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The imbricate blocks tossed by waves to the rear of the cliff top
The largest blocks on the cliff top are over 100 m3. The blocks were probably flipped from nearby sockets on the cliff top.
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Grey Bools, WickSignificance: this site provided one of the first records of cliff-top storm deposits In Scotland.
Beside the car park at the end of the minor on the cliff tops south of Wick is a remarkable accumulation of large flagstone boulders. First described by Hugh Miller, the boulders are less extensive than formerly, many having been cleared from the field east of the road. The boulders lie between ~12 and 17 m above sea level at head of a ~150 m long stepped rock ramp that slopes to the north. The largest boulder, Charlie's Stone, has a volume of 110 m3 and weighs around 500 tonnes. Many boulders are longer than 1 m. The boulders are stacked towards the north and northeast and the strength of this imbrication leaves little doubt that the blocks were deposited by storm waves from this sector. The blocks have been torn from a rock step at around 5 m asl on the ramp. Although there are some small boulders and sockets that appear relatively fresh it is clear that these cliff-top storm deposits have not been mobilised over the past century.
Bruce Woodman-Smith (2004) has compared the edge rounding of the boulders with that in local kirkyards. He estimates that the boulders were emplaced between 1800 and 1850 and notes that the most extreme storm in this part of the North Sea occurred in January 1830. With recent records from oil rigs of rogue waves up to 26 m high in the North Sea, it is clear that northerly storms have the potential to generate very large waves that may have major impacts on cliffs in Caithness. |