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Tuesday, January 12, 1999 Published at 15:48 GMT


Sci/Tech

The fragile white cliffs of England

The Seven Sisters: Vulnerable to erosion since they were first formed

By Environment Correspondent Alex Kirby

The collapse of hundreds of thousands of tonnes of chalk into the sea below Beachy Head on the Sussex coast is a vivid demonstration of what erosion can do.

But erosion has been happening since the start of geological time, and this latest collapse does not necessarily mean that climate change is to blame.

The gleaming white chalk cliffs in Sussex, and further east near Dover, are familiar and well-loved landmarks in southern England.

For many travellers, they are still the last - or first - glimpse of England itself.

But the fact that they are so white and clean is evidence of the constant erosion that is always chipping pieces off them.

Wet weather partly to blame

Chalk is a soft, weak rock, easily fissured, and much more vulnerable to the power of winds and waves than tougher rocks like granite and limestone.

Another factor which appears to have triggered the collapse is rain.

The rainfall in southern England has been above average for eight of the last twelve months.

And over Christmas and the New Year there were two weeks of almost continuous downpour.


[ image: Confronting nature to save the Head would be costly]
Confronting nature to save the Head would be costly
Martin Culshaw, an engineering geologist at the British Geological Survey, thinks the rain will have penetrated the ground and built up increased pressures in the already fissured chalk beneath.

He is sceptical about the role of climate change in the cliffs' downfall.

"It's dangerous to blame it on global warming, because coastal erosion has been going on ever since there were coasts.

"It will continue around the coast of Britain, especially where you find cliffs made of softer materials, like chalk, clay or sand.

"Parts of the Dorset coast are susceptible, and the Kent side of the Thames estuary.

"And in Holderness, in east Yorkshire, the land has retreated hundreds of metres in historical times.

A high price to pay

"What you can say is that climate change will alter the rate at which erosion happens. So if we can expect more rain to fall in Britain, we can also expect more coastal erosion."

Martin Culshaw is also doubtful about attempts to save beauty spots from the ravages of erosion.

"The cost of trying to protect these coasts can be quite large, and we have to decide whether it's worth it.

"Beachy Head is scenically beautiful. But in a hundred years, it will still be there.

"What is the point of trying to stand in the way of nature ?"


[ image: Rising wave heights also threaten coasts]
Rising wave heights also threaten coasts
The problem is made slightly worse by the fact that southern Britain is sinking very slowly.

This is because the northern part of the island is gently rising, as it gradually springs back from the great weight of ice which weighed it down 10,000 years ago.

And there is also the increase in wave height in the Atlantic and the English Channel, something which may be connected with climate change.

A collaborative European study reported recently that wave heights in the north Atlantic had increased by about 10% over the last 40 years.

Even so, it said, they were now comparable only with the heights observed a century ago.

But with the science of global warming advancing rapidly, nobody will guarantee what the picture may be a few years from now.



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