At the beginning of the XXI century, increased eruptive activity of the largest volcanoes of the Northern group of Kamchatka is observed: Sheveluch, Klyuchevskoy, Bezymianny and Tolbachinskay fissure zone. The features of growth of andesitic Sheveluch volcano extrusive dome are noted: the height of the dome has reached 600 m during 38 years of almost continuous eruptive activity. After an eight-year period of relative rest, nine terminal eruptions and two lateral breakthroughs of the Klyuchevskoy basalt volcano occurred. Explosive-effusive eruptions of the andesitic Bezymianny volcano were observed almost annually. After 36 years of rest, a new eruption occurred in the Tolbachinsky regional fissure zone.

The paper presents data on specified northern boundary of the Holocene volcanic activity in Kamchatka. This boundary is located 80 km to the north for the frontal volcanic zone and 180 km to the northwest from Sheveluch Volcano for the zone of the Sredinny Range. For the first time numerous evidence for the Holocene volcanic activity within the Kamchatkan zones with no deep seismicity and located to the north from the Aleutian transform fault were detected, studied and dated using geologic methods and isotope geochemistry. Radiocarbon age for the eruptions was estimated.

Tephrochronological and radiocarbon investigations of soil-pyroclastic depositsalong the line Shiveluch Volcano - Chernyi Yar - Bering I. have detected and identified the ashes oflargest (for the past 6500 years) eruptions on Shiveluch Volcano in the southeastern sector of the ashabundance area, as well as the ashes of Bezymyannyi, Ksudach, Klyuchevskoi, Avacha and Khangarvolcanoes. A detailed radiocarbon dating of peat deposits in Chernyi Yar has not only improved the agedeterminations of the eruptions themselves but also helped in the determination of ash fall rate for thelower Kamchatka R. valley, namely, once in 191 years. Apart from the 1964 tephra, we suggest for useas regional geochronological markers the ash horizons of Shiveluch Volcano having the followingrounded radiocarbon dates: 265 (SH1), 965 (SH2), 1450, 2800, 3600 (SP), 4105 (SHDV), 4800, as well asthe ashes from Ksudach 1806 (KS1) and Avacha 5489 (AV2) volcanoes.

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.