THE GEOLGICAL FORMATION OF POSTGLACIAL FINLAND

The basins of Saimaa and Pielinen are ancient Finnish and Lappish lake landscapes that are stamped with their own spirit. The lake landscapes of eastern Finland were formed in that millennia-long churning of the land during which the waters of ancient Great Saimaa and other lakes and the leftovers of the melt-waters of the continental ice sheet sought their outlets to the sea. A cultural landscape that formed in the minds of people when they first encountered these new lands is preserved in popular memory and spiritual tradition, and it persists even when the whole landscape is in the grip of change.

Finland took shape as the result of a long process following the end of the last Ice Age; the process began from the Norwegian coast around Lofoten around 14 000 BP and worked its way towards the interior of Finland by around 10 000 BP. Amongst others, the ridges of the Salpausselka, Suomenselka and Maanselka were formed by the thawing of the great ice masses; a drifting ice block, a couple of kilometres thick, moved and as it melted it deposited moraine in different areas (Pajunen 2006). The pressure of the ice brought about changes in the landscape which still persist. The land level on the edge of the Gulf of Bothnia rises around 8 mm a year and, inland, the lake districts of Finland are taking on a new shape. In the next couple of millennia the northern part of the Gulf of Bothnia formed a lake when an isthmus formed between Finland and Sweden.

Around 9000 to 8000 BP Lakes Saimaa and Paijanne, much larger than today, emerged from Lake Ancyclus. Until about 7000 BP these two great lakes flowed out along common waterways via Pielavesi, Kolima, Alvajarvi, Muurasjarvi and Kalaja to the mouth of the Kalajoki, then located near the site of modern Haapajarvi. The waters first flowed westwards, along Kalajoki, then along other routes to the Gulf of Bothnia. However, the greater rise of the land surface along the shores of the Gulf of Bothnia than further south resulted in a change of direction of the outflow to the south: at first together and later via different routes the two great lake systems broke out southwards through Kymijoki to the Gulf of Finland.