|Holocene Kamchatka volcanoes||
Institute of Volcanology and Seismology
Volcanic Landforms and Deposits
Calderas are large volcanic depressions formed as a result of collapse of an underlying magma chamber roof due to withdrawal of magma. Some large calderas formed during voluminous explosive eruptions (Krakatau-type calderas). Holocene Kamchatka examples of Krakatau-type calderas are (from north to south): Karymsky caldera, Ksudach calderas, Kurile Lake caldera.
Some smaller calderas formed as a result of lava eruptions (Hawaii-type calderas). Holocene Hawaii-type calderas can be found in Kliuchevskoi volcanic group: on Ushkovsky (Plosky Dal'nii) and Plosky Tolbachik volcanoes; and on Krasheninnikova volcano.
Some voluminous explosive eruptions occurred from large craters (like Novarupta crater in Alaska). In Kamchatka, the most prominent Holocene craters of such kind are Khangar summit crater in Sredinny Range and three craters in South Kamchatka: Chasha crater at Tolmachev plateau, Baranii Amphitheater at the foot of Opala volcano, and Khodutkinsky crater near Khodutka volcano.
Sector collapses resulting in large debris avalanches were common for Kamchatka volcanoes in the Holocene time. The largest of them occurred at Shiveluch, Bezymianny, Kamen', Gamchen, Taunshits and Kambalny volcanoes.
Voluminous ignimbrite sheets are associated with Holocene Karymsky, Ksudach, and Kurile Lake calderas. Smaller pumice pyroclastic flow deposits occur at the foot of many volcanoes, but they are most typical of andesitic Shiveluch, Bezymianny, Kizimen, Khangar, and Avachinsky volcanoes.
Most typical block-and-ash pyroclastic flows occur at the foot of Bezymianny, Kizimen, Ichinsky, Zheltovsky and Dikii Greben' volcanoes.
Active extrusive domes can be found at Shiveluch and Bezymianny volcanoes. Kizimen and Ichinsky summit domes now are dormant, but fumaroles indicate they are still alive. Some domes like those at Taunshits and Zheltovsky volcanoes do not show signs of current activity. The largest extrusive volcano in Kamchatka is Dikii Greben', which is composed of many domes of different ages and now is dormant. In addition, domes are located within the large craters such as Baranii Amphitheater and Khodutkinsky.