• Economic and Environmental Geology
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• v.24 no.4
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• pp.399-408
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• 1991

There are several tuff cones and tuff rings, now only apparent on the western shoreline in Cheju Island. The observation of their landform, bedform, particle size and sorting reveals that these deposits are mainly emplaced by base surges and/or slurries originating from Surtseyan eruption which is attributed to explosive hydrovolcanism influenced by interaction of magma with external water. These are subdivided into two groups based on the plateau basalt. It is recognized that the distal limb of early tuff cones and ring at Dangsanbong, Dansan, Sanbangsan and Hwasun (lower group) are overlain by plateau basalt, on which later tuff rigns at Suwolbong and Songaksan(upper group) further extend the distal limb from each vent. The tuff cones and tuff rings are closely associated with the evidences which shelly fragments are comprised within them, and reworked tuffs, raised beach deposits, Sinyangri formation and littoral cones are deposited around them. The evidences suggest that the Surtseyan eruption resulted from direct or indirect interaction of magma with sea water.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.39-50
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• 2010

Zeolites were formed by the alteration of volcanic glass in the volcaniclastics including tuff cone/rings and subsurface Seoguipo Formation, Jeju Island. Phillipsite and analcime were identified by X-ray diffraction and electron microprobe analysis. Si/(Si+Al) atom ratios of analcime and phillipsite were similar to that of parent basaltic glass. In comparison with the simple chemistry of analcime, phillipsite showed a range of cavity cation compositions. Na is the major cavity cations of phillipsite in the Dangsanbong and Yongmeori tuffs bearing analcime, while K and Ca in core samples of Seoguipo Formation. Microtextural analysis by scanning electron microscope showed a general sequence that early phillipsite encrustification of pores was followed by later analcime infilling. Zeolites are abundant in the older tuff cone/rings but nearly absent in the younger ones.

• The Journal of the Petrological Society of Korea
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• v.25 no.2
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• pp.143-149
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• 2016

Eruptive volumes of three monogenetic volcanoes (Songaksan tuff ring, Biyangdo scoria cone, and Ilchulbong tuff cone) with the youngest eruption age are calculated using the model, applied to Auckland Volcanic Field in New Zealand, to investigate the volcanic eruption scale and to evaluate volcanic hazard of Jeju Island. Calculated eruptive volumes of the volcanoes are $24,987,557m^3$, $9,652,025m^3$, and $11,911,534m^3$, respectively, and the volumes include crater infill, tuff ring (tuff cone), scoria cone, and lava flow. Volcanic explosivity indices of Songaksan tuff ring, Biyangdo scoria cone, and Ilchulbong tuff cone are estimated based on the eruptive volumes to be 3, 2, and 3 respectively, and eruption type is Strombolian to Surtseyan. It is assumed that the amount of emitted sulfur dioxide gas is $2-8{\times}10^3kt/y$ according to the correlation between volcanic explosivity index and volcanic sulfur dioxide index. Recent age dating researches reveal evidences of several volcanic activities during the last 10,000 years indicating the possible volcanic eruption in Jeju Island in the near future. Therefore, it is necessary for appropriate researches regarding volcanic eruption of the island to be accomplished. In addition, establishment of the evaluation and preparation system for volcanic hazard based on the researches is required.

• The Journal of the Petrological Society of Korea
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• v.10 no.1
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• pp.13-26
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• 2001

Songaksan volcano, which occurs as a monogenetic volcano on the southwestern promontory of Hallasan shield volcano, is composed of tuff ring, cinder cone, lava pond and cinder conelet complex on wide basalt plateau. Except for an influx of external quartz xenocrysts in the tuff ring. Totally the volcano ranges from trachyandesite to trachybasalt in petrography and chemical compositions, which confirm the continuum between the evolved and primitive compositions widely occurring in the Jeju volcanic system. Chemical data for the volcano show quantitative compositional variation from the lower to the upper part of the volcanic sequences. The continuous compositional variations generally define a compositionally zoned magma storage. The chemical data suggest that the compositiona1 donations might have resulted from the fractional crystallization of a parental alkali magma. As result, the Songaksan volcano initially tapped the lop of the zoned magma storage and subsequently erupted successively more primitive magma.

• Journal of The Geomorphological Association of Korea
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• v.18 no.3
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• pp.1-10
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• 2011

Sanbangsan and Yongmuri Beach as geosites are very wide areas, and tourists have accessed them via various courses; hence the need to double the number of geosite signs and disperse them at each point. The signs should read "Sanbangsan lava dome," "Yongmuri tuff ring," and "Relationship between the Sanbangsan lava dome and Yongmuri tuff ring." The contents of the sign should be systemic, simple, and clear because tourists have to read it in a short time. The viewpoint of the research area can be largely divided into Sanbangsan View, Yongmuri Beach View, Sanbangsan, and Yongmuri Beach View. Three of each viewpoint (total of 9 viewpoints) can be placed. In the geosite of Sanbangsan and Yongmuri Beach are 5 sub-theme views including the boundary sheet of Sanbangsan and Yongmuri tuff ring, xenolith basalt, marine pothole, tafoni, and crossed sedimentary layer. These sub-theme views are important in understating not only the geosite but the overall geopark as well, so they should be developed and utilized aggressively.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.365-376
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• 2023

Songaksan, formed about 3800 year ago, is one of the tuff rings in the Jeju Island. Mantle xenoliths, spinel peridotites, are enclosed in the Songaksan Trachybasalt. The spinel peridotites are less than 2 cm in size and are composed of olivine, orthopyroxene, clinopyroxene, and spinel. The uniform compositions of the minerals from core to rim indicate that equilibrium was reached in the spinel peridotites before these were enclosed in the host magma. The spinel peridotites originated at depths between 55 and 60 km with equilibrium temperatures ranging from 915 to 968℃. The spinel peridotites from Songaksan reveal porphyroclastic texture with a lot of neoblast minerals. Olivines display strong kink banding, indicating that the upper mantle of Songaksan has been deformed. The spinel peridotites from Songaksan have undergone about 5~7% fractional melting, and cryptic metasomatism by an silicate melt. The period of entrainment and transport of the spinel peridotites in the host magma is about 15 days.

• Journal of the Korean Geographical Society
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• v.41 no.4 s.115
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• pp.391-403
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• 2006

The Hanon volcano located in the southern pan of Cheju Island, Korea has a wetland in its crater being used as a farmland. Previous researchers presumed this wetland was a maar lake in the past. Based on the seismic refraction method, the wetland sediment layer was estimated between 5 to 14 m deep, which is mostly in accordance with previous researches. However, this shows only the depths at some sites, not representing the whole spatial distribution. This study is an attempt to reconstruct the volcanic lake in Hanon crater by applying the spatial statistical techniques based on the depth information from the seismic survey and known data. The procedure of reconstruction is as follows: First, the depth information from the seismic survey and known data were collected and it was interpolated by IDW and Ordinary Kriging method. Next, with the interpolation map and the present DEM the paleo DEM was constructed. Finally, using the paleo lake level on core data, the boundary of volcanic lake was extracted from the paleo DEM. The reconstructed lake resembles a half-moon in the north of the central scoria cone. It is estimated that the lake was 5 m deep on average and 13 m deep at the deepest point. Although there are slight differences according to the interpolation techniques, it is calculated that the area of the lake was between 184,000 and $190000m^2,$ and its volume approximately $869,760m^3$. Because of the continuous deposition processes after the crater formation, the reconstructed volcanic lake would not indicate an actual lake at a specific time. Nevertheless, it offers a significant clue regarding the inner morphology and evolution of the crater.

• The Journal of the Petrological Society of Korea
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• v.21 no.4
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• pp.385-396
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• 2012

Jeju island is the biggest volcanic island in Korea and there are over 455 Quaternary monogenetic volcanoes, of which approximately 373 volcanoes(82.0%) are cinder cones. Other volcanic forms in the island include sharp-pointed lava cone without crater(9 volcanoes; 2.0%), shield volcanoes(27 volcanoes; 5.9%), tuff rings(17 volcanoes; 3.7%), tuff cones(3 volcanoes; 0.7%), a maar(1 volcano; 0.2%) and lava domes(25 volcanoes; 5.5%). The monogenetic volcanoes include 15 small nested cinder cones(aloreum). The monogenetic volcanoes are more abundant in the eastern part of the island than in the western part. If the main cause of the weathering such as precipitation affected the shape of the monogenetic volcanoes, more monogenetic volcanoes(BC, CC, DC, etc.) are supposed to be present in the southern part that have more precipitation than in the northern part. But the distribution of the monogenetic volcanoes shows no difference between the southern and the northern parts. So we suggest that the difference of the climatic conditions did not affect the distribution or the shape of cinder cones. Tuff rings, tuff cones and a maar are distributed beneath the island or in the low-altitude areas along the shore although cinder cones are distributed in the interior of the island. This means that the volcanic activity which formed the monogenetic volcanoes resulted from either phreatomagmatic eruption or magmatic (hawaiian or strombolian) eruptions depending on the reaction with water (underground water or shallow waters). The distribution of the monogenetic volcanoes according to the altitude shows that 253(55.6%) volcanoes occur in low-lying coastal areas at an altitude below 300 m, 110(24.2%) in a middle mountainous area at an altitude between 300~600 m and 92(20.2%) in a high mountainous area at an altitude above 600 m. So more than half of monogenetic volcanoes are distributed in low-lying coastal areas.