Geologically, the Finnish territory constitutes a section of the Baltic shield, the archaeozoic base that forms the substratum of the entire Scandinavian peninsula. Affected by the Caledonian orogeny during the Paleozoic – an era in which there were also volcanic manifestations – and subsequently peneplanated by erosion, the reliefs did not undergo further dislocations, but were profoundly modeled by the ice that during the Quaternary era completely covered Scandinavia. The ancient reliefs sometimes come to the surface with slight humpbacks and rounded profiles; more frequent, however, are the coverings of the recent sedimentary, fluvial and glacial layers, often of considerable thickness. The retreating glaciers determined the formation of powerful moraine apparatuses; in particular, during a prolonged stop during the withdrawal phase, the two cords called Salpausselkä and about twenty kilometers away from each other, which encircle the country entirely to the S, were deposited. Finland is therefore morphologically presented as a very vast penepian, devoid of real reliefs, with surfaces that for the most part have heights of less than 200 m; the uniformity of the landscapes and the marked glacial imprint predominate, derived not only from the morainic rises (typical hills in the shape of a whale’s back, the drumlins), from the many lakes of glacial origin that dot the territory. However, three main morphological regions can be distinguished: Lapland, the so-called “lake platform”, the coastal plain. AN extends Lapland, which, located on average over 400 m in height, is the highest area in the country. It features bare isolated peaks, the tunturit, which reach altitudes of over 600 m, such as Paistunturit (640 m) and Pallastunturi (807 m), culminating at 1324 m in Haltiatunturi, the highest peak in Finland, at the northwestern end of the country. The lake platform – the name clearly derives from the thousands of lakes that occupy a large part of the territory (the inland waters together occupy an area equal to ten percent of the country) – corresponds to the central-southern portion of Finland. It is a flat expanse closed to the S by the Salpausselkä moraines, to the N by those of the Suomenselkä, in which the moraine bands are particularly evident, usually a few tens of meters high, which separate the lakes as natural dams: they often develop for a few kilometers and are used as communication routes. Finally, the coastal plain is a strip, on average 40 km wide, which borders the lake platform to the S and W, beyond the Salpausselkä; the territory is almost entirely flat, scarcely marked by the furrows dug by the rivers in the terminal stretch of their course. Finland overlooks the gulfs of Bothnia and Finland with a densely articulated coastline, fronted by approx. 75,000 islands, including the Åland archipelago. The complex coastal and insular morphology is the result of a slow process of emergence, still in progress (it is estimated that the land rises by 1 m every century along the northern shore of the Gulf of Bothnia, by 40 cm along the Gulf of Finland) and destined to last until the soil, strongly compressed by the Quaternary ice, will have reached the original level. Check sunglasseswill to see Quick Facts About Finland.
10% of the territorial surface is occupied by lake basins, the presence of which is linked not only to the glacial action, but also to the poor permeability of the soils. The number, variously calculated, is between 50,000 and 60,000; the largest are the Päijänne, the Saimaa (which forms, with numerous communicating basins, a lake complex of 4400 km²), the Inari, the Oulu, the Kalla. With the exception of the Inari, located in Lapland, they are all located in the central-southern area, where approx. one fifth of the soil is covered by lake basins. The contours of the lakes are very varied, but mostly elongated; the watersheds are generally just hinted at, so that the various basins can easily be placed in communication with each other. Instead, rivers of a certain importance are missing; among the main ones are the Kemi, which partly crosses Lapland and flows into the Gulf of Bothnia near the city of the same name, and the Kymi, which flows into the Gulf of Finland at the city of Kotka. The waterways have young characters, often forming rapids and waterfalls, very important for hydroelectric exploitation; the flow rates are abundant at the time of the autumn rains and the spring melting of the snow, while in winter the expansion of the ice slows down the flow of water considerably.