Home Na Špičáku Cave - Natural conditions

Na Špičáku Cave - Natural conditions

GEOLOGICAL DEVELOPMENT OF THE AREA

The complicated geological structure of the Králický Sněžník Mountains, the Hrubý Jeseník Mountains, the Rychlebské Mountains, the Hanušovická Highlands and the Zlatohorská Highlands is the result of a long-term and complex development lasting more than one billion years. That is why most of the local rocks are intensely metamorphosed, i.e. converted into so-called crystalline rocks – crystalline complex. To the west of the system of deep faults crossing the area in the NE – SW direction lie rocks of the geological area of the Lužické Mountains, which are probably of Proterozoic origin. In an easterly direction from these faults there are rocks of the Moravian-Silesian Region formed probably in Proterozoic to Early Paleozoic. Primarily marine sediments of rather mixed composition with interbeds of volcanites were intensely folded, broken and repeatedly metamorphosed, mostly by the so-called Variscan (Hercynian) folding at the end of the Paleozoic.

The process also included deep magmatism with the product of the Žulová massif composed of granitoids. The rocks were converted to gneisses, mica schists, phyllites, graphitic shales, quartzites and erlans. Limestones and dolomites recrystallized under high pressures and temperatures to marbles (crystalline limestones). During that process the originally contiguous limestone formations were broken into smaller objects in which karst phenomena were formed by water during the following long-term processes.

Other remarkable changes and today's rough appearance were imprinted on this area by the Alpine folding in the Tertiary. It restored movements on older faults and prepared conditions for the formation of today's mountain relief. Old karst phenomena in principle were destroyed and their new current appearance began to be formed. In the Early Quaternary (Pleistocene) the continental glacier affected the area from the north. The result is hills smoothened by the glacier – humps, remains of glacier moraines with dragged erratic blocks of exotic red northern granite, abraded pieces of rock – dreikanters and mighty beds of so-called glacifluvial sediments – alluviation of gravels by melting waters. The development of the Na Špičáku Cave was also significantly influenced by the glacier and its waters.

Thicker layers of limestones with karst phenomena and cave emerged particularly in variegated formations of the so-called Stroňská group in the Králický Sněžník massif and, to an even greater extent, in the so-called Branná area, forming an almost contiguous band from Olšany in the south up to the village of Lipová – lázně in the north (the Na Pomezí Caves are situated near the village), where limestone islets of the metamorphosed mantle of rocks of the Žulová massif, such as Supíkovice marbles with the Na Špičáku Cave, is connected to them.

Important products of rock metamorphosis in the Jeseník region are numerous ore deposits of mineral raw materials, including gold. In the Middle Ages gold was mined in the Hemberg district close to Špičák Hill. Also many beautiful specimens of precious minerals in numerous museum collections originate from the Jeseník localities.

STALACTITE AND STALAGMITE DECORATION

The Na Špičáku Cave no longer has rich stalactite and stalagmite decoration. It was destroyed to a large extent by visitors during the last century. Nevertheless, the bigger sinter coatings on the walls and parts of floors together with small stalactites and sinter curtains in niches were preserved. The small sinter lake in Velký dóm (Big Dome) is also notable. A remarkable phenomenon is the current rather fast growth of new stalactite and stalagmite formations, in the meantime in the form of thin straws and small draperies.

The cave is also one of the few sites with the occurrence of moonmilk – white pulpy material, in principle unconsolidated sinter. It grows rather quickly on the walls and ceilings of some corridors and its white coatings decorate the cave. Older dry layers form aggregates of cauliflower-like shapes.