Sandstone

We walk along a narrow path northwards from Birkhams Quarry where the sandstone is still a raw, bright red, and – because the sandstone layer is tilted -we also walk backwards through time, to a face where the blocky layers of rock are whitened by lichen, and partly hidden by fern and heather.

Despite the vegetation, there are plenty of clues, and we scramble around on the banks to look at the exposed rocks. My companion, geologist David Kelly, shows me how the layers of sandstone are interspersed with shallow bands of red shale, like flaked tuna between slices of solid rye bread.  The shale, formerly silt that has been compressed and solidified, is easily-fragmented, soft and shiny when rubbed with a finger. The greasy red mud smeared on my fingertip may be 230 million years old, give or take ten million years or so.

‘Naming of names’: there’s something exclusive but poetic about scientific jargon, and David enjoys the proper names of the features he shows me: ‘load casts’, ‘shale flake conglomerate’, Brockram and breccia, and small pockets of muddy ‘rip-up clasts’. There is evidence everywhere to show that this sandstone was sedimented from rivers. In places the rock shows parallel lines, indicative of fast strong currents; on one block the lines fold back on themselves, suggesting the soft sediment was folded, perhaps when a river bank collapsed. There is ‘cross-bedding’, sloping lines that intersect the horizontal, signs of ancient sandbanks with variously-angled slopes. There are, too, boulders with bulbous growths, where the sand was pressed down into mud before it was hardened into rock. David hands me a fragment of the rock, turning it to catch the light; it sparkles. ‘You see those glittery bits? They’re mica flakes that settled out of the water.’ The rock’s colour is due to haematite, in which the iron has been oxidised to the red ferric form; in the St Bees’ formation, here on the west coast of Cumbria, the sediment was exposed to oxygen in the rivers and on the flood-plain.

Millom poet Norman Nicholson had a sculptor’s eye when he wrote about St Bees’ sandstone:

Smooth as a walnut turned on a lathe,
Or hollowed in clefts and collars where the pebbles
Shake up and down like marbles in a bottle.
Here the chiselling edges of the waves
Scoop long fluted grooves, and here the spray
Pits and pocks the blocks like rain on snow.

We slither down the cliff, towards the Barrowmouth gypsum mine. The path is buckled and indistinct, interrupted by slippage of the shales. There is a small square bridge of cut and faced red sandstone blocks; the remains of a sandstone pumphouse and weigh-house, tipped backwards by the rotated slip face; a few hard white rocks of anhydrite; and ‘John Smith 1935’ – he had carved his name at the top of the cliff, and the looped and flowing script of his name is carved here too.

Muddy and damp, we reach the shore, amongst boulders that have tumbled from the cliffs above us, many of them now disguised by slime-green seaweed; but neither algae nor the salty white encrustation can completely hide the colour of the slabs beneath our feet. It’s sandstone, again, but of a deep purplish colour, a different age, a different origin: Coal-Measure sandstone. Where we’re standing was a humid tropical swamp, about 290 million years ago in the Carboniferous.  Originally pale, the rock’s surface was oxidised to this characteristic purple-red when the swamp dried out and transformed into arid desert.

Today the Robin Rigg windfarm is the most obvious sign of human intervention in the Firth but, fifty years ago, there would have been hundreds of men working out there,  beneath the seabed.  Coal has been mined in the Whitehaven area since the 1700s, and Haig Pit, the last to close, was shut down in 1986, so there are still people around who worked in the colliery or remember the pit and the machinery, the locomotives and coal-ships. Haig Colliery Museum is enormously important as a reminder of West Cumbria’s past, and of the major role that coal has played in our social and economic history.

A map of the collieries, hand-drawn and  coloured by one Ted Wilson, gives a shocking insight into the sheer scale of the collieries, the quite extraordinary size and interconnectedness of the three-dimensional maze of tunnels out there beneath the sea. From the headland and harbour, outlined on the map, are blocks of colour stretching Westwards, each representing a mine: green for Haig, pink for Saltom, brown for Kells. Within the blocks of colour are exquisitely-detailed plans of the thousands of ‘roads’ and faces and tracks beneath the sea, mile upon mile of them, with some of the pits interlinked by other roads that functioned as escape routes. The map reveals even more: dotted across the mainland are tiny circles that indicate small, sealed-off workings, with names like Knockmorton pit, Burnt pit, Wood-a-green and Thicket. Most of them would have been forgotten, except for the subsidence they still cause.

The coal lies in several seams or ‘bands’ at different depths, separated by sandstone or shale. The mighty Haig Pit was 1200 feet deep, and its workings were dug out nearly four miles under the sea. In some places, water – fresh water – had seeped down through the various fault lines and formed shallow lakes between the layers. The late Norman Hammond once told me that he had some freshwater mussel shells that had been found in one of the mines – dating from the time when the Solway basin was a forested and fluvial plain.

Haig Pit was closed for economic reasons, but a rich store of coal remains beneath the Firth: hundreds of millions of tons, apparently enough to produce a million tons of coal per year for 800 years. According to Professor Nicholas Stern,  the proven reserves of the world’s top 100 listed coal companies and top 100 listed oil and gas companies – reserves like this – could produce 745 billion tonnes of carbon dioxide. Stern says that at least two-thirds of these reserves will have to remain underground if the world is to meet existing internationally agreed targets to avoid the threshold for ‘dangerous’ climate change. There is little sign of this happening. If it were to do so, these reserves would be in effect unburnable, and thus worthless – leading to massive market losses. It does not make economic sense to leave this coal under the sea; it does not make any other kind of sense not to.

Out in the Solway Firth, their feet buried in the sea-bed above the coal-seams, the sixty Robin Rigg turbines capture the same wind which blows me along the cliff above St Bees’ Head, and has churned the sea into great brown breakers that are crashing onto the shore; their booming is amplified by the dripping cave where I eventually sit to eat my sandwiches. Low tide has exposed a red sandstone platform, pitted with deep circular pools, each fringed with pink corallina. The sandstone has been eroded into shapes that are so tactile that you need to feel and stroke them. Parallel grooves are separated by edges so thin and fine that they must surely break.

For more about coal, stone, stone-masons and sculptors, or for information about guided walks on the Solway shore, visit Solway Shore Stories. Ann’s personal website is www.annlingard.com

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