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Evaluation of Volcanic Processes and Possible Eruption Types in Ulleung Island
울릉도에서의 화산과정과 발생 가능한 분출유형의 평가
Econ. Environ. Geol. 2020 Dec;53(6):715-27
Published online December 31, 2020;  https://doi.org/10.9719/EEG.2020.53.6.715
Copyright © 2020 the Korean society of economic and environmental gelology.

Sang Koo Hwang1,2*, Seong Wook Jeong2, Han Young Ryu3, Young Woo Son3 and Tae Ho Kwon4
황상구1.2* · 정성욱2 · 류한영3 · 손영우3 · 권태호4

1Department of Earth and Environmental Sciences, Andong National University, Andong 36729, Korea
2 Institute of Basic Sciences, Andong National University, Andong 36729, Korea
3 Korea Water Resources Corporation, Daejeon 34350, Korea
4 Korea Ohyeon Mineral Museum, Paju 10859, Korea
1안동대학교 자연과학대학 지구환경과학과, 2안동대학교 기초과학연구소, 3한국수자원공사, 4오현광물박물관
Received October 12, 2020; Revised November 15, 2020; Accepted November 17, 2020.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
Volcanostratigraphy in Ulleung Island is divided into 4 stratigraphic groups: Dodong Basaltic Rocks, Ulleung Group, Seonginbong Group and NariGroup. The main pyroclastics in them includes lapilli tuff intercalated within the Dodong Basaltic Rocks, lapilli tuff at the top of Sadong Breccia, Sataegam Tuff, Gombawi Welded Tuff, Bongrae Scoria Deposits, Maljandeung Tuff, Nari Scoria Deposits and Jugam Scoria Deposits. Analysing eruption types, The lapilli tuff in the Dodong Basaltic Rocks is derived from Surtseyan eruption, and the Bongrae, Nari and Jugam Scoria Deposits are caused by Strombolian eruptions or/and sub-Plinion eruptions, but the Sataegam Tuff and Maljandeung Tuff are derived from Plinian and phreatoplinian eruptions. Among them the large-scaled eruptions. In particular, the eruptions of Maljandeung were large enough to result in caldera collapse, and had falled out tephras to the eastern Korean peninsula but even Japan Islands. The magma with high potential to be still alive is judged to be trachyandesitic and phonolitic in composition. If the trachyandesitic magma explodes, it will probably result in a strombolian eruption and have a fairly low explosivity, but if the phonolitic magma explodes, it will probably result in a plinian eruption and have a much higher explosivity. If the eruption had a high explosivity, there is a possibility that it could easily be converted into a phreatoplinian eruption due to the influx of groundwater by the easy generation of fractures. These large-scaled eruptions could fall out tephras to the eastern Korean peninsula but even Japan Islands.
Keywords : Ulleung Island, eruption types, strombolian eruption, plinian eruption, explosivity

 

February 2021, 54 (1)