We abandon the car at Eshaness, outside the lighthouse swinging its torch in an endless, unstoppable arc, and head north along the cliffs.

Only a few months ago, the crags were crowded with life: tens of thousands of seabirds – fulmars, gannets, arctic skuas and the aggressive bonxies, as they call great skuas locally, that will divebomb anyone who comes near their nests – but now they are long gone, all except the hardiest fulmars gone south for the winter.

All that can be heard is the boom of the water over the edge. We have to shout; after a while we give up and simply stare, thrilled by the ferocity of the ocean that hammers the rock into shape

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Once this bleak, windbeaten expanse was the site of an enormous volcano belching lava and smoke. The fire has long gone out, but steam still seems to rise from around the edges: sea spray, plumes thrown high in the air by the smash and crash far below, or fired from blowholes like cannons.

A single raven appears from the gloom and hangs overhead, watching with naked curiosity. He follows us when we move off, landing only a little distance behind. In Norse mythology the god Odin is served by two raven spies, Hugin and Munin, sent out each day to report back to him what they have seen. I wonder: which one is he?

Ahead the water has chiselled away at a fracture in the basalt and burst in to create Calders Geo: a great rent in the earth where two sheer cliffs face off. Here the layers of volcanic flow are displayed for inspection, and the distinctive knobbled lava pillows where it squeezed out like toothpaste, then hardened to stone.

Under our feet lies the largest sea cave in Britain: vaulted ceilings rising 20 metres high. In calm weather it can be accessed by sea kayak, through a hole in the walls of the geo.

Sea kayaks! What an impossible thought today, with salt in our mouths and the roar in our ears and a malevolent wind pushing us toward the precipice.