Some of Finland's rocks are among the oldest anywhere in the world. The most common rock types are ancient igneous granites and metamorphic gneisses formed over two billion years ago.
These rocks were then compressed and fractured in the roots of ancient fold mountains higher than today's Himalayas, but the subsequent billions of years of erosion have left Finland as largely low-lying country - except for the high fells of the northwestern ‘arm' of Finland, which form part of the Scandinavian mountain range. Finland's highest high-spot is the summit of Halti Fell (1,328 m) on the Norwegian border.
Traces of the Ice Age
Today's landscapes are mainly the product of much more recent geological activity, during successive ice ages. The most recent ice age ended in Finland about 10,000 years ago when the Scandinavian ice sheet slowly melted away, leaving behind features created by glacial erosion such as smoothed rock surfaces and the hollows now filled by thousands of lakes.
Extensive ridges of sandy and gravely moraine running across Southern Finland mark the locations of the edge of the ice sheet at various times during the ice age. Winding sandy ridges know as eskers stand out above the surrounding terrain today, revealing where meltwater rivers once flowed through the ice.
Land Rising out of the Sea
The ice sheet that covered Finland was up to 3 km thick and weighed heavily on the Earth's crust. The land in most parts of Finland is still slowly rising, recovering from its icy burden. The rate of land uplift is highest (about 1 cm a year) in the west, near the city of Vaasa, where this unique phenomenon is featured at the Terranova - Ostrobothnia museum (www.pohjanmaanmuseo.fi). This region's emergent archipelagos will eventually join up to form a land bridge all the way across the Gulf of Bothnia to Sweden. Kvarken Archipelago has been UNESCO's World Heritage site since 2006. Kvarken Archipelago is the only World Heritage site in Finland based on natural values.