Восстановлена история формирования вулкана. Динамика его активности реконст­руирована в соответствии с абсолютной хронологической шкалой. Показано, что вулка­ническая активность имела пульсационный характер. Каждый период активизации ха­рактеризуется закономерной сменой состава вулканитов. Возраст собственно стратовулкана Безымянный составил около 5500 лет. Датированы крупнейшие пирокластические извержения. Подсчитан объем продуктов и средняя интенсивность выноса вещества за время жизни вулкана. Отмечено резкое возрастание интенсивности выноса вещества на современном этапе. Анализ реконструированной истории вулкана позволяет полагать, что его активность сохранится в ближайшие 200—300 лет.

The largest Plinian eruption of our era and the latest caldera-forming eruption in the Kurile-Kamchatka region occurred 1700-1800 14C yr BP from the Ksudach volcano. This catastrophic explosive eruption is similar in type and characteristics to the 1883 Krakatau eruption. The volume of pyroclastics ejected was 18-19 km3, including 15 km3 of tephra and 3-4 km of pyroclastic flows. The eruptive column reached 23 km height. A collapse caldera was 4 X 6,5 km in size with a cavity volume of 6.5-7 km3. Tephra was deposited to the north of the volcano to a distance of more than 1000 km. Pyroclastic flows accompanied by ash cloud pyroclastic surges were as long as 20 km. The eruption was first phreatomagmatic, then it became rhythmic, and each rhythm began with the pumiceous tephra eruption followed by the pyroclastic flow formation. Erupted products were rhyolite-dacite remaining invariable during the whole eruption. At the post-caldera stage when the Shtyubel cone started to form within the caldera the basaltic-andesite material began to come to the surface. The driving mechanism of the onset of the eruption is suggested to be an intrusion of magma of basic composition and its mixing with acid magma from a previously existed chamber. The eruption had substantial environmental impact and may have produced a large acidity peak in the Greenland glacial shield.

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.