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| Sunday, 9 January 2005 |
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Archaeological evidence of tectonic activity in Sri Lanka by S. U. Deraniyagala, Former Director General of Archaeology Investigations conducted by the Archaeological Department under the direction of the writer in 1969-72 revealed traces of prehistoric human activity within coastal alluvia. These were gravels, incorporating stone tools, which had been deposited at levels corresponding with the then existing sea levels. The gravels with artifacts are today at considerable heights above the present sea level; 15 metres at Bundala-Patirajawela dated to 125,000 years ago and 8 metres at Bundala-Wellegangoda dated to 80,000 years before the present. Occurrences of ancient coastal gravels inland around Mankulam and on Aruakalu at 60-80 metres and at Minihagalkanda in Yala at 40 metres have yet to be scientifically dated. This phenomenon of uplifted shores has been attributed principally to pressures generated by tectonic factors within the last one million years or less as indicated by the presence of man-made tools within the gravels. The above-mentioned findings were presented in publications of the universities of Cornell and Harvard in the USA and the Archaeological Department (Deraniyagala 1976, 1988, 1992). They were contrary to the prevailing view that Sri Lanka is situated in a stable tectonic environment. However, the article by Professor C. B. Dissanayake on South Asian plate tectonics, that appeared in the Daily News of 31st December 2004, geologically corroborated the geo-archaeological evidence, which had been secured some thirty-five years ago, that Sri Lanka is indeed in a region of potential tectonic instability. In view of these indications, it is a matter of urgency that the rates of coastal uplift in Sri Lanka be investigated with state-of-the-art scientific methods. The locations for sampling have already been mapped out by the Archaeological Department and a scientist, Dr. Mohan Abeyratne of the Central Cultural Fund, trained at the Australian National University in radiometrically dating the sediments. What is needed at present is the equipment for 'optically stimulated luminescence' testing. A project proposal has apparently already been submitted by Dr. Abeyratne to the Atomic Energy Authority and an estimate prepared for procuring the equipment. It is now necessary to implement an enhanced version of it and since the dating techniques are being regularly upgraded, a back-up from international scientific institutions and consultants would probably be needed. This project could constitute an important component of the proposed Indian Ocean-rim earthquake monitoring programme. Since the said project is of direct relevance to risk assessment in developing the coastal regions of Sri Lanka, its rapid implementation should be a national priority. |
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