The other end of the North Downs - Kent August 2014

Canterbury - Kentish Stour - Dover and the White Cliffs - Samphire Hoe - Dryhill Quarry

13th - 18th August 2014

Evening light on Canterbury Cathedral from the University of Kent campus

Entrance to Cathedral area, Canterbury

During mid-August, I travelled to Canterbury by train along the coast, looking forward to the Open University Geological Society (OUGS) Symposium at the University of Kent - Marine Geotales, about marine and coastal processes, management of the coast, exploitation and exploration of resources such as oil and gas. All of the lectures were high quality, with good speakers. Highlights for me were the lectures about oil and gas exploration in the Arctic, recent tsunamis and the paleogeography / changes to the coasts and river systems of Britain and northern Europe during about the past three million years. On the Sunday morning a good field trip to Samphire Hoe, the nature reserve beneath the chalk cliffs between Folkestone and Dover the ground underfoot formed from the Channel Tunnel spoil.

Before the Symposium, I had a couple of nights at YHA Canterbury, to look round the area a bit more. Having lived in the west Surrey / northeast Hampshire area for much of my life, I knew the western end of the North Downs very well. Yet, I hadn't been to the south eastern end along the Kent coast since childhood camping holidays near Folkestone during the 1970s. The chalk outcrop is at its widest here. Canterbury is situated near where the Kentish Stour river cuts through the North Downs.

The time flew by, particularly the Symposium weekend. It was good mental break from the rush of art related preparations, rushing and convergences back home during the summer.

Dover - The White Cliffs - a thorough  soaking followed by serious failure of footwear Thursday 14th August

Took the train from Canterbury East station to Dover Priory. Indeed at one time, there had been a Priory on the site, illustrated in my book of old photos of Dover. Sign near the station to the North Downs Way. I headed through the town centre, along the run down looking high street. Then, along the Greenway (foot cycle way under main road) to the sea front and the Harbour. A glimpse of the River Dour. This rises near Temple Ewell to the NW of the town. During Roman times, there was a wide estuary here, forming the harbour. With the modern development of the harbour, its lower reaches got culverted. Here now, then, a somewhat forlorn, constrained looking stream.

Probably roughly where it flowed originally, I came out onto the sea front where I had today’s first view of the French coast and large stretch of water enclosed by the harbour walls. There’s now a cruise terminal on the west side. Before that, there was a rail terminal here.  At the eastern end, the largest continental ferry port in Europe, with sailings to / from Calais and Dunkirk, though as with all cross-Channel ferries since the opening of the Channel, sailing routes have been cut substantially. Lines of lorries thundered in and out of it along the A20 along the seafront and A2 via a flyover (Jubilee Way) just after the gap between the Castle and White Cliffs.

Dover Castle

I made my way up to onto the White Cliffs, passing the Castle (on a separate hill to the White Cliffs, the valley between occupied by the A2). Walked eastwards along the prom, following the Sustrans cycle route – Calais 21 miles, Inverness 1196 miles - across the main road to Back Lane West, beneath a sheer looking steep cliff with flint bands. Then took a steep, narrow path. 

Mathematical graffiti

Under the flyover some mathematical graffiti complete with the quadratic formula for solving quadratic equations, which I had to know for my maths O’level, but have forgotten now. Warnings of rock falls, wish I’d brought the hard hat I’d packed for the OUGS weekend.  The path then opened out on the higher ground near the National Trust car park and White Cliffs Visitor centre. The NT have managed part of the White Cliffs area east of the A2 since 1988. Footpaths at various levels on the cliffs which were stepped, the cliffs shaped by past landslips.

I got as far as Langdon Hole, where there was an info board about Tilden Smith’s aerial rope for bringing in coal mined seven miles offshore in the C19th. At the higher level a bench, overlooking the constant stream of shipping crossing the Strait, mostly ferries. Behind me the coastguard rotating radar hummed, scanning the Channel. 

I was tempted to go on to the lighthouse at South Foreland, which was not that far. Until now it had been sunny and warm, a bit too warm for me in the sheltered areas lower down. The Channel, at least when I arrived was calm. Then about 11:45am, I looked round and saw a big black cloud creeping over the Downs and along the Channel from the west. Thought I’d better turn round. The kids in front of me were singing I hear thunder.  For a brief while the sun lit the twin lighthouses either side of the western harbour entrance, against a the darkening cloud behind. Then, that went and down came the rain. A loud rumble of thunder.

Dark clouds roll in from the west...

It lasted all of half an hour, but the rain was more than heavy enough to get me thoroughly soaked through within minutes, boots included. I joined the line of people trudging back to the shelter of the car park and the visitor centre. Had to take real care on the slippery chalk, puddles quickly pooling on the paths, water rapidly running off the short grass. Another clap of thunder, but no lightning. By now, France had gone.

During the OUGS weekend, I heard a local weather saying: if you can see France, bad weather coming in, if you can't, it’s here. Bang on today. My waterproof was past its best and most people had come up to the cliffs by car.  Nonetheless, I don’t know where everyone else had got to. Before the rain came down, the cliff paths were fairly busy, people of various nationalities, including a group of French guys carrying their mountain bikes on their shoulders as they walked passed me along a narrow stretch of path. Hoped those two older ladies who didn’t look dressed for anything more than a very fair weather stroll in park, were OK.

I spent the rest of the afternoon drying out, starting in the café at the Visitor Centre, thankfully more down-to-earth / soggy- walker-walker friendly than tends to be typical at the NT’s stately homes. I had some crisps, a latte and a cake to supplement the sandwiches hastily eaten outside on the wet benches.

 

The ferry port from the White Cliffs

Leaving the café, I didn’t want to stray too far from cover, in case it tipped it down again and I got another soaking. At least two more dark clouds rolled in over the Downs, though they didn’t look as ominous or bring in as much rain as before. Later they seemed to linger inland. I wondered if they were getting a more prolonged soaking in Canterbury.

I walked up on to nearby Fox Hill Down, an area being conserved a chalk downland meadow. Here I took a short but contemplative stroll, reflecting on the historical and geological happenings in this area through time: right from the formation of the Strait of Dover (note – why do some call it Straits of Dover, when there is only the one?) and the Channel as we now know it during the Quaternary period, something I was to hear much more about at the Symposium over the weekend. The history of the area spans at least 2000 years, from Roman times. As a port at the narrowest part of the English Channel, it has always been a busy places with comings and goings, firsts and lasts. Earlier this month, of course ceremonies marking the centenary of the beginning of WW1 in which the toll was well into the millions. From WW2, of course, the famous Vera Lynn song Then in during the thankfully more peaceful latter twentieth century, childhood holidays.

Lots has happened in the area since those camping trips. For one thing then, no Channel Tunnel and I don’t think the roadwork was as direct / fast as it is now.

Two masts higher up the hill to the north, coastguard mast and radar to the east. At one spot, at the end of a hedge, the sounds from the docks drifted in with the wind and echoed back off the cliff. Mostly snippets from the standard on-board ferry announcements. I took them to be weather reports and other communications passing across the Channel. A return to the other (eastern) end of the North Downs was long overdue. Here, the chalk outcrop is at its widest, though strictly, it doesn’t end here. Instead, it continues beneath the Channel and comes out again in NE France around Calais, on the SE limb of the Weald-Artois anticline (again more on this over the weekend). At the western end – Hogs Back-Farnham Park , either side of the valley of the upper Wey north branch – the outcrop is narrow, without the prominent scarp slope seen in north Kent. Around the Strait of Dover, the dip must be to the east.

Across the main road along the seafront, a row of multi-storey terraces beneath the Castle, dated 1834. Presumably at one time old hotels / guest houses, some maybe still going; though as with the cottage size terraces along the Back Lane to their rear, they looked tired and very run down. To my artist’s eyes, this appealed to me, especially with the sheer cliff towering over them precariously behind. Certainly more so than the later C20 / early C21 blocks to the west, especially the big brick built block between the Castle and where I’d come out onto the seafront earlier. An ugly glass-fronted façade just inland from there, too, 1970s era I’d have guessed.

Followed the prom as far as I could go up towards the ferry port. A memorial plaque on a brick wall facing westwards: In memory of the young people from China who died near here on 18th June 2000. I took this to be the 58 who died in a lorry coming off a ferry from Zeebrugge, vaguely remembered from that time. One of the more grisly port comings and goings in the recent history of Dover.

My boots got me back down the hill to the seafront alright, where they just about stayed in one piece; but when I got to the western dock, the sole of my right boot came unstuck at the heel. Flip flopped like this back to the Priory Station. By the time I got there, the left one was the same. Back in Canterbury, got up the hill to the YHA OK, embarrassed and knowing that my task for Friday was to get some new ones. Never before have I had such a spectacular failure of footwear. These boots had got me up all three of the Yorkshire peaks on our June holiday in the dry. But obviously not up to any rain. Given the vagaries of the British weather not so good…

Canterbury and the Kentish Stour

Westgate Gardens

After shopping for new boots following the spectacular footwear disintegration on the White Cliffs yesterday, I strolled along the  River Stour in Westgate Gardens, past the Toddlers Cove play area towards the railway viaduct and water meadows. Beyond here, the Stour Valley Walk / cycleway continued upstream for three miles to Chartham, staying close to the river for much of the way. Green and pleasant in the parkland of Westgate Gardens, particularly considering the proximity with to the busy ring road. Aside that was from the piercing power cutting tool in one of the gardens which was a bit close to the frequent soundtrack to the summer back home lately. The water, nonetheless, looked fairly peaceful, the sun shining into the clear water, lots of ducks about.

Near the Marlowe Theatre

Lunch near the Marlowe Theatre, then downstream and along the eastern branch of the river.  They run guided boat trips, in shallow gondola type boats. A couple moored near the bridge by the theatre, where I picked up a few snippets over heard from the guides while I was by the river. The lady leading the walking party said there were several River Stours. I can think of at least five (not counting the various variations on the naming of the Kentish Stour and its tributaries). As with Avon, it must mean something like river or water. The paler green ribbon-like waterweed is taking over. I watched it drifting restfully with the current as I looked into the clear water from a footbridge in Westgate Gardens. I’ve seen it in the Lavant and other chalky waters closer to home. Apparently, it is thriving thanks to the higher levels of nitrate and phosphate from fertiliser / farmland run-off. Along some stretches through Canterbury, it has become so prolific that it’s impeding the passage of the boats. It’s not easy clearing it. Heard something about a machine with a propeller, but that disturbs the nesting ducks. Presumably it must be outcompeting the grassy green coloured species characteristic of chalky waters. 

Westgate Gardens

The Stour’s not strictly a chalk stream like the Itchen, which issues from chalk springs around Arlesford and has a chalk catchment throughout with over 90% of its flow coming from chalk groundwater. The Stour rises on the Lower Greensand to the west of Canterbury, rising as two streams converging near Ashford. The West Stour rises near Lenham, a watershed with the nearby River Len flowing into the Medway.  The East Stour rises further south along the Greensand ridge. It cuts through the North Downs between Ashford and Canterbury, the chalky section with the clear water being the baseflow of groundwater out of the chalk. At Horton, the baseflow index is healthy 69% (National River Flow Archive). Not far downstream from Canterbury, at Fordwich, it becomes tidal. At Plucks Gutter it is joined by the Little Stour which rises near Hythe. It now meets the sea at Pegwall Bay to the north of Sandwich, after meandering around a tight loop just inland. Presumably this formed when this stretch silted up, cutting off Sandwich, one of the cinque ports, from the sea. The loop has been short circuited by the Stonar Cut. Saltmarsh borders the bay. At one time, too, there was an outlet to the north, via the Wantsum Channel.

Kentish Stour Countryside Partnership

Downstream of the Westgate, along the easterly of the two channels, it was busier and more built up. Went as far as the new, expensive looking apartment blocks near what was presumably a converted and prettified watermill.

More views of the river through Westgate Gardens

Rampant waterweed

Samphire Hoe – Sunday 17^th August

This was one of the OUGS Symposium field trips on Sunday morning. Led by Leslie Richmond of OUGS and Melanie Wrigley, White Cliffs Country Park.

After going through Dover and following the main road along the coast, entered the nature reserve via a narrow tunnel into the cliff just west of Shakespeare Cliff. Then followed the road downhill to the foot of the cliff. Here, a flat area, about 1km end to end, surrounded by a seawall. The Dover-Folkestone railway at the foot of the chalk cliff. Within this area, a car park and air vents for the Channel Tunnel. Mostly though, a nature reserve given over to diverse flora and fauna.

The land here is a new bit of Britain created from the spoil bored out of the sea during the construction of the Channel Tunnel. All 4.9 million cubic metres of it. Similar amount languishing somewhere on the French side, too. The spoil consists of chalk marl. Since the Tunnel opened, the nature reserve has thrived ecologically and the area has become a very successful country park.

Samphire Hoe looking east towards Shakespeare Cliff

We walked at leisurely pace along the path on the southern side of the reserve, with views across the sea to France, eastwards to Dover and its dock. In the far distance to the west, the Dungeness peninsula.  France 21 miles across the Strait of Dover (similar sort of distance to more familiar views between the North and South Downs when standing on either ridge in Surrey or West Sussex  and looking across the Weald).

The name Samphire Hoe comes from the Shakespeare, as does Shakespeare Cliff. In the play King Lear, "In a field near Dover", with reference to precarious Samphire collecting from the cliffs here. We saw samphire growing in the reserve.

At the top of the cliffs behind the railway, a thin layer of golden, sandier looking material. This was windblown loess deposited in the periglacial conditions of the Pleistocene cold stages.

Looking west towards Folkestone

The railway line was built during the mid-C19, by blasting out chalk from the cliffs. This stretch of railway didn't look as opposed or as close to the sea as the section of the west coast mainline taken out by storms last winter. Nonetheless, the high the cliffs here being prone to rockfalls and landslides, the railway has proved expensive to run. Particularly at Folkestone Warren, the cliffs are susceptible to rotational sheering due to the Chalk slipping on the underlying Gault Clay. At Dover, where the chalk is thicker and the clay isn't exposed, the landslips occur in blocks as waves undercut the foot of the cliffs. Just beyond the western end of the reserve was a rockfall which had occurred last spring. The building of the harbour wall at Folkestone has halted / reduced the supply of shingle from the west through longshore drift. This would give the cliffs less protection against the waves.  From there, we could see towards Folkestone, with The Warren chalk cliffs just east of the harbour wall. Nearer the harbour were lower, muddier looking cliffs. This was Gault Clay. It contains marcasite, a form of iron sulphide, like pyrite. This would explain the pyrite like pebbles I recall seeing on the beach at Folkestone first camping holiday at The Warren. Mel showed us a sample back at the van, along with an impressive collection of Cretaceous marine fossils from the Lower Greensand which outcrops to the west of Folkestone - hence Folkestone Beds, Sandgate  and Hythe Beds, familiar from the Western Weald.

Varne lightship offshore.

View across the Channel beyond the sea wall

The sea was fairly placid today, but a sturdy seawall around the reserve is well needed as the waves can be big: big enough to crash over the top, turning the lagoonal ponds within the reserve from freshwater to brackish. As I'd suspected seeing the choppy water near the eastern harbour entrance at Dover from the White Cliffs around high tide during the afternoon, the narrowing of the sea through the Strait means strong currents, as much as 4 knots, apparently. Tidal range around 7m on spring tides, similar to London.

A bit about the formation of the Strait of Dover, from the breeching of a land bridge formed by the extension of the Weald anticline (Weald-Artois anticline) into northern France. Probably two megaflood events during the past 450ka, the first being at the end of the Anglian glaciation. A head of water formed behind the landbridge by a glacial lake sandwiched between the southern end of the ice sheet and northern Europe. Lake fed by ice beginning to melt, the Thames, Rhine, Weser, Oder and Elbe. I was familiar with this from multibeam sonar work by Sanjeev Gupta et al during the 2000s. Thanks to the data, now the mostly widely accepted theory. The megaflood, possibly one of the largest on Earth, caused scouring of the floor of the English Channel, forming tear dropped shaped chalk islets separated by deep grooves. In the Strait of Dover, too, depressions formed by plunge pools 120m deep as water cascaded over the ridge into the Channel. These have since been infilled with sediment which is less stable / looser than the chalk / chalk marl. The Tunnel engineers had to consider these when routing the Channel Tunnel and how deep to dig it beneath the seabed, which is why it isn't dead straight via the shortest route. The depth of the tunnel beneath the seabed is 50-75m.

Between the late c19 -1918, there was a colliery on the site of Samphire Hoe. Picture of this in our book back home with old photos of Dover. The colliery was on the chalk platform formed from the railway blastings, the shafts offshore. The coal is in seams about 450m beneath the chalk marl. During Mel's bit some discussion among the group about this coal. As with all / most of the coal in Britain and Europe, it's Carboniferous. Thinking of the Carboniferous Coal Measures in northern England and south Wales, I hadn't twigged until now how there could be coal anywhere near the chalk. Then Di Clements mentioned the extension of the London Platform - Anglo-Brabant Paleozoic landmass underneath the Strait of Dover and across to Belgium, where it's nearer the surface and more economical to mine. The Kent coal at Samphire Hoe / Dover Colliery was never really viable. There is an unconformity between the Palaeozoic beds and the Cretaceous, with much of the late Paleozoic and Mesozoic missing beneath London.

Cretaceous greenhouse - the excess CO2 would have been from volcanism, but they reckon it was as much as 1300ppm. With fossil burning, it's now edging to 400ppm, but the warm Cretaceous greenhouse world was conducive to coccoliths capturing some of this CO2  and laying down shells of calcium carbonate. Hence all the chalk in northern Europe. Discussion about this vs increased CO2 leading to ocean acidification which would swing the CO2 - carbonate equilibrium equation in favour of CO2, meaning less removed from atmosphere and reduced hard shell production by sea creatures.

Kentish earthquakes - epicentre beneath eastern England, northern Europe or offshore, felt in Kent. Mel said she felt the most recent one, in 2007. Notable earthquakes in 1320, 1580, 1950, the third one with a small tsunami wave, still big and sudden enough to kill someone swimming at Folkestone. At least one quake magnitude 5.8. I think there's been one beneath the North Sea in historical time in excess of M6.0 (Doggerland?) Both figures big for these areas, well away from a plate boundary. When I asked, my fellow OUGS members put it down to ongoing compression of the continental crust following the Alpine Orogeny 50-30Ma which flipped the Weald from a trough / syncline into a dome / anticline, and a major fault running through Germany formed as a consequence of it. This is the Central European Cenozoic Rift (see notes from lecture this afternoon) which is still active.

Both groups back at the coaches for about midday. Back to Canterbury via the coast westwards along the coast (now bypassing Capel-le-Ferne), then north across the Downs through the village of Denton (one of the place names noted during car journeys from Folkestone to Canterbury while camping). This brought us into Canterbury via New Dover Road, passing the yha.

Dryhill Quarry 18 August

Lift this morning from one of the other OUGS Symposium delegates to from Canterbury along the A’roads and motorways of Kent.  Glimpses of the north Kent coast. Last bit, on the A25  north of Sevenoaks slower and more winding. As in Surrey, the building of the M25 has seems to have made this road even busier and more congested than it had been before. Glimpses of the prominent North Downs escarpment from the road to Dryhill. Motorway here built on the Gault Clay, in the dip between the chalk escarpment and the Lower Greensand quarried at Dryhill. Dryhill Quarry was just to the west of Sevenoaks, now a country park. There, we met our leader David Bowler and got our eyes into the rock layers.

I recognised the layer cake slice wedge of rock outcropping near the car park, though more overgrown than I'd expected from the pictures at Canterbury. To look more closely, we had to wade steeply up through the brambles beneath it. Hard hats reasonable here, though I could have do e with a walking pole, too.

The first bit was measuring dips and mapping (which I was a bit rusty on), The gist of it all was, we were looking at layers of sandy limestone and cherty sandstone - 'rag and hassock' used locally as building stone. Saw some of this on house fronts and walls on the way to Sevenoaks station afterwards. This was part of the Hythe Formation in the Lower Greensand. The dips ranged from 25 degrees to 60 degrees, mainly north. At the far end of the quarry and amphitheatre, with a cliff with beds dipping 20 degrees to the south, on the south side, a fault, and north 45 degree dip on the north side. We were looking at saddle folds, smaller scale folds superimposed on the larger scale structure of the Wealden anticline where the dip is only 5 degrees. David outlined the larger scale structure, with reference to BGS field guides. The Lower Greensand beds were deposited at a time of ecstatically rising sea levels. The then Weald Basin was offshore from the landmass formed by the London Platform-Anglo-Brabant landmass. The presence of chalk overlying the London Platform beneath London shows that the rising sea overtopped it. Since the Alpine Orogeny uplifted the Weald, flipping the basin into an anticline, and uplift relative to sea level, a 2km layer of chalk has been eroded above the anticline exposing the older beds beneath it.

The trip ended around lunchtime. On the way to the station, David pointed out the rag and hassock in the local buildings, the bricks from Gault Clay. Lime from the Chalk. From Sevenoaks I took the train home via London after a stimulating few days.