastal/1development.pdf | accessdate = July 24, 2007-->The horizontal impact of waves on the North Sea coast gives rise to eroded coasts; the eroded material is an important source of sediment for the mudflats on the other side of the North Sea.{{Citation | last =CE3A8SMJGeologyforEngineers | first = | author-link = | last2 = | first2 = | author2-link = | title = Coasts: Geomorphology and Management | date = | year = | url =http://www.tcd.ie/Geology/MAIN-PAGE/CE3A8/coast.pdf | accessdate = July 24, 2007--> The cliff landscape is interrupted by large estuary with their corresponding mud and marshy flats disrupt, notably the Humber and the Thames, in southern England.

In southern Norway, as well as on the Swedish Skagerrak coast, skerry are to be found.{{Citation| last = Drömresan | first =Micke W | author-link = | last2 = | first2 = | author2-link = | title =Sailing in Sweden and the Baltic | date = | year =1997-2005 | url =http://www.dromresan.com/english/index.shtml | accessdate = July 24, 2007 --> Formed by similar action to that which created the fjords and firths, the glaciers in these places affected the land to an even greater extent, so that large areas were carried away. The coastal brim (''Strandflaten''), which is found especially in southern Norway, is a gently sloping lowland area between the sea and the mountains. It consists of plates of [bedrock, and often extends for kilometers, reaching under the sea, at a depth of only a few meters.

Southern shoals and mudflats The shallow-water coasts of the southern and eastern coast up to Denmark were formed by Ice Age activity, but their particular shape is determined for the most part by the sea and sediment deposits.{{Cite web| publisher= Natural England | title =Bridlington to Skegness: Habitat: Earth heritage | date = | year = | url =http://www.english-nature.org.uk/science/natural/NA_HAbDetails.asp?Name=Bridlington+to+Skegness&N=101&H=65 | accessdate = 2007-07-24--> The whole of the coastal zone is shallow; the tides flood large areas and uncover them again, constantly depositing sediments. In the micro tidal area (a tidal range of up to 1.35 m (4.43 ft)), such as on the Dutch or Danish coasts,{{Citation| last = Drs. Teunis Louters | title =Impact of Sea Level Rise on Dutch Wetlands: Morphological and ecological consequences over the next 50 -100 years | date = | year =1996 | url =http://www.netcoast.nl/publications/sealevel.doc | accessdate = July 24, 2007 --> barrier beaches with dunes are formed. In the mesotidal area (a tidal range of between 1.35 and 2.90 m (4.43-9.5 ft)), barrier islands are formed; in the macrotidal area (above 2.90 m (9.5 ft) tidal range), such as at the mouth of the Elbe, underwater sandbanks form.

The Dutch West Frisian Islands and the German East Frisian Islands are barrier islands. They arose along the breakers’ edge where the water surge piled up sediment, and behind which sediment was carried away by the breaking waves. Over time, sandplates arose, which finally were only covered by infrequent storm floods. Once plants began to colonize the sandbanks the land began to stabilise.{{Cite web| publisher= WorldAtlas.com | title =North Frisian Islands | date = | year =2007 | url =http://worldatlas.com/webimage/countrys/europe/denorthfrisian.htm | accessdate = 2007-07-24-->

Even though today they are established islands, some of them continue to be in motion. On the East Frisian Island of Juist for example, since the year 1650 there are five different proven sites for the church, as the spot for rebuilding the church had to keep pace with the ever-moving island. At times, Juist even consisted of two islands, which eventually grew back together. The neighboring island of Wangerooge in the last 300 years has moved a distance equivalent to its own length to the east, its church tower, destroyed at the outbreak of WW1 apparently moving from east to west.{{Cite web], on the other hand, arose from the remains of old Geestland islands, where the land was partially removed by storm floods and water action and then separated from the mainland. They are therefore often higher and their cores are less exposed to changes than the islands to the south. Beyond the core, however, the same processes are at work, particularly evident on Sylt, where in the south of the island, a break threatens, whilst the harbor at List (village) silts up.{{Citation| last = Ahrendt | first =Kai | author-link = | last2 = | first2 = | author2-link = | title =Expected Effects of Climatic Change on a Barrier Island - Case Study Sylt Island/German Bight | date = | year = | url =http://www.iczm.de/sylt.pdf | accessdate = July 24, 2007 --> The Danish Wadden Sea Islands, the next in the chain to the north, arose from sandbanks. Right up into the twentieth century, the silting up of the islands was a serious problem. To protect the islands, small woods were planted.On the southeastern coast there are several broad estuaries, such as the Meuse, Rhine, Weser, Elbe and Eider.

The Southern Bight has been especially changed by land reclamation, as the Dutch have been especially active. The largest project of this type was the diking and reclamation of the IJsselmeer.The Wadden Sea stretches between Esbjerg, Denmark in the north and Den Helder, Netherlands in the west. This landscape is heavily influenced by the tides and important sections of it have been declared a National Park. The island of Helgoland is an exception, as it was not formed by sediment deposition; in fact it is considerably older and is composed of Early Triassic sandstone.

Storm tides , LondonStorm tides threaten in particular the coasts of the Netherlands, Belgium, Germany, and Denmark. These coasts are quite flat, so even a relatively small increase in the water levels is sufficient to put large stretches of land under water. Storms from the west are especially strong, so the most dangerous places are on the south-east coast. Over the years, floods caused by storm tides have cost hundreds of thousands of lives and have significantly helped to shape the coast. Until early modern times, the number of victims from a single storm tide could be in the tens of thousands, even exceeding a hundred thousand, though to what extent these historically-reported casualties are accurate can only be estimated with difficulty.

The first recorded storm tide flood was the Julianenflut, on February 17, 1164. In its wake the Jadebusen began to form. Ancient records tell also of the First Marcellus Flood, which struck West Friesland (region) 1219. A storm tide in 1228 is recorded to have killed more than 100,000 people. The Second Marcellus Flood also known as the Grote Mandrenke in 1362 hit the entire southern coast of the North Sea. Chronicles of the time again record more than 100,000 deaths as large parts of the coast were lost permanently to the sea, including the now legendary town of Rungholt (see Lost city). The Strand (island) emerged from the remainders. During the Burchardi flood in 1634 the Strand was destroyed. Limfjord was first connected with the North Sea on February 3, 1825 when a flood pierced an opening. In 1862, another flood pierced another opening, the Thyborøn Channel, through the remainder of Agger Tange.

In the twentieth century the North Sea flood of 1953 flooded several nations' coasts and cost more than 2000 lives.{{Citation| last =Investigating Rivers | title =Coastal Flooding: The great flood of 1953 - A case study | date = | year = | url =http://www.naturegrid.org.uk/rivers/gt%20stour%20case%20study-pages/fld-cstl.html | accessdate = July 24, 2007 --> 315 citizens of Hamburg died in the North Sea flood of 1962. The "Century Flood" of 1976 and the "North Frisian Flood" of 1981 brought the highest water levels measured to date on the North Sea coast, but because of the dike (construction) built and improved after the flood of 1962, these led only to property damage.{{Cite web| author =home weather-uk | title = press pack Ready-prepared articles on rainstorms, deluges, and floods | date = | year = | url =http://www.weather-uk.com/press/flood.html | accessdate = 2007-07-24-->

Coastal preservation (Closure-dike) is a major dam in the Netherlands., North Sea Protection Works or Delta Works.The southern coastal areas were originally amphibious. The land included countless islands and islets which had been divided by rivers, streams, and wetlands and areas of dry land were regularly flooded. In areas especially vulnerable to storm tides, people settled first on natural areas of high ground such as Spit (landform) and Geestland. As early as 500 BC people were constructing artificial dwelling hills several meters high. It was only around the beginning of the High Middle Ages in 1200 that inhabitants began to connect single ring dikes into a dike line along the entire coast, thereby turning amphibious regions between the land and the sea into permanent solid ground.

The modern form of the dikes began to take form in the 17th and 18th centuries, built by private enterprises in the Netherlands. The Dutch dike builders exported their designs to other North Sea regions. The North Sea Floods of 1953 and 1962 were impetus for further raising of the dikes as well as the shortening of the dike line through land reclamation and river weirs so as to present as little surface area as possible to the punishment of the sea and the storms.{{Citation| last = Compare Infobase Limited. | first = | author-link = | last2 = | first2 = | author2-link = | title =North Sea Protection Works - Seven Modern Wonders of World | date =2006-2007 | year = | url =http://www.allwondersoftheworld.com/seven-modern-wonders/north-sea-protection-works.html | accessdate = July 24, 2007 --> Currently, 27% of the Netherlands is below sea level protected by dikes, dunes, and beach flats.{{Citation | last =About, Inc., A part of The New York Times Company. | first = | author-link = | last2 = | first2 = | author2-link = | title =Dykes of the Netherlands | date = January 30 | year = ©2007 | url =http://geography.about.com/od/specificplacesofinterest/a/dykes.htm | accessdate =July 19, 2007 -->

Coastal preservation today consists of several levels. The dike slope reduces the energy of the incoming sea, so that the dike itself does not receive the full impact. Dikes that lie directly on the sea are especially reinforced. The dikes have, over the years, been repeatedly raised, sometimes up to 10 m (32 feet) and have become flatter in order to better reduce the erosion of the waves. Modern dikes are up to 100 m (328 ft) across. Behind the dike there runs an access road and generally a thinly inhabited area. In many places another dike follows after several kilometers.

Where the dunes are sufficient to protect the land behind them from the sea, these dunes are planted with beach grass to protect them from erosion by wind, water, and foot traffic.{{Citation| last =Pat Gowen NSAG | first =NSAG | author-link = | last2 = | first2 = | author2-link = | title =The North Sea Action Group on Britains new EA Flood Plain Maps | date =31 December | year = 2000 | url =http://members.aol.com/ruraleye/fpmap.htm | accessdate = July 24, 2007 --> See also:

• Flood control in the Netherlands
• Zuiderzee Works
• Delta Works
• Thames barrier
• Afsluitdijk

History Roman occupation The Romans started exploring the North Sea starting 12 BC, with expeditions led by Nero Claudius Drusus and Tiberius. They conquered indigenous tribes and by 5 BC progressed to the river Elbe. Pliny the Elder describes Roman sailors going through Helgoland and as far as the northeast coast of Denmark.{{Citation| last = By Redbad | first = | author-link = | last2 = | first2 = | author2-link = | title =HISTORY OF THE FRISIAN FOLK Permission granted for publication on Boudicca's Bard - Part One - (1750 B.C. - 785 A.D.) Origins of the Frisians (1750 B.C. - 700 B.C.) | date = | year = | url =http://www.boudicca.de/frisian1.htm | accessdate = July 24, 2007 --> Following preliminary military actions by Julius Caesar in 55 and 54 BC and [Aulus Plautius, Britain was formally invaded and occupied starting in 43 AD, establishing trade across the Channel. The [Classis Britannica sailed right round mainland Britain before Roman rule ended in [.

In the power vacuum left by the retreating Romans, the Germanic Angles, Saxons, and Jutes began the next great migration across the North Sea. They had been used as mercenaries in Britain by the Romans. Many people from these tribes migrated across the North Sea during the Migration Period, conquering and perhaps displacing the native Celtic populations.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =Germany The migration period | date = | year = | url =http://www.britannica.com/eb/article-58084/Germany | accessdate = July 24, 2007-->

Around the seventh century a wave of Frisian migrants moved to several islands in the North Sea, and a second wave moved to what is now Nordfriesland in northern Germany and South Jutland in southern Denmark in the 11th century.

Viking expansion The attack on Lindisfarne in 793 is generally considered the beginning of the Viking Age. For the next 250 years the Scandinavian raiders of Norway, Sweden, and Denmark dominated the North Sea with their superior longships, raiding monasteries, towns and fortresses along the coast and along the rivers that ran inland. According to the Anglo-Saxon Chronicle they began to settle in Britain in 851. They continued to settle in the British Isles and the continent until around 1050.{{Citation| last =Nick Attwood MA | first = | author-link = | last2 = | first2 = | author2-link = | title =The Holy Island of Lindisfarne - The Viking Attack | date = | year = | url =http://www.lindisfarne.org.uk/793/index.htm | accessdate = July 24, 2007-->

Alfred the Great, who is counted as the first English king, was the first to mount significant opposition to the Vikings eventually relegating them to the Danelaw and carving out his own kingdom. Harthacanute of Denmark and England was the last Viking king to rule over a territory spanning the North Sea as after his death the kingdom broke apart.{{Citation| last = | first = | author-link = | last2 = | first2 = | author2-link = | title =British Kings and Queens - Historical Timeline | date = | year = | url =http://www.britroyals.com/timeline.asp | accessdate = July 24, 2007-->

With the rise of William the Conqueror the North Sea began to lose some of its importance. The new order oriented most of England and Scandinavia's trade south, toward the Mediterranean and the Orient. The Baltic Sea became increasingly important for northern Germany and Scandinavia as well as the powerful Hanseatic League began to rise.

Hanseatic League Though the Hanseatic League was centered in the Baltic, it also had important Kontors on the North Sea, including Bergen, the Steelyard in London, and Bruges.{{Citation| last =David K. Schreur. | first = | author-link = | last2 = | first2 = | author2-link = | title =The Hanseatic League | date = | year = | url =http://members.bellatlantic.net/~baronfum/hansa.html | accessdate = July 24, 2007-->

The rise of Bruges as a center of trade and a corresponding revival of the North Sea economic importance began in 1134 when a storm tide created a deeper waterway to the city allowing the entry of large ships to port. A lively trade sprang up between Bruges and London, mostly in textiles. Bruges became the end point of the Hanseatic East-West trade line that began in Novgorod and was very important for maritime connections between France, Spain, Italy, and the Netherlands and the Hanseatic regions of Northern Europe.

in 1441 the Hanseatic League was forced to recognize the equality of the Netherlands as Antwerp had risen as an economic power and tied itself to Denmark. After the so-called Count's Feud, a war of succession in Denmark, the Dutch were able to encroach upon the League's monopoly on Baltic trade and the reign of the Hanseatic League was at an end as the Netherlands became the center of the Northern European economy.

The Netherlands as a world economic power

In the 16th century, the Netherlands became the preeminent economic power in the world. For the Dutch merchant marine the North Sea served more as a starting point for their oceanic voyages. It had become the gateway and crucial outlet allowing Dutch merchants direct access to world markets.{{Citation| last =Donald J. Harreld, Brigham Young University | first = | author-link = | last2 = | first2 = | author2-link = | title =EH.Net Encyclopedia: Dutch Economy in the "Golden Age" (16th-17th Centuries) | date = | year = | url =http://eh.net/encyclopedia/article/Harreld.Dutch | accessdate = July 24, 2007-->

During the Eighty Years War, the Dutch began a heavily invested worldwide trade - hunting whales around Svalbard, trading spices from India and Indonesia, founding colonies in Brazil, South Africa, North America (New Netherlands), and the Caribbean. The empire, which they accumulated through trade, led to the Dutch Golden Age in the 17th century.

In 1651 England passed the Navigation Acts, which damaged Dutch trade interests. The disagreements concerning the Acts led to the First Anglo–Dutch War, which lasted from 1652-1654 and ended in the Treaty of Westminster (1654), whereby the Dutch were forced to recognize the acts. of 1666 by Willem vand de VeldeIn 1665 the English declared war on the Dutch once again, beginning the Second Anglo-Dutch War. With the support of the French, who, between the war, had marched into the Spanish Netherlands--present day Belgium, the Dutch gained the upper hand. In 1667, the English and the Dutch signed a peace treaty, the Treaty of Breda (1667) after the Dutch Admiral Michiel de Ruyter destroyed a large part of the British fleet in the Raid on the Medway. The peace dictated that the English would take over administration of Dutch possessions in North America (present day New York City) while the Dutch would get Suriname from the English and got to adjust the Navigation Acts to their benefit.

1672 is known in the Netherlands as "Rampjaar," the year of disaster. England declared war on the Netherlands once again, beginning the Third Anglo-Dutch War, and were quickly followed by France, the Prince-Bishopric of Münster, and the Archbishopric of Cologne in an alliance against the Dutch. The three continental allies marched into the Netherlands while the landing of English troops along the coast could only be briefly held up.{{Citation| last =David Ormrod, University of Kent | first = | author-link = | last2 = | first2 = | author2-link = | title =The North Sea as a core region in the early modern world: the shift from Amsterdam to London | date = | year = | url =http://www.helsinki.fi/iehc2006/papers1/Ormrod.pdf | accessdate = July 24, 2007-->

Britain: naval superpower England's climb to the pre-eminent sea power of the world began in 1588 as the attempted invasion of the Spanish Armada was defeated by the combination of outstanding naval tactics by the English under command of Sir Francis Drake and the breaking of the bad weather. The strengthened English Navy waged several wars with their neighbors across the North Sea and by the end of the 17th century had erased the Dutch's previously world-spanning empire.{{Citation| last =britishbattles.com | first = | author-link = | last2 = | first2 = | author2-link = | title =The Spanish Armada : Sir Francis Drake | date = | year =2007 | url =http://www.britishbattles.com/spanish-war/spanish-armada.htm | accessdate = July 24, 2007-->

The building of the British Empire as a domain on which the sun never set was possible only because the British navy exercised unquestioned control over the seas around Europe, especially the North Sea. The only significant challenge to British domination of the seas came during the Napoleonic wars. The Battle of Copenhagen took place in the Kattegat and ended the League of Armed Neutrality, a union of lesser naval powers including Denmark-Norway, Russia, and Prussia, which had united to protect neutral shipping against the British. The Battle of Trafalgar took place off the coast of Spain against a combined French and Spanish fleet and was won by Admiral Horatio Nelson, ending Napoleon plans to invade Britain and securing British dominance of the seas for more than another century.

The Dogger Bank incident in 1904 during the Russo-Japanese War was an attack by Russian naval vessels on British fishing boats mistaken for ships of the Japanese navy. The Russian sailors, on edge due to false reports of Japanese torpedo boats, also fired upon each other in the confusion. The incident resulted in the deaths of 3 British fishermen, a Russian sailor, and a priest aboard one of the Russian ships. The incident, also called "The Russian Outrage," caused a diplomatic crisis between Great Britain--which had an Anglo-Japanese Alliance with Japan at the time--and Russia. The crisis was defused after the Russian fleet was crushed by the Japanese and the Russian government paid compensation to the fishermen.

First World War sinks in the Battle of Dogger Bank on 25 January 1915. During the First World War, Great Britain's Grand Fleet and Germany's Kaiserliche Marine faced each other on North Sea.

The North Sea was the main theater of the war for surface action. The British Grand Fleet took position against the German High Seas Fleet. Britain's larger fleet could maintain a blockade of Germany, cutting it off from overseas trade and resources. Germany's fleet remained mostly in harbor behind their screen of mines, occasionally attempting to lure the British fleet into battle in the hopes of weakening them enough to break the blockade or allow the High Seas Fleet to attack British shipping and trade. Britain strove to maintain the blockade and, if possible, to damage the German fleet enough that British ships could be used elsewhere.

In general, Britain, though not always tactically successful, was able to maintain the blockade and keep the High Seas Fleet in port, although the High Seas Fleet remained a threat that kept the vast majority of Britain's capital ships in the North Sea.

The set-piece battles and maneuvering have drawn historians' attention but it was the blockade of German commerce through the North Sea, which ultimately starved the German people and industries into seeking the Armistice with Germany (Compiègne).

See also: Naval warfare of World War I#Theaters

Second World War The Second World War was, in terms of naval warfare, again mostly a submarine war on the German side. However, this time the main action was not in the North Sea but rather the Atlantic. Also different from the first war, the North Sea was no longer the exclusive territory of the Allies. Rather, it was, above all in the first years of the war, the stage for an intensive coastal war, featuring mainly small vessels like submarines, Minesweeper (ship), and Fast Attack Craft.{{Citation| last = Campaigns of World War II | first = Naval History Homepage | author-link = | last2 = | first2 = | author2-link = | title =Atlantic, WW2, U-boats, convoys, OA, OB, SL, HX, HG, Halifax, RCN ... | date = | year = | url =http://www.naval-history.net/WW2CampaignsStartEurope.htm | accessdate = July 24, 2007--> However, despite early successes, which brought about a supply crisis in Britain, the Germans did not succeed in breaking the British resistance. Like in the first war, the allies soon controlled the seas,