Krkonose/Karkonosze - Czechia

The Krkono?e Mountains and several adjacent ranges of the Sudetes form the northern fringe of the Bohemian Massif, a wedge of the European Hercynids protruding between the Fenno-Sarmatian platform and the Alpine-Carpathian system. The Krkono?e-Jizerske Mts. complex of crystalline metamorphic rocks (mica schists, phyllites, and orthogneisses) of Proterozoic to Palaeozoic age (100 to 400 million years) forms much of the Krkono?e Mountains. This crystalline complex was folded twice in the Palaeozoic and, during the second period of folding in the Carboniferous, was intruded by a granite pluton that forms most of the main ridge and almost the whole of the Polish side of the mountains. Around the pluton is a hard contact zone; this has been of great importance for the mountains? geomorphological evolution, and this is where the major ore deposits are found. Quartzites, basalt, and crystalline limestones also occur in the region and, despite their limited extent, are important in determining relief and vegetation structure. In the Mesozoic and the first half of the Tertiary, when tropical and subtropical climates predominated in Central Europe, chemical weathering remodelled Krkono?e into flat and smoothed ?grading surfaces?. Subsequently, the mountains were intermittently and slowly uplifted during the Upper Tertiary by orographic movements, related to folding in the neighbouring Alpine and Carpathian systems. While they thus attained their prominent height through uplifting, this was followed by rapid water erosion and the dissection of the grading surfaces into today?s broken mountain relief. Another important geomorphological factor was mountain glaciation during the Quaternary Ice Ages, when the relief was modelled both by alpine glaciers (the origin of glacial cirques, lakes, moraines, etc.), and by frost processes (the origin of cryoplanation terraces, frost cliffs and screes, polygonal soils, etc.). These forms are the most valuable abiotic features of the national park and biosphere reserve. In the Postglacial era, the main remodelling factors have been water erosion, landslides, and anthropogenic influences. Frost and biological weathering are less pronounced and proceed together with avalanche erosion and, in the limestone area, with karstic processes. Geological Evolution The Krkono?e Mts., together with Jizerské hory belong, from the geologic point of view, to one complex called krkono?sko-jizerské crystallinicum. Crystalline schists (mica schists, phyllites, quartzites and crystalline limestones) of the archeozoic or Paleozoic age, (i.e. about one billion years old) prevail in it. The orographic processes of the Palaeozoic age were significant for the origin of the Krkono?e Mts. when they, after the last siluric sea flood, about 400 million years ago, became dry land. In that time so called caledonian folding occured which determed the main features of Krkono?e Mts. crystallinicum. During the later variscian (hercynic) folding a very significant process occurred when into the core of cystalline schists granite magma arose and created the so called the Krkono?e Mts. granite massif (Krkono?e Mts. granite pluton) to a thickness of about 5 kilometers. The granite hardened in the depths, and it reached the surface of the mountains only later by grinding off the upper layers of rock. The main part of the Polish Krkono?e Mts. and the entire Hrani?ní h?bet from Harrachov to Sn??ka is built up by the granite massif. The Krkono?e granite is pervaded by a system of cracks which condition its characteristic ashlarshape decomposition (well seen on the edge of Labské jámy (pits) or on the top rocks, so called tors), unlike the crystalline schists by which mainly the inner ?eský h?bet and the adjacent mountain saddle bows are made. The rocks break into smaller sharp edged fragments, so while the granite Hrani?ní h?bet is a rather round shape, the mountain parts being built up by the crystalline schists have a more sheer shape (e.g. Kozí h?bety, Ob?í h?eben (Giant Ridge)).