We have identified, and describe in this paper, a phase of multifactor natural catastrophism that has been the greatest during our era in Kamchatka, to be dated 0-650 A. D. Its chief components were. The last catastrophic eruptions to have occurred (a caldera-generating one at about 240 A. D., the pyroclastics volume being 18-19 km3 and a subcaldera one around 600 A. D. with the volume of lava and pyroclastics 9.5-10.5 km3) which were followed by irreversible relief changes over areas of hundreds of square kilometers and have affected rather injuriously many other environmental components. An exceptionally intensive activity of the other volcanoes (at least 75-80% of all active and potebtially active Kamchatkan volcanoes were erupting, tens of large and catastrophic eruptions occurred). Regional catastrophic and large ashfalls. A sharp, large-amplitude (between 1.5-2 and 12-15 m) tectonic uplift of various blocks in Kamchatka. Large earthquakes accompanied by large-volume rockfalls, landslides, large and frequent tsunamis. The catastrophic events of that time are argued to have been part of a worldwide phase of natural catastrophism that we hypothesize to have occurred at the beginning of our era.

Abstract-This study is the first to show, using data from the eruption of Koryakskii Volcano, Kamchatka that began in December 2008 and continued through 2009 that the water in permanent and temporary streams that start on the slopes of the volcanic cone and in temporary lakes when contaminated with fresh tephra is a specific hazard factor related to long-continued hydrothemial-phreatic eruptions on that volcano. This water is characterized by increased acidity (pH 4.1-4.35) and large amounts (up to 50-100 cm /liter) of solid suspension and is unfit for drinking and irrigation. When combined with tephra, it probably produced mass destruction of a number of animals who lived on the slopes and at the base of the volcano. The water contaminated with tephra is an important component of the atmospheric mud tlows occurring on Koryakskii Volcano; for several future years it will be a potential source for enhancing the acidity of ground water in the volcanic edifice.

For the first time, tracks from 5 catastrophic lahars associated with subsynchronously occurring rueptions of the Avachinsky (great explosions with a large volume ejections of juvenile pyroclastics) and Koryaksky (voluminous lateral lava effusions) volcanoes have been found, described and dated by the C-14 method. Their reconstruction has been conducted. The C-14 ages of lahars are from 3500 to 3200 yrs ago, the calendar ages are from 1900 to 1500 BP. These lahars were significantly greater in volume, degree of hazard, and intensity of impact on the natural environment than those triggered by historic (19th - 20th centuries) eruptions from the both volcanoes. In particular, they caused a considerable (1-3 km) SW migration of the Avacha river down-stream channel, the largest waterway in Southern Kamchatka.

Results are presented from gravity, seismic and electromagnetic studies. Main features of the deep structure of the area have been identified. A multidisciplinary geologic-geophysical model has been developed for the crust beneath Avacha Volcano. The model involves a crustal magma chamber at a depth of about 15-25 km, an intrusion that overlies it, and a peripheral chamber under the volcanic cone at 0-2 km depth, as well as a fluid-saturated zone in the Avacha Graben. We discuss possible geodynamic processes that are going on in the crust at present. Importance is attached to the fluid-containing crustal permeable zone. Recommendations are provided for drilling a deep well in the Avacha Graben area to search for a geothermal field.

The article presents the methods and results of the magnetotelluric sounding within the Avacha-Koryaksky group of volcanoes. Geoelectrical section was studied within the period range from 0.0001 to 1000 seconds and above. The authors performed a numerical two-dimensional modeling. Initially, we used test models for possible distortions of curves. The analysis of the magnetotelluric parametres allowed us to characterize the geoelectrical inhomogenuities. Curves along the strike and across the strike were used as main curves. Since longitudinal curves are less prone to coast effect, they were used with transverse curves in order to create a geoelectrical model based on a 2D magnetotelluric field numerical modeling. The created geolectrical model has a conductive bed in the upper part of the section that is connected with an igneous-sedimentary cover. The deep part of the model includes near-vertical conductive zones, which denote a zone with deep faults. The paper describes possible nature of the revealed anomalies and provides rough estimation of rock porosity in the conductive zones.

The actual collective monograph presents the results of both theoretical and experimental studies of the multi-disciplinary problem on volcanic hazard assessment and development of techniques for prediction of catastophic eruptions. The volcanism of Kamchatka and other regions of Russia has been analyzed. On the basis of geological, volcanological and tephrachronological studies including radiocarbon dating, there have been defined certain groups of volcanoes on different stages of evolution. At the same time the problem of determination of the internal structure of volcanic dome using modem theoretical methods and technologies is well investigated. The new techniques of estimation of volcanic hazard were developed. Whenever ti is required, theoretical approaches are confirmed by results of in-field observations.

The book will satisfy the needs of Earth sciences specialists from a variety of backgrounds, volcanology, geo-mechanics, ecology, industrial constuction applications and hazard assessment.