Geografie 1975, 80, 184-192
Cryogenic Forms in the Orlické Mountains
The relief of the Orlické Mountains, north-east Bohemia, similarly as other parts of the Bohemian Highlands shows cryogenic forms. Most frequent are rock outcrops re-modelled by frost occurring on the summit plateaus, ranges, slopes and valley sides in the form of frost cliffs and abrupt walls, isolated rocks and rocky ridges. They are predominantly composed of crystalline schists (migmatites, orthogneiss, paragneiss, garnetic mica schists, quartzites, a. o.). Due to a different lithological and structural composition of the rock also the selective destruction influenced the development and the modellation of the rocky outcrops. Consequently, only more resisting parts have survived. Frost cliffs are of assymetrical profiles with abrupt foreheads (arranged in grades or overhanging) situated along fissures. Their gradient is usually identical with the gradient of the planes of schistosity. At the foot of the frost cliffs cryoplanes occur with mild gradients of 5-15 ° covered with waste of sharp-edged boulders. On the summit flat range of the Orlické Mountains cryogenic forms are not so frequent as on smaller ridges. Most often they occur in deep river valleys where they are due to the erosion activity of the river as well as to a strong frost splitting. Large rocky outcrops occur in the slopes of the fault gap of the Divoká Orlice above Klášterec n/O. Similar outcrops may be found in the valleys of the rivers and tributaries, such as the Bělá, the Zdobnice, the Říčka, the Tichá Orlice a. o. Even if cryogenic forms are not typical of the relief of the Orlické Mountains, they have been produced in this area by the periglacial climate. Most of them are fossil forms whose recent development is negligible.
