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 most of which were Savonians. After the Finnish War, the Treaty of Fredrikshamn converted all of Finland from Swedish territory to a Russian possession, the Grand Duchy of Finland. The Finnish–Russian border was moved back to the pre-1721 location, so that the Grand Duchy gained the so-called "Old Finland", territories previously held by Sweden, in 1812. After Finland became independent in 1917, there was the Finnish Civil War in 1918, and even after this war, the Russian Civil War continued. Finnish activists often crossed the border into Soviet territory in order to fight in the "heimosodat", wars aiming at Finnish