Old Man of Hoy and St John’s Head
Hoy, Orkney, Scotland
The Old Man of Hoy is Britain’s tallest and probably most photographed sea stack. At 137m high and only about 30m wide at its base, this imposing rectangular stack has been carved from layer upon layer of Old Red Sandstone (Devonian) rocks. The shaping of the stack can be traced back through the centuries through paintings and maps. In 1750, the Old Man was depicted as a headland, but by the 1820′s stormy seas had carved the rock into a stack and arch – two legs gave the Old Man his name. A severe storm however, washed away one of the legs to leave the pillar that remains – for now!
The rocks of the Old Man are composed of alternating layers of soft sandstones and more resistant flagstones of the Upper Old Red Sandstone. These rocks lie over a base of dark Old Red Sandstone basalt lava flows. Jointing and faulting in the sedimentary rocks occurs in rectangular form and this is reflected in the blocky shape of the Old Man and surrounding cliffs. The stack stands about 60m away from the cliffs; in between lies a pile of debris which is the remains of the roof of the arch that collapsed.
The future will almost certainly bring the total demise of the Old Man. There is already a large 40m crack running vertically from the top of the stack which threatens its upper reaches. Waves will also continue to erode the base of the stack until the entire pillar collapses.
Text from ScottishGeology.com