Municipalities
| Genesis of lake Saimaa |
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| 16.11.2009 13:20 |
 A true relic of the Ice Age, Lake Saimaa's history is also closely bound with the various stages of development of the Baltic Sea. About 11 500 years ago all of Scandinavia was covered by a thick continental ice-sheet. Present-day Finland was also under a mass of ice, with a thickness of up to 2000-3000 metres.As the ice began to thaw, it started to withdraw towards the north-east. During that time, the climate underwent great changes, and from time to time it was as warm as it is today. The thaw however was interrupted by a colder period lasting about two hundred years, during which the edge of the glacier remained within an area 10-20 kilometres wide. This is where a fringe formation (generated by loose stone masses transported by thaw waters) began to accumulate. The "fringe" is called today the first Salpausselkä Ridge, and its formation was in fact one of the prerequisites for the genesis of Lake Saimaa. When, two to three hundred years later, the thaw of the ice-sheet was once again interrupted, the second Salpausselkä Ridge was formed approximately 30 kilometres north-west from the first Ridge. As the continental ice-sheet continued to thaw and to withdraw from the Salpausselkä Ridges, the development of the Baltic Sea underwent first a sea stage (Yoldian Sea) and subsequently, a lake stage (Ancylus Lake). Following the sea stage, the water masses then broke through and created a link with the sea around the area of the present-day Sound (Øresund), causing the water level to drop by about ten metres. This in turn caused lakes Päijänne and Saimaa to detach as two separate water areas. |
