Structural control of landslide disasters in Karangmoncol, Purbalingga Regency, Central Java

Abstract

Landslide is one of the annual natural disasters that occur in the Karangmoncol area, especially during the rainy season. Karangmoncol is located in the central part of Java Island, which is a mountainous area with steep slopes. How the geological structure affects the occurrence of landslides is the objective of this study. Field data of the research include the dimensions of the landslide, the constituent rocks and measurements of the joints. The dimensions and direction of the landslide are drawn on a topographic map. The types of rocks constituent and the direction of the joints/fractures are also drawn on the map, so that the relationship between fracture structures, soil/rock types and landslides in the Karangmoncol area is known. The geological structures in the Karangmoncol area are in the form of bedding planes, shear-fractures, tentional fractures, and intrusional contacts. Intensive layering and joint structures are found in the volcanic sandstones of the Halang Formation. These structural fractures accelerate the weathering of volcanic sandstones to form thick soil. The intrusion of younger sill or dyke type andesite rocks creates a zone of alteration/mineralization of rock and creates a load on the underlying claystone. These main things are internal factors that cause the phenomenon of landslides in the Karangmoncol area.