J. Stemberk (Institute of Rock Structure and Mechanics, Czech Academy of Sciences, Prague, Czech Republic)

J. Novotny (K+K Pruzkum Co., Novakovych 6, Prague 8, Czech Republic)

In 1995 a considerable increase of the slope movements in the Bohemian Massif was registered. The Vaćov Landslide, a huge landslide activated in 1995, is situated on the left bank of the Labe River. The sliding area is about 300 m long, denivelated by 160 m. Movements originated in places where older landslides had been reported. Local geological conditions appear to influence the dip of the slope and the origin of individual movements here. The upper part of the slope is built by 220 m thick complex of the Tertiary volcanic rocks overlying the Cretaceous sediments outcropping in the lower part of the slope. A landslide scarp of the active flow-type slide evoluated just under separated ba salt blocks. The flow slide located in a place of frequent old sliding, was strongly accelerated in May and June 1995 up to a maximum rate 6 cm per day. Thid happened after the long-term precipitation balance culmination. This increased amount of the rainfall can be blamed for slide reactivating as the main factor under conditions of favourable ge ological predisposition and its state of limit balance.