Представлены материалы исследований деятельности вулканов Карымского долгоживущего вулканического центра на Камчатке в 1996 г. Рассмотрены особенности динамики и вещественный состав пород одновременно начавшихся извержений вулкана Карымский и в кальдере Академии Наук. Эффузивно-эксплозивное извержение Карымского вулкана возобновилось после 14-летнего периода покоя и в течение года поставило через вершинный кратер -30 млн.т вещества андезитодацитового состава. Предполагается длительная эруптивная активность этого вулкана в ближайшие годы. Одновременно с типичной для Карымского вулкана активностью в 6 км южнее впервые на Камчатке в историческое время наблюдалось субаквальное эксплозивное извержение в озере, занимающем кальдеру Академии Наук. За 18ч извержения в северной части Карымского озера выросла постройка из пирокластического материала базальтового, андезитобазальтового состава с кратером диаметром 650 м. Объем извергнутого пирокластического материала оценивается в 0.04 км3, общий вес >70 млн.т. Обсуждены последствия извержений для окружающей среды, описаны оживление гидротермальной деятельности и образование новой группы горячих источников в кальдере Академии Наук, сделаны оценки прорывных паводков из Карымского озера и т.п.

Shiveluch Volcano, located in the Central Kamchatka Depression, has experienced multiple flank failures during its lifetime, most recently in 1964. The overlapping deposits of at least 13 large Holocene debris avalanches cover an area of approximately 200 km2 of the southern sector of the volcano. Deposits of two debris avalanches associated with flank extrusive domes are, in addition, located on its western slope. The maximum travel distance of individual Holocene avalanches exceeds 20 km, and their volumes reach ∼3 km3. The deposits of most avalanches typically have a hummocky surface, are poorly sorted and graded, and contain angular heterogeneous rock fragments of various sizes surrounded by coarse to fine matrix. The deposits differ in color, indicating different sources on the edifice. Tephrochronological and radiocarbon dating of the avalanches shows that the first large Holocene avalanches were emplaced approximately 4530–4350 BC. From ∼2490 BC at least 13 avalanches occurred after intervals of 30–900 years. Six large avalanches were emplaced between 120 and 970 AD, with recurrence intervals of 30–340 years. All the debris avalanches were followed by eruptions that produced various types of pyroclastic deposits. Features of some surge deposits suggest that they might have originated as a result of directed blasts triggered by rockslides. Most avalanche deposits are composed of fresh andesitic rocks of extrusive domes, so the avalanches might have resulted from the high magma supply rate and the repetitive formation of the domes. No trace of the 1854 summit failure mentioned in historical records has been found beyond 8 km from the crater; perhaps witnesses exaggerated or misinterpreted the events.

Most of the hot .springs and all high-temperature hydrothermal systems are located within the three volcanic belts: East Kamchatka, South Kamchatka and Srcdinny Ridge connected with the zones of subduction. At the present time subduction beneath the Sredinny Ridge has stopped and the Central Kamchatka depression is now a relict of the continental slope of deep-sea trench. This is supported not only by the geological data but also by the fact that heat release by hot springs in the Sredinny Ridge is an order of magnitude lower then within East and South Kamchatka. Distribution of the hot springs is similar in all three belts. At 90-100 km width of the volcanic belts and of zones of the hydrothermal activity over 95% of heat is released by the sources located within the 45-km wide near-frontal zones. Voicanic fronts of the arcs are the clear boundaries beyond which heat release discontinues sharply. The descreate heat release is observed along the volcanic belts at the typical distances of 70-100 km between the maxim of heat release. Quantitative estimation of the probable heat and water contribution into the hydrothermal system formation showed that the only real heal source are the near surface magmatic chambers. Scenario of the probable heat and mass transfer leading to the formation of the hydrothermal systems and connected with them ore deposits has been considered.

A detailed reexamination of the deposits and comparison with the descriptions of the eruption revealed that on March 30, 1956, a collapse and a landslide 0.5 km3 in volume took place on the eastern slope of Bezymyannyi (Central Kamchatka). After a series of explosions, an old dome was slowly uplifted by rising magma, and a cryptodome intruded the eastern flank prior to a cataclysmic explosion. A rockslide changed to a cold (< 100°C) debris avalanche which rushed down at a speed of more than 60 m/s and covered a distance of 10 km from the volcano. The avalanche split into three branches that flowed along the river valleys. The central flow covered the largest distance (22 km). The avalanche stripped and pushed the material at the volcano's foot (snow, soil, alluvium, and vegetation), which produced long mud flows. The landslide unroofed the cryptodome and triggering a devastating lateral blast followed by the eruption of pyroclastic flows.