The Huge Jiroft Landslide: Introduction, Indications and Characteristics

The huge and historical landslide of Jiroft, being about 53 Km2 in area, is located in 35 Km NW of Jiroft town just adjacent to Jiroft Dam and in coordinates of 28ْ 45َ to 28ْ 53َ N and 57ْ 20َ to 57ْ 30َ E. This slide which has taken place as a result of massive movement of upper reefal part of Qom formation dipping only 6ْ, 8 cubic kilometers in volume and about 300 meters thickness over the underlying marls, is recognizable based on shattered rocks, anomaly along the course of Halil Roud and the presence of well-rounded igneous boulders in some parts among the shattered rocks. As a result of this slide, the course of Halil was completely blocked and an ephemeral lake was created. Afterwards, the lake overflowed in another place (the present place of the Dam) which was the lowest point in its periphery. Due to this river detour, the Halil Roud incised its fan, created a gorge from the overflowing point to its confluence point, as well as incision of several small fans along its course. The presence of several active faults and low slope of the sliding mass imply the probable influence of earthquake and heavy precipitation as triggering mechanisms. The main characteristics of this slide include very low slope (6ْ), its size (53km2 in area and maximum run- out distance of about 7 km), comprising four parts, specific mechanism (like other sturztorms) and its time of occurrence (probably 60000 to 100000 years ago). Depending on the classification of landslides, it may be considered as extremely rapid rock slide, sturzstorm, rock avalanche as well as debris avalanche. The desert varnish of boulders engaged in the slide mass and the solution runnels generated after the slide suggest that the age of the slide is about tens of thousands to several thousands years ago.