Belousov A, Belousova M, Auer A, Walter T R, Kotenko T
Institute of Volcanology and Seismology, FED RAS, Petropavlovsk, Russia.
Department of Geoscience, Shimane University, Matsue, 690-8504 Japan.
Bull Volcanol. 2021;83(1):4. doi: 10.1007/s00445-020-01426-z. Epub 2021 Jan 6.
Ebeko is one of the most active volcanoes of the Kurile island arc, producing frequent mild Vulcanian explosions with eruption clouds up to 5 km high. The volcano poses a serious threat to the Severo-Kurilsk town with a population of around 2500 inhabitants, located at a distance of only 7 km on a fan of the volcano's laharic deposits. Here, we report an overview of the activity of the volcano in the 20th-21st centuries and the results of our geological and petrological investigations of the ongoing Vulcanian eruption that started in 2016. We have found that eruptions of Ebeko span a range of mechanisms from purely magmatic to phreatic/hydrothermal. Three of its historical eruptions (the 1934-1935, 1987-1991, and the 2016-ongoing) involved fresh magma, while during the others (1967-1971, 2009-2011) fresh magma was not erupted. Juvenile material of the ongoing eruption represents highly crystalline and highly viscous (more than 10 pa s) low-silica (56-58 wt% SiO) andesite. Historical data and our observations of the ongoing eruption allowed us to suggest a functional model of the volcano where Vulcanian explosions are caused by shallow intrusions of small diapir-like batches of strongly crystallized and highly viscous andesitic magma ascending into water-saturated, hydrothermally altered rocks composing the volcano summit. We suggest that the diapir's ascent is governed by their positive buoyancy. Some of the diapirs reach and breach the ground surface producing magmatic eruptions of Ebeko, while the others are stuck at the shallow subsurface level and feed intensive hydrothermal activity as well as phreatic eruptions of the volcano. Positive buoyancy of the diapirs is too weak to allow them to extrude high above the ground surface to form lava domes.
The online version contains supplementary material available at 10.1007/s00445-020-01426-z.
埃别科火山是千岛群岛弧形地带最活跃的火山之一，频繁发生温和的武尔卡诺式喷发，喷发云高达5千米。该火山对位于其火山泥流沉积物扇形区域仅7千米处、约有2500名居民的南库里尔斯克镇构成严重威胁。在此，我们报告20世纪至21世纪该火山的活动概况以及对始于2016年的持续武尔卡诺式喷发进行地质和岩石学调查的结果。我们发现，埃别科火山的喷发机制涵盖从纯岩浆作用到潜水/热液作用的一系列过程。其历史上的三次喷发（1934 - 1935年、1987 - 1991年以及2016年至今）涉及新鲜岩浆，而其他几次喷发（1967 - 1971年、2009 - 2011年）则未喷出新鲜岩浆。此次持续喷发的幼年物质为高度结晶且高粘性（超过10帕·秒）的低硅（56 - 58重量% SiO₂）安山岩。历史数据以及我们对此次持续喷发的观测使我们能够提出该火山的一个功能模型，即武尔卡诺式喷发是由类似底辟的小批次强烈结晶且高粘性的安山质岩浆浅层侵入到构成火山顶部的水饱和、热液蚀变岩石中所引发的。我们认为底辟的上升受其正浮力控制。一些底辟到达并突破地表，引发埃别科火山的岩浆喷发，而其他底辟则被困在浅部地下层面，为火山的强烈热液活动以及潜水喷发提供动力。底辟的正浮力太弱，无法使其挤出到地面上方很高的位置形成熔岩穹丘。
在线版本包含可在10.1007/s00445 - 020 - 01426 - z获取的补充材料。
