Few localities combine the wealth of geological interest with the stunning setting of Yesnaby. As the swell crashes in from the Atlantic, the cliffs resonate with the blows and the compression of air in hidden caves bubbles air through ponds high on the cliff top. The modern pulse of erosion has exposed a far older history, for here is laid out the desert of the Devonian.
To the south lies the granite basement, with the original scree still plastered on the sides of ancient hills. The sub-Devonian surface is buried by many hundreds of metres of flagstones that accumulated in Lake Orcadie. The sandstones show many signs of a desert origin, with dune bedding, sun cracks and the formation of gypsum crystals. The sands were transported in large rivers and the channels can still be seen. Signs of life are everywhere, from tracks to burrows and fish and hardened hydrocarbons. The horse-tooth stromalites are easily found, close cousins of the few surviving colonies on Earth.
The cliff feels the full force of Atlantic storms when spray jets high into the air. Waves arrive here unchanged from the deep ocean and during storms the cliff top is washed, shifting blocks landwards and scouring away the soil. All the classic landforms of coastal erosion are revealed on a walk on the cliff tops – caves, arches and stacks.