Effects of Hydrothermal Alterations on Physical and Mechanical Properties of Rocks in the Geysers Valley (Kamchatka Peninsula) in Connection with Landslide Development

Abstract

The geothermal system of the Geysers Valley is composed of highly porous pumice-rich Quaternary tuffs. Thermal water altered them and transformed into hydrothermal rocks. Two hydrothermal facies are distinguished in geological section: low-temperature argillized propylites and hydrothermal argillites with high-silica zeolites. In some zones tuffs are totally altered into clayey soils. Mineralogical alteration of rocks decreases their physical and mechanical properties that promotes the slope instability and triggers hazardous geological processes such as landslides. The most notable example is the catastrophic landslide which occurred in the Geysers Valley in 2007. This paper describes hydrothermal alteration of volcanic rocks in the Geysers Valley and relationship between petrophysical properties and secondary alteration.