"Stacks", like this one off t tie coast 

 of Orkney, are left after erosive forces 

 of the sea have crumbled the arch that once 

 joined the stone column to the mainland. 



a flat gradient and their sandy slopes are usually smooth at low 

 water. The finer the sand of these beaches, the flatter their slope 

 and the less the waves will be likely to change them. 



When landings were taking place in the Mediterranean during 

 World War II, many of the landing craft suddenly found themselves 

 grounded on sand bars hidden beneath the water, with deep water 

 left between them and the shore. These bars, common in tideless 

 seas such as the Mediterranean, Baltic, and the Great Lakes, move 

 about as the waves change in height: high waves move the bars 

 offshore, but as the waves grow smaller the bars gradually move 

 back toward the shore. These shifting bars are not formed by con- 

 structive waves, as are those found on tidal beaches, but by storm 

 waves. The higher the storm waves, the deeper the water they 

 break in, and it is at the break point of the waves that the bars form. 

 Here sand is pushed landward outside the break point, but inside it 

 nearer the shore the steeper waves carry sand seaward, back to the 

 break point where it accumulates from two sides and so builds the 

 break point bar. These bars form only in the tideless seas because 

 it is only in such seas that the break point of the waves can remain 

 constant enough — free from the tides — for the sand to accumulate. 

 The interplay of waves, loose sand, shingle, and solid rock all 

 contribute to the limitless variety of the coast. As the waves break 

 against bare rock they loosen tiny pieces which become abrasives 

 that help wear away the cliS. So the waves gradually eat into the 

 coast, sometimes cutting a platform across which they advance on 

 their endless attack. Or they carve out caves which over centuries 

 may unite and form a natural arch, and centuries later the arch may 

 collapse and leave a stack, such as the Needles off the Isle of Wight, 

 or Old Harry in Dorset. 



Cliffs are constantly being reshaped by the waves, the reshaping 

 depending on the kinds of rock making up the cliff. Rocks composed 

 of chalk make spectacular cliffs such as Beachy Head and the white 

 cliffs of Dover. Nearly all rocks that are hard can stand as vertical 

 cliffs, such as the cliffs on the north coast of Scotland where the 

 Old Red Sandstone forms the cliffs of Duncansby Head. In other 

 areas the cliffs may be composed of soft rocks, clays, or loose sands. 

 When the cliffs are made of soft rocks they become waterlogged, 

 and parts of them collapse in landslides when the foot of the cliff 

 is washed away by the sea. Loose material such as sand and gravel 

 cannot stand so steeply to the sea and is more hkely to be washed 

 away. People living on the east coast of England are lucky that the 

 waves are not fierce, for the east coast rocks are soft. On the other 

 hand, people living on the exposed southwest shores, where the 

 waves violently attack the coast, are protected from the sea's en- 

 croachment by the hardness of the rocks. 



Some of the material washed down by the rivers and worn from 

 the cliffs remains at the edge of the sea and builds new land. One 

 place where the land seems to be gaining over the sea is Dungeness 

 foreland. This promontory has grown out into the sea since 

 Neolithic men lived there. In its shelter are the rich pastures of 

 Romney Marsh, reclaimed probably by the Romans, since the 

 Rhee Wall running across them is Roman in date. The stretches 

 of shingle ridges protecting the marshes were formed by the 

 storm waves that have long been throwing the shingle high 

 onto the beach and well out of the reach of normal waves. The 



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