Geomorphological indications of hazardous phenomena in the Baikal rift zone

Abstract

In the marginal sections of the Baikal rift zone, some landforms produced by natural disasters are identified. Most of them have seismic origins. Pure tectonic landforms are piedmont scarps and trenches. They originate during seismic rejuvenations of faults at the rift valley slopes. In the subsurface segments of the young faults high-grade tectonic disintegration of rocks is observed. Therefore seismogenic trenches and scarps are accompanied by great rock falls, rock slides and gravity faults. Geomorphological indications of high-grade disintegration of rocks in the zones of young faults are badlands and rock streams. In the Barguzin rift valley traces of major outbursts of rock material from the ridge along the valleys of large rivers are revealed. These are aggregations of angular blocks in the marginal parts of the depressions near the mouths of the large valleys. Near the basin slopes they are represented by compact heaps of boulder. The sizes of individual boulders amount to 200 m3 and over. At a distance from the mountains their scatter over the surface of the piedmont fans is observed. Evidently, quick outbursts of large volumes of rock material into the basin occurred after the destruction and collapse of landslide dams which barred the valleys during earthquakes.