Gravitational shifts of rock blocks in Flysch Carpathians

 

Jan Lenart, Lukáš Šesták

Geoscience Research Reports 49, 2016, pages 239–246

Full text (PDF, 3.57 MB)

Published online: 30 September 2016

Export to RIS

 

Abstract

The flysch rocks of the Outer Western Carpathians are typically and repeatedly affected by deep seated gravitational slope deformations with evolution of typical landforms such as rocky headscarps and tens of meters deep crevice type caves. The origin of these forms can be dated most frequently to the humid phases of Holocene. The relief is typical with structurally predisposed rock scarps and rock towers. The rock surfaces are very often disrupted by subvertical joints, which divide the rock massif into particular rock blocks. Some joints can be gravitationally widened with a vertical shift of the rock blocks greater than 1 m.
In the years 1988 and 1990, members of the Czech speleological society installed the glass indicators on such joints between the rock blocks in four different crevice type caves for identifying active gravitational shifts. In total, 120 glass indicators were installed there. We investigated the recent state of glass indicators after 26-28 years since the installation. We found 68 indicators. Twenty four indicators were fully intact, nineteen indicators were destroyed or were missing, but we didn’t find any shift. We didn’t reconstruct the shape of 6 other indicators. Nine glasses were broken. Shifts up to 5 cm were identified by 10 indicators. The shifts of particular blocks do not indicate the overall movement of the whole rock massif, neither the overall movement of the slope, and it should not be interpreted in that way. We don’t know if the shifts (movements) were gradual or sudden.