Discovery of Ancient Volcanoes in the Okhotsk Sea (Russia): New Constraints on the Opening History of the Kurile Back Arc Basin

Here we present the first radiometric age and geochemical (major and trace element and isotope) data for samples from the Hydrographer Ridge, a back arc volcano of the Kurile Island Arc, and a newly discovered chain of volcanoes (“Sonne Volcanoes”) on the northwestern continental slope of the Kurile Basin on the opposite side of the arc. The 40Ar/39Ar age and geochemical data show that Hydrographer Ridge (3.2–3.3 Ma) and the “Sonne Volcanoes” (25.3–25.9 Ma) have very similar trace element and isotope characteristics to those of the Kurile Island Arc, indicating derivation from a common magma source. We conclude that the age of the “Sonne Volcanoes” marks the time of opening of the Kurile Basin, implying slow back arc spreading rates of 1.3–1.8 cm/y. Combined with published data from the Kurile fore arc, our data suggest that the processes of subduction, Kurile Basin opening and frontal arc extension occurred synchronously and that extension in the rear part and in the frontal part of the Kurile Island Arc must have been triggered by the same mechanism.

Vulcanian/hydrothermal eruptions of Ebeko volcano, Kurile Islands

<p>Ebeko is a small (1156 m a.s.l) andesitic volcano located in the northern part of Paramushir island of Kurile Island Arc. It is not well studied but in fact represents the most active volcano of the Kuriles  with > 10 eruptions recorded in the 20th century.  All historical eruptions of the volcano had similar style. They were purely explosive, mild (VEI 1 – 2) series of frequent short-lived outbursts of ash and bombs with eruptive clouds up to 3 km high. Some of the outbursts were more extended in time (lasted minutes-hours) and produced mostly fine ash. Common explosions occurred in the summit area of the volcano which characterized by strong hydrothermal activity and multiple fumaroles depositing sulfur. Each eruption produced broad, shallow craters surrounded by low rims of the ejected material. Commonly the craters are later occupied by shallow lakes.</p><p> In 2019 we realized a field work to investigate the most recent eruptive activity of Ebeko that commenced in 2016.  We installed seismometers, monitoring cameras and recorded the terrain using unmanned aerial systems (UAS) together with optical and infrared cameras. The drone data shows dimensions and structures of the newly forming crater and shows deposition of erupted materials. Ejected material was probed and analysed. It is represented by ash and bread crust bombs composed of moderately vesicular two pyroxene andesite with glassy crusts. We found evidence for recycling and rewelding of ash shown by the clastic domains, which are enclosed / mantled by coherent lava. The eruptions of Ebeko volcano were in part phreatic (hydrothermal) and in part magmatic / phreatomagmatic (vulcanian in a broad sense). Mechanism of this (and probably of some other eruptions) can be explained by shallow intrusions of small batches of strongly crystallized andesitic magma into water-saturated hydrothermally altered rocks composing the volcano summit. We suggest a model of the Ebeko eruptions, where new batches of fresh magma incorporate and amalgamate previously erupted fresh material.</p>

VOKKIA and KVERT information systems for data integration on the volcanoes of the Kuril-Kamchatka region and analysis of their activity

Описаны особенности реализации, структура и возможности информационных веб-систем, созданных в Институте вулканологии и сейсмологии ДВО РАН, цель которых обеспечить доступ к большому объему распределенных вулканологических данных для комплексного использования в научных исследованиях. Информационная система VOKKIA предназначена для интеграции и систематизации данных по наземным и подводным вулканам Курило-Камчатского региона и их извержениям, KVERT для сбора и интеграции данных оперативного мониторинга активности вулканов. Реализованные в информационных системах сервисы поиска и визуализации данных помогают обнаруживать взаимосвязи, закономерности и тенденции изменения вулканогенных процессов во времени. A large amount of unique scientific data has been collected in the Institute of Volcanology and Seismology (IVS) FEB RAS over the past years of investigations of the Kamchatka and the Kurile Island Arc volcanoes. The distributed nature of information storage makes it difficult to search and effectively use data in scientific research. Actual tasks include the integration of data into thematic information resources, organization of data access on the Internet, as well as the designing of tools for their comprehensive analysis. VOKKIA (Volcanoes of Kurile-Kamchatka Island Arc) and KVERT (Kamchatkan Volcanic Eruption Response Team) information web-systems have been developed in the IVS FEB RAS to solve these tasks. VOKKIA is designed to integrate and systematize the heterogeneous scientific data for the terrestrial volcanoes of Kamchatka, the Kurile Islands and submarine volcanoes of the surrounding seas including data on historical eruptions of active volcanoes. The KVERT system contains brief information about active volcanoes of Kamchatka and the Nothern Kuriles including their hazard. It provides collection and storage of operational data of visual, video, and satellite monitoring of volcanoes as well as automated preparation and sending KVERT releases on volcanic activity. The paper describes the development technology, structure and content of VOKKIA and KVERT. Besides, it describes data search and visualization services and statistical data analysis. The created services allow detecting the relationship, patterns and trends in volcanic processes over time.