Types of terrain
The present landforms are a mosaic of forms from different times. The sub-Cambrian peneplain is more than 600 million years old. The joint aligned valleys and the undulating hilly land probably date from Mesozoic times, whereas the plains with residual hills are probably from the Tertiary. Also the mountain plateaus are probably mainly Tertiary but may have residual relief from earlier times. The formation of valleys has probably been affected by the uplift of the western border of Fennoscandia related to the formation and development of the Atlanctic Ocean. A geographically very distinct line separates the middle-Swedish lowlands and coastal plains from the northern uplands � the �Norrland terrain�. It is also a divide in climate, vegetation and traditional agricultural land uses.