Duncansby Head sits atop high cliffs that rise to the east of John o' Groats. Following the path brings you first to the sight of the Geo of Sclaites, a huge cleft bitten deeply into the cliffs and further to the Thirle Door and the Stacks of Duncansby.
The Stacks of Duncansby are some of the most impressive in the British Isles. The Great Stack rises well above the summit of the adjacent cliff. The stacks rises above a narrow shore platform and its partially-submerged reefs along a stretch of shoreline where cliff retreat appears to have been significantly more marked than to the north at Duncansby Head and to the south beyond Fast Geo to Skirza Head.
The pyramids and pillars (or "cletts") cannot simply be coastal forms exhumed from a till cover as these delicate forms are unlikely to have survived the passage of glacier ice, although more substantial rock bosses may have done. The tallest stack now lies around ~200 m from the cliff edge and this gives a maximum estimate of the amount of postglacial marine erosion. More generally, stacks in Caithness are <100 m from the backing cliffs. As sea level has been close to sea level only during the last 6000 years then maximum rates of retreat are of the order of 33-16 mm/yr but probably vary widely over short distances. A minimum rate of retreat is perhaps indicated by the width of the narrow platform just above present sea level at the base of these cliffs.
If this platform relates to the main postglacial shoreline then erosion over the past 6000 years has failed to remove it.
To get credit for this Earthcache please answer the following questions and email us your findings:
a. Estimate the height of the stacks.
b. From the path you are walking down to the water, estimate the depth of the cleft.
Please do not include your answer in your log.
It would be very nice if you would post a photo of the area, maybe you have great shot of some birds or other attractions.
Sea level change
World coasts have seen sea-level variation of approximately 100 metres within the past 11,500 years through melting of the ice caps. When the ice caps melt the sea level rises globally (eustatically). The relative sea-level at any location is measured proportionate to the nearby land, which is itself subject to tectonic movement both up and down.
During the Ice Age, there was over 1 km of ice over central Scotland. On melting the downward pressure was released and the land surface moved up (isostatic rebound) quicker than the eustatic sea level rose. This gives the appearance of a relative sea-level drop over much of Scotland during the Holocene.
There is widespread evidence around the Caithness coast of the emergence of erosional landforms from beneath a cover of till. Similar inherited landforms occur on Orkney and elsewhere around the Scottish coast.