By Tom Bradwell
As Scottish islands go Foula is off the beaten track. 180 km N of mainland Scotland, 30 km W of the Shetland mainland and 280 km SE of the Faeroe Islands. One of only a handful of places west of Orkney and Shetland where the topography of the UK continental shelf protrudes above the surface of the ocean. The others being the uninhabited island of North Rona, and the rocks of Sula Sgeir and Sule Skerry. Home to just 38 inhabitants and Scotland’s 2nd highest sea cliffs (after those on St Kilda), Foula is a stunning island mountain, devoid of trees but teeming with seabirds. But was it glaciated by the last ice sheet? And if so when? Britice Chrono members Tom Bradwell, Derek Fabel and David Small went there to find out.
After a short flight from Tingwall Airport in an 8-seater islander operated by (Directflights) we landed at Foula Airstrip bang on time at 9.30am. We had chosen to visit Foula today (a Wednesday) as it is only one of 2 days a week when you can visit the island and return the same day. Well… only if the weather plays ball. Something which we were keenly aware of as thick sea fog had shrouded the island for the previous 4 days, restricting all access by plane. To make things more challenging we had been informed by the aircrew as we boarded that there were no guarantees that the return flight would go ahead today and that we should be prepared for an extended stay on the island, perhaps until Friday or perhaps even longer. I was naturally hoping to get back tonight to catch a bit of Cash in the Attic at 5.30, and after David thought in light of this news he may have to start rationing his caramel bars: 1 bite per meal. But we had made it to the island, with only 6 hours to hunt for and sample glacially transported rocks, and that was the most important thing.
Given the size of the island and the task in hand we decided to split up: Derek taking the low ground in the south where granite erratics transported from the Shetland mainland had been previously reported; whilst David and I took the ground in the east and north. The cloud base was down at 200 m and we knew that searching the high ground on Foula would probably not yield the type of material we needed for cosmogenic dating. But we were confident that by splitting up we could tackle the two best sites and secure the maximum number of samples (hopefully 10 or more).
After walking the length of the island by the only road, passing Da Toon o the Ham, and Da Loch we arrived at Da Heights, with great views across Da Sheepie and Gaada Stack. Sampling the 3 largest glacially transported sandstone boulders on this ridge took us up to lunch satisfied that we had at least bagged some good rocks. On the other end of the island Derek was working his way across Da Daal to Da Noup. He had seen one or 2 different looking rounded grey boulders on a hillside of more angular rounded grey boulders. The rounded grey boulders were granites sourced from the Shetland Mainland; the less rounded grey boulders were sandstones from the old red sandstone. By covering the ground in a slow and systematic way Derek was able to find 5 granite boulders and sample a few hundred grams of each – the old fashioned way with hammer, chisel and brute force. Meanwhile David and I had climbed up to Da Loch o Ouvrafandal searching for more boulders laid down by the last ice sheet, only to be disappointed by their absence. Two bedrock samples were taken before we walked back to the airstrip in glorious sunshine… backpacks considerably heavier than when we set out.
With 15 minutes to spare before the plane arrived we had time to chat to Jane the island’s primary school teacher, who was keen to tell her class the next day what we had been up to. The boulders we sampled contain a signal that has grown in them since they were last eroded and transported their current location, this signal is like a clock that we can use to work out when Foula was last covered by ice probably more then 20,000 years ago. I hope this blog helps!
All in all a great day: 11 rock samples, 50 field observations, 200 photographs and experiencing a stunning landscape and place. Our work should help to constrain the timing of the last ice sheet to cross Foula, the most westerly and glaciologically most important of the Shetlands islands. Tomorrow North Maven, Friday Skerries, hopefully. Saturday, Cash in the Attic on ‘Catch Up TV’. We will keep you posted on our progress over the next eight days…..