Geological History

Lakes can be seen as a mirror of the landscape that has been formed over thousands of years. The landscape of Europe is diverse, and major controls on this diversity are the north-south climatic gradient and geology. In the north, an ancient mass of crystalline rocks created a stable shield. This shield contains the oldest rocks of the European continent. During the Pleistocene epoch, large ice sheets formed that scoured and depressed the shield's surface. The entire landscape of the north has been shaped by the advance and the retreat of glaciers, leaving depressions where thousands of lakes and streams originated. Mineralization in these cold northern regions has always been quite slow. Together with moist conditions and bedrock relatively resistant to weathering, this results in surface soil layers that are generally quite poor in calcium carbonate but rich in humic substances. These types of surface soil layers explain why many lakes in Northern Europe are naturally acidic.

Much of the landscape in Western and Eastern Europe is characterized by a belt of sedimentary rocks that are covered by a layer of glacially deposited debris. Some of Europe's best soils can be found in this region, which includes the Great European Plain. Agricultural activities are intensive and the quality of inland waters is much influenced by these activities. Bordered at the belt of sedimentary rocks follows a mixed geological structure created by faulting (the Vosges and Black Forest mountains), folding (the Jura range), and volcanism (the Massif Central). Consequently, mountains, plateaus, and valleys alternate, with lakes located at various altitudes.

Southern Europe is characterized by comparatively recent mountain-building activity. In mid-Tertiary time, about 40 Ma, the Afro-Arabian plate collided with the Eurasian plate, triggering the Alpine Orogeny and resulting in ranges such as the Pyrenees, Alps, Apennines, Carpathians, and Caucasus. These ranges are not only the highest mountains of Europe but also exhibit the steepest topography. The frequent occurrence of earthquakes in this region illustrate that changes are still taking place. In this mountainous region, Europe's most famous high altitude lakes are located. Further south lowland lakes are found, which are commonly nutrient-rich. The soils in these southern regions are usually rich in calcium carbonate, resulting in relatively good pH buffering capacities.

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