The thick layer of fish clay at Stevns Klint tells us much about the demise of the dinosaurs 65 million years ago. Limestone from the cliff was used to form a constituent part of important buildings like Absalon’s Fortress and way back in the Stone Age, flints from here were used in making tools. Stevns Klint documents the planet’s development over the course of several million years.
by Geologist Tove Damholt, Eastern Zealand’s Museum and Ranger Peer Nørgaard, Stevns Nature Center
“Where is Stevns Klint?” Actually, it’s quite often that people ask this question, even while they are standing very close to the cliff. From the point of view on the land’s side, the place that can presumably be called Northern Europe’s most important geological locality does not pass itself off as being anything special. Its beauty cannot really be appreciated until we look at the area from all the way out on the edge, from the shoreline or from the sea.
Stevns Klint is the very best place to study the great mass deaths that befell the Earth 65 million years ago and wiped out more than half of all the planet’s animal and plant species, including the dinosaurs.
Together with the Faxe Limestone Quarry, Stevns Klint is also instrumental in the naming of an entire geological epoch: The Danian Age (the oldest age or lowermost stage of the Paleocene epoch or series, the Paleogene period or system and the Cenozoic era or erathem), i.e. the Danish epoch.
Cliff avalanche served to lay bare the scientific facts
At Højerup, you can see the remnants of the old church that lost its chancel to the sea in 1928 as a consequence of a catastrophic cliff avalanche. A solid staircase leads down to the beach, from where one can study the cliff at close range.
Both from the cliff’s edge and from the beach, you can clearly see that the cliff is divided into two strata: at the lowermost section, there is the soft, white chalk with horizontal layers of black flint. At the uppermost part of the cliff, we find the harder bryozoan limestone, with its many exquisitely undulating layers of gray flint.
Fish clay in between layers of limestone
The sea has slowly been washing away the cliff’s lowermost level of soft chalk, with the result that the slightly harder bryozoan limestone juts out over the white chalk. It is precisely between these two layers that the renowned layers of fish clay are to be found, the layers containing traces of the great mass death.
The lowermost part of the cliff, comprised of white chalk, actually consists of microscopic shells from algae. These algae lived in the free volumes of water situated in the ocean that covered Denmark more than 65 million years ago. The algae slowly sifted down onto the seabed. Gradually, over a long lapse of time, a thick layer of white chalk was deposited – a little at a time.
When you study the fossils carefully, you can see that in the topmost layer of white chalk there are indications of crisis. At the very top layer, the algae suddenly vanish and the white chalk is replaced by a few centimeters thick layer of fish clay. Scientific analysis bears out that the sedimentation of this clay coincides exactly with the point in time – and demarcates the limit – when more than half of all the Earth’s plant and animal species became extinct.
Disputes concerning history
This great mass death has been the focus of research for a good many years. Until the 1980s, it was generally believed that the great mass extinctions were caused by extensive vulcanism in India, a vulcanism that entailed that large quantities of dust and gasses were released into the atmosphere and brought about climatic changes.
However, sometime around 1980, a team of researchers led by Nobel prize-winning physicist Luis Alvarez, his son, geologist, Walter Alvarez, and chemists Frank Asaro and Helen Michels started to study the fish clay in Stevns Klint. To their great surprise, they found that in the fish clay, there were large concentrations of iridium, an element that is rare on Earth but is commonly found in cosmic material. For this reason, they arrived at the conclusion that 65 million years ago, the Earth was hit by a giant asteroid.
The new theory, and especially the way it was presented, perhaps, gave rise to an out-and-out scientific scuffle that heaved back and forth in a lively way and although many people today are convinced that the volcanoes in India and an asteroid-splashdown on our planet both exerted their influence on the large mass death, the scholarly brawl is still not over.
Stevns Klint still plays a central role in the ongoing debate – not only is it the place of origin for the theory about the asteroid but is also the best place to read and try to decipher just what species of flora and fauna lived before and after the point in time when the mass death occurred.
For this reason alone, Stevns Klint happens to be one of the world’s most famous geological sites.
The limestone acquires its own time
It’s not only the fish clay that makes the cliff something special. The hard bryozoan limestone found at the uppermost strata of the cliff, with its beautifully undulating layers of flint, is an outstandingly fine example of precisely these types of hills and has itself become the object of study, in order to gain an understanding about just how these types of hills expand in stature.
In the 1840s, there was a special interest in the limestone, which is also found at the Faxe Limestone Quarry. The Swiss geologist, Pierre Jean Édouard Desor, arrived at the conclusion that the limestone layers were of the same age as certain layers of chalk found in France. Because these layers were most elegantly visible in Denmark, he chose to call the geological period from which this limestone stems the “Danian Age.”
The use of flint and limestone
During the Stone Age, flint from the cliff was used for making tools. In the Middle Ages, the limestone was utilized for building stones used in constructing churches and for Absalon’s Fortress, as can still can be seen in the subterranean chambers below Christiansborg Palace. From the year 1800 and on, limestone was used for making building stones in local houses. In the 1950s, a large fortification was cut right into the rough limestone rock, with the result that today, the cliff contains Denmark’s only cliff fortress, the Stevns Fort.
Going for a walk on the stomping path
A “stomping path” runs along most of the length of the cliff but if you want to touch the chalk you’ve got to go down to the beach. The classic visiting place is Højerup, near the old church. But you can also reach the cliff through one of the two old limestone quarries, Holtug or Boesdal, or else you can take a guided tour that moves its way underneath the ground and into the chalk at The Cold War Museum, at Stevns Fort.
Did you know that ...?
- Stevns Klint Trampesti [the Stomping Path] extends for more than 20 kilometers between Rødvig Harbor and Bøgeskov Harbor. Along the way, you can see Rødvig, Boesdal Limestone Quarry, The Stevns Fort, Højerup, Stevns Lighthouse, Stevns Chalk Quarry, Flag Hill, Holtug Chalk Quarry, Kulsti Rende [Coal Path Trench] and Bøgeskov Harbor.
- during the autumn months, Flagbanken [Flag Hill] at Stevns Klint is one of Denmark’s best places to watch birds’ migrations. In 2008, almost 3,000 sparrow hawks were spotted in a single day; this is a world’s record. On good days, more than 5,000 birds of prey, of many different species, can be spotted here: eagles, hawks, Harris hawks and kites. Moreover, large flocks of small migrating birds come to this spot. On the cliff in front of Mandehoved, thousands of house martins are hatched.
- there are still more than 1,000 tons of chalk quarried every day at Stevns. Most of this is used as filler in paper products.
The biggest crash at Stevns
On March 16, 1928, the following story appeared in Stevns Avis :
“Højerup Church came crashing this morning: the largest landslide at Stevns Klint in living memory. What had been feared but not expected happened this morning. Two fishermen, who were at sea, heard a creaking and then a loud crash. They looked toward the church and saw the tall trees slowly pouring out over the water. An enormous crevice opened up and about 400 feet of the cliff and the cemetery slid into the depths, taking along with them the church’s chancel.
“A tremendous cloud of dust rose up and after it had subsided it could be clearly seen that the church appeared to have been sliced up with a knife and the doorway to the chancel was balanced ever so precisely on the cliff’s precipice. This was a sight that only a few people were granted the privilege of beholding. The old church has now spoken with its own voice in the ongoing dispute about whether to preserve it or not.”