Rocks of the kRkonoše tundRa Podpořeno grantem z Islandu, Lichtenštejnska a Norska. Supported by grant from Iceland, Liechtenstein and Norway. Rocks of the Krkonoše Tundra Rocks and rocky outcrops are an unmis- extensive canyons, gorges, castellated takable part of a mountain range, even rocks, cliffs and castle koppies, as well though, according to their type, the char- as individual points of interest, such as acter of their geological development, waterfalls, caves, overhangs, rock towers representation and diversity of minerals, and pinnacles, balanced rocks and many climatic conditions, as well as various others. The rocks are also of importance local conditions, there are mountain for their connections with human activi- ranges which are rich in rocks, while ties, as people have long sought them others are poor. Rocky areas without out for building castles and due to their a cover of weathering products are not landscape dominance, for the construc- only a significant helper for geologists tion of various chapels, tourist chalets and geomorphologists who study these and last but not least, lookout towers mountains, but also play a fundamental and vantage points, often accessed by role for lay tourists and undemanding stairs, ladders, footbridges etc. visitors, because it is the quantity and shape of the rocks which are probably Krkonoše is a very old mountain range the most important factors in determin- and of course this also determines ing the landscape attractiveness of each its relief. Although there are certain region, i. e. its wildness and romantic exceptions, we can generally say that character. Of course there are mountain our developmentally younger moun- ranges with almost no exposed rocks, but tain ranges, where erosion is more they will never be as attractive for visitors rapid and contributes to the shaping as those ranges which are decorated by of the rocks, have a higher number of interesting rock formations. Even more rock formations than older mountain so, that they are very often connected ranges. Whatismore, neither the sedi- with other popular destinations, such as mentary rocks, such as sandstones, Dívčí kameny Tor Rock basins are the most interesting microform on granite rocks (Pielgrzymy) conglomerates, dolomites and lime- are relatively easy to see from close up. stones (the local ones belong to the crys- After the forest is felled they are perfectly talline limestones, which we now include visible, even from a distance, and in the amongst the metamorphic rocks), nor case of extensive collections of outcrops, the young volcanic rocks, which cre- we can see them as a whole. However, ate the greatest number of rock forma- the critical period comes as the new tions, are represented here in Krkonoše. growth flourishes, as it often covers the Therefore, with a few exceptions, the rocks so completely that we can forget rocks in Krkonoše are not the dominant about trying to photograph them for the relief or landscape features, but on the next few years. other hand, there are plenty of rock for- mations here. The high percentage of for- Isolated granite rocks, tors and est cover is also a certain “handicap” for the rocks, because with the exception of castle koppies the mountain ridge rock formations, the great majority of the rocks here are par- These types of rocks are the most typi- tially covered, and the lower-lying rocks cal for the summit, or tundra areas of are completely covered, by forests. Of the Krkonoše, but even here they are not rocks which are located in the forests, so numerous. The majority of them are we can observe a kind of “three-phase found at lower, montane positions in the system” from the perspective of human mountain range, so are hidden in the life. If they are in a mature forest, they forests. On the other hand, it is clearly 4 l Rocks of the Krkonoše Tundra visible that in the colder periods of the and a number of Polish localities). Some Quaternary, most of these rocks also of the castle koppies in summit areas found themselves in places with a tun- could be transformed into tors (Svinské dra climate. kameny, Pielgrzymy). At first we should explain the termino- The modelling of these types of rocks logical distinction between tors and is strongly influenced by the primary castle koppies. Genetically, the way in fracture system of the Krkonoše granite, which they were formed is the same, which formed during the solidification but they differ in the ratio between their and contraction of magma in the granite height and width (dimensions). With nar- massif already. Granite belongs to the row, tower-like tors their appearance is abyssal igneous rocks. Magma rising up clearly dominated by their height, but on from the Earth’s core was stopped deep the contrary, with castle koppies, often underneath the strata of older overlying with a quite irregular footprint, their area rocks (in Krkonoše these are schists: is the dominant feature. However, there mainly gneisses, mica schists, phyllites), are no binding criteria, so the distinction where it gradually solidified at depth is often a subjective one, and in fact, in and only emerged on the surface after many localities tors and castle koppies the erosional-denudational removal stand next to each other (Dívčí kameny of the overlying rocks. The German The rocky outcrops in the Labské jámy cirques are the largest in the Czech Republic most important is exfoliation. Exfoliation fractures most commonly have an arched character and in places, where their sloping section emerges on the surface, they may conform with the slope of the valley or cirque, where they create extensive and smooth rock plates, which are sometimes mistaken for glacial polishing by the visitors (Velká Kotelní jáma Cirque, Navorské plotny in the Labský důl Valley, the upper part of the Důl Bílého Labe valley). The forma- tion of exfoliation fracturing is explained by the unloading of the massif after the removal of the overlying crystalline rocks by erosional processes, as well as by climatic influences during the previous warm geological periods. Much more probable is a new theory, that they were already formed by primary (compres- sive) factors inside the granite pluton. The largest tor of the Svinské kameny complex Opinions on the conception of these cliffs are not entirely unanimous. Some geologists and geomorphologists look geologist H. Cloos described the frac- at them only from the perspective of ture system of granite according to the their shape and apply these terms to three basic directions of fracturing and all isolated rock formations, emerging their German names as the LQS system. above their surroundings from all direc- L are bedding-parallel fractures, mostly tions. However, the predominant opinion horizontal or slightly inclined, Q are that only rocks which meet the criteria transverse, vertical (or steep) fractures, concerning shape, but mainly those roughly perpendicular to the main, which formed in a specific two-phase Silesian Krkonoše Ridge, and S are genesis, should be referred to in this longitudinal, vertical fractures, roughly way, is undoubtedly more correct. Even perpendicular to the Q fractures. This in this case, however, the opinions of results in ashlar- to cubic-shaped blocks the geomorphologists are not complete- of rock, which we can observe in various ly uniform: for example, the age of the modifications on most of the cliffs; in individual phases but also the effect of places where the L fractures predomi- the glacial periods (ice ages) on their nate, the blocks usually transform into formation are still being discussed. a more slab-like shape. However, this is the “ideal form”, which, under the influ- Their development already began in the ence of local conditions and second- warm and damp climatic conditions of ary fracture systems can change into the interglacials in the Early Quaternary a multi-directional fracture system. Of (Pleistocene), but according to some the secondary fracture systems, the experts this began in the Late Tertiary. 6 l Rocks of the Krkonoše Tundra The groups of rocks (castle koppies the whole rocky outcrop. In this case the or tors) represent the remnants of the fracture system played a very impor- original mass of the parent material, tant role: in general the outcrops with a more resistant core (usually in places dominant bedding-parallel horizontal or where it was harder and less fractured), sub-horizontal fractures were the most which formed underground during the resistant, because the least water pen- first phase of sub-surface weathering. etrated into them. For this reason they In the climate described, this took the have retained their pillar-like shape with form of intensive chemical weathering sharp sides, and almost without weath- of the rock (granites, which form the ering products at their foot (Svinské majority of Krkonoše, are especially kameny, Dívčí kameny, Słonecznik). susceptible to this), the result of which These rocks were later transformed by are fine-grained weathering products, weathering, including frost weathering, most commonly called coarse sand mainly in the form of rounding of the by laymen. In the second phase, after edges of individual blocks, which could the climatic changes and the onset take on the shape of an oven, or even of a temperate to cold climate, these a ball, or rarely, a false balanced rock or hard sections were exhumed, because a true balanced rock. the surrounding fine-grained weather- ing products (often coarse-sandy) were On the contrary, where the predominant rapidly transported away as a result fractures were vertical and sub-vertical, of mechanical removal, and the rock respectively where irregular fractures were formations began to emerge on the abundant, water penetrated the rocks surface, rising above the surrounding more easily and deeper into the massif, relief and landscape.