Compton Mackenzie said when he stood here that he felt ‘swung between heaven and earth’. No place I know feels more like the centre of the universe
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SOMETIMES, EARLY IN THE SPRING, around the middle of April, before any true signs of summer arrive, when the grass on the islands is still dull and tawny from the rigours of winter, when the sheep are poor and thin and an air of exhaustion hangs over the place, a break can come in the weather which seems like a gift from Heaven. Stillness is wrapped around the Shiants for a day or two and the sun bathes their cold, bruised limbs. Once, ten or twelve years ago, I was there on my own when one of these openings came. I watched it in the sky, arriving from the south. The clouds folded back towards me, like the ravelling up of a screen, leaving behind them a sky as pale as an eighteenth-century ceiling, in which the colour went from blue to pale blue, and at the horizon scarcely blue at all.
I could feel the islands sighing in the light, their pores expanding, the vegetable life reaching out from its winter retreat. It seemed to me then – it is the only time I have ever witnessed it – that as the days went on, opening each morning to another new brightness, I could see the Shiants beginning to move towards their summer condition, like the pelt of an animal as it regains its health, the big flanks of Garbh Eilean greening between the ribs of rock, the tight winter-bitten surface of Eilean Mhuire softening under the millions of grass tips and sorrel shoots prodding up into the light, the body of Eilean an Tighe turning towards the vivid luxuriance of its summer life.
I only had a small dinghy with me then and the calm meant I could take it around to the north side of Garbh Eilean. For weeks at a time when the weather is bad you can’t visit that northern face, because in any kind of sea it is terrifying, thrashed at by the Minch and merciless in the way it would deal with any boat. When the calm descends, that is the place, more than any other, to which I am drawn. It is where you can sense the Shiants’ power, a place of turbulence only ever encountered in tranquillity.
I rowed the boat around, slipped easily through the natural arch at the corner of Garbh Eilean, where, every time you pass, a black guillemot drops out of the cracks in the ceiling on to the sea and then panics and flusters away to the north. The boat slides out across the liquid glass of the Minch. The seals asleep on the skerries wake, stare, shuffle seawards and plunge horrified into the water. The boat rounds the corner of those rocks and then the Shiants reveal their heroic heart. A curtain of columns half a mile long, five hundred feet high and each column up to eight or nine feet wide, drops into the Minch. The black lichen of the splash zone coats them to a height of a hundred feet or more. They bend slowly as they rise from the sea, a wonderful subtle elasticity in the mass. On calm days you can take a dinghy right up to the cliff foot, the boat just nosing and brushing at the giant forms. Afloat on the ink of the green sea, it is like being in the elephant house at the zoo, intimate with hugeness, pushed up next to a herd of still, alien, unembraceable bodies.
This was how William Daniell, the early nineteenth-century topographer of the British shore, portrayed the Shiants in his pair of 1819 aquatints: a vastness of form, a solidity and scale of presence, a tranquil sea passive at their feet.
I had this picture on the wall of my room at school and it remains a consoling image for me. Daniell does not attempt any heroics, any wild dynamism in the picture. He portrays the islands as a place of quiet, with a glow in the light and the huge, brooding stability of the cliffs behind them.
It never lasts. The Atlantic drives its next weather system on towards the islands and that sullen, lit beauty is taken up and twisted into a new and familiar frenzy. The Shiants’ temper is like a child’s: unbidden, unexplained rage; sudden quiet; a new paroxysm as total as the one before. Awake at night in the house, I lie listening to the weather. I see the Shiants as if from above, laid out beneath the storm. The cloud shadows beat across them. The swells cram themselves, one after another, through the natural arch, filling it, forty feet high and thirty wide, a tube of white water a hundred yards long, squeezed in there, until they burst out on the far side, released into huge, disintegrating flowerheads of surf. The cliffs and the islands are unmoved. Besieged by the Minch, they remain there, black, impassive and irreducible.
It is tempting to see the Shiants in that way. Perhaps any island owner would like to think of his property as a hedge against erosion but it couldn’t be more wrong. I once spent a few days on the Shiants with a pair of geologists and under their steady rational analysis all idea of the island fortress was soon whittled away. It was a highly enjoyable experience. Fergus Gibb, the Reader in Igneous Petrology at Sheffield University, and his friend Mike Henderson, now Research Professor of Petrology at Manchester University, both know more about the Shiant rocks than anyone on earth. They have been studying the islands since the 1960s and in a small dinghy they guided me around the cliffs and shore, pointing out to me where the story of the Shiants was to be found.
It was a charming, affectionate and mutually impatient double act. Fergus – Mike calls him Fergie – is the more bullish and macho of the two. He plays tennis for the Yorkshire Veterans, talks with fervour about ‘stonking great sledge-hammers’, likes to give things ‘welly’, wears dark glasses and short-sleeved tartan shirts, and looks after Mike, whose balance on the rocks is uncertain. Fergus’s big seamen’s stockings are always pulled up over his trousers to his knees. He takes charge and one falls into line. Mike – knitted wool tie, glasses, green V-neck, baseball cap well down on the brow – plays the complementary role. He and his wife Joan are keen on organic food, a certain kind of witty late nineteenth-century novel and the finer of the performing arts. Mike must be the only geologist in the world who has had a ballet dedicated to him and the first thing he asked me, as I sat him down to a supper of roast lamb in the house on the Shiants, was what I thought of Giselle.
Neither talks of immovability or irreducibility. They are engaged with something richer and deeper: the huge, slow dynamism of this extraordinary place. Everything in the geologist’s mind is a symptom of something happening. We layman landscapists may see the thing itself, the immovable rock, the huge columns, the stand of swaying bamboo, the Elizabethan ruff, the clustered organ pipes; they see the process, the mineralisation, the conductive cooling, the developing faults. ‘Don’t think of what it is,’ Fergus said to me. ‘Think of how it came to be.’
The Shiants, or at least most of them, are about fifty-eight and a half million years old. They are formed from a series of hot, intrusive magmas, giant plugs of molten rock rising from deep within the Earth’s mantle, which squeezed between much older fossil-bearing rocks above them. The process is about as dramatic, and as unlocal as it could be. The ‘emplacement’ of the magma was part of an event of planetary scale. About sixty million years ago, a whole zone of the Earth’s crust began to come under immense strain. Whether the weakness in the crust caused the upwelling of hot rock from deep below; or whether the upwelling of the magma, a huge bubble of heat and energy in the mantle, caused the weakness in the crust, is not certain. What is sure is that this was a stretched, tensed time. Heavy convection currents in the mantle, rising in a plume beneath this spot, put the whole of the Hebrides under pressure. A boil covering half a continent wanted to burst. The whole depth of the Earth’s crust was being stretched here, one part being pulled south-west, the other north-east. The result was one of the most cataclysmic episodes in the history of Britain. The precise geography of this is still not quite clear but it is certain that the enormous volcanic outpourings would have been visible from another planet. Signs of the rift system run from Disco and Nunavik on the west coast of Greenland, to Kangertittivaq on the east coast, out to Jan Mayen Island, deep within the Arctic Circle, besieged by drift ice, across tens of thousands of square miles of what is now the North Atlantic, through Iceland, the Faeroes, Rockall and St Kilda, down through the Shiants, all the way through Skye and the Inner Hebrides, to Staffa
and the Giant’s Causeway in Antrim, on to Slieve Gullion and the Mountains of Mourne, before ending in the granite of Lundy in the Bristol Channel.
The rift may perhaps have been the first attempt at the opening of an Atlantic Ocean. If so, the Hebrides would have been pulled apart. Floating in Freyja between the islands, I am directly above one of the world’s great might-have-beens. From within the centre of the Shiants, America and Europe would have moved slowly away, eased apart on giant conveyor belts of hot rock in the mantle. The Galtas and Garbh Eilean would now be off the coast of a New England shore made principally of the old and twisted rocks of Lewisian gneiss which form the Outer Hebrides. Eilean Mhuire would be the westernmost island of Europe, looking out not to the screes and green puffin slopes of Garbh Eilean, a mile away, as it now does, but across three thousand miles of grey Atlantic.
It didn’t happen. The rift never opened beyond a slit. The Atlantic opened to the west of Rockall and the Hebrides remained whole. All that is left of this cataclysmic episode now are the roots and the remnants. Nearly sixty million years of erosion has done its work and almost nothing of the surface landscape which this vulcanism produced now survives. The great mountain punctuation points of the volcanic province, Slieve Gullion and Mourne themselves, the hills of Mull and Ardnamurchan, the Cuillins of Rum and Skye, represent only the hardened footings of the enormous volcanoes through which this spasm of the Earth’s intestinal juices were vented on to the surface.
The Scotland into which the lavas poured was tropical and paradisical. America, Britain, and the Europe of which it was a part, would have been unrecognisable then. Lotus lilies, magnolias and several species of proteus, the tender plant which now flourishes in South Africa, were all thriving in the Hebrides. After each eruption there was a pause. Earth and life accumulated on the ragged, fissured surface of the lava before the next eruption destroyed and enclosed it. In Morvern, one can see the upper parts of each flow stained red where the weather had broken down the rock and turned the iron in it rusty. Each of these red layers is buried under the basement of the flow that came after it. On Mull, at Rudha na h-Uamha, John Macculloch, the fiercely opinionated geologist who was one of the first to give an account of the Shiants’ rocks in 1819, discovered the fossil of a tree still standing embedded in a river of lava, twenty feet deep, which had overwhelmed it. You can still see it there today.
The Shiants themselves, though, can never have known any of this. They never had their Hawaiian period and parakeets never flitted along these shores. These islands – or what are now these islands – came into existence two miles or so underground, perhaps under another volcano which has entirely disappeared.
That much was known in the nineteenth century. Since World War II, the understanding of the Shiant rocks has developed enormously, largely in the hands of Fergus Gibb and Mike Henderson, who, in five visits and with extensive laboratory analysis, have, quite extraordinarily to my mind, been able to establish a sequence of events that occurred here over a few decades about sixty million years ago.
It is a vast poem written in heat and liquidity. Remove the sea from your mind. That has nothing to do with it. You are in the dark of the Earth’s crust, several miles down. About a hundred and twenty million years before, in the Lower Jurassic, enormously thick accumulations of mud, silt and sand had built up in layer after layer on the floor of an earlier sea. These mud stones and shales have become rock. Beneath them, a huge bubble of hot molten rock starts to rise. The pressure it exerts opens fissures and ruptures in the overlying layers and it is between those laminations that the magma wants to squeeze.
This is the moment of the Shiants’ creation. The liquid rock, deep underground, probably took the form of what geologists call ‘a cedar tree laccolith’, a set of leaf-like chambers arranged around a central stem like the boughs of a cedar tree. The magma, pulsing from below, still hot from the energy generated when the planet first formed, runs into each chamber and beyond it into new leaves, new extensions of the form. The idea of a single tree is wrong: more likely a forest of them, the forms connected through the bough tips or a branching of the stem. The growth of this red-hot forest, each tree fifteen miles high and its canopy spreading as much as ten or fifteen miles wide, was moving north from the southern Hebrides. The whole floor of the Little Minch is covered in the leaves of that infernal cedar grove. In the far more recent past, glaciers have gouged hollows between them in the softer Jurassic sediments, leaving a family of submarine Shiants between here and Tiree. Occasionally they break surface, in the islands of Staffin Bay, the Ascrib Islands, Fladda-chuain, Eilean Trodday, all off the northern tip of Skye and in Sgeir Inoe, the lonely and vicious rock off Scalpay. Most are unseen, apparent only in the kicking of the tide.
Deep inside those ancient layers, the Shiants came into being in an orgasm of incandescent liquid. It was enormously hot: the greatest heat reached in the most violent fire in a burning building is about 850°C. That can melt bricks, turning them into pools of liquid glass. The Jurassic mudstones melt at about 900° but the heat of the magma itself was about 1150°C.
The Shiant intrusion would have been pulsed, the impulse coming and going, like a breath, an exhalation, pushing at the rocks above it and distending them. That dynamism is now fixed in the form of the rocks. You can find precisely the point – it is revealed on the shore in the bay next to the house – where the inrush of radiant magma came up against the cold mudstones in the roof of the cavity. Pull away the kelp and the serrated wrack. The little green crabs scuttle for the dark, the tiny transparent shrimps wriggle like rugby players in a tackle, and you can see the instant of creation frozen and preserved in front of you. The raging heat of the magma meets the old, cold mudstone and that meeting has had a double effect.
Elsewhere on the islands, you can see in the mudstones the layering of the sediments as they had settled onto the Jurassic sea-bed and you can find many fossils of ammonites and belemnites embedded in them like meat in a cold pie. Here, though, that has all been lost in the cataclysm. The mud stones have been baked hard into the solid grey stone called hornfels, without layers in it and without fossils. If you break the stone open, though, as Mike Henderson showed me, you can find the ghosts of the life once preserved here. Heat and pressure has transformed everything that was once in them and a faint, coppery, gilded sheen coats the inner surfaces of the rock. These are what Mike Henderson called ‘the pyritised remains’, the only evidence of the fossils which the rock once held, reduced in the furnace to this undiagnosable inkling, a breath of a suggestion, like the ash of an abandoned hearth. But the mud stones also exacted their price from the magma. Where the hot, molten intrusion came into contact with the country rock it was suddenly chilled. The semi-crystalline mush of the liquid, a kind of hot granita, was shocked into solidity by the old, cold stones. In suddenly becoming solid, the minerals in the magma are small, almost instantly formed and so the rock is as smooth and as fine-grained as cheese. That analogy is curiously exact: where you have broken the rock open, the fracture marks are exactly like those you find on the open face of a piece of broken Parmesan. ‘Chill’ or ‘chilled margin’, as this frozen magma is called, sits all alongside the hornfels on the beach, the twin products of intense heat meeting ancient cold, fifty-eight and a half million years ago.
Many things are still not clear about the making of these islands, nor is the precise order of events certain. Broadly though, it seems that several blades or ‘sills’ of magma were intruded here over a period of perhaps a century or two. One fairly narrow one, having cooled quite quickly, can be seen in the Galtas. Another makes the rib of rock through which the natural arch passes at the north-east corner of Garbh Eilean. A third forms Eilean Mhuire and the fourth, by far the largest, 537 ft. thick, created the vast bulk, about four hundred acres, of Garbh Eilean and Eilean an Tighe. No one has yet found how these sills are related to each other, nor how they are connected to the huge feeder pipe along which the magma arrived from the sou
th, but it is obvious that some of the old Jurassic rocks, the mudstones and shales, were caught up in the process. Most of the top of Eilean Mhuire consists of a huge raft of those older rocks buoyed up like a baulk of wood on the flood of magma which poured in, mostly below but some also above it. Another slab of old rock crosses the north-east corner of Garbh Eilean and has been eroded in the bay that stretches out below the puffin slopes there. Those soft and crumbly rocks, full of the nutritious minerals which accumulated on the Jurassic sea-bed, make far better soils than the hard, solidified magma of the sills. These Jurassic rocks, richer than almost anything in Pairc or Harris, and comparable in Lewis only to equivalent rocks around Stornoway, have been the basis for most of the farming on the Shiants. Without the wealth of Eilean Mhuire and the beautiful meadows at the Bagh on Garbh Eilean, it is difficult to think that life on the Shiants would ever have been possible.
For the professional geologists, this story is only the introduction to the book. They seek to penetrate much further into the arcana of chemical detail, above all into the diagnostic mineralogy of the different sorts of rocks to be found on the islands.
Previously it had been thought that the different minerals that can be seen in different places were the result of large crystals settling towards the bottom of the sill as the magma cooled. That was the old orthodoxy developed in the 1930s but Fergus Gibb and Mike Henderson have over the last four decades pushed most of that aside and discovered a quite different process.
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