Three stages of study of active and potentially active volcanoes on Kamchatka and the Kurile Islands were distinguished: the anterior stage (1700-1935), the new stage (1935-1962) and the recent stage (from 1962 till present time).
This paper provides a new, for the first time scientifically based term of «active volcano». Updated catalogues display active and potentially active volcanoes of Kamchatka and the Kurile Islands. Here we propose a long-term forecast of behavior and parameters of impending eruptions and related volcanic hazards for the typical volcanoes of the 1st and the 2nd stages of evolution.

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.

During 1988 gas samples were collected by one technique from the following volcanic fumaroles within the Pacific ocean ring: Momotombo (Nikaragua), the White Island and Raul (New Zealand), Sheveluch (Kamchatka) and Ebeko (the Ku-rile Islands). Gas temperature of fumaroles varied between 92° and 882° C. In this connection, oseveral types of fumaroles were distinguished: magmatic - high temperature (850° C), .mean temperature (300-500° C), low temperature (100-120° C), and aqueous carbon dioxide low temperature (100°C). Independently of the state of activity, location and evolution stage of volcanoes, the atomic composition beeing similar, the molecular ratios of volcanic gases are controlled by mineral buffers of partial oxygen pressure!. The paper is of interest in searching for eruption precur-sors in the change of gas composition when visible variations of fumarole temperature are lacking