Surrounding seas and coastline

The British Isles are of the continental origin. Situated off the north-west coast of Europe, they once formed part of that continent. They only became islands when they were separated from it. The separation took place thousands of years, ago, after the last Ice Age. When the ice melted, the level of the oceans rose and drowned the low-lying coastlands round the continents. This was when the English Channel, which was formerly a westward extension of the North European Plain, became a shallow stretch of sea. It was a change which greatly affected the history as well as the geography of these islands.

It seems probable that the last glacial advance was at its maximum about 20,000 years ago. Since then a general warming of the climate has caused the glaciers to shrink, until today they have disappeared entirely from the British Isles. The withdrawal of the ice had an influence on the development of coastal features, for with the melting of the ice much water 'locked up' in the glaciers was returned to the sea. As a result, sea-level during the post-glacial period rose by over 60 m. It was during this rise in sea-level that Britain was separated from the continent of Europe by the formation of the Strait of Dover. Other coastal areas suffered 'drowning' with various results. In western Scotland glaciated valleys were flooded to form sealochs, the smaller islands were separated from Great Britain and Ireland, and in England the lower parts of many river valleys were submerged to form deeply penetrating inlets.

Around the coasts of north-west Europe the land slopes gently down into the sea. At a certain depth of sea the slope becomes steeper, and the sea bed descends to much deeper levels. This change of slope takes place at a sea depth of about 200 m.

The zone of shallow water which at present surrounds the continent thus resembles a shelf above the really deep water of the oceans: it is called the continental shelf. A line joining points at a depth of 200 m shows the approximate boundary of the continental shelf. The British Isles lie entirely on the shelf.

The fact that the British Isles were once part of the European mainland means that their rocks often resemble those of the closest parts of the continent. The ancient hard rocks of the Scottish Highlands, for example, such as granite, are similar to those of Scandinavia. Then there is the chalk of south-east England, seen in the white cliffs of Dover and across the Strait of Dover in northern France. The limestone ridge, or escarpment that crosses England from north-east to south-west also has its counter-part in northern France. And one more important example is the way in which the European Power Belt is continued into Britain.

From the European continent the British Isles are separated by the English Channel and the North Sea. The English Channel, in its widest part in the west is 220 km wide, and in the narrowest, what is called the Strait of Dover, only 32 km. The average depth of the Channel is 60 m, and that of the strait of Dover — 30 m. Here the two opposite coasts of England and France come so near, that on a clear day the cliffs of each side can be quite well seen from the opposite shore. There were a number of schemes in the past how to connect the two coasts.

Despite the fact that the people in Kent, the south of England, were not enthusiastic about the venture as they feared damage to the environment, the old idea prevailed and major industrial and financial corporations swung into action. The final decision has now been made. Meeting at Lille, France, on January 20, 1986, the President of France and the Prime Minister of Great Britain chose one of the four projects which had been submitted.

This scheme, put forward by the Anglo-French Channel Tunnel — France Manche consortium, envisages the construction of two rail tunnels 40 metres under the Channel bed. The tunnels will be 7.3 metres in diameter and about 50 km long, of which 37 km will be under the Channel. Cars, trucks and coaches will drive into specially built flat-cars and high-speed trains (160 km ph) will leave every few minutes, reaching the terminal on the opposite side in 30 minutes.

In the west the British Isles are washed by the Atlantic Ocean, in the east — by the North Sea, the average depth of which is 95 m. The two largest islands of the British Archipelago, Great Britain and Ireland, are separated from each other by the Irish Sea and the two straits, the North Channel — 20 km wide, and St George's Channel — over 100 km wide. The distance between the ports of Liverpool and Dublin is 230 km.

Apart from Britain the territories of six European countries look into the coasts of the North Sea — France, Belgium, the Netherlands, the Federal Republic of Germany, Denmark and Norway and for some of them this sea is the only exit to the World Ocean. The most important sea routes pass through the English Channel and the North Sea linking Europe with the Americas and other continents. The advantageous geographical position of Great Britain created favourable conditions for the development of shipping, trade and the economy as a whole.

A place on the continental shelf has been of great advantage to the British fishing industry. Edible fish feed largely on plankton, the minute organisms which abound in the shallow waters above the continental shelf, so that stretches of water such as the North Sea have long been rich fishing-grounds. Catches have been reduced by over-fishing, but other valuable resources have been discovered and exploited beneath the continental shelf — oil and natural gas.

The North Atlantic Current, the drift of warm water which reaches the islands from across the Atlantic, spreads out over the shelf magnifying its ameliorating effect on the British Isles. This rather shallow skin of surface water, light because it is warm, is driven north-eastward across the ocean by the westerly winds. It forms part of the Gulf Stream system, which begins where Florida Current pours vast quantities of remarkably warm water into the circulation of the North Atlantic. In its journey across that ocean the water loses part of its heat, but retains enough to keep the ocean surface west of the British Isles warm in winter. During the winter months water which has been heated in far lower latitudes is arriving in the North Atlantic. Furthermore, the ocean surface becomes warmer or cooler, according to season, far more slowly than does a land surface in similar latitudes. The maximum surface temperature of the British coasts is reached in August, or even as late as September. Thus, when winter comes, there is much heat available to warm the air of the westerlies, and the seasonal fall of air temperature over Britain is slow and slight.

The British Isles are known for their greatly indented coastline. Therefore there are many bays and harbours, peninsulas and capes on the coast, which were formed as a result of the raising and submerging of the land surface in the process of the geological development of the islands. The indentity pattern of the island of Great Britain greatly resembles that of the Norwegian coast abounding in numerous deep and winding, like rivers, fiords. Due to its extreme indentity the coastline of Great Britain despite its relatively modest size, is 8,000 km long.

Very much indented is the western coast, especially the coasts of Scotland and Wales. The highlands here rise quite abruptly from sea level, so that westward-flowing rivers are short and swift. Many long narrow lochs, or lakes, especially in the North-West Highlands, are finger lakes. Along the west coast are many inlets that are called lochs, such as Loch Pyne. These are sea lochs, or fiords: the ends of glaciated valleys which have been submerged by the sea.

The east coast is less lofty and more regular than the west coast, land sloping gradually down to the low sea shore and the coastal lowlands being flooded frequently.

Steep is the English coast of the Strait of Dover, where the chalk ridge comes right up to the sea repeating the chalk break of the French coast on the other side of the English Channel.

The Irish coasts are more like those of England. The west coast is more indented with long rias and peninsulas, while the south coast conforms more with the general run of the relief. The east is relatively smooth with a few major estuaries in the north but it is only in the southeast that lowland coasts with spits and bars blocking the estuaries are found. Gliffed coasts predominate here, and some are very beautiful.

Most of the British ports are situated in the mouths, wide estuaries of rivers. Of great importance for the port activity are tides when the rising water reaches its maximum mark (high tide) of 6 m in the lower Thames (London), 8.5 m in the Mersey estuary (Liverpool), 10 m in the Bristol Channel (Cardiff) and 12 m at Bristol. Thanks to the high tides many of the towns which are situated dozens of kilometres from the coast (London — 64, Glasgow — 35, Hull — 32, and many others) have become sea ports.

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