The Adour-Garonne basin

The Fennoscandian Shield encompasses roughly the northern half of Sweden, all of Finland, and the westernmost part of European Russia, ranging in northern latitudes between 60 and 70 degrees, and intersecting the Arctic Circle. This region also represents the westernmost extension of the taiga biome and is well within the boreal zone, covering a tetragon-shaped area between longitude 11 degrees (southwest) and 41 degrees east (northeast). Bedrock is Precambrian, dating back 1.7–1.9 billion years and including metasedimentary, metavolcanic rocks and several generations of granitoids. Even older (2.5–3.1 billion years) rocks (mainly gneisses and greenstone belts) characterize the Archean geological province in northern Finland and Kola Peninsula. These rocks often are overlaid by moraines shaped by erosion of repeated glacial events into a hilly landscape with numerous lakes and watercourses. Most rivers flow into the Baltic and its fringing bays. In Sweden, originating in the mountain chain along the border to Norway, rivers generally flow in an easterly or south-easterly direction, whereas Finnish rivers flow westward, or southward into the Gulf of Finland. The Koutajoki is the exception and drains in an easterly direction into the White Sea. At a mean annual discharge of >2500 m3/s, the Neva River, draining Lake Ladoga, the largest lake in Europe, is the largest river on the Fennoscandian Shield.