Underbroen’s open source kayak

October 12th, 2018

Copenhagen’s harbour is turning into a theme park, with swimming pool, kayak hire, water buses and ever more numerous tourist boats. Here is a complicated and decorated structure with no discernible purpose other than sauntering by the open air art and hiring a kayak.

copenhagen harbour

A little further north is a relatively ancient bridge, Langebro, with its green copper control tower and the openable span on the right.


The left abutment of the bridge is in the vast shadow cast by a bank office, whose tax helps transform Copenhagen into the remarkably humane metropolis it has become. This bridge support contains a surprisingly spacious suite of rooms, once used by the people servicing the bridge, but now taken over by “Underbroen” (under the bridge), which is a cooperative of craftspeople, artists, nerds and people who combine all these titles to make things.

kayaks in harbour

To compete with the roto-moulded polyethylene kayaks, Underbroen has a kayak building project, a kayak whose structure is designed to be cut by a computer controlled mill out of a single, standard sized sheet of plywood, 12 mm thick.

vector diagram

The components are drawn in a vector drawing program.

milling the plywood sheet

This two dimensional drawing is then converted by another program which drives the cutter.

plywood negative

The resulting negative image is decorative in its own right.

andreas yannis and boat

The components are tied together with nylon zip ties.

Electrical conduit tubes in PVC form the keelson and the side stringers.

bow detail

The computer controlled cutter allows very precise fitting of the various parts. Careful detail design ensures accurate relative positions of the gunwales and keel to make a symmetrical boat.

painting the canvas

Once the frame was assembled a cotton canvas was stretched around the hull and sewn at bow, stern and cockpit. One can see a defect towards the stern where the stress from the stretched cotton has distorted the line of the side stringer. We probably need to put an extra cross piece to stiffen the frame here. Also the sewing is a slow job, so we aim to test stainless steel staples instead of sewing.

deformation of hull

The final covering was several coats of linseed oil paint.

All this took a long time. The many adjustments took four people about a year at three hours a week, so I was taken by surprise to turn up at Underbroen one evening and immediately be invited to test drive the boat.

test paddle

Photo: Yannis Bampos

I did not have my usual paddling kit, so used the opposite technique of stripping down to minimal clothing that, if it got wet, could be packed away for the train and bus journey home to Roskilde. Note the Greenland style paddle, also made from laminated layers of plywood.

At this point traditional kayak building experts will complain that this boat is not compostable, being full of industrial materials, cut by expensive automated machinery, controlled by computer programs and completely at odds with the trend towards natural materials and green techniques.

Our argument is that our kit, when perfected, can be put together in one day, by almost anyone, using just the printed instructions and very few tools. A traditional Greenland kayak, even using pre-dimensioned timber pieces, takes at least a week of full time work, and some skill in bending the ribs.

tim 2018-10-12

Roskilde fjord – the southern end

September 22nd, 2018

Within a day paddle from Roskilde harbour is a semi-natural area of meadows, woodlands and islands of great charm and variety, though without rocky drama.

map of south end, Roskilde fjord

Leaving the jetty of the sailing club is occasionally impeded by the only biggish ship on the Fjord, a sailing restaurant.


Otherwise there has not been much traffic for centuries, ever since ships got deeper than the 2 metres of reliable water depth through the 40 km long fjord.

The urban fringe is a line of expensive houses on the road leading north from Roskilde. There is strong re-building activity in Roskilde, which is a satellite town to booming Copenhagen, 35 km to the east.

Houses on Frederiksborgvej

The east side of the fjord is quite steep in parts, which makes a newly seeded slope vulnerable to torrential rain after a long drought.

Continuing northwards we pass Roskilde’s official bathing beach and campsite and then come to the self-proclaimed kingdom of Elleore (founded 1945), a tiny island with no permanent occupants but furnished with a quixotic sub-set of the attributes of an independent nation, but evidently no border guard to check our visas.

Elleore landfall

There is one tree on the island, a few scrubby bushes, concrete blocks from the second word war and a mysterious tower with a fine wrought iron ladder leading to an absent roof.

Paddling on northward one passes the cylindrical reactor building of the Risø nuclear research establishment, disused since the 1950s. The energy production priority has changed to wind power, with a multi-rotor turbine tower.

At the very top of the map is the mysterious plateau, Bolund, 12 m high. It is a piece of moraine from the ice age.

Bolund from sw

It has a varied flora and a colony of sand martins which nest in the softer strata of the moraine, which also has extremely hard parts in the form of huge stone blocks ready to fall out at any time.

Bolund cliff

Bolund is connected to land by a narrow neck, which is sometimes submerged.

This has a regular stratification with long strips of dried sea grass and blue mussel shells.

Bolund blue mussels

On the west side of the fjord is the wooded peninsular called Bognæs. It is accessible to walkers, cyclists, and of course paddlers, as is nearly all Danish woodland.

Lunch at Askehoved

Moving south now, one comes to a group of very low lying islands called Hesteholme. Even a kayak cannot sneak between them at low water.

Wading at Hesteholme

The water level in the Fjord rarely strays more than half a metre from its average level, but this allows exploration of some places which are often inaccessible.

Ringoen from Boserup

Between Bognæs, in the distance, and Boserup is the strange ring of gravel called Ringøen. Its lagoon can be visited when the water is high, and when birds are not nesting there.

Ringoen entrance

The passage into the lagoon is only a paddle length wide. Within, the water is shallow and good for a short pause from the 6 m/s wind blowing outside.

Ringoen lagoon

The abundant fertiliser from the birds supports a rich flora, here one of the last seashore flowers of summer, the Sea Aster (or a related species).

Ringoen asters

There is said to be a spring within the lagoon, which ensures that water is always moving out from the lagoon, but no-one has found it and I suspect reporting bias: it is easier to pass by the outside of the island than to land and tramp over to check the flow into the lagoon. Anyway, it should be easy to check with modern sensors and the internet of things.

Boserup wood is relatively ancient, surviving through the chance of ownership and is now a public park with primitive camping huts.

Boserup shelter

Further west one reaches Kattinge works, a water mill fed by damming a portion of the fjord to make a big lake. The dam is from the 14th c. but the water mill was first established here in the 18th c. The present building is 19th c., I suspect. It stopped working as a mill in 1910 and now serves as one wall of a concrete fish ladder, aesthetically brutal but good for wildlife and fishing people.

Kattinge work

A present day activity is shooting ducks. Here is the boat yard for the camouflaged shooting punts.

Kattinge shooting boats

Apart from risking a shower of tungsten pellets in the shooting season, the main hazard on the fjord is the abundance of stones hiding just below the surface. So far, my canvas kayak has proved resilient.

Parcelgaard cows and stone

Returning to harbour one meets another form of water traffic – the replica Viking boats with woolen sail spread to the wind.

Viking ship replica

tim, 2018-09-22

A sleeker Greenland style kayak

August 3rd, 2017

at fjord edge

I wrote about making a Greenland style skin on frame kayak in July 2011. Since then, I have moved to Denmark. To save moving expense, I stripped the skin off the kayak and discarded it; then I took out the ribs and cut the frame lengthways into three pieces with diagonal cuts, numbered for rebuilding.

The original version had too small a primary stability for my style of dawdling with a camera and landing in small coves to explore. It was also much too voluminous for my small bulk, thus riding high in the water and subject to wind pressure. Here is how I revised the design with minimal effort.

Firstly, I sliced about 12 mm off each end of most of the ribs, making adjustments to ensure that they give a smooth profile when forced back into the holes, which they did under protest because of the changed angle of entry to the mortices in the gunwales.

The chines have a limited range of position on the ribs, otherwise the rib will touch the skin. So I put the chines as far apart as possible and also pushed them away from the ribs with cross shaped pieces of cork, 5 mm thick, lashed to prevent them escaping. This is equivalent to changing the chine dimension from 20 x 20 mm to 25 x 20, which would have been a good idea originally because it allows freer placing of the chines to adjust the primary/secondary stability balance.

chine pads

To save weight, I left off the centre beams which connected bow to cockpit and cockpit to stern. This made the decks flatter both fore and aft, which provides a more secure bed for fastening down the paddle as an outrigger to aid entering and exiting.

Here is the finished frame. Note the hinged plate footrest. It can be pulled up with strings to allow goods and airbags to be pulled deep into the bow by a cord running over a pulley on the bow post. There is another pulley and cord loop to allow dragging stuff into the very confined space under the back deck.

kayak frame

Now I can fasten the paddle as an outrigger in front of the cockpit. It is much easier to use than sitting on a paddle behind the cockpit.

sliding in

Now for the skin. Because there is no centre beam, and because of sewing difficulties described later, I adopted Christopher Cunningham’s (Building the Greenland Kayak) method of first stapling the stretched skin to one gunwale, then sewing the seam along the gunwale.

For the skin, I changed from the original nylon to a tightly woven heavy cotton duck, 600 g/m^2 (= 20 ounce). This proved really difficult to handle. It was difficult to get a needle through, even with the sailmakers palm to drive the needle in and pliers to pull it through. I was averaging 30 seconds per stitch, through three layers of cloth. The cotton cloth is completely inelastic, so it forced pleats on the deck and stitching at bow and stern. It also demands a convex form everywhere, any concavity causes the cotton to lift away from the frame, however much tension one applies. Since my original kayak had a built in skeg under the nylon skin, I had to saw this off to make a very slightly convex keel line, shown below before mounting the protective beech strips.

keel profile

To sew the pleats flat without any hard structure below, and without access beneath the deck, I had to drill holes through the three layers before using a semicircular bent needle. To locate the needle tip under the deck I used a powerful LED lamp in the hull to cast a shadow of the needle tip. This only works in a shady place.

kayak skin fold

In the end I needed four pleats on the deck. The pleats are marked by stripes of varnish, to waterproof the drill holes. The main line of sewing is on the upper gunwale.

deck view hanging

Since I was working alone, the sewn skin was a bit baggy, so I sprayed it with water and passed a hot dry iron over it to shrink the cotton. This worked amazingly well. Just using a steam iron was not so effective.

For waterproofing the hull I used an unusual, but logical, formula from Claeys and Hugenin (Construire et utiliser les Kayaks de l’Arctique). The first two coats were by weight 10 parts of talc, 10 mineral turpentine, 10 raw linseed oil, 100 commercial varnish, in this case Hempel’s ‘Classic’ varnish, which appears to be a mix of linseed and tung oil with added siccative and various solvents to improve levelling. The talc is first mixed with a spatula into a portion of the linseed oil to ‘wet’ it, before dispersing into the main mix. The purpose of the talc, which is a silicate mineral with a plate like crystal structure, is to fill in the pores of the cloth to help make it waterproof, the mineral turpentine is to thin the mix to aid penetration and the extra linseed oil is to plasticise the varnish, which is really intended for wood surfaces. A further two coats were the undiluted oil varnish. The keel, chines and sewing lines were given extra coats of varnish.

The deck treatment is just a silicone water repellent (Hempel’s fabric protection) to give a water repellent rather than a watertight finish. The cotton cloth tightens up when it gets wet, which makes it effectively waterproof. My Klepper folding kayak uses the same principle, which gives a nice sweat-free interior.

The stitching of the bow and stern joins needs extra care in waterproofing. I used sikaflex polyurethane sealant (there are many product numbers, I used number 11, don’t know why), which hardens by reaction with water vapour. After that, bent beech wood strips were screwed through to the frame to give protection as well as to cover the messy sewing plus sicaflex.

The bow was further protected by tough nylon woven strapping in a form which fits into a recess on the towing system fitted to my bicycle for the 400 m journey to Roskilde fjord.

bike connector

The result of this effort, particularly with the heavy cotton cladding, is a boat that paddles well and straight and is stable enough that I can eat a sandwich without having to deploy the paddle float. Spreading the chines and shortening the ribs greatly improved the primary stability. The bow looks ridiculously sharp. It adds weight and wind resistance, and is unnecessary because I don’t intend to paddle among the ice slabs that occasionally form in the fjord. The cotton skin will not stretch even over this long bow section so a sewn seam was needed. The previous nylon skin could stretch over the bow with a seam only needed along the deck ridge, so there was some sense in making an elongate bow.

all set

The maiden voyage was around Roskilde harbour, passing first the decaying concrete of the Viking Ship Museum, containing the decayed relics of four Viking age vessels.

viking ship museum

Next to the museum is the harbour and workshops devoted to studying and replicating the Viking age technology. Here is a small boat recently fashioned using old fashioned tools by modern people.

faering on slip

The demonstrations of woodworking technique are the most interesting aspect of the Roskilde Viking revival for the age of tourism. There is now a whole fleet of reproduction boats which take people out on the fjord for a row, or a sail under a square of wool, if there is the right amount of wind.

viking ships in harbour

Viking rowers

The linked pdf below gives the dimensions of this kayak, which is suitable for a person 60 – 70 kg with slim thighs, because the cockpit rim sits fairly flat so there is not much space to slide in. Even so, the bow rides a bit high, so maybe the masik needs raising to tilt up the cockpit rim, then the bow ribs can be made shorter. The boat is heavier than I intended, about 19 kg. Next time, I will return to a nylon skin and make lightly loaded frame pieces from Western Red Cedar, and shorten the boat while keeping the present waterline.



Tim, August 2017

A few days later I invited an experienced paddler to test my boat, while I paddled my Klepper folder.

boats on grass

There are two alternate design principles for skin on frame kayaks. The Klepper has five plywood frames holding the longitudinal pieces, My Greenland style boat has 15 thin springy oak ribs doing the same job. The ribs only weigh one kilo altogether, so compare favourably with the fewer, but more massive frame pieces of the Klepper. The 6 mm thick oak strips are, however, tricky to heat bend to the exact curve needed at each point.

Yannis, my reviewer, has the same weight and build as me. The calm water profile shown below seems about right, as a compromise between freeboard to keep dry and side wind sensitivity, and ease of rolling.

skin boat lines

In the background is Roskilde’s campsite “Vigen”, where one can rent a plastic kayak. That is a sensible choice for the shallow fjord with many stones lurking a few millimetres below the surface. Fortunately they are mostly glacier rounded lumps which bump rather than cut.

The cross wind performance was tested in the 15 m/s blast down the long north west fetch of the fjord. There was some scum forming on the steep chop but the boat steered easily, and was quick enough to avoid the only sizeable boat which plies the fjord – The “Sagafjord” travelling restaurant.


It was a successful sea trial in most respects, except for the litre of water that entered the boat during the 8 km voyage. Now I will have to tip the boat into a water bath to find the leak. I suspect the sewing line at the bow or stern, or both, since the waves were not high enough to break often over the deck, which is not waterproof.

Tim, August 2017


October 9th, 2016

A brisk north easterly gale frustrated our hope of paddling round Møns Klint – the 130 m high cliffs of chalk which appear on every tourist brochure about Denmark, which is otherwise short of landscape drama.


Instead, we crept around the south of Møn, following the motor road causeway for a long stretch. There were also stretches of marshland with flocks of waders testing the air currents for the journey south.


We took a coffee break at Bogø harbour, where the ferry goes across to Stubbekøbing.



Our lunch stop was a strangely remote grassy path which led nowhere but whose planted vegetation provided shelter with the added buzz of wasps feasting on fallen apples.


We returned the same way, passing Fanefjord church.


Back on land, we visited the church, which is the man-made wonder of Møn which features in the tourist brochures.



The wall and vault paintings are from around 1500 and are attributed to the Elmelunde master, Elmelunde being a neighbouring church. The paintings were released from concealment under layers of limewash, then finely restored by conservator Lind around 1930. It is not obvious how much of the painting is original, because its appearance is now quite uniform, but if you have good light and binoculars you can detect the original mortar by its spots of black charcoal left from the lime burning. 20th c. lime was made without charcoal, so the conservator dipped a stiff brush in ink and sprayed the ink onto the surface. There is a lot of splashed black.

The next day dawned not quite so windy but wet and misty. We tugged the boats by trailer to a launching pad at Kalvehave at the north end of the bridge to Møn.


One pleasure of kayaking is travelling very close to shore, but in this region the fishermen deploy their nets from the shore outwards for a hundred metres or more. If one remembers to raise the rudder or skeg the boat glides over the ropes without causing damage.

We paddled round Langø and returned to our starting point near the bridge.


My thanks, as often, go to the members of the Vedbæk kayak club (north Copenhagen) who organise these excursions and offer transport to exotic places.


Fegen and Nissan

September 8th, 2016

river map, sweden

The Nissan (the terminal -an means river in south west Sweden) is a medium size river that meets the salt sea at Halmstad.

nyebro location

Our lodge for exploring the river, and the nearby lake Fegen, was at Nyebro, marked as an orange disk on the map above.

Nyebro house

breakfast at nyebro

The house has been modernised to provide what travelers expect now, but has some nice 19th c features surviving from a harsher age.

tiled stove

Our first excursion was to Fegen, a lake about 20 km due north of Nyebro.

fegen map

It was a delightful sunny day and the lake was exactly as a Swedish lake should be: peaceful and dotted with islands covered with trees.

island in fegen lake

The water is brown from the tannin released from the boggy acid soil. I saw one fish during the three day tour, and the footprint of an otter. I suspect that we moved too fast to detect the wildlife.

lunch on fegen island

We paused for an afternoon break on the island marked in orange on the map above.

The next day we set out on the Nissan. Launching at Hestraviken, which is about 13 km north of Gislaved, our destination, but 23 km down the winding river.

water level sensor

There is a scarily high water level sensor at our starting point. But this day the water level was low, which is not an advantage, because more rocks, and particularly fallen trees impede progress.

nissan - hestavik

gussjo map

The route starts as a river but soon opens out into a long lake. To the north is Isaberg at about 240 m. It is a ski resort, with tower on top and ski lift, from 1919, and more recently installed snow cannons, to keep the snow falling as this very modest mountain warms up.


pause on gussjo

At the south end of Söndra Gussjö we paused before entering the river again.

rapids on nissan - gussjo

The shallow sill where the river leaves the lake is the nearest we got to white water on this trip.

tree dam

The main hazard to navigation was fallen trees. This is a popular canoe trail, so there is regular pruning of fallen trees to give passage, while retaining the impression of an adventurous wilderness.

nissan paddlers

The route down the river is a continuous sequence of curves with dappled shade from trees just beginning to realize that autumn is here.


sand bank

For stretches of several kilometres the banks are high and sandy, with low reedy interruptions where former meanders now lie stagnant.

lunch in long grass

It was not always easy to find a congenial and accessible landing place, and there were calls to continue round the next bend, and the next.


Fortunately, the engineers in the party were good at facilitating the ascent, and particularly the descent towards kayaks precariously close between steep ground and deep water.

damp bank + horsetail

The sluggish, meandering course of the river made for boggy ground. The ground cover here is a mixture of reed and horsetail, without anything eatable.

bridge at gislaved

The Nissan valley has also a railway line and a major road, so the wilderness shown in these pictures is a fairly narrow belt.

gislaved weir

The river has long been exploited for industrial power. here our journey ended at the weir of the Gyllenfors (fors = rapids) power station in the industrial town Gislaved.

gislaved empty rapids

The dam was built in 1898 but the hydropower installation is from 2009.

gislaved roller mill

There is an industrial museum in town, with a giant and threatening roller press exhibited on the town park.

On the last day the group planned an up and down paddle on another section of the river, but I suspected it would be exercise without pause, so two of us opted for exploration of the forest near Nyebro.
tyttebaer + blueberry

The acid peaty soil, drained by ditches to improve the new tree growth, supported an abundance of blueberry and cowberry (Swedish: tyttebær = Vaccinium vitis-idaea), with a few late raspberries, so we were able easily to collect a kilo of mixed fruit to provide dessert to the returning paddlers, who landed just upstream of Fröslida dam (1983).

froslida dam

danger sign

I end this account with an eloquent sign, not to walk on fast flowing water. There is, however, a more subtle danger to kayaking in Sweden. I detected one tick, sucking blood from my arm. The prize, however, goes to Ms V, who gathered about twenty ticks, but she wore shorts.

I give my warm thanks to sympathetic companions and fine organisation and leadership from members of the Vedbæk kayak club. Having no driving licence, I rely on the generosity of others to share these exotic country pursuits.


The south Sweden archipelago

August 21st, 2016

evening at Jarnavik campsite

Our starting point was the campsite at Järnavik, 15 km west of Karlskrona in the (relatively) warm deciduous forest region of the extreme south of Sweden. It took a while to get there from Copenhagen, so our first glimpse of the Baltic sea was near sunset.


I had the privilege of sole occupancy of this miniature house (stuga) with four bunks. No one wanted to share, so it was luxurious and correspondingly expensive.

crab supper


The social arrangement started with a crab feast in the campsite restaurant. I have never mastered this art without getting sticky hands, masses of chitin fragments and very little meat, but the cheese tart was also good.

route map

The next day was lightly overcast but warm. We set off south west into an intricate arrangement of islands, shown on the map (click for usable view), which is accurate in the placing of the rocky bits but impressionistic in its kayak traces. The grid lines are at 2 km intervals. Routes 1,2,3 are day 1. I welcome corrections from the navigators.

which way?

Navigation in these low lying islands is not trivial. From the paddler’s eye level, 60 cm above the water, one seems to be surrounded by an unbroken wall of rock, occasional boats and houses, and mostly surmounted by trees. The passages between are only visible when one is close, so a compass is indispensible.

map reading

These navigation pauses gave everyone a chance to gather, which is why this post is unusual, for me, in showing paddlers’ front side.


Our first landfall was on Mjöö. We arrived together, thanks to the civilised tour leaders who kept us in a 100 m long bunch.

cake on float

Some people preferred to stay afloat. However, we shipped out two pieces of cake by wind-blown paddle float.


The paddle to our lunch stop was an intricate passage between islands of glacially rounded stone with trees clinging to the shallow pockets of soil. Many of these islands are maintained as nature reserves with carefully managed grazing to keep an open landscape with trees. The only grazing animals we saw were goats, but in other seasons there is also abundant bird life, as shown by the abundant carpet of dried goose shit.

lunch boko

Lunch was on an unnamed tiny island just west of Bokö The landscape of close cropped herbs interspersed with trees was showing the first signs of autumn – yellowing leaves and flowering heather. The trees were juniper, birch, rowan and oak, with beech in more sheltered places. The autumn maritime flora was still rich in bloom.

boko botany

The Swedish nature authorities are generous with wild information panels put up in unlikely places and informing of local species and geology. I noted some interesting cultural differences.

viola tricolor

Viola tricolor is called Stepmother violet (styvmorsviol) here. I remember its abundance near our house high on the Yorkshire moors, growing on the lead mine waste tips where little else could endure the poisonous soil. It is hardy and pretty; an attractive combination of virtues. Hence its English names: Love in idleness (Shakespeare) or more commonly Heartsease.

We arrived for dinner at the restaurant on Tjärö, with time for a pre-dinner drink in the dappled sunlight. This island is stated, on the wild information posters, to be the loveliest in the province. However, its connection to the mainland by ferry has brought enough people to make it just another tourist place with hard tramped paths and affluent ugliness.

red barn and paddlers ashore

path on tjaro

There are remains of the earlier hard life of the farmers and fishermen, stone walls and wooden barns, preserved under the ubiquitous Falun red paint – another toxic mine waste product, re-purposed to the conservation of buildings.

We paddled back to our camp in the gathering dusk.

morning mist

The next day was devoted to the gentler waters of the fjords fingering inland to expire in reed beds. However, the morning mist made me doubt our success in navigating the maze of channels.


Swedish prosperity, proclaimed by numerous flagpoles, is well displayed on these sheltered, mild coasts. Here on the mainland peninsula of Eriksberg.

fish farm

There is also modern industry here. I was puzzled by the sudden appearance of jellyfish, in abundance, with scarcely a hands breadth between them. The mystery was solved as we rounded a bend and came to the fish farm which was supplying nutrients to both caged fish and to the adjacent water in the tideless fjord.

rocky outcrop

We enjoyed calm water and muted sunshine for most of the time. A south east wind and the exposure to open water gave some waves as we rounded the peninsula of Västra udden.

concrete bunker

This exposed place is also fortified by concrete bunkers and a mysterious set of heavy iron rings fastened to the rocks exactly at water level. We were not far from the Swedish naval base at Karlskrona, whose 17th c defenses are shown in an earlier post.

last lunch

We returned to camp for a final lunch together, before the two and a half hour journey back to Vedbæk.

I enjoyed the trip because it was nicely paced with frequent stops to examine land as well as water and with everyone paddling together, for which the leaders deserve much praise.


Stevns klint, Denmark

June 9th, 2016

The long cliff (klint) line that extends for 14 km in a north south arc starts just south of our launching pad at Bøgeskov harbour, near Holtug, which is about 25 km south of Copenhagen.

The moraine debris cliffs here are not very stable.

house on the edge

Just south of this unhappy sight, the chalk cliff begins. It has a consistent profile of hard grey chalk which overhangs whiter softer chalk.

stevns klint 2609

The harder chalk consists mainly of bryozoa, which are tiny colony-forming animals with calcite exoskeletons, a bit like corals, which are also found in this district. They form bumps on the sea bed, which accounts for the wavy arrangement of flint layers in the picture.

This is a world famous geological site because the thin layer of clay just below the overhang contains an unusually high concentration of the rare metal iridium, which is thought to come from a colosal meteorite impact, currently thought to have been in the Yucatan peninsula of Mexico and proposed as the cause of the extinction of the dinosaurs.

stevns klint 2624

While we talk of distant locations, the soft lower chalk is ascribed to the Maastrichtian stage in geological history, at the end of the cretaceous period. The hard chalk above is put in the Danian stage of the neogene period (formerly known as the early tertiary). Denmark has the honour of labelling this period of earth history because it has a good sediment record of this time, having been mostly sunk below the sea.

This is a fairly good building material, and even better for making cement and lime, so it has been extensively quarried, here in the disused Holtug quarry, which is now a nature reserve.

holtug quarry 2616

we did not get very far on this excursion because the east wind was whipping up some chop as we approached the headland, so we turned back to take lunch at the harbour.

lunch landing

After lunch we paddled a bit northward in the shadow of a vast beechwood. Here the low cliffs are of glacial sand and gravel. The black specks of the flint within the chalk are here replaced by the black entrances to the holes made by the sand martins.

sand martin holes

We plan a visit to the southern end of Stevns klint later in the year, so I may have the chance to extend this short post. There is also intermittent access from the coast path.

Meanwhile, there is some interesting literature.

A Danish text, with good pictures is at:

A more academic geological article, in English, is here:

tim, June 2016