Ages of most of the active volcanoes, calderas and craters of subcaldera eruptions in the Kurile-Kamchatka region were determined based on the results of geological, geomorphological, tephrochronological and isotope-geochronological studies using more than 600 l4C dates. It has been revealed that the active volcanoes are young, their maximum ages are 40 000 - 50 000 years. Most of the volcanoes that are active at present time started to form at the very end of the Late Pleistocene and in the Holocene. The l4C age was determined for the majority of volcanoes that started to form in the Holocene. It was found that all polygenic stratovolcanoes in Kamchatka formed in the Holocene only within the Eastern volcanic zone. The l4C age was determined for most of the Late Pleistocene calderas that formed within 30 000-40 000 years ago. All Holocene calderas and some craters of subcaldera eruptions were dated. The periods of synchronous intensified activity of volcanoes were determined in the Holocene between 7500 and 7800 years ago and between 1300 and 1800 years ago.

This paper gives data on the volcanic belts of Kamchatka. Recognition of !hc volcanic zone of the Central Kamchatka Depression as an independent, extensively developing structure is validated. Data available in the literature arc systematized and the quantitative characteristics are recalculated for all the active volcanoes of Kamchatka: the total volume of volcanic rocks, relative heights, absolute and relative volumes of rocks of basic, intermediate and acid composition, mean production rate of edifices, duration of formation (in thousands of years) etc. Their calculated mean statistical values for a Kamchatkan volcano for the entire region and for separate groups of edifice types have been obtained for the first time. This study shows that the basic volcanism plays the leading part in the formation of volcanic edifices.

На склонах Ключевского вулкана и вблизи него на площади 30x40 км изучены линейные формы рельефа (линеаменты) и тектоническая трещиноватость. Выделены зоны с преобладанием линеаментов различного направления. По пересечению одних зон другими установлен их относительный возраст (возраст последней активизации).
Показано, что наиболее молодой и активной в последние годы является линейная зона северо-западного простирания. Особо выделены две зоны, отличающиеся своеобразным структурным рисунком: дуговая, окаймляющая вулкан с востока на высотах 900—2500 м, и на крутом склоне конуса (выше 2500 м). В пределах последней выделена система дуговых трещин и сбросов, свидетельствующая о растяжении конуса («паукообразный» структурный рисунок). На основании анализа распространения подобных систем трещин и сбросов на других вулканах установлено, что они могут служить прогностическим
признаком, указывающим на процессы разрушения, происходящие на вулканах, и на места будущих побочных прорывов или обрушений склонов. Для Ключевского вулкана установлено, что наиболее опасен его юго-восточный склон, где в будущем возможны крупные обвалы или проседания.

EARTHQUAKES OF THE KARYMSKY VOLCANIC CENTER AND THEIR RELATION
TO TECTONICS, by Leonov V. L. and Ivanov V. V. We studied the origin of earthquakes of the Karymsky seismically active area (Kamchatka) which is situated in the center of the Karymsky ring structure. Earthquakes are inferred to be related to the crustal magma bodies of this region and to magma movement along the relatively ancient northeast — trending faults whose remobilization occurs in modern times.

We have summed up and supplemented new data on the eruptions of 1926-1927, 1938 and 1945 plus added the description of the last eruption of the volcano in January 1991. Considering the dynamics of the eruptive activity of the Avachinsky volcano in 1737-1991 we have presented a classification for these eruptions. Also we made a forecast of the type and parameters of possible future eruption as well as estimated the volcanic hazard associated with it. Because of high degree of volcanic hazard in the SW and S sectors of the base of the volcano it is proposed to prohibit constructions of any kind in these areas.