Geologiczne uwarunkowania rozwoju osuwisk w rejonie Krynicy-Zdroju
Abstract
Geological conditions of the development of landslides in the Krynica-Zdrój region.
A b s t r a c t. The paper presents the final results of mapping work of the Polish Geological Institute – National Research Institute, carried out in the Krynica-Zdrój area in 2010–2012. In the Beskid Niski and Sądecki there are numerous landslides of surface sediments. They also occur in the spa zone of Krynica-Zdrój, posing a threat to its functioning. The basic problem is to recognise the nature of these geohazards and their occurrence in this region. For these reasons, a landslide inventory map was constructed for the whole study area (urban-rural commune). As a result of the analysis, a large variation in the distribution, type and range of landslides has been documented. The landslide surface index and the landslide density index were calculated, concluding that the two indexes differ from each other depending on the geographical position of the analysed area. Both indicators are 2.5–3 times higher for the Krynica-Zdrój town area than for the rural commune area. This variability is associated with different lithologies, tectonics, and geomorphologic features in the area. Krynica-Zdrój lies in the area predisposed to the development of landslides, where the overlapping effects of several passive factors causes mass movements. The Krynica Zdrój area is composed of thick-bedded sandstones of the Krynica Sandstone Member and the Piwniczna Sandstone Member. They are underlain by variegated shales and thin-bedded turbidites of the Zarzecze Formation. In addition, tectonics of the deep basement is very important. Under the town, there is a deep Krynica fault zone additionally cut by sets of strike-slip faults that altogether cause severe disintegration of the subsurface material and the weakening of cohesive force. The area with the dense sets of faults is an active stress zone. Epicentres of earthquakes probably clustered along all these faults, causing the development and rejuvenation of many landslides in the Krynica-Zdrój area.
A b s t r a c t. The paper presents the final results of mapping work of the Polish Geological Institute – National Research Institute, carried out in the Krynica-Zdrój area in 2010–2012. In the Beskid Niski and Sądecki there are numerous landslides of surface sediments. They also occur in the spa zone of Krynica-Zdrój, posing a threat to its functioning. The basic problem is to recognise the nature of these geohazards and their occurrence in this region. For these reasons, a landslide inventory map was constructed for the whole study area (urban-rural commune). As a result of the analysis, a large variation in the distribution, type and range of landslides has been documented. The landslide surface index and the landslide density index were calculated, concluding that the two indexes differ from each other depending on the geographical position of the analysed area. Both indicators are 2.5–3 times higher for the Krynica-Zdrój town area than for the rural commune area. This variability is associated with different lithologies, tectonics, and geomorphologic features in the area. Krynica-Zdrój lies in the area predisposed to the development of landslides, where the overlapping effects of several passive factors causes mass movements. The Krynica Zdrój area is composed of thick-bedded sandstones of the Krynica Sandstone Member and the Piwniczna Sandstone Member. They are underlain by variegated shales and thin-bedded turbidites of the Zarzecze Formation. In addition, tectonics of the deep basement is very important. Under the town, there is a deep Krynica fault zone additionally cut by sets of strike-slip faults that altogether cause severe disintegration of the subsurface material and the weakening of cohesive force. The area with the dense sets of faults is an active stress zone. Epicentres of earthquakes probably clustered along all these faults, causing the development and rejuvenation of many landslides in the Krynica-Zdrój area.