Role of the weathered granites in the formation of landslides on the northern slopes of Sredna Gora Mountain

Weathered granites can contribute to the initiation of natural hazards due to their specific characteristics and response to the environmental conditions. They absorb water during periods of intensive precipitation, and the water saturation further weakens the structural integrity and increases the potential of slope failures and mass movements. Additionally, the breakdown of weathered granite into smaller particles can further contribute to the volume of material available for mobilization during mass-wasting events. This study focuses on rainfall-induced slope failures that occurred in one watershed on the northern slope of the Sredna Gora Mountain which was severely affected by heavy rainstorms in September 2022. Despite the area’s typical stability, these events highlighted the influence of geological conditions, particularly the weathering of granites. Through field investigations, we examined the interactions in weathering profile, chemical transformations in granites and structural discontinuities, assessing their contributions to slope instability and hazard processes.