Western Finland the area rises. A new coastline is created every year. When the rise continues, will the Perämere become a lake and will it be possible to walk from Vaasa to Sweden?
However, land uplift is not the only factor that affects Finnish geography, says the professor of geology Antti Ojala from the University of Turku in the Tiede magazine exam.
Why is the land rising on the west coast?
About 20,000 years ago, continental ice covered the whole of present-day Finland. In the region of Pärämere and Vaasa, the ice was up to three kilometers thick, and it strongly pressed the ground on the pit right there. The edge areas of the ice crust were significantly thinner. That is why, for example, the land in Eastern Finland did not sink as strongly.
The ice sheet began to gradually melt 20,000 years ago, and since then the land chamber has been rising. The increase in meters has been the greatest around the Pärämere.
What happened when the continental ice began to melt?
As the mass of the glacier decreased, the earth chamber immediately began to rise. During this initial recovery, the rise was slow at first.
As the melting continued, the ancient Baltic Sea began to emerge. The Vaasa area was freed from under the ice about 10,000 years ago. At that time, the sea covered all of Finland except the eastern parts and northern Lapland. The earth rose most strongly then, and that is why the time is called the main recovery.
Today we live in a time of much slower recovery. About 150 meters of land elevation is left. This will take another 10,000 years.
What kind of traces have the old seashores left?
There are many traces, and the most recognizable of them are the devil's fields. They are formed from old beach pebbles, from which the water has washed away the rest of the loose material, apart from the stones. The best-known Baltic Sea beach is located south of Rovaniemi in Vammavaara, where the pirunelto is about 220 meters above the current sea level.
How fast is the earth rising these days?
The area of the sea cucumber increases by about nine to ten millimeters per year. In the Helsinki region on the south coast, the rise is significantly slower, only about three to four millimeters per year.
What is the exposed seabed like in Merenkurku?
It is rocky and load-bearing land. The area is known for the so-called De Geer moraine ramparts, which were created by the impact of the continental ice and form an entity somewhat resembling a clothesline. The Merenkurku Archipelago is classified as a UNESCO World Heritage Site.
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You can walk from Vaasa to Umeå in approximately 2,000 years.
In the world heritage area, a hundred hectares of new land is added every year, which means more islands are being created all the time. Elevation can make navigation difficult, especially when the De Geer ridges are rocky on the surface and in the gaps. Merenkurku is a very remote area, and you have to know exactly where you can walk.
The rise is so fast that the boat's propeller can suddenly take hold in a place where this has never happened before.
What will Finland's border look like in 2,000 years?
The sea area between Vaasa and Umeå is now around 20 meters deep at its deepest point. When the earth rises about one centimeter a year, it has risen by ten centimeters in ten years. So you can walk from Vaasa to Umeå in approximately 2,000 years.
Then Perämeri has become isolated from the rest of the Baltic Sea, and it has become “Lake Peräjärvi”.< /p>
However, only the effect of land uplift is taken into account in this development process. In reality, the location of the beach is also affected by sea level rise.
How would sea level rise affect Finland?
Today, the global sea level rises by more than three millimeters per year, while at the beginning of the century the rise was between one and three millimeters.
If the sea level were to rise by one meter, i.e. one centimeter per year by the year 2100, the coastline in the Vaasa region would remain roughly the same due to land uplift. In the Helsinki area, on the other hand, the sea level would rise by 70 centimeters, because the land rises more slowly there.
It is very difficult to accurately predict global warming and the resulting sea level rise.
The biggest uncertainties are related to the melting rate of the glaciers.
If all the mountain glaciers melted, it would have an impact of a few tens of centimeters on global sea levels. If all of Greenland melted, it would raise ocean levels by seven meters already. The melting of Antarctica would raise sea levels by 60 meters. Worryingly, the Antarctic continent is melting at a faster rate than has been realized.
Another uncertainty is related to the thermal expansion of the oceans. It is known that the surface waters of the seas have warmed, but the effect of this on the deep water is not yet known. It is also unclear how much the sea level would rise only due to thermal expansion.
Published in Science in Nature 8/2023.
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