Tag Archives: jurassic

The Jurassic Coast – where do you start?

The East Devon and Dorset coast in the south west of the UK, popularly known as the Jurassic Coast, was designated as a UNESCO World Heritage Site in 2001 putting it on a par with the Grand Canyon and the Great Barrier Reef.  The Jurassic Coast is unique in being the only place on the planet where 185 million years of the earth’s history are sequentially exposed in cliffs, coves, and other coastal features.   Since 2001, museums and visitor centres have sprung up along its 95-mile length and a fine stone sculpture, the Geoneedle at Orcombe Point, Exmouth celebrates the beginning of the World Heritage Site in East Devon.  On a sunny day in early November, just before the second lockdown, I went to take a look.

The Geoneedle at Orcombe Point with the view towards the Exe estuary and Dawlish Warren

The sea front at Exmouth was quiet when I arrived, there were just a few people about taking morning walks or enjoying the beach and the sunshine.    I left the car and walked to the end of the promenade where red cliffs strike out across the beach.  From here, it is an easy walk up a zig zag path, past the café, to the cliff top and the area known as the High Land of Orcombe.  By now, the early mist had evaporated affording spectacular views from the cliff top across the Exe estuary, Dawlish Warren and the south Devon coast as far Torquay.  The mild sunny weather had also brought out late season insects including bumblebees, hoverflies and an ageing red admiral butterfly.  A short stroll then took me to an open grassy area above the cliffs where the Geoneedle stands and the Jurassic Coast begins.  

A hoverfly that I saw near the Geoneedle

An ageing red admiral butterfly (Vanessa atalanta)

The Geoneedle is an impressive modernist sculpture about 5 metres in height and one-metre square at the base tapering to a stainless-steel point that takes on the colour of the sky, a clear blue that day but catching the sun at certain angles.   It was designed by public artist, Michael Fairfax and is constructed from three kinds of Portland stone with insets of eight different rocks representing the principal building stones found along the Jurassic Coast. The site also includes a compass showing some of the local landmarks and a Jurassic Coast hopscotch, both made from stones set into the ground.  The sculpture was inaugurated by Prince Charles in 2002. 

Not only is the Geoneedle a beautiful object, it also cleverly encapsulates the story of the Jurassic Coast in its design.  The eight stone insets are arranged so that they correspond to the three different geological time periods of the many kinds of rock found along the 95 mile stretch of coast between Orcombe Point and Studland Bay.  Starting at the bottom, the first two stone insets come from the oldest time period, the Triassic (about 250 million years ago); the hard, red rocks and softer mudstones below Orcombe Point are from this time period and were formed as sediment accumulated when the earth was an arid desert.  The middle four insets are from the Jurassic period (about 170 million years ago) when southern England was under a tropical sea; some of the best-known coastal features in West Dorset, Portland and the Purbecks were laid down at this time.  Finally, the two topmost insets are from the Cretaceous period (about 65 million years ago) when sea levels fell and sediments from lagoons, swamps and rivers were deposited.  The Cretaceous rocks are the youngest along the Jurassic Coast and can be seen at various points notably in the white cliffs at Beer in East Devon and in the chalk stacks of Old Harry Rocks near Studland.  

The Geoneedle showing the eight stone insets

Much of our knowledge of the origins of the different rocks comes from studies of the fossils and minerals found along the coast giving important information on the plants and animals that lived there and the climatic conditions prevailing during the different time periods.  The findings of local geologists and palaeontologists were crucial in this and the most important of these was Mary Anning, working in the 19th century, discovering fossils dating from the Jurassic period in the mobile cliffs around Lyme Regis.  Her discoveries illustrated a hitherto unknown, bygone world dominated by massive marine reptiles swimming in a tropical sea.

When I had finished looking at the Geoneedle, I walked back down the zig zag path, across the promenade and on to the beach.   By now, the tide had receded leaving large swathes of pale, firm sand and the area was very busy with people, many walking dogs, all enjoying the gift of this sunny pre-lockdown day.  There were even two horses with riders at the water’s edge making for a very evocative image.  

The low tide made it possible for me to walk around Orcombe Point to examine the red cliffs and their rocks. Starting from the beach road, red cliffs extend at right angles up to the jagged outcrop of Rodney Point.  The exposed rock here is a hard sandstone of the Triassic period with considerable honeycomb weathering caused by wind and rain.  Beyond Rodney Point, red cliffs continue but there is also a very striking red rock formation, the Devil’s Ledge, a broad wave-cut platform.    Orcombe Point lies a little further to the east with the Geoneedle just visible, high above.  These red Triassic rocks owe their colour to iron oxides and they continue with some interruptions along the coast to Ladram Bay, Sidmouth and beyond Seaton before Jurassic rocks take over near Lyme Regis.

The red cliffs near Orcombe Point showing the downwards tilt in the strata

To the east of Orcombe Point, the hard, red sandstone is overlaid by softer rocks and the strata exposed in the cliffs exhibit a pronounced downwards tilt to the east.  This tilt occurred after the Jurassic period and brought the older Triassic rocks to the surface.  Cretaceous material was then deposited and, after many millions of years of weathering, the Jurassic Coast of today was created with its distinctive pattern of exposed rocks from the three time periods. 

If, therefore, we take a notional walk along the entire length of the Jurassic Coast, starting at Orcombe Point and finishing at Studland Bay, we will encounter a multitude of different landforms including dramatic cliffs, stone stacks, pebble beaches and rocky coves.  These coastal features, and the rocks they contain, represent an almost continuous record of 185 million years of the earth’s history, rather like the pages of a book or the travels of a time machine. 

That day, of course, I had only skimmed the pages of the first chapter of the book.  As I walked back to the car, though, on that mild late autumn day, I reflected on how my visit had given me a renewed sense of the importance and of the unique nature of the Jurassic Coast.

This article appeared in the December 2020 edition of the Marshwood Vale Magazine

The oil well and the beach – a clash of the human and the natural at Kimmeridge Bay

The Isle of Purbeck in south east Dorset is an area of outstanding natural beauty but it is also Dorset’s oil country. I wanted to see how the demands of the oil industry could be reconciled with the demands of nature, so a few weeks ago I drove through the Purbeck Hills to Kimmeridge Bay.

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The view from the limestone ridge down to Kimmeridge Bay

 

The final stage of my journey took me over the coastal limestone ridge into open countryside where the views became wider, the colours and contrasts more intense. The wide sweep of Kimmeridge Bay lay below me in the sunshine: greens and blues, shadow and light, like an image from a travel magazine. From here the road descended, tentatively, through several broad arcs to reach the thatched, stone-cottaged village and the narrow beach access road. I left the car at the cliff-top car park and got out to look. The wide semi-circular bay, backed by moderate cliffs, spread either side of me and narrow, dark-stone ledges extended from the beach like giant fingers. A few white wavelets interrupted the surface of a deep blue sea and across the water, the vast mass of Portland loomed out of the mist.

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Kimmeridge Bay with the limestone ridges. The WW2 pill box shows prominently and its distance from the cliffs gives a rough indication of erosion.

 

I walked away from the cliffs and followed the access road westward around the row of 19th century, grey-stone cottages. The landward side of the road was lined by sodden arable fields enlivened only by a group of pied wagtails, jittering, fluttering. Soon I reached a large wire-mesh enclosure set back from the cliff edge. Inside the enclosure were pipe work, storage tanks and a “nodding donkey” oil pump, its huge black beam moving ponderously up and down as it sucked crude oil out of the reserves buried deep below the cliff.

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The oil well and pump

 

The pump has been working here since 1961 and is the oldest continuously working oil pump on the UK mainland. The oil-bearing rocks are located about 350 metres below the cliff, yielding 65 barrels of oil a day together with some natural gas. This is a modest deposit but it led to the discovery of the much larger Wytch Farm oilfield located ten or so miles away, stretching long distances under Poole Bay.

The oil pump itself is virtually noise-free as it is powered by electricity and, when I visited, there was nobody working nearby. The enclosure is some distance away from the centre of the Bay and partially screened by bushes so it is invisible to many visitors. Nevertheless, I find it incongruous to come across an oil well in this isolated, somewhat desolate and very natural place. To give myself some perspective I went to see more of the bay.

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One of the limestone ledges at low tide. Hen Cliff is prominent with the former fishermen’s huts below and the Clavell Tower above.

 

The beach is accessible down a precarious wooden stairway through a break in the cliffs, the Gaulter Gap, a narrow valley containing a fast-flowing stream. It’s a stony beach with pebbles, rocks and sand of many shades of grey, giving way to the dark stone ledges. These are visible at low tide reaching outwards into the sea and tilting slightly upwards to the west. The ledges provide great opportunities for rock-pooling and Ralph Wightman also speaks of a game of pebble bowls played along them.

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The World War 2 military pillbox

 

Near the Gaulter Gap the natural feel of the beach is rudely interrupted by a white cylindrical WW2 military pillbox standing on the beach looking as though someone planned to take it away but forgot. It used to sit on the cliff and its current position gives us an idea of how much erosion has occurred in the passing of 70 years.

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The rock layering in the cliffs

 

The beach is backed by grass-topped cliffs about 10 metres high containing distinct layers of rocks of different colours and textures. Bands of pale reddish brown and grey rock appear repeatedly in a semi-rhythmic pattern; differences in the hardness of the rocks and their resistance to erosion give the cliffs texture and a fascinating mosaic of colours. The rock layering in the cliffs make this both a geologist’s paradise and a geological time machine as each of the layers represents a discrete event in the Jurassic period, 200-150 million years ago.

Within the grey layers of rock is an oil shale for which Kimmeridge has been justifiably famous in the past. The richest deposits of oil shale, the “Blackstone”, are found in cliffs east of the bay. The Blackstone contains flammable hydrocarbons and used to be called “Kimmeridge Coal”. For many years it was used as a fuel, initially for cooking and heating and later for various industrial enterprises despite its high sulphur content and foul smell when burnt. In the 19th century it was mined here on an industrial scale and processed to make a range of petroleum products in Wareham and Weymouth in a series of short-lived enterprises.

The oil shale contains flammable hydrocarbons but it does not contain crude oil. Crude oil forms when the remnants of microscopic animals and plants accumulate at the bottom of the sea and are subjected to conditions of high temperature and pressure. Organic molecules are gradually converted to crude oil and this is what happened, many millions of years ago, in the rocks deep below the oil pump. The oil shale deposits exposed in the cliffs began in the same way but were never subjected to high enough temperatures or pressures to produce mature crude oil.
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The Clavell Tower

 

It’s a pleasant walk along the beach and out along the ledges towards the eastern end of the bay with its slipway, its jumble of boats and the cluster of black-painted, former fishermen’s huts. Behind the huts and partially hidden in the bushes is a scrub-lined, stone stairway heading steeply upwards to the top of Hen Cliff, standing 100m over the bay. This is a hard climb but worth it for the coastal views and for getting close to the Clavell Tower, a 19th century folly and observatory. This three story tower with its Tuscan colonnade stands on Hen Cliff with long views over the bay and the coast. Decked out in pink render and pale stone, it certainly looks very smart. But so it should, as starting in 2006 it was taken apart piece by piece and reassembled 25 metres away from the original site to prevent it falling in to the sea as the cliff eroded. It opened again in 2008 as an upmarket holiday rental. The Tower is now an integral part of Kimmeridge Bay but, in the past, reactions were divided. Frederick Treves, for example, referred to a “ridiculous tower” but to the Dorset dialect poet, William Barnes, in his poem “The Leady’s Tower”, it was “stately”.

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The view across Kimmeridge Bay from the cliffs near the Clavell Tower. If you click on the picture and enlarge it you will be able to see (from right to left) the tops of the former fishermen’s huts, the cliff top car park, the stone cottages and the oil well.

 

As I stood on the high cliff by the Clavell Tower, the full sweep of Kimmeridge Bay and its various landmarks were spread out below me. I had expected to be offended by the oil pump, fearing it might intrude on the natural world. But I was wrong: the oil pump is just one of several traces left by human hand at Kimmeridge Bay; it has little or no direct impact on the bay or its natural setting and is now part of the scenery. If you are looking to be offended by intrusions of the human on the natural, you could focus on the slew of wind-blown litter along the sides of the Gaulter Gap valley or the derelict, red fire engine gradually decaying behind the stone cottages.

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A more fundamental question does, however, arise about whether we should continue to extract this oil. Towards the end of last year the Paris Agreement recognised the need to reduce greenhouse gas emissions in order to limit the increase in global average temperature above pre-industrial levels to 2 degrees or less. Although the Agreement can be criticised for its lack of enforceability, it clearly defines the climate change problem as one of greenhouse gas emissions. A major contributor to these emissions is the burning of fossil fuels such as the oil extracted underneath Kimmeridge Bay.

Early in the 20th century, the novelist EM Forster stood a few miles north east of Kimmeridge and wrote in Howards End: “If one wanted to show a foreigner England, perhaps the wisest course would be to take him to the final section of the Purbeck Hills, and stand him on their summit….”. From this vantage point, Forster saw the rivers and landscapes of Dorset and neighbouring counties as a microcosm of all that existed in England. It wasn’t all beauty as he also saw creeping suburbia and its ill effects. Today we might relocate Forster’s vantage point and stand him by the Clavell Tower to look down on an eroding coastline under attack from increased storm activity and rising sea levels. He would also look down on the oil pump working away to extract more fossil fuels. Perhaps this alternative Purbeck view would illustrate some of the tensions inherent in contemporary England.

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Kimmeridge Bay from the stairway up Hen Cliff. Click and enlarge the picture to see the Kimmeridge landmarks. The WW2 military pillbox can be seen standing on the beach below the stone cottages

 

The photographs were taken on February 24th 2016