Nature in the History of the Baltic

The Geographic limitation for our symposium is the Baltic Sea area or the Baltic Rim, sometimes referred to as the Baltic for short. The linguistic precision is better in German: Ostseeraum. By this we mean the water, countryside and countries around one of the world’s largest inner seas; an inner sea whose state of health is not the best. Industrial pollution, motor traffic, inadequate sewage treatment and mineral nutrients from agriculture all contribute to the clinical picture. But we should not despair and above all not begin our symposium on a minor chord. Our patient – the water of the Baltic Sea – is beginning to recover thanks to our joint national efforts.

As a geographer I consider the map an excellent aid in defining and illustrating spatial limitations. The drainage basin of the Baltic Sea is such a possible geographic limitation. This drainage basin is more than 4 times the size of the sea itself. It reaches all the way into Norway in the west. In the south it reaches as far as the northernmost parts of the Czech Republic and Slovakia and in the east far into Russia, Belarus, and the Ukraine. The Öresund Sound, Bay of Kiel, Danish Great Belt and Kattegat and their drainage basins are also counted as parts of the inner sea of the Baltic Sea. Over 80 million people live in this area.

Consider the Baltic Sea as an organism. An organism needs oxygen to live. Supplying oxygen to the Baltic takes place through a couple of narrow arteries – Oresund Sound and the Great Belt – in combination with westerly – north-westerly storms that carry in oxygen-rich saltwater from the North Sea and Skagerrak. This oxygen-rich, heavy saltwater sinks to the depths of the Baltic Sea pushing aside the hydrogen sulphide accumulated in the deepest parts of the ocean floor. Parts of the saltwater are mixed with fresh water from rivers producing a surface water that also needs to exit via the Öresund Channel and the Great Belt.  Water catchment must balance drainage. Due to the narrow passages in both the Öresund Sound and the Great Belt an exchange of water in the Baltic Sea takes a long time. It is estimated that it takes between 35 to 40 years to change all the water in the Baltic Sea. We will have to live with our present pollution for decades.

The Baltic is changing even if slowly. Parts of the Baltic region are becoming land while others are drowning. During the earth’s latest geological period – the Quaternary period – that lasted about a million years, the Baltic has gone through not only one but at least ten glaciations. At present we are living in an inter-glacial period with a new ice age expected in about 15,000 years. The latest inland ice covered at its largest extent about the same area as the Baltic’s present drainage basin. The thickness of the ice mass varied from 200 meters at its marginal areas to 1500 meters in its central parts. Through its great weight the ice exerted an enormous pressure on the surface of the earth. The primary rock plateau that the ice rested on and which is usually called the Baltic Shield sank under the weight of the ice and layers beneath it were pressed to the side. The areas around the inland ice were exposed to pressure from below as well and these land areas rose. This took place in Denmark and northern Germany, for instance. We have a land elevation by 9 meters every 1000 years in the area around the Gulf of Bothnia. At the same time the coast in northern Germany sinks by over a meter every 1000 years. These are the changes taking place in the Baltic Sea in a shorter perspective.

In a somewhat longer perspective from the retreat of the ice about 27,000 years ago until about 5000 BC, the Baltic region has experienced several developmental phases.

When the ice began to melt away, a lake was created south and east of the ice edge – the Baltic ice lake. It was a freshwater lake that drained to the southwest and north towards the White Sea. The edge of the ice lay at the northern point of the mid-Swedish highland plateau. Due to climate deterioration, the ice masses remained in this position for 800 years. When the ice began to melt again and retreat the water masses broke through to the Western Sea at just this place. The drainage catastrophe that took place happened about 8300 BC. This was an enormous natural catastrophe since the Baltic ice lake was lowered 26 meters. In this way a connection to the sea was opened up and saltwater forced its way into the Baltic basin. This period in Baltic development is referred to as Yoldia Sea, named after a mollusc (snail), Portlandia yoldia arctica, whose migration can be followed in the area since the beginning of the Yoldia Sea. Through the land evelation which followed the ice melt-off, land rose from the sea. Run-off water from the ice led to a dilution of the Yoldia Sea. This resulted in an inland lake with freshwater called Ancylussjön after the freshwater snail, Ancylus fluviatilis. To begin with the lake had its outlet across middle Sweden but later it went via Öresund. The water connections through Öresund Sound and the Danish waters grew through time resulting in large amounts of saltwater once again forcing their way into the Baltic basin. The snail Littorina litorea that followed the saltwater up through the Baltic Sea gave its name to the sea that was now created – Litorina Sea. Since the Sound was much wider and deeper in the south than it nowadays, this also meant that the salinity was higher as well. In the mid-Baltic the salinity was about 0.2% compared with 0.08% at present. The slow elevation of land with time, recaptured the sea’s conquests once more, leading to constriction and silting of the Sound between Denmark and Sweden, thus restricting the influx of salt water. Great volumes of freshwater flowing from the rivers in the present ice-free land areas lead to continual dilution of the water in the Baltic and have, in turn, resulted in the inland sea with brackish water, we now call the Baltic Sea.

In the long term, we must transport ourselves over 500 million years back in time to find the rock formations that lie above the Baltic Shield’s primary rock and are another two million years older. The Gotlandic bedrock was formed during a geological period called the Silurian period. The lime- and sandstone that make up Gotland’s topography are about 400 million years old. The same kinds of formations are found in the Swedish provinces of Öster- and Västergötland, as well as around Lake Siljan and Storsjön. The greatest incidence is in central Estonia and on Saaremaa. This limestone is exciting from several aspects. It is exceptionally rich in fossils and attracts fossil hunters from near and far. Originally this geological period was called gotlandicum, which indicates the importance Gotland enjoys from a geological point of view. The fossil treasures reveal a nearly complete picture of the marine animal life of that time, the most important fossil being coral.

Coral requires the same environmental conditions to live and grow today as it did 400 million years ago. It needs to have water with a high degree of salinity and an average temperature no lower than 22 degrees (Celsius/centigrade). This in turn means that the Baltic Sea region – or more to the point, the Baltic Shield – must have been an equatorial region. The Baltic region has taken a trip as part of a continental plate. The different continental plates don’t remain still but are constantly moving. Since the earth’s climate zones always lay parallel with the equator because of the angle of the sun’s rays – the warm tropics have always been located around the equator and the cold polar regions at the earth’s axis – the continental drift leads to these continental plates slowly but surely moving through different climatic zones over millions of years.  The speed is not great – about 5 centimetres a year – but from a geological perspective, where we calculate in millions of years, this means a trip of about 9,000 kilometres for the Baltic region. Continental drift is the main explanation for the fact that fossils of tropical plants and animals can be found nowadays in Polar Regions and deposits from ancient ice ages can be found in the middle of the Sahara.

Bedrock in combination with the effect of inland ice and climate has created the rich variety of landscape that is characteristic of the Baltic region. Without the hard, unyielding primary rock – we would not have had the archipelagos along the coasts of Sweden and Finland. Finland wouldn’t have been “The land of a thousand lakes” and Sweden’s water-filled rift valleys would not exist if it hadn’t been for bedrock. We who live in Sweden and Finland have ever-present rocky hills and granite cliffs. We don’t think about it – it’s completely natural. Those who live along the southern Baltic coast in Poland and Germany have entirely different references as landscape. Here there is no archipelago, no small lakes and those who wish to see solid rock at the surface or a cliff have to travel hundreds of kilometres to the north coast of Rügen or to Möns cliff in Denmark, for example. The countryside south of the Baltic Sea consists of some 150-200 kilometres of wide sand. Bedrock lies several hundred meters under the surface. On the sands of Poland, Finnish troops have fought and bled according to the poet, Johan Ludvig Runeberg. The softly billowing, dry, sandy terrain was an excellent fighting ground for the cavalry and later for military tanks. The beach itself is one of the world’s longest playas stretching the whole way from Pärnu in Estonia to Lübeck.

The bedrock creates differences in elevation. In our region there is everything from mountainous areas on the border between Sweden and Norway to lowlands with marshy characteristics in Schleswig-Holstein. The primary rock, granite, has due to the effect of inland ice been flattened into softer shapes. The younger sedimentary rocks like those found here on Gotland are easily eroded. Here a landscape with a sharp profile has been created in the shape of rocky plateaus and steep cliffs. The bedrock sets its stamp on the buildings, too. In the mainly Silurian regions of middle Sweden, Gotland and Estonia, limestone has been used as building material, thus producing a characteristic building style with hewed, well-joined massive limestone blocks in a whitish-grey range of colour. Visby and Tallinn are the foremost examples even if this building style is also found in the countryside. Where no natural stone is available, as is the case along the eastern and southern coasts of the Baltic, it has been customary to make bricks. The brick-red cities of these areas contrast vividly with the grey limestone buildings on Gotland and in Estonia. In the bedrock areas, rock is available to be sure, but it is hard to quarry and difficult to work with. On the other hand the wet conditions in the bedrock areas provide excellent growing conditions for evergreen forests of pine and spruce. Wood was the most common building material both in the towns and countryside. Moreover wood was an alternative to natural stone and brick throughout the entire Baltic region.

There’s not much more I want to say about the shaping of the Baltic landscape so I would like to conclude my exposé with a quotation from one of the finest descriptions of a Swedish cultural landscape in a coastal area: “The cottage, which was really two built together, lay on a rocky hilltop at the southern inner end of a long, rather shallow bay in the inlet and the bay cut so far into land that you couldn’t see the big lake but more think of yourself as being at a little inland lake. The hilltops rolled down to a valley with pastures, meadows and grasslands, bordered by deciduous woods of birch, alder and oak. The north side of the bay was sheltered from cold winds by a ridge covered with spruce forests and the southern part of the island consisted of pine groves, birch meadows, bogs and marshes broken here and there by a patch of arable land. Further away, towards the pasture lay the stable and barn. In a stand of tall oaks, the sauna and root cellar had their shady spots and, furthest out in the southern meadow, one could catch a glimpse of the roof of a tumbledown smithy. Down at the inner end of the bay the boathouses lay beside the pier and this was also the harbour for the boats. Without praising the beauties of the countryside Carlsson seems to be pleasantly attracted by it all. The rich fishing in the bay, the smooth meadows, the sloping fields protected from the winds and with good drainage, the thick timber forests, the beautiful trees for lumber in the woods, everything offered promise of good returns if only a strong hand could set the powers in motion and expose the buried treasures to the light of day.”

As most of you have probably guessed – perhaps just by the mention of a person by the name of Carlsson – this is a piece out of August Strindberg’s novel, Hemsöborna. Hemsö’s real name is Kymmendö and it lies in Stockholm’s archipelago. Strindberg spent several summers in the archipelago and with his pen he has painted an exceptional picture of the settlement and cultural landscape around a coastal farm whose economy was not only based on agriculture and livestock-raising but just as much on hunting and fishing. In conclusion, I would like to say: thank goodness for good authors who can translate the terms Silurian period, moraine, rift valleys, sand deposits and the like to pictures of landscapes; transforming geographic and geological terms and concepts to prose.


Lecture given at the Visby conference on "The Baltic in Literature and Art" in November 2002