Evolution of rock slope failures in the flysch area − insight from the Babia Góra massif (Western Carpathians, Poland)

Abstract

The Babia Góra (1725 m a.s.l.) is the highest and most prominent mountain massif in the Western Flysch Carpathians (WFC). Its monoclinal flysch structure, combined with tectonically controlled high local relief, has led to the development of a striking pattern of rock slope failures (RSFs), particularly along the steep, anti-dip northern slope cuesta. This study integrates field geomorphological, geophysical, and sedimentological data, along with Schmidt-hammer relative age dating, to provide a detailed account of the development and relative chronology of ancient RSFs in this area. The northern slope of Babia Góra exhibits all major types of RSFs, including rock slope deformations, rock slides and rock avalanches, with a total volume of approximately 418 M m³. The inventory encompasses 125 RSFs, which affect 45 % of the northern slope, and up to 77 % of the sandstone cuesta slope. Among these, multi-temporal rock slides with long-runout, flow-like tongues represent the largest mass movement complexes in the range and rank among the largest in the WFC. Morphotectonic analysis suggests that the primary mechanism of gravitational failure involved backward rotation along listric-shaped structures, with vertical displacements ranging from 6 to 90 m, although the depth of gravitational disintegration may exceed 150 m. The Schmidt-hammer weathering index provides evidence for the multi-temporal activity of RSFs, identifying five distinct phases of RSF activity. The oldest of these phases corresponds to the timing of local deglaciation and periglacial processes.