© V. V. Ivanov1, G. P. Ponomaryov1,2

1 Institute of Volcanology and Seismology, Piip boulevard, 9, Petropavlovsk-Kamchatsky, 683006, Russia
2 Kamchatka State University, Petropavlovsk-Kamchatsky, 683032

The 70-th anniversary of the Kluychi
volcano observatory are dedicated

We studied some features of the active volcano process in a case of the giant basaltic Klyuchevskoy volcano (Kamchatka) in XX century and peculiarities of its new active cycle started in 1995. Our research work was focused on: analysis of eruption rhythmics; distinguishing of the new cycle’s active phases, the assessment of the current condition of the volcano magmatic feeding system; forecasts issue and their proving to be correct. The following parameters were used as a base: intensity of the volcanic tremor; the height and the character of the volcanic plumes; the length of the lava and mud flows according to the video, photo and visual data; the depth and the diameter of the summit crater; eruption’s duration and inter-eruption temporal intervals. We proved that the Klyuchevskoy volcano eruptions are grouped into series of events with relatively short time intervals between them. The series are separated by relatively long periods of rest. For Klyuchevskoy volcano for the first time we have calculated the time limits for the probability distributions: a) between the eruptions in a serie from 3 to 15 months; b) between the series from 3 to 8.5 years; c) duration of the two cycles from 0.8 to 2.6 years (volcanic one) and from 6 to 18 years(activity one). We used the term of the volcanic activity cycle introduced by F. Perret (1924) and P. I. Tokarev(1971). For the current activity cycle started in 1995 we distinguished the phases: of rest (1995 - 1997), of the preparation for the new series of eruption (since 1997 till February 2003), the first eruption (since March, 2003 till January, 2004) and the second eruption (since January till April, 2005). Scenario of the Klyuchevskoy 2003 eruption has been successfully predicted: the volume of erupted products and duration of the eruption is supposed to be correct, although the predicted volcanic hazard was lower than real one. We have drawn a conclusions that the volcano feeding channel is supposed to be as so-called “free-penetratable” system and its current active cycle is not yet completed. On 2005, June 20 forecast estimations are as following: the beginning of the new summit eruption accompanied by the lava flows is expected to start between 2005, June and 2006, August. The probability of the flank eruption in the nearest decades is estimated as low.