Learn about a natural phenomenon caused by the Earth’s climate change. In Simo post-glacial rebound park, the continuously rising land causes the sea to retreat further from the continent. Every year the land surface in the park area increases the size of a house lot, shipping routes are becoming shallower and new islands are formed all the time. Information plaques and maps in the park will help you see the signs of post-glacial rebound and the changes the landscape has gone through during the past few centuries. Learn more about post-glacial rebound!
In Scandinavia, land is rising as a result of the ice age.
The last ice age, called “Veiksel”, covered Scandinavia and part of Europe with a thick glacier. The glacier covering Scandinavia was 1,000–3,700 metres thick, and it pressed the 60-metre thick continental plate underneath it into a dent. In the park area the pressure of the ice against the crust of the earth was approx. 3000 tons per square kilometre. The depth of the dent caused by the glacier varied from tens to hundreds of metres. In the area of the park the dent was about 900–1000 metres deep.
During the past 10,000 years the dent has started to straighten out, which can be seen in the seashore moving further from the continent. Simo post-glacial rebound park has 10 information points where you can learn about how the shoreline has moved during the last 500 years. Because the land rebound is strongest in the Bothnian Bay area, changes in the shore landscape are also very clear here. The oldest residents in the area can remember when the seashore used to be closer to habitation and boat harbours closer to houses. Change is slow, but the sea level has gone down by almost a metre during the lifetime of the area’s oldest inhabitants.
Today there are still places where glaciers are pressing the earth’s crust in this way. For example, the current situation in the Antarctic and Greenland are similar to that in Scandinavia 15,000 years ago. In Greenland the thickness of the glacier in the middle of the island is over 3 km, and it has pressed the earth’s crust underneath it below the sea level.
Kemi 25 km, Oulu 85 km, Rovaniemi 120 km, Tornio 50 km
Airport 30 km, Harbour 30 km
Pohjolan Sanomat Oy
Rantakairan Sähkö Oy
Simon Turvejaloste Oy
Simonkylän maa-ja vesialueen osakaskunta
Stora Enso Oy
The glacier of the last ice age 15,000 years ago covered Scandinavia and part of Europe. The ice age was a result of the earth’s climate change. The glacier covering Scandinavia was 1,000–3,700 metres thick. The mass of the glacier in Scandinavia pushed the continental plate on top of the molten core of the earth into a dent. In the park area the pressure of the ice against the crust of the earth was approx. 3000 tons per square kilometre. The depth of the dent caused by the glacier varied from tens to hundreds of metres. In the area of the park the dent was about 900–1000 metres deep.
The furnace-like heat at the earth’s core keeps the magma in a molten state. The surface, however, is cool and has hardened into a continental plate, which consists mostly of light minerals. Thus the continental plate floats on top of molten magma. The thickness of the continental plate in Finland is about 60 km, and it is almost completely submerged in the magma. When 3 km of ice accumulated on top of the plate, it caused the plate to sink, creating a dent of about 1 km.
MELTING OF THE ICE
As a result of the earth’s climate becoming warmer, the glacier began to melt. Melting took several thousands of years, and the meltwater transformed the earth’s crust by transporting rock materials and sand to wide areas all the way to Central Europe. Rock materials transported by the water transformed the bedrock, creating different shorelines and sand and gravel eskers, which can be found far inland. Several so-called Giant’s kettles were formed in the bedrock by stones transported by glacial meltwater. Rokua, located to the south of Oulu, is home to sand eskers created and transformed by glacial meltwater flows. Deep kettles formed by draining glacial floodwaters can be found in many places around Finland. Also large erratic boulders that were transported around the country by moving and melting ice masses can be found. In many places exposed bedrock shows grooves in the north-south direction, created by boulders and stones transported by the glacier.
The picture shows the seashore about 10,000 years ago.
Land rebound, which is a result of glacier weight being removed, still continues now after 10,000 years. The extent of land rebound varies in different parts of the country, being at its strongest in the Bothnian Bay shoreline area. Here the land rises about 8.5 mm per year. Land rebound is most evident on the shores, where new land is exposed.
When the ice melted, the continental plate started to straighten. Though Finland has not seen glaciers in 8,000 years, the continental plate still continues to straighten. The straightening process is slow, and might still continue for thousands of years. It is estimated that in the Gulf of Bothnia the land will rise another 80–120 metres, which would take another 7,000–12,000 years. This probably means that the Gulf of Bothnia will become a chain of lakes, connecting the northern rivers of Finland and Sweden, which flow into the North Sea and the Atlantic Ocean through the Baltic Sea.
Land rebound is measured with a GPS method, where the location and height of the measuring station is defined using several satellites. The measuring place is no longer bound to the seashore, but can also be located inland. The GPS method has been tested in the Nordic BIFROST project. Measurements covering just a few years give an exact picture of the land rebound.