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 paper presents data on identified and described short-term local (1955−1976) enhanced volcanic activity within the Northern Group at the Central Kamchatka Depression and regional disasters (1907-1976), clearly revealed within Kamchatka Peninsular and the Kurile Islands. In scale (volume is about 9 km3, weight of erupted and replaced productswas calculated to be about 16×109 t), the local volcanic disaster was the most powerful in Kamchatka and Kurile Islands over the period of the last 2000 years. This volume exceeds 80% of ~19×109 t totally erupted by all volcanoes over the same period of time. Over the period 1907−1976, the Kamchatka and Kurile volcanoes erupted and transported about 29.5×109 t of juvenile and resurgent material while other volcanoes in the world erupted about 122×109 t.

It is shown that the cardinal revision, attempted in 1988 and 1998, of the G.S. Gorshkov hypothesis as to the explosive origin of the debris avalanche (“directional explosion agglomerate”) caused by the 30 March, 1956 culminating phase of the catastrophic eruption on Bezymiannyi Volcano, Kamchatka does not rest on a safe foundation. The hypothesis of a different (avalanche-landslide) origin, similar to the May 18, 1980 Mount St. Helens, U.S. event, must be rejected owing to an absence of necessary evidence. New arguments are adduced to support the Gorshkov hypothesis, corroborating that the main factor that caused the debris avalanche was a giant directional explosion.

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.