Article on other languages:
- Noordsee
- Nordsee
- Norþsǣ
- بحر_الشمال
- Mar_d'o_Norte
- Mar_del_Norte
- উত্তর_সাগর
- Паўночнае_мора
- Nordsee
- Sjeverno_more
- Mor_an_Hanternoz
- Северно_море
- Mar_del_Nord
- Çурçĕр_тинĕсĕ
- Dagat_Amihanan
- Severní_moře
- Môr_y_Gogledd
- Nordsøen
- Nordsee
- Põhjameri
- Βόρεια_Θάλασσα
- North_Sea
- Mar_del_Norte
- Norda_Maro
- Ipar_Itsasoa
- دریای_شمال
- Mer_du_Nord
- Noardsee
- An_Mhuir_Thuaidh
- Mar_do_Norte
- 북해
- उत्तरी_सागर
- Sjeverno_more
- Norda_Maro
- Laut_Utara
- Norðursjór
- Mare_del_Nord
- הים_הצפוני
- ჩრდილოეთის_ზღვა
- Mor_Kledh
- Bahari_ya_Kaskazini
- Deryaya_Bakur
- Mare_Germanicum
- Ziemeļjūra
- Nordmier
- Šiaurės_jūra
- Noordzie
- berti_xamsi
- Északi-tenger
- Северно_Море
- उत्तर_समुद्र
- Laut_Utara
- Хойд_тэнгис
- Noordzee
- 北海
- Nordsjøen
- Nordsjøen
- Mar_del_Nòrd
- Noordsee
- Morze_Północne
- Mar_do_Norte
- Marea_Nordului
- Северное_море
- German_Ocean
- Deti_i_Veriut
- Mari_dû_nord
- Severné_more
- Severno_morje
- Северно_море
- Sjeverno_more
- Pohjanmeri
- Nordsjön
- வடகடல்
- ทะเลเหนือ
- Bắc_Hải_(châu_Âu)
- Баҳри_Шимолӣ
- Kuzey_Denizi
- Північне_море
- بحیرہ_شمال
- Mar_del_Nord
- Nôordzêe
- צפון_ים
- Noôrdzeê
- 北海_(大西洋)
| North Sea | |
|---|---|
 |
|
| Location | Atlantic Ocean |
| Coordinates | Coordinates: |
| Primary sources | Forth, Ythan, Elbe, Weser, Ems, Rhine/Waal, Meuse, Scheldt, Spey, Tay, Thames, Humber, Tees, Wear, Tyne |
| Basin countries | Norway, Denmark, Germany, Netherlands, Belgium, France and the U.K. (England, Scotland) |
| Max length | 960 kilometres (600 mi)[1] |
| Max width | 580 kilometres (360 mi)[1] |
| Surface area | 750,000 square kilometres (290,000 sq mi)[1] |
| Average depth | 95 metres (310 ft)[1] |
| Max depth | 700 metres (2,300 ft)[1] |
| Water volume | 94,000 cubic kilometres (23,000 cu mi)[1] |
| Salinity | 3.4 - 3.5 %[2] |
| Max temperature | 17 °C (60 °F)[1] |
| Min temperature | 6 °C (40 °F)[1] |
The North Sea is a marginal, epeiric sea of the Atlantic Ocean on the European continental shelf. It is more than 970 kilometres (600 mi) long and 560 kilometres (350 mi) wide, with an area of around 570,000 square kilometres (220,000 sq mi). A large part of the European drainage basin empties into the North Sea including water from the Baltic Sea. The North Sea connects with the rest of the Atlantic through the Dover Strait and the English Channel in the south and through the Norwegian Sea in the north.
Much of the sea's coastal features are the result of glacial movements. Deep fjords and sheer cliffs mark the Norwegian and parts of the Scottish coastline, 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 dikes have been constructed to protect coastal areas.
The development of European civilisation has been heavily affected by the maritime traffic on the North Sea. The Romans and the Vikings sought to extend their territory across the sea. The Hanseatic League, the Netherlands, and finally the British sought to dominate commerce on the North Sea and through it to access the markets and resources of the world. Commercial enterprises, growing populations, and limited resources gave the nations on the North Sea the desire to control or access it for their own commercial, military, and colonial ends.
In recent decades, its importance has turned away from the military and geopolitical to the purely economic. Traditional economic activities, such as fishing and shipping, have continued to grow and other resources, such as fossil fuels and wind energy, have been discovered and developed.
Contents |
Geography
The North Sea is bounded by the east coasts of England and Scotland to the west and the northern and central European mainland to the east and south, including Norway, Denmark, Germany, the Netherlands, Belgium, and France.[3] In the south-west, beyond the Straits of Dover, the North Sea becomes the English Channel. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively. 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, the North Sea is generally considered to be bounded by an imaginary line from Lindesnes, Norway to Hanstholm, Denmark running towards the Skagerrak. However, for statistical purposes, the Skagerrak and the Kattegat are sometimes included as part of the North Sea.[4][5]
The surface area of the North Sea is approximately 750,000 square kilometres (289,576.62 sq mi)[1] with a volume of around 94,000 cubic kilometres (22,553.65 cu mi).[1] Around the edges of the North Sea are sizable islands and archipelagos, including Shetland, Orkney, and the Frisian Islands.
Submarine topography
For the most part, the sea lies on the European continental shelf. The only exception is the Norwegian trench, which reaches from the Stad peninsula in Sogn og Fjordane to the Oslofjord. At its deepest point, off Arendal, it reaches a depth of 700 metres (2,300 ft). The trench is not a subduction-related oceanic trench, where one tectonic plate is being forced under another. It is mainly a deep erosional scour, while the western part follows the North-South line of an old Rift Valley formed during the Jurassic and Cretaceous periods.[6]
To the east of Great Britain, lies the Dogger Bank, a vast moraine, or accumulation of unconsolidated glacial debris, which rises up to 15 to 30 m (50 - 100 ft) deep.[7]
The Silver Pit is a valley-like depression 45 km (27 mi) east of Spurn Head in England that has been recognised for hundreds of years by fishermen. Nearby is the Silverpit crater, a controversial structure initially proposed to be an impact crater, though other geologists interpret it to be the result of the dissolution of a thick bed of salt which permitted the upper strata to collapse.[8] Devil's Hole is a group of trenches, around 130 metres (430 ft) deeper than the surrounding sea floor, about 200 km (125 mi) east of Dundee, Scotland.[9]
"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.[10] 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.[11]
Name
One of the initial namings was Septentrionalis Oceanus, or Northern Ocean which was cited by Pliny.[12] The moniker North Sea was used by the Frisians, who have inhabited the south-west coast of Denmark and northwest coasts of Germany and the Netherlands since pre-Roman times. Other seas that they named in relation to their own territory include the East Sea (Oostzee, the Baltic Sea) and two which have since been wholly or partly reclaimed, the South Sea (Zuiderzee, today's IJsselmeer) and Middle Sea (Middelzee). In mediaeval times the spread of maps used by Hanseatic merchants popularised the name "North Sea" throughout Europe and it was adopted by German.
Other common names in use for long periods were the Latin terms Mare Frisia, and Mare Frisicum[13], Oceanum- or Mare Germanicum[14] as well as their English equivalents, "Frisian Sea"[15], "German Ocean"[16], "German Sea"[17] and "Germanic Sea" (from the Latin Mare Germanicum).[18][19] By the late nineteenth century, these names were rare, scholarly usages.[19]
History
Early history
The first records of marine traffic on the North Sea come from the Roman Empire, which began exploring the sea in 12 BC. Great Britain was formally invaded in 43 AD and its southern areas incorporated into the Empire, beginning sustained trade across the North Sea and the English Channel.
The Romans abandoned Britain in 410 and in the power vacuum they left, the Germanic Angles, Saxons, and Jutes began the next great migration across the North Sea during the Migration Period invading England.[13][20][21]
The Viking Age began in 793 with the attack on Lindisfarne[22] and for the next quarter-millennium the Vikings ruled the North Sea. In their superior longships, they raided, traded, and established colonies and outposts on the Sea's coasts.[23]
From the middle ages through the 15th century, the north European coastal ports exported domestic goods, dyes, linen, salt, metal goods and wine. The Scaninavian and Baltic areas shipped grain, fish, naval necessities, and timber. From the Mediterranean in this era would be high grade cloths, spices, and fruits.[24] Commerce during this era was mainly undertaken by maritime trade due to underdeveloped roadways.[24]
In the 13th century the Hanseatic League, though centred on the Baltic Sea, started to control most of the trade through important members and outposts on the North Sea. The League lost its dominance in the 16th century, as neighbouring states took control of former Hanseatic cities and outposts and internal conflict prevented effective cooperation and defence.[26] Furthermore, as the League lost control of its maritime cities new trade routes emerged which provided Europe with Asian, American, and African goods.[27]
Early modern history
Dutch power saw its zenith during her Golden Age in the 17th century. During this era, they had expanded their herring, cod and whale fisheries to an all time high.[24] Important overseas colonies, a vast merchant marine, and a powerful navy made the Dutch the main rivals of growing England, which saw its future in these three spheres. This conflict was at the root of the first three Anglo-Dutch Wars between 1652 and 1673. Despite Dutch victories in these wars and others, the ascension of the Dutch prince William to the English throne, caused a dramatic shift in commercial, military, and political power from Amsterdam to London.[28] By the end of the War of Spanish Succession in 1714, the Dutch were no longer a major player in European politics.[29]
_-_De_verovering_van_het_Engelse_admiraalschip_de_%27Royal_Prince%27.jpg)
Scotland emerged as a prominent economic power during the Scottish Enlightenment of the 18th century. The advancements of this era established a great herring fishing industry resulting in Scotland becoming a European leader.[24]
Between 1700 and 1815, the North Sea saw only 45 years of peace, and could be regarded as the most dangerous eras to sail the sea.[30] Several conflicts involved interruptions in maritime trade in the North Sea, though none which had decisive effects on the wars' outcomes: the French and British cut off Russia's Baltic ports during the Crimean War[31] and the First[32] and Second Schleswig Wars[33] saw Prussia's coasts blockaded, as did the Franco-Prussian War[34]. The British did not face a challenge to their dominance of the North Sea until World War One broke out in 1914[35].
20th century
Tensions in the North Sea were again heightened in 1904 by the Dogger Bank incident, in which Russian naval vessels mistook British fishing boats for Japanese ships and fired on them, and then upon each other. The incident, combined with Britain's alliance with Japan and the Russo-Japanese War led to an intense diplomatic crisis. The crisis was defused when Russia was defeated by the Japanese and agreed to pay compensation to the fishermen.[36][37]
During the First World War, Great Britain's Grand Fleet and Germany's Kaiserliche Marine faced each other on the North Sea,[38] which became the main theatre of the war for surface action. Britain's larger fleet was able to establish an effective blockade for most of the war that restricted the Central Powers' access to many crucial resources. Major battles included the Battle of Heligoland Bight, the Battle of the Dogger Bank[39], the Battle of Jutland[39], and the Second Battle of Heligoland Bight. Britain, though not always tactically successful, maintained the blockade and thus kept the High Seas Fleet in port. Conversely, the German navy remained a threat that kept the vast majority of Britain's capital ships in the North Sea.[40]
World War One was also the first in which submarine warfare was used extensively and a number of submarine actions occurred in the North Sea[41], including the sinking of the Pathfinder, the first combat victory of a modern submarine,[42] and the exploits of U-9, which sank three British cruisers in under an hour, establishing the submarine as an important new component of naval warfare.[43]
The Second World War also saw action in the North Sea[44], though it was restricted more to submarines and smaller vessels such as minesweepers, and torpedo boats and similar vessels.[45]
In the last years of the war and the first years thereafter, hundreds of thousands of tons of weapons were disposed of by being sunk in the North Sea.[46]
After the war, the North Sea lost much of its military significance because it is bordered only by NATO member-states. However, it gained significant economic importance in the 1960s as the states on the North Sea began full-scale exploitation of its oil and gas resources[47]. The North Sea continues to be an active trade route.[48]
Political status
The countries bordering the North Sea all claim the 12 nautical miles (22.22 kilometres) of territorial waters within which they have exclusive fishing rights.[49] The Common Fisheries Policy of the European Union (EU) exists to coordinate fishing rights and assist with disputes between EU states and the EU border state of Norway.[50]
After the discovery of mineral resources in the North Sea, Norway claimed its rights under the Convention on the Continental Shelf. The other countries on the sea followed suit. These rights are largely divided along the median line. The median line is defined as the line "every point of which is equidistant from the nearest points of the baselines from which the breadth of the territorial sea of each State is measured.[51]" The ocean floor border between Germany, the Netherlands, and Denmark was only reapportioned after protracted negotiations and a judgment of the International Court of Justice.[52][49]
Archaeological sites
Several major archaeological finds were made in recent years in areas under the North Sea. From 2002 through 2005, Danish and Swedish scientists studied in secret the ruins of an ancient city several dozen square kilometers in size.[53] In 2007, archaeologists uncovered a huge, prehistoric "lost country", from the east coast of Britain, to the Shetland Islands, and to Scandinavia.[54] The third major find occurred in February of the following year when an amateur archaeologist dredged up Palaeolithic hand axes in the area between present-day Britain and Holland, leading scientists to believe that humans lived alongside mammoths approximately 100,000 years ago off Great Yarmouth.[55][56][57]
Geology
Shallow epicontinental seas like the current North Sea have since long existed on the European continental shelf. The rifting that formed the northern part of the Atlantic Ocean during the Jurassic and Cretaceous periods, from about , caused tectonic uplift in the British Isles.[58] Since then, a shallow sea has almost continuously existed between the highs of the Fennoscandian Shield and the British Isles.[59] This precursor of the current North Sea has grown and shrunk with the rise and fall of the eustatic sea level during geologic time. Sometimes it was connected with other shallow seas, such as the sea above the Paris Basin to the southwest, the Paratethys Sea to the southeast, or the Tethys Ocean to the south.[60]
During the Late Cretaceous, about , all of modern mainland Europe except for Scandinavia was a scattering of islands.[61] By the Early Oligocene, , the emergence of Western and Central Europe had almost completely separated the North Sea from the Tethys Ocean, which gradually shrank to become the Mediterranean Sea as Southern Europe and South West Asia became dry land.[62] The North Sea was cut off from the English Channel by a narrow land bridge until that was breached by at least two catastrophic floods between 450,000 and 180,000 years ago.[63][64][65] Since the start of the Quarternary period about , the eustatic sea level has fallen during each glacial period and then risen again. Every time the ice sheet reached its greatest extent, the North Sea became almost completely dry. The present-day North Sea coastline formed when, after the Last Glacial Maximum (the peak of the glaciation during the last ice age) 20,000 years ago, the sea began to flood the European continental shelf.[66] The Cenozoic era covers the period from 65.5 million years ago and is still ongoing. The North Sea coastline still undergoes changes following earthquakes, storm surges, erosion, the rise and fall of sea levels, shingle drifts as well as the deposition of sands and clastics in paralic environments.[60][67]
Biology and the environment
Fish and shellfish
Copepods and other zooplankton are plentiful in the North Sea. These tiny organisms are crucial elements of the food chain supporting many species of fish. The North Sea is home to about 230 species of fish. Cod, haddock, whiting, saithe, plaice, sole, mackerel, herring, pouting, sprat, and sandeel are all very common and the target of commercial fishing.[68] Due to the various depths of the North Sea trenches and differences in salinity, temperature, and water movement, some fish reside only in small areas of the North Sea. The blue-mouth redfish and rabbitfish are examples of these.[69]
Crustaceans are also commonly found throughout the sea. Norway lobster, deep-water prawns, and brown shrimp are all commercially fished, but other species of lobster, shrimp, oyster, mussels and clams are all found. Recently non-indigenous species have become established including the Pacific oyster and Atlantic jackknife clam.[68]
Birds
The coasts of the North Sea are home to nature reserves including the Ythan Estuary, Fowlsheugh Nature Preserve, and Farne Islands in the UK and The Wadden Sea National Parks in Germany. These locations provide breeding habitat for dozens of bird species. Tens of millions of birds make use of the North Sea for breeding, feeding, or migratory stopovers every year. Populations of Northern fulmars, Black-legged Kittiwakes, Atlantic puffins, razorbills, and species of petrels, gannets, seaducks, loons (divers), cormorants, gulls, auks, and terns, and many other seabirds make these coasts popular for birdwatching.[68]
Marine mammals
The North Sea is also home to marine mammals. Common seals, grey seals can be found along the coasts, at marine installations, and on islands. The very northern North Sea islands like the Shetlands are occasionally home to a larger variety of pinnipeds including bearded, harp, hooded and ringed seals, and even walrus.[70] North Sea cetaceans include Harbour porpoises, common dolphins, bottlenose dolphins, Risso's dolphins, long-finned pilot whales and white-beaked dolphins, minke whales, killer whales, and sperm whales.[71][68]
Flora
Plant species in the North Sea include species of wrack, among them bladder wrack, knotted wrack, and serrated wrack. Algae, including kelp, such as oarweed and laminaria hyperboria, and species of maerl are found as well.[68] Nori, (P. umbilicalis) is found along the coast of the North Sea and is a widely marketed edible seaweed.[72] Eelgrass, formerly common in the entirety of the Wadden Sea, was nearly wiped out in the 20th century by a disease and has struggle to reestablish itself. Similarly, sea moss used to coat huge tracts of ocean floor, but have been damaged by trawling and dredging have diminished its habitat and prevented its return.[73] Invasive Japanese seaweed has spread along the shores of the sea, growing up to 10 metres (33 ft) long and sometimes clogging harbours.
Biodiversity and conservation
Historically, flamingos, pelicans, and Great Auk could be found along the southern shores of the North Sea.[74] Gray whale also resided in the North Sea but were driven to extinction in the Atlantic in the 1600s[75] Other species have seen dramatic declines in population, though they are still to be found; right whales, sturgeon, shad, rays, skates and salmon among other species were common in the North Sea into the 20th Century, when numbers declined[76][77][78][79].
A variety of factors have contributed to decreasing populations of North Sea fauna. The introduction of non-indigenous species, industrial and agricultural pollution, overfishing and trawling, dredging, human-induced eutrophication, construction on coastal breeding and feeding grounds, sand and gravel extraction, offshore construction, and heavy shipping traffic all threaten marine life in the North Sea.[68]
In recent decades, action has been taken by the border countries to address many of these threats. The OSPAR convention was created in 1992 as an expansion of the 1972 Oslo Convention. It is managed by the OSPAR commission and has taken action to counteract the harmful effects of human activity on wildlife in the North Sea and preserve many endangered species.[80] All North Sea border states are signatories of the MARPOL 73/78 Accords.[81] Germany, Denmark, and the Netherlands also have a trilateral agreement for the protection of the Wadden Sea, or mudflats, which run along the coasts of the three countries on the southern edge of the North Sea.[82]
Hydrology
Basic data
The average ttemperature im summer is 17 °C (63 °F) in the summer months and 6 °C (43 °F) in the winter.[1] Global warming has been causing a rise in the average temperature of the North Sea, increasing to 14.2 °C (57.6 °F) in 2006.[83]
Temperature varies according to water depth. Channel water is 1 °C (34 °F) to 2 °C (36 °F) colder than water on the coastal shores during summer months. However, channel water is 1 °C (34 °F) to 2 °C (36 °F) warmer than water on the coast shores in the winter months. In summer, the temperatures rise to maxima of around 15 °C (59 °F) to 17 °C (63 °F), and in the winter the temperature maximum is between 5 °C (41 °F) to 7 °C (45 °F)[2] [84][85] The diurnal temperature varies with cloudiness and wind velocity. In the North Sea, the diurnal temperature varies 0.1 °C (32.2 °F) to 0.2 °C (32.4 °F) during the winter months, and between 0.4 °C (32.7 °F) to 0.7 °C (33.3 °F) in the summer months. Increasing cloudiness and increasing wind velocity are both factors producing small diurnal temperature variations.[86]
The salinity of sea water is dependent upon location and season. Salinity is lower in the summer than in the winter.[84] The salinity averages between 34 to 35 g salt per litre of water (0.34 to 0.35 pound/gallon (UK).[87][1] The salinity has the highest variability where there is fresh water inflow, such as at the Rhine and Elbe estuaries, the Baltic Sea exit and along the coast of Norway.[86]
Around 184 million people live in the catchment area of the rivers that flow into the North Sea.[85][88] This area contains one of the world's greatest concentrations of industry.[89]
Water circulation
The main pattern to the flow of water in the North Sea is a counter-clockwise rotation along the edges.[90] The North Sea is a part of the Atlantic Ocean receiving the majority of its content from the north west opening, and a lesser portion from the smaller opening at the English Channel. These tidal currents leave along the Norwegian coast.[2] Surface and deep water currents may move in different directions. Low salinity surface coastal waters move offshore, and deeper, denser high salinity waters move in shore.[86]
Water from the Gulf Stream flows in both through the English Channel towards Norway, and around the north of Britain, moving south along the British coast. From the south-moving current smaller currents are pulled off eastwards into the central North Sea. Another significant current sweeps south in the eastern part of the Sea. This is cold North Atlantic water and is strongest in late spring and early summer when the British offshore waters remain cool while the sea off the Netherlands and Germany starts warming up. Water from the Channel, and water flowing out of the Baltic Sea eventually move north along the Norwegian coast back into the Atlantic in what is called the Norwegian Current.[92] The current moves at a depth of 50 to 100 m (165-330 ft). "The mean residence time of water in the North sea is between one and two years."[92]
Tides
There are three factors which influence tidal waves in sea basins which possess weak wave systems; the sea oscillation period, the ocean tide range approaching the North Sea and the entrance dimensions between the ocean and the North Sea.[93] The Kelvin tide of the Atlantic ocean is a semidiurnal wave which travels northward. Some of the energy from this wave travels through the English Channel into the North Sea. The wave still travels northward in the Atlantic Ocean, and once past the British Isles, the Kelvin wave turns east and south and once again enters into the North Sea.[94] The North Sea located on the continental shelf has different waves than those in deep ocean water. The wave speeds are diminished and the wave amplitudes are increased. In the North Sea there are two amphidromic systems and a third incomplete amphidromic system.[95][96] At an amphidromic point the rise and fall of tidal waves is zero due to cancelling of tidal waves, and the semidiurnal high and low tides rotate around these points twice in a tidal day.[94][97][98]
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.[99] Shallow coasts and the funnel effect of narrow straits increase the tidal range.[94] The tidal range is at its greatest at The Wash on the English coast, where it reaches 6.5 metres (21.33 ft).[100][101] In the North Sea the average tide difference in wave amplitude is between 0 to 8 metres (0 to 26 ft).[1]
Coasts
The eastern and 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 glacial sediment, which was left directly by the ice or has been redeposited by the sea. The Norwegian mountains plunge into the sea, giving birth, north of Stavanger, to deep fjords and archipelagos. South of Stavanger, the coast softens, the islands become fewer. The eastern Scottish coast is similar, though less severe than Norway. Starting from Flamborough Head in the north east 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, particularly along Belgium and Denmark.[102][2]
Northern fjords, skerries, and cliffs
.jpg)
The 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.[103] Fjords arose by the action of glaciers[104], 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.[105][2]
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.[106][107] 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”.[108][109]
Towards the south the firths give way to a cliff coast, which was formed by the moraines of Ice Age glaciers.[67] The horizontal impact of waves on the North Sea coast gives rise to eroded coasts.[67] The eroded material is an important source of sediment for the mudflats on the other side of the North Sea.[110] The cliff landscape is interrupted in southern England by large estuaries with their corresponding mud and marshy flats, notably the Humber and the Thames.
There are skerries in southern Norway and on the Swedish Skagerrak coast.[111] 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 scraped 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 kilometres, reaching under the sea, at a depth of only a few metres.[112]
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.[113]
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.[114] The whole of the coastal zone is shallow; the tides flood large areas and uncover them again, constantly depositing sediments.[115] The Southern Bight has been especially changed by land reclamation, as the Dutch have been especially active.[115] The largest project of this type was the diking and reclamation of the IJsselmeer.[116]
In the micro tidal area, (a tidal range of up to 1.35 metres (4.4 ft), such as on the Dutch or Danish coasts,[117] barrier beaches with dunes are formed.[115][118] In the mesotidal area (a tidal range of between 1.35 and 2.90 m (4.43-9.5 ft), barrier islands are formed[118] ; in the macrotidal area (above 2.9 metres (9.5 ft) tidal range), such as at the mouth of the Elbe, underwater sandbanks form.[118] [115] A soft rock coast is formed in the meso-macro tidal areas located in the southern North Sea. These soft rock coastal bedrock plains are interspersed with soft rock (shale and sandstone) cliffs. [119]
The Dutch West Frisian and the German East Frisian Islands are barrier islands.[120] 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.[120] Once plants began to colonise the sandbanks the land began to stabilise.[121]
The North Frisian Islands, 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 the south of the island threatens to be broken away, while the harbour at List in the north silts up.[122] The Danish 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.
The small, historically strategic island of Heligoland was not formed by sediment deposition; it is considerably older and is composed of early Triassic sandstone.[123]
Storm tides
Storm tides threaten, in particular, the coasts of the Netherlands, Belgium, Germany, and Denmark.[2] 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 recorded 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 17 February 1164.[124] In its wake the Jadebusen began to form. Ancient records tell also of the First Marcellus Flood, which struck West Friesland in 1219.[125]
A storm tide in 1228 is recorded to have killed more than 100,000 people.[126] In 1362, the Second Marcellus Flood, also known as the Grote Mandrenke, 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 lost city of Rungholt.[126]
The coastline of the North Sea changed again following the flood of 1825; the Jutland Peninsula is now called the North Jutlandic Island.[127][128] In the twentieth century, the North Sea flood of 1953 flooded several nations' coasts and cost more than 2,000 lives.[129] 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 dikes built and improved after the flood of 1962, these led only to property damage.[130]
Tsunamis
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 metres (66 ft) high that swept through the North Sea, having the greatest effect on Scotland and the Faeroe Islands.[131][132] The Dover Straits earthquake of 1580 is among the first recorded earthquakes in the North Sea and caused extensive damage in as far north as London England both through its tremors and a tsunami.[133] The largest earthquake ever recorded in the United Kingdom was the 1931 Dogger Bank earthquake, which measured 6.1 on the