23rd February 2018
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You too can enjoy the geologist’s palette

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WEST Sandwick beach in Yell used to run pink in waves and bands, spreading like blush trails out from the burn at the north end of the sands. Year after year I took visitors or friends to marvel at the natural pigment which had been etched from garnet rich schists and ground into pale plum dust by abrasion with everything along its path. We would fill jam jars, carefully, with silky layers of bleached cream sand grains, alternating with the rosy layers to make stripy gifts. But things change.

What better surprise for a beach wedding, than a transformation from subtle pink and cream to silver and cream? Somehow, the garnet had gone! Silver mica flakes had arrived in its place. I hunted around, mystified. Where had the garnet vanished to? Surely the huge local garnet-rich rock had not been exhausted. I found just a trace, a film of that sugary tinge across sand beyond the far north bank of the burn; a whisper of mulberry amid the parchment.

But having reluctantly come to terms with the loss of one geological novelty, I made an effort and turned to welcome the other. Garnet out, mica schist in. I scooped a little glitter from a hollow just out of reach of the waves. The flakes of mica were unusually large. They settled after each wave into small collections and flashed freckles of minute dazzles at your eyes as you walked along the ebb. On the 8th of the 8th of the 8th, it was perfect for wedding confetti under the bare feet of the bride. Catherine, Stephen and wedding guests walked on a silver carpet.

At some point no doubt, the sea will finish nibbling and grinding away at the silvery rocks too and yet another chapter of eroding history will begin. The beach will gradually lose the glitter and new effects will take their place. Maybe another garnet rich mass will become exposed again, and sift rose shades across the paler silica fragments. Maybe shells will begin to be cast from new shellfish beds offshore the waves will start to strew white shell particles in lacy frills across the strand line. There are countless variations.

At Ling Ness last Sunday Nils Groneberg found magnetite among the sand of the White Ayre. His tripod has a magnetic plate at one end. After it had been laid down during a sun-soaked, leisurely refreshment break, he found tiny particles of iron rich grains standing to attention across the magnet. They stood in little threads, clinging end to end like iron filing in schoolroom lessons on magnetism. Tresta beach in Fetlar has even more of these grains and I’m sure there are others.

The White Ayre on Sunday was exquisite. You could not have found a more beautiful setting. A seal homed in on us and delighted three young newcomers to the walks. Rachel, Matthew and Jonathan Dorrat watched as the seal swam close in, stopping to lift its head and stare at the party of walkers relaxing on the shore. It played to the gallery, twirling and rolling in the turquoise water, an indigo shadow against the transparent background.

A second seal joined the first. They were common seals, with great dark eyes and short, snub noses. Their skin was wonderfully pale, shining silver grey in the intense light. Now and again one or other would make a mock terrified dive, thrashing the surface with a powerful tail in a small explosion of white spray. Their necks appeared to be extraordinarily supple, as they could twist their bodies right round in the shallows, while keeping their eyes fixed on us throughout the turn.

We looked in vain for otters during the day, but the wind was against us and any otter with a nose out of the water would have caught our scent long before we might have caught a glimpse of them. We were a bit noisy too. Folk were enjoying themselves too much to be truly silent. Otters may have poor vision, but their hearing is razor sharp. Charles Gear, our guide, nevertheless showed us where the local family of otters holed up. They must have been snoozing deep in the Otter Hadd, only a score of yards away on a skerry.

One oddity on the White Ayre was the shells. They were all enormous. There were cockle and clam shells, limpets and an occasional razor shells and every one of them was massive. They were heavy, remarkably thick and almost certainly the biggest of their kinds that I have ever seen. We couldn’t work out why this should be. I wonder if there are any conchologists in Shetland who could explain this curiosity. There were literally, no small shells at all.

Ling Ness has beaches at many points around the headland, facing at one time or another every point on the compass, and every one told its own story about the geology of the area. We had geology maps of Nesting with us, both the “solid” version, which shows the variation of rock types below ground, and the “drift” map, which shows the natural land surface details. The latter was easy to follow, showing clearly where bedrock was exposed and where glacial activity had left deposits.

The solid map was a real treat. Some geologists, we had been told once, bought geology maps of Shetland just to frame and hang on their walls, to gaze at for pleasure, revelling in the extraordinary jangle of colours. A Nesting map would probably be the best of all. The whole area is a dazzling maze of red, orange, pink and purple, with green streaks and light and dark blue patches. Each coloured blob or stripe tells a story and the stories have been made marvellously easy to interpret, by some inspired design work.

I would love to know who first came up with the idea of colour matching the different rock types to their origins, rather than to the colours that you see on the beach. Geology is always horrendously complex, but the solid maps help a lot. Anything blue has probably been associated with water. Crystalline limestone and the related rocks at one time were formed from sediments accumulating on lake or sea beds.

Fiery colours, hot reds and orange shades represent igneous rocks, which have been molten and cooled into their present state. Green comes for serpentines and hornblendes which often come in a range of greens from light, to almost black greens and sandy colours, pale tans, creams and gingers are usually sandy or silty in origin. After this, purple and mauve remain to bring in the rest of the rocks, along with a whole gaddery of tiny symbols and letters which are printed against the colours. If you are, like me, an enthusiastic but untrained rock collector in Shetland, treat yourself to a solid geology map and scrutinise your own corner, depicted in vibrant, scientific colour.

Jill Slee Blackadder

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