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Thursday 5 April 2012

Geophysical Survey On Skomer Reveals Buried Archaeology





Olly and Louise carefully survey Skomer’s heavily burrowed landscape
Skomer Island, located off the south-western coast of Pembrokeshire, is famed for its bird life and puffins, but its relict archaeological landscape of prehistoric houses and fields is among the best preserved anywhere in the British Isles. Arriving on the island in beautiful, still, sunny conditions, a small team from the Royal Commission and Sheffield University have been embarking on a second season of fieldwork to discover more about how people lived and farmed the island in the past.

During our first season back in April 2011 we had undertaken a typological study of the prehistoric settlement remains in the north of the island and identified a number of new sub-megalithic monuments. Guided by an extraordinary new LiDAR survey of Skomer, which uses a laser mounted on an aircraft to create a highly detailed terrain model of the island’s ground surface, we identified staggering new complexity to the field systems and clear phasing of boundaries, particularly within the interior of the island.

Returning this year, confident we had mapped the majority of the surviving upstanding remains we wanted to look below the ground surface by using non-intrusive geophysical survey to see if there was evidence of buried archaeological features.

No one has ever attempted geophysical survey on Skomer before so we did not even know if it would work, especially given the volcanic, igneous geology of the island, although its undertaking was potentially hugely rewarding. But it would be by no means easy – just getting the sizeable and heavy equipment to the island needed the helping hand of some willing passengers on the ferry from Martin’s Haven, and particular care would be required when walking with the survey instruments over the fragile, heavily burrowed landscape.

We concentrated our work in the south of the island and the sunny weather of our first two days allowed for good progress. Two approaches were tried; magnetometry, where a hand-held probe is walked over the ground surface along a grid, and resistivity, where a two-pronged probe is lightly inserted into the ground at 1 metre, or 50 cm, intervals.

However, conditions on the island can change rapidly, and by day three, a band of rain and a strong northerly wind, gusting up to 50 mph, forced us inside to seek shelter. Keeping warm with mugs of tea, we began to process the data we had collected with tantalising results. The plots of the combined geophysical techniques give an ‘x-ray’ effect when draped over the map of the fields and have allowed us to begin to identify buried ditches and some circular structures which are not visible on the ground surface. These first results show that both magnetometry and resistivity work on the island, showing slightly different views of the buried archaeology. Further work this week, and in future years, will continue to reveal more of Skomer’s secrets.

Skomer fieldwork blog, April 2012
Louise Barker, Oliver Davis, Toby Driver and Bob Johnston


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1 comments:

Project Engineering & Controls Pvt. Ltd said...

I really enjoyed this post great article.

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