Geographia.Studia et Dissertationes, T. 31 (2009), s. 65-80
This article takes up the problem of rock strength of the Silesian Upland. Results of the fieldmeasurements of the rock outcrops hardness presented here became the basis for settlement of therock resistance classes on the Silesian Upland and the view on following relation: bedrock resistancevs relief.The definition of rock strength is the resistance of the rock to destruction processes e.g.: weathering,erosion and denudation. Instead of ‛strength’ definition one often uses: hardness, compression,crushing, compactness, etc. These terms describe strength features of rock mass and the right meaningof rock strength consists of their sum (union).This paper undertakes a study to determine approximate rock strength on the Silesian Uplandsurface. For that purpose the author exploited a field method with the Schmidt hammer usage. Thistool was designed by E. Schmidt in 1948 for carrying out in situ tests on the hardness of concrete.The instrument measures the distance of rebound of a controlled impact on a rock surface. Becauseelastic recovery (the distance of repulsion of an elastic mass upon impact) depends on the hardness ofthe surface, and hardness is related to mechanical strength, the distance of rebound (R) gives a relativemeasure of surface hardness or strength.Effect of this work was approximation of diversification of rock strength by the one parameter— hardness. This kind of rock resistance is more significant for group of mechanical relief processesthan for other processes (rock solution).Over 75% of all solid rocks of the Silesian Upland is characterized by high and very high hardnessmeasured by Schmidt hammer. Rocks of these strength build the biggest morphological units ofthis region (Próg Środkowotriasowy, Próg Górnotriasowy, Zrąb Mikołowski). These areas are verystrongly diversified on that altitude — differences of altitude are over 100 m in some places. Thesedata imply structural character of this relief.At 5‑gradualresistance scale the mean value of all tested rocks averages 3.5 — which correspondsto mean class and high class (see Table 3), so solid surface rocks of Silesian Upland are strongrocks.Deposits, not‑classified in resistance classes, contain over 80% contemporary Silesian Upland’ssurface. These deposits are mainly in subsidences (Dolina Małej Panwi, Kotlina Raciborska,Obniżenie Liswarty, Obniżenie Górnej Warty i Prosny). Maybe, if it could remove these pleistocene‑holocenedeposits — that stepping out there rocks are little resistant and that is why they came intosubsidences. If we accept such hypothesis — it would be the next proof on the structural characterof the relief of this region.