PRAA SANDS

The mile-long beach at Praa Sands is well known for its sandy stretches which attract thousands of visitors during the summer months, as well as a regular armada of surfers throughout the year. But what is it about the low, earthy-coloured cliffs and dunes behind the beach that has drawn so many geologists for more than a hundred years to visit the site?

The reason is that not only do they contain a fuller and more complex sequence of Ice Age deposits than is exposed elsewhere in West Cornwall, but they also contain a partial record of events associated with the rise of sea level following the last Ice Age which finished abruptly 10,000 years ago.

This piece of Praa Sands' later geological history was unravelled in the early 1980s by a young Cornish student, named Colin French, who studied the pollen assemblages in the peat layer obvious below the dunes, and is now well known in wildlife conservation circles and to Trust members.

The older history of Praa Sands is best seen west of the Welloe Rock Inn, beyond the slipway, where two distinct raised beach deposits can be seen, formed when the sea level was high and the climate warm. These have been dated recently by a laboratory in France as being over 300,000 years old and, if confirmed, will be the oldest yet known raised beaches in Cornwall. The drab cliffs above, made of "head" deposited during times when Cornwall was frozen, contain a far more fascinating history than their appearance would suggest. In the early 1900s a former buried soil, called a "palaeosol" by geologists, was discovered within this sequence with carbon fragments and fossil plant root marks and possible evidence of habitation by Palaeolithic man. During 1996 this old land surface was particularly well exposed, and could be seen to undulate with low ridges and hollows. The age of this palaeosol is still a mystery despite repeated attempts to date it over the years. Are we dealing with a warm period within the last Ice Age or the warm period at end of the penultimate Ice Age? The rubbly head above the old land surface passes up into very fine sandy material towards the top of the cliff. This material is wind-blown ("loess") which is known to have been deposited on the Lizard Peninsula some 16,000 years ago and covered much of the south of West Cornwall. One can imagine that the landscape at this time must have looked distinctly lunar!

Praa Sands was approved as a Regionally Important Geological/geomorphical Site (RIGS) in 1995. The site is prone to severe coastal erosion (up to 10 metres in 100 years) with the result that vital pieces of its Ice Age history come and go. To keep track of the geology in the ever-changing cliffs, RIGS volunteers regularly monitor the site and keep a centralised database. In 1997, during the construction of sea defences in the vicinity of the Welloe Rock Inn, a major effort was made to document the geology below the beach as it was gradually exposed. The most spectacular discovery was that of a buried peat channel with large oak tree trunks, which are now lodged with two local museums. Recently the Cornwall RIGS Group received national recognition for its work on Praa Sands. This was only achieved through the active support of Kerrier District Council during the construction of the sea defences and local Praa Sands residents who keep a watching eye on the fragile stability of the cliffs and inform the group of developments.

Peter Ealey