Geology of Finland subsequent uplift and erosion would have eroded all of these sediments. In Finland, Caledonian nappes overlie shield rocks of Archean age. Despite occurring in about the same area the Scandinavian Caledonides and the modern Scandinavian Mountains are unrelated. The ice sheet that covered Finland intermittently during the Quaternary grew out from the Scandinavian Mountains. By some estimates the Quaternary glaciers eroded away on average 25 m of rock in Finland, with the degree of erosion being highly variable. Some of the material eroded in Finland has ended up in Germany, Poland, Russia and the Baltic states. Ground till left by
Finland–Russia border Finnish reindeer fence. Unlike other Western countries, the government of Finland did not protect illegal border crossers but returned them to the Soviet authorities if captured. Illegal border crossers had to get through Finland to e.g. Sweden in order to defect to the West. In the Moscow Armistice signed on 1944 between Finland, Soviet Union and United Kingdom, a small peninsula towards the Gulf of Finland, Porkkala, was rented to Soviet Union as a military base. This created in effect a southern border crossing to the Soviet exclave, operating all the way to 1956. Border crossings were in and .