ANALYSIS OF THE PARAMETERS OF THE ANCIENT CATASTROPHIC LANDSLIDE IN THE VALLEY OF THE RIVER PSLUH (WESTERN CAUCASUS) USING LASER SCANNING DATA

Abstract

A detailed analysis of the relief structure and development of gravitational and fluvio-gravitational processes in a valley of the Mzymta river basin (Western Caucasus) was fulfilled using digital elevation models created on the basis of materials of laser scanning. We discovered and mapped a giant complex landslide with syndynamical block-and-ground flow. The genetic and age relationship of processes of various types and resulting landforms and sediments were determined.

The landslide has a volume of about 32 million m3 , thickness up to 70 m; its body was displaced at a distance of 150–500 m to the WNW direction over the slip surface with inclination about 12–15°. The formation of the landslide we can presumably associate with the seismic impulse with an azimuth of 280–290°, which occurred about 830–950 A. D. Judging by the orientation of the landslide, the earthquake trigger can be a slip along the Main Caucasian fault. Simultaneously with the landslide the outburst of stone-ground mass down the valley of brook Pslushonok occurred (11–12 million m3 ). Mudflow material from the slopes of the left (southern) side of the valley constitutes a significant part of the volume of the terrace formed. The mudflow also filled the bottom of the Pslushonok valley and the part of the Psluh river valley below the mouth of the brook (the total length being 7.2–7.4 km) and created a dam across the Psluh valley, which was partly eroded after this event.