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 8 pa s) low-silica (56–58 wt% SiO 2 ) 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.

中文翻译：

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北千岛群岛埃贝科火山的历史和正在进行的火山喷发机制

Ebeko 是千岛岛弧中最活跃的火山之一，经常产生温和的火山爆发，喷发云高达 5 公里。这座火山对拥有约 2500 名居民的 Severo-Kurilsk 镇构成了严重威胁，该镇位于距离火山喷流沉积层仅 7 公里的地方。在这里，我们报告了 20 至 21 世纪火山活动的概述，以及我们对 2016 年开始的正在进行的火山喷发的地质和岩石学调查的结果。我们发现埃贝科火山的喷发跨越了一系列机制，从纯岩浆到潜水/热液。它的三个历史喷发（1934-1935、1987-1991 和 2016-持续）涉及新鲜岩浆，而在其他（1967-1971、2009-2011）期间没有喷发新鲜岩浆。正在进行喷发的幼年物质代表高结晶和高粘度（超过 10 8 pa s）低二氧化硅（56-58 wt% SiO 2 ）安山岩。历史数据和我们对持续喷发的观察使我们能够提出一个火山的功能模型，其中火山爆发是由小批底辟式强结晶和高粘性安山岩浆的浅层侵入引起的，这些岩浆上升到水饱和的热液蚀变岩石中组成火山顶峰。我们建议底辟的上升受其正浮力支配。一些底辟到达并破坏了地表，产生了埃贝科的岩浆喷发，而其他的则被困在浅表层，并为强烈的热液活动和火山的潜水喷发提供食物。