Walking the bones of Scotland

A bright spring morning in the Isle of Lewis, outermost corner of the Western Isles. On the pristine sands of Tolsta Bay I contemplated a riot of strikingly coloured cliffs and sea-stacks of ancient rock known as gneiss, as naked and contorted as when they first formed in the nascent earth’s crust 3,000 million years ago. This was the first step of a journey by foot and ferry across the geological history of Britain, all the way from these most ancient rocks to the youngest, a thousand miles away on the muddy Essex shore.

I used to think of geology as baffling and boring, a stew of technical terms about a pile of dusty old rocks. But after forty years of exploring every corner of these islands on foot, I came to see that what lies beneath our boots, the rocky bones of Britain, has shaped everything I love about the country – its wonderful shapes and colours, its curves and hollows, the dramatic cliffs and subtle lowlands, the way we build and farm and make our livings, our ongoing story through smooth and troubled times. I made up my mind to string together a line of paths that I could walk from end to end of the country, learning our geological story as I went along.

You can’t walk through Scotland without bumping into ancient volcanoes and the sites of catastrophic asteroid hits, great rips in the body of the land, old rocks that mysteriously sit on top of younger ones, rocks that have been melted and squashed out of recognition. It’s as though the land has been through a giant blacksmith’s forge or a monstrous lemon squeezer. It has certainly shifted up and down the globe, thousands of miles apart from what would become England until the two land masses crunched together some 400 million years ago.

Over on the mainland I made my way north of Ullapool to follow a geological trail round the coast of the Coigach peninsula. Here some 1,200 million years ago an asteroid half a mile wide slammed into the planet at 25,000mph. A smear of rough-textured red rock at the site still shows how the collision liquefied and splattered the sandstone far and wide, like pancake batter. And here not long afterwards, in what was still a barren, lifeless world, stromatolites or primitive single-celled forms of life began to cluster and prosper, spreading oxygen around the globe to help kickstart life on Earth. I sat on the Coigach shore beside the layers of finely leaved limestone rock that the stromatolites built up, watching an otter playing on the cliff and smelling the sun-warmed heather, and felt the tingle of connection with life in all its forms emergent over unimaginable spans of time.

Further south in rainy Wester Ross I followed an old cattle droving trail east through the squashed and metamorphosed sand, mud and silt that shaped the rugged and remote mountains of Glen Quoich some 500 million years ago. After that came the massive split in Scotland’s body that formed the Great Glen around 400 million years ago, the same era as the petrified violence of the volcanic landscapes of Ben Nevis (its summit views miraculously clear of cloud) and Glencoe. Last kick of the fire and fury of that early world was felt in the heart of Edinburgh as I climbed the pluton or column of basalt that forms Arthur’s Seat, iconic landmark for miles around.

As for the human element – I found that connections between mankind and the rocks that underpin their land resonated throughout my journey through the bones of Britain. Men of Lewis laboriously split and shaped their ancient iron-hard gneiss to fashion the Callanish stone circle 5,000 years ago. Skye drovers walked the black cattle from the harsh environment of the volcanic isles to the sweet grass and shelter of the mainland. Miners dug coal and ironstone out of the Kelvin valley, ‘good men doing a rotten job tae the best o’ their ability,’ as one of them testified. And everywhere the gneiss and basalt, sandstone and limestone lies exposed in everyday use, built into the walls of houses and byres, piled up along field boundaries and crunching under the wheels of cars and lorries.

In the 18th century most thinkers accepted, if not quite wholeheartedly, that God had created the world in a short space of time and had laid the rocks in neat layers like a celestial brickie, fixing the oldest at the bottom and the youngest at the top. But James Hutton, a Scottish farmer, mineralogist, chemist and pioneer geologist, begged to differ.