Theories are presented about the time of origin, dynamics and formation mechanism of active volcanoes in the Kuril-Kamchatka zone during the Late Pleistocene-Holocene period. The study was based on more than 500 radiocarbon dates and the results of geological, geomorphological, tephrochronological and isotopic geochronological research. It is noted that there are different rhythms in the activity of the volcanoes and in the mechanisms and rates of formation of the volcanic structures. Periods of synchronous activity of the volcanoes on Kamchatka and the Kuril islands, and apparently, in other volcanic areas are identified, suggesting their global nature. The concept of "active volcano' is discussed. -P.Cooke

Four Plinian eruptions from Ksudach volcano ha' been reconstructed and dated by the 14C method. Three collapse calderas formed as a resu of these eruptions: KSi and caldera V 1700-1800 yrs ago; KS2 + KS3 and caldera IV 6000- 6100 yrs ago; KS4 and caldera III 8700-8800 yrs ago. KSi was the most voluminous eruptio with 18-19 km of pyroclastics and column height reaching 23 km. The volume of produci of KS2 + KS3 was 10-11 km3 and that of KS4, at least 1.5-1.7 km3. Sizes of calderas wer as follows: V - 4 X 6.5 km, IV - 5x5 km, III - presumably 2-3 km across. The juveni pyroclastics were supplied during eruptions rather rhythmically. Each rhythm began wil tephra ejection and completed with the formation of pyroclastic flows. The composition < products varied from andesited to rhyodacites: KS2 and KS4 - andesites dominated, KS3 - dacites and rhyodacites, and KSi - rhyodacites. It is possible that "the mechanism triggering onsets of all caldera-forming eruptions was the intrusion of very hot fresh magma of basi composition and its mixing with less hotter acid magma in the magma chamber existe previously. The eruptions, in accordance with their scales, may have had an impact on clima and ozone layer of the Earth. It is likely that the large acidity peaks in Greenland ice cor* result from these eruptions.

This study is concerned with the structure of Nemo III caldera which came into being 24.500-25.000 B.P. in the north of Onekotan Island, Northern Kurils. We describe the pyroclastics of the caldera- generating eruption sequence, and estimate its volume (9-11 km3) and weight (12-14) * 10^9 t. The composition of juvenile products was found to vary in an antidromous manner during the eruptions from dacytes to basaltic andesites. The pre-caldera rocks and the pyroclastics of the caldera-generating eruption belong to the tholeiitic series, while the post-caldera rocks to the calc-alkalic. Evidence was found in the pumice discharged by the terminal eruption to indicate mixed magmas of dacyte and basaltic andesite (basaltic?) composition. The caldera-generating eruption sequence is supposed to have been caused by a "fresh" basic magma injected into a pre-existing acid magma chamber produced by fractionation of the magma which had been supplied to the pre-caldera volcanic structures.

The present paper, the first in the serives "The 300 Years of Kamchatka Volcanoes", examines the 350-year eruptive history of Young Shiveluch Volcano, which is the northernmost of the active volcanic edifices in Kamchatka; the history was reconstructed from historical documents and evidence, results of geological volcanological research and tephrochronologic dating using the 14C method. The results include the types, parameters, geologic-geomorphologic effect of the volcano's eruptions, environmental impact, estimated volume and weight of erupted and displaced material, the volcano's discharge rate. Since 1964 the dimensions of the new volcanic forms, the dynamics of their growth and decay, and the volume of ejecta were found using photogrammetric techniques. Part I. 1650-1964.

The first paper in the series “The 300 Years of Kamchatka Volcanoes” has examined the 350-year eruptive history of Young Shiveluch Volcano, which is the northernmost of the active volcanic edifices in Kamchatka: the history was reconstructed from historical documents and evidences, results of geological volcanological research and tephrochronologic dating as well as the 14C method. The results include the types, parameters, geologic-geomorphologic effect of the volcano’s eruptions, environmental impact, estimated volume and weight of erupted and redeposited material, the volcano’s discharge rate. Since 1964 the sizes of the new volcanic forms, the dynamics of their growth and destruction, and the volume of ejecta were calculated using photogram-metric techniques. Part II. 1965-2000.

The eruptive history of Ebeko since its arising about 2400 years ago to the beginning of the 17th century was reconstructed based on data of special geological, gecmorphological, tephrochronological researches using the 14С dating (more than 20 dates). Six stages of increased activity with the duration of 200-300 years were recognized. These stages are divided by quiet periods of the same duration. It is shown that the eruption of juvenile material (lava and pyroclastic) took place only at the first stage (420-200 years before our era). All the next eruptions were phreatic, but of different power. Large-scale maps and lopoplans of the Ebeko volcanic group (Ebeko, Neozhidanhy, Nezametny) with the nearest areas were compiled and the present-day morphology of the Ebeko summit part was described m detail based on ariborne materials of 1987, 1988, 1990. It is presented that, not considering the first eruptive stage, the main volcanic hazard for the Ebeco region and the town of Severo-Kurilsk situated near the volcano came from the moving of large lahars and tephra fall.

Consequences of the Ebeko eruptions in 17-20 centuries were reconstructured in detail based on history information and data of tephrochronoSogical investigations and air photography of 1960, 1987, 1988, 1990. It is shown that all the eruptions were phreatic and conditionally phreatomagmatic with thermal alimentation as a very heated dike-sill complex with volume of more than 1 km , in the zone of extension NNW (Az. 25°), where volcanoes of the Vernadsky ridge are located (Paramushir island). It is supposed that the main future hazard for the Severo-Kurilsk town and the nearest areas is expecting from the moving of lahars of large-volume along the Kuzminka and the Matrosskaya rivers originated from the Ebeko volcano. Lesser hazard is expecting from ashfalls produced by the Ebeko and other volcanoes of the North Kuril and the Souih Kamchatka. It is proved that a big hazard for the may arise from the future eruption of the Ebeko similar to those eruptions of 1934-1935. It is recommended some ways for defence of the town.