The volcanic activity on Kamchatka manifests itself periodically, that is to say, there are periods when many volcanoes become active and also there are periods of quiescence. Eruptive periods consist of cycles of eruptions of separate volcanoes. These cycles either coincide with each other, or being late, overcover one another. The existence of eruptive epochs shows that some kind of a region wide stimulating force acts upon the volcanic reservoirs.
The last eruptive period which began at the end of 1944 and apparently is not quite finished up to the present moment, consisted of cycles of eruptions of four largest volcanoes of Kamchatka, namely the volcanoes of Klyuchevskoy, Shivelouch, Avacha and Mutnovskaia.
Just as earlier, the eruptive cycle of the Klyuchevski volcanoes has again manifested itself in the form of a therminal eruption but of the main crater and the lateral one proceeding on the volcano slope.
Having begun in early December 1944, the therminal eruption gradually increased and on the 1-st of January attained its culminating intensity. This eruptive phase with its enourmous cloud of gases, ashes and red-hot bombs, 10 km up above the crater, with lightning rumbling and with dozens of seismic shocks as well as with streams of water and mud which came down to a distance of 35 km from the crater during a terrible frost, was quite an uncommon phenomenon for ordinary eruptions of the Klyuchevskoy volcano. The lateral eruption occurred on the South-Eastern slope of the volcano 5 months after the activity of the main crater had ceased. As the result of the gas and lava eruption there was formed a whole series of craters and there was an effusion of lava, having about 5.5 km in length. The study of this eruption gave a lot of interesting material, the most interesting being the oxidation procests of the lava and the genesis of fumarole gases.
The activity of the Avacha volcano lasted a comparatively shorter period of time. Its eruption began on the 25th of February 1945 and lasted 7 hours.
Just like the former eruptions this was a strong explosive activity, which resulted in the formation of an enormous cloud of gases and ashes formed about 6 km above the crater.
Following the course of the wind in the south-east, this cloud proved to be of great interest, because of its electric phenomena (lightning and St Elm fires) as well as by being strongly crarged with lava particles. The deposit of these particles had a strong admixture of pumice, was 45 cm thick and was found 25 km from the crater. When compared with the three erupitons of the former eruptive cycle, the present eruption was still more intensive.
The erupt ons of the Shivelouch volcano began at the end of December 1944, lasted throughout the whole 1945 and was still noticeable in the first part of 1946. Eruptions like single shots were feeble; there were short explosions (5—15 m) of gases and ashes occurring at long intervals. The volcanic cloud that would appear at those moments 1-2 km above the crater, was soon blown away by the wind and dispersed in the air.
The eruptions of the Shivelouch volcano and their long lasting cycle proved to be similar with the activities of an extremely complex by its structure ancient and extinguishing American volcano Lassen Peak.