• Journal of the Korean earth science society
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• v.37 no.6
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• pp.346-358
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• 2016

This study built the volcano Data Base(DB) of 289 active volcanoes around the Korean Peninsula, Japan, China (include Taiwan), and Russia Kamchatka area. Twenty nine more hazardous volcanoes including Baekdusan, Ulleungdo and 27 Japanese volcanoes that can cause a widespread ash-fall on the Korean peninsula by potentially explosive eruption were selected. This selection was based on the presence of volcanic activity, whether or not containing dangerous explosive eruption rock types, distance from Seoul, and volcanoes having Plinian eruption history with volcanic explosivity index (VEI) 4 or more. The results of this study are utilized for screening high-risk volcanoes that may affect the volcanic disaster caused by a widespread fallout ash. By predicting the extent of spread of ash caused by these hazardous volcanic activities and by analyzing the impact on the Korean peninsula, we suggest that it should be used for helping to predict volcanic ash damages and conduct hazards mitigation research as well.

• The Journal of Engineering Geology
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• v.34 no.1
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• pp.25-38
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• 2024

Laboratory tests of accelerated artificial weathering compared the effects of seawater and acidified distilled water on rock weathering. The experiments simulated chemical and physical weathering of five different types of volcanic rock by applying 45 freeze-thaw cycles using seawater and acidified distilled water (pH 3), both at 70℃. The physical properties and uniaxial compressive strength (UCS) of the rocks were measured after 15 and 45 cycles of artificial weathering. Most of degradation of physical properties appeared within the first 15 cycles, and acidified distilled water had a greater effect than seawater. Analysis of variance (ANOVA) statistically evaluated the differences in UCS of the different rock types during the tests. The rate of UCS reduction after 45 cycles was similar across the samples, being independent of the rock type and the trend of changes in physical properties. In contrast to the changes in the physical properties, the UCS was more affected by seawater than by acidified distilled water.

• Journal of the Speleological Society of Korea
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• v.34 no.35
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• pp.32-42
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• 1993

The Paektu-san mountains are geographically situated in the Korea strait to the north of the main peninsula, coordinated between the longitudes of W(127$^{\circ}$15'~128$^{\circ}$00')and E(128$^{\circ}$15'~129$^{\circ}$00'), and between the latitudes of S(41$^{\circ}$15'~42$^{\circ}$00') and N(42$^{\circ}$10'~42$^{\circ}$40'). The volcanic group of the Paektu-san mountains can be devided into 2 main kinds of volcanos by the method investigation, The ashes are mainly made of tremolite, trachte, basalt and pumice, or, a little quartz, labradorite and volcanic glass. These sorts, ratios and forms of the rocks are respectively similar. The Haeven lake is surrounded by 19 peaks. The central volcanic cone is a secant cone in shape, with an altitude of the 1800m to 2749,2m (Chang-kun-bong), an average diameter of 10km, and a shape of an ellipse seen high from the plane. They say there were several eruptions in 1668, 1700 and 1702 A. D. The crystal structure of the rock sample collected at the cave of Mt. Paektu-san is monoclinic. The quantitative analysis of the rock samples in the cave is done by using XRF this time. The chemical compositions by XRF fundamamental parameter analysis is : SiO$_2$: 50.72Wt%, TiO = 2.422Wt%, $Al_2$O$_3$= 17.65Wt%, Fe$_2$O$_3$= 9.371Wt%, CaO = 8.711Wt%, MgO = 4.l19Wt%, MnO = 0.l15Wt%, $K_2$O = 1.369Wt%, Na$_2$O : 3.028Wt% and P$_2$O$_{5}$ = 0.365Wt%. The K-Ar age of the rock sample is also determined to be 0.16Ma. This paper describes some problems experienced in dating young volcanic rocks, and then discusses chemical compositions, X-ray fluorescence analyses and the age of the formation of a lava tunnel such as in Mt. Paektu-san.n.

• 한국지구과학회:학술대회논문집
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• 2002.02a
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• pp.35-35
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• 2002

• The Journal of the Petrological Society of Korea
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• v.2 no.2
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• pp.139-155
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• 1993

We have shown that the volcanic rocks from the northern part of Cheju Island can be divided into high $P_2O_5/K_2O$(HPK) and low $P_3O_5/K_2O$(LPK) groups, each with distinct geochemical characteristics(Park and Kwon, 1993a and b). This study reports mineral compositions for plagioc-lase, olivine, and clinopyroxene in order to see the dependence of mineral chemistry on the whole rock composition, and discusses equilibrium relationships between crystal and liquid. Plagioclase and olivine phenocrysts show no compositional differences for the two rock group. However, $Al^{ⅵ}/Al^{ⅳ}$ ratios of clinopyroxenes suggest that pyroxenes have fractionated at deeper level, and that the LPK group might have fractionated at higher pressure than the HPK group. These are in good agreement with our previous interpretation based on whole rock chemistry(Park and Kwon, 1993a). Although subhedral or euhedral form and homogenous composition for most plagioclase and clinopy-roxene phenocrysts suggest equilibrium relationship with liquid, the uncertainties associated with liquid, the uncertainites associated with equilibrium constant for these minerals do not allow testing equilibium relationship between mineral and liquid on the basis of chemistry. On the other hand, olivine phenocrysts in hawaiites, for which Kd is well known, show distinct nonequilibrium relationship with calculated liquid composi-tions, while those in other rock compositions are in equilibrium from those for other rocks. We report for the first time as far as we know plagioclase xenocryst and pigeonite inclusion in plagioclase, which indicates assimilation process. In conclusion, these mineralogical observations imply that mag-matic processes underneath the Cheju volcano were not simple.

• Economic and Environmental Geology
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• v.33 no.4
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• pp.249-260
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• 2000

The development of dual volcanic chains, parallel to the trend of the subduction trench, is observed in the southern part of Korea. Elsewhere on the Earth volcanic arcs dominantly consist of two such chains. In the southern part of Korea, two volcanic chains within a single volcanic arc was developed. Kyongsang basin, where the first volcanic chain located, and Youngdong-Kwangju depression zone where the second volcanic zone located, showed sub-parallel volcanic rock distributed areas. Concentrations of incompatible elements in the southern part of Korea samples show clear across-arc variations, with lavas from the first volcanic chain being most depleted in these elements, all incompatible element concentrations increase towards the second volcanic chain. The above across-arc variation may be caused by the difference in solid phases coexisting with the fluid phases during the dehydration processes. The concentrations of incompatible elements, Zr/Y ratios, and Rb/K ratios indicate that the second volcanic chain (Youngdong-Kwangiu depression zone) was generated by low degrees of partial melting at the deeper depth compared to the conditions of the first volcanic chain (Kyongsang basin) and residual garnet probably attributed to the their partial melting.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.619-630
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• 2018

The purpose of this study is to investigate the existence of faults and intrusive rocks in the volcanic rock mass of Ulleung-do using magnetic anomalies. The magnetic survey data show that basaltic (mafic) rocks have high magnetic anomalies and that trachytic (felsic) rocks have low magnetic anomalies, implying that the anomaly distributions can be used to distinguish between different volcanic rock types that may be covered by regolith (such as alluvial and colluvial deposits) and other sedimentary layers. Our results show that basaltic rocks are not present within the Nari caldera. However, outside the caldera, the occurrence of high magnetic anomaly values of >$1,000{\gamma}$ is presumed to reflect the existence of basaltic craters or volcanic vents that formed prior to the eruption of the trachytic rocks. In particular, the area with anomaly values of >$1,000{\gamma}$ in the vicinity of Namyang-ri, southwest of Ulleung-do, is interpreted as having a high probability of hosting a crater and vent originating from mafic volcanism.

• 한국해양학회지
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• v.30 no.5
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• pp.480-492
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• 1995

Petrographic investigation has been carried out to determine the composition of the beach sediments and the affecting factors which have controlled their compositional variations from Hyupjae, Aeweol, Iho, Samyang, Hamdeok, Sehwa, Pyoseon, Jungmun, and Hwasun areas along the coast of the Cheju Island. Average mean sizes of the beach sediments are Hyupjae 2.2ø, Aeweol 0.8ø, Iho 1.4ø, Samyang 2.4ø, Hamdeok 1.6ø, Sehwa 1.5ø, Pyoseon 2.1ø, Jungmun 0.4ø, and Hwasun 0.9ø, thus, aries from 0.4 to 2.4ø. The beach sediments from Pyoseon and Hwasun areas are poorly sorted, those from Aeweol and Jungmun areas are moderately sorted and those from the rest of the areas are moderately well sorted. While-colored beach sediments in Hyupjae, Aeweol, Hamdeok, Sehwa, and Pyoseon areas are mostly composed of calcareous shells (more than 85%) such as mollusk, red algae, benthic foraminiferas, etc., whereas volcanic rock fragment is the dominant component of the black-colored beach sediments in Iho, Samyang, and Hwasun areas. Especially, the relatively white-colored beach sediment in Jungmun area, which is on e of the carbonate-dominant areas, shows a higher content of rock fragments than the other carbonate-dominant areas. The beach sediments in Pyoseon area show a high content of carbonate intercalates. Considering the contributions by organisms according to grain size, grains with the size range of 1∼2ø are mostly composed of calcareous red algae fragments, and grains with the size range of 2∼3ø consist of mollusk fragments. It is also notable that bryozoan fragments comprise about 48% of the sediment in Samyang area with the size range of 0∼1ø. The composition of the beach sediments in Cheju Island appears o be controlled by the riverine supply rate of volcanic rock fragments, the lithology of the rocks distributed ear the beaches, the direction of alongshore currents, and the direction of storms, etc.. It is suggested that the beach sediments in Iho and Samyang areas show black color because of the higher supply rate of the volcanic rock fragments from the nearby rivers, whereas those in the rest of the areas show white color due to the relatively lower content of volcanic rock fragments and higher content of carbonate components transported from shallow marine environment. In Hwasun area, the content of volcanic rock fragments is high, and they are directly from the tuffaceous rocks distributed nearby. Also, the volcanic rock fragments in Jungmun area are transported not only from the rivers nearby but also from the nearby tuffs by storm activities. The beach sediment in Pyoseon area contains a high content of carbonate intercalates, which formed in the nearby shallow marine environment through marine cementation. This indicates that active marine cementation occurs in shallow marine environment near Pyoseon area.

• Journal of the Korean earth science society
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• v.29 no.3
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• pp.305-314
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• 2008

The purpose of this study is to analyze the concept of igneous rock textures and to uncover incorrect descriptions regarding the concept found within high school Earth Science II course seventh curriculum textbooks. Based upon this analysis suggestions will be made so as to improve descriptions regarding the concept of igneous rock texture. At least some incorrect descriptions regarding igneous rock texture were found in all the textbooks examined. Textures of volcanic rocks are described as being either fine-grained and glassy or porphyritic, while those of plutonic rocks are described as hollocrystalline, granular, coarse-grained or equigranular. These descriptions may contribute to forming and/or reinforcing misconceptions about both the classification criteria for, as well as the general concept of igneous rock textures. Therefore, some improvement schemes for the classification of igneous rock textures have been suggested. These schemes suggest that volcanic rocks be classified as either aphanitic or porphyritic, while plutonic rocks be classified as phaneritic, hollocrystalline or equigranular according to granularity, crystallinity, and both the absolute and relative sizes of the crystals within the rock.

• The Journal of the Petrological Society of Korea
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• v.5 no.1
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• pp.108-120
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• 1996

This study reports petrography and geochemical characteristics of the Cretaceous volcanic rocks that are distributed in the vicinity of the Cheonsungsan area, Yangsan-Gun, Gyeongsangnam-Do. The Cretaceous volcanic rocks composed of andesitic rocks, Wonhyosan tuff, Cheonsungsan tuff in ascending order. Sedimentary rock is the basement in the study area cofered with volcanic rocks. These volcanic rocks are Wonhyosan tuff and Cheonsungsan tuff that represented the early phase of the Bulgugsa igneous activity. Wonhyosan tuff are classified into dacite tuff and dacite welded tuff based on the rock texture and their mineral composition. They are covered with Cheonsungsan tuff. Dacite tuff composed of lithic lapilli ash-flow tuff and vitric ash-flow tuff. Most dacite welded tuff are lapilli ash-flow tuff. Cheonsungsan tuff overlying the Wonhyosan tuff consists of rhyolite tuff and rhyolite welded tuff. Rhyolite tuff are lithic crystal ash-flow tuff and crystal vitric ash-flow tuff with somewhat accidental fragments of andesitic and sedimentary rocks. Rhyolite welded tuff is distinguishe from rhyolite tuff by is typical eelded fabrics and its rock color. According to petrochemical data, the volcanic rocks in study area belong to high-K orogenic suties. On the discriminant diagrams such as La/Yb versus Th/Yb, these rocks falls into the discriminant fields for the normal continental margin arc.