The Diatomite Cliffs (Moler)

In the cliffs that run along the banks of Denmark’s Liim Fjord, we find the diatomaceous earth that tells a story about the formation of our planet and a story about the volcanic eruptions that separated the continents. Valuable and outstanding fossils of creatures, plants and insects have also been found in the area.

by Dr. Stig Schack Pedersen, senior researcher at the Geological Survey of Denmark and Greenland - GEUS

In the middle of the 1990s, Her Majesty Queen Margrethe II visited the island of Fur. There, she had a chance to look at the diatomaceous earth. When she was informed that the more than 100 black layers of basaltic ash were approximately 54 million years old, her spontaneous response was: “Well, that corresponds to the age of the Faroese basalts.” The queen was pointing out, and quite rightly so, that in this way, our kingdom hangs together, geologically speaking.

The connection that the queen was making here, then, was actually a prophesy of the knowledge that geologists were then in the process of arriving at, precisely during those years. The many layers of basaltic ash correspond to the major volcanic eruptions that occurred when Greenland’s and Norway’s continental edges were separated and then drifted, respectively, to the west and to the east, while the basalts, of which the Faroe Islands actually consist, created the new ocean floor in the North Atlantic.

The beginning of this development occurred 55 million years ago and still today, the ocean floor in the middle of the Atlantic is undergoing a continuous process of formation; Iceland serves as a striking proof of this. However, Iceland did not emerge in the middle of the ocean until after 1,000 square meters of ocean floor were created – around 50 million years ago.

Secrets of the diatomite
The diatomaceous earth at the Liim Fjord consists of a mixture of fine clay and incomprehensibly vast quantities of diatoms, which are microscopic kieselgur algae that once lived, died and sank to the seabed in the diatomite ocean. All together, these many diatoms eventually formed a layer that was 60 meters thick; this layer was formed over the course of three million years.

It is not only in the diatomaceous earth area at the Liim Fjord that we find volcanic layers of ash. Such concentrations of this material were spread across most of northwestern Europe. But in most other places, the ash layers have been buried by marine clay. In these types of sedimentary deposits, typically, the volcanic glass was readily transformed into clay minerals. In the diatomaceous earth, on the other hand, the layers of ash have been preserved.

There are more than 100 species of diatoms, but the largest and most predominant type is the Coscinodiscus salt-water diatom, which consists of a saucer-shaped round case that can measure up to 0.2 millimeters in diameter. The shell consists of opal and the high concentration of silicon has been a factor in preventing the volcanic glass from being further transformed.

Like pages in a newspaper
The diatomaceous earth and the layers of volcanic ash were delivered and deposited in the great ocean which, at that time, covered the area of today’s North Sea and most of Denmark. Just as algae and diatoms can flourish and thrive on the warm summer days in Danish waters today, diatoms were evidently flourishing and thriving in the Eocene oceans, in various periods.

Sometimes there was a sharp increase in the preponderance of diatoms, which resulted in a high concentration of withered diatoms on the ocean floor, forming a thin layer. Eventually, as the thin layers became embedded on top of each other, the material came to resemble the pages in a pile of newspapers.

However, this presupposed that the ocean floor was anoxic, so that epifauna and benthic fauna could not survive there. Where the water at the bottom of the sea did contain oxygen, though, so that epifauna and benthic fauna could live, the stratification was disturbed by the epifauna’s and benthic fauna’s borings. Whenever a large cloud of ashes happened to drift over the sea, the boring channels could become filled up with black sand. The whole boring channel’s pattern can therefore be seen quite clearly in the diatomaceous earth.

Petrified remains of animals

But it was not only diatoms that filled the sea with life. A large number of fish were swimming around in the water masses. The most common fish at that time was the Argentina sphyraena, which measured about 5 centimeters in length. From territories in England and Scandinavia, birds and insects were blown out over the open sea, where they eventually sank to the bottom of the oceans and were preserved as fossils.

Taken together, the many finds serve to offer a vivid picture of the interesting animal life that existed 50 million years ago in and around the diatomite seas. At museums on Mors and Fur, there are splendid examples of the best finds from the diatomaceous earth. Many of these are worthy of the special “Danekræ” designation – that is to say, natural historical finds like fossilized animals and plants, skeletons from the Ice Age or special crystals that have been found in the soil in Denmark, which the State owns and which possess outstanding scientific or exhibitional value.

The diatomaceous earth would still be lying at the bottom of the Liim Fjord had it not been pushed up in folds and geological thrusts by the advancing ice during the most recent Ice Age. From having been buried below the surface of the sea at depths exceeding 20 meters, the diatomite was pushed up into the hills on the northern part of Mors, on Fur, in Salling and in Thy, about 25,000 years ago.

The diatomite cliffs are our mountain ranges

By this time, the Scandinavian ice shield had expanded to a thickness of 3 kilometers. The ice was spreading down across Denmark, which was laid out at that time in the form of mammoth steppes covered with lakes. With the coming of the ice, the rising grounds were pushed into the ranges of hills that are so pronounced in relation to the diatomaceous earth area’s landscape, where the cross-section cutting through the hills’ composition can be seen in the large cliffs, which mirror themselves in the calm tranquility of the Liim Fjord’s sea.

The structures are particularly visible on a dry summer’s day, when the diatomite earth appears completely white and the ash layers, as black stripes, delineate the geological displacements’ forms. On a modest scale, it could even be said that the slivers of diatomaceous earth correspond to small mountain ranges in the Danish landscape.

The diatomite’s applications
Around the turn of the twentieth century, people began to exploit the diatomite industrially as raw material in the manufacture of moler bricks and other insulating materials. The first such bricks were produced at Frederiksholm Teglværk [Brickworks].

Today, the diatomite industry on Mors produces different types of granulates with high absorbency for use in industry and private households, as in so-called “cat litter.” These granulate products are exported to many countries. Diatomite can also be used in ovens, chimneys, as a stabilizing component in making dynamite and in the filtration of yeast-brewed beer.

The exquisite landscape, with its elongated hills, where the white-yellow cliffs make their appearance as notches carved into the hills’ internal structure, is unique. The many wonderful finds of fossils, which have been exquisitely preserved in the diatomite, and the invaluable geological documentation, where the full gamut of geological topics is represented – from sedimentary deposits in the ocean to volcanoes, from fossils to crystals, from structural geology to glacial geology – all play their part in making the diatomaceous earth something entirely outstanding in Denmark.

The diatomaceous earth: nature-created art

People who see the diatomaceous earth at the Liim Fjord for the first time have exclaimed: “I didn’t have any idea that Denmark can boast of such an elegant geology.” The same kind of reaction turns up sometimes when foreign tourists visit a spot like the 60-meter high Hanklit, which can elicit as dramatic an effect on foreigners as when they catch their first glimpse of the Jura Mountains located north of the Alps.

Actually, it might be said that you don’t even have to know the word “geology” in order to appreciate the beauty of the pale yellow cliffs, which reflect themselves in the Liim Fjord’s sky blue waters, where the gaze is captured by the black bands in the cliff. You can immediately see how the geological layers have been bent and wrinkled.

Here, it is clear to see that great forces have been at play. The Liim Fjord’s waves have done their part, also, with the result that today, we can stand and admire the nature-made sculptural forms in the diatomite cliffs on the islands of Fur and Mors.

Sidst opdateret: 20.05.2010