• Economic and Environmental Geology
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• v.29 no.3
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• pp.257-267
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• 1996

One hundred of thirty volcanic rocks col1ected from the Jeju island， Jeongog， Guryongpo and other areas were analyzed for major elements and trace elements with Au by inductively coupled argon plasma and graphite furnace atomic absorptiom spectrometry. The Au content is the highest values (0.2~43.4 ppb, average; 10.34 ppb) from the Jeju island volcanic rocks and the lowest (0.5~11.0 ppb, average; 1.23 ppb) from the Guryongpo volcanic area. The content of Au tends to be higher in the Quarternary volcanic rocks than Tertiary or Cretaceous volcanic rocks. The Au content of the calc alkali volcanic rocks tends to increase from mafic to felsic volcanic rocks, but that of the alkalic volcanic rocks tends to increase from felsic to mafic volcanic rocks. The Au content of the volcanic rocks collected from the Jeju island shows the highest values in the feldspar olivine basalts. Elements or oxides which have positive or negative correlations with Au are Ag, Mo, Rb, V, Y, $K_2O$, MgO and $SiO_2$, but other elements analyzed are not shown correlations with Au. It has a tendency to show that samples from the Jeju with 5 ppb gold and more are plotted in the non-Dupal area and those with less than 5 ppb gold in the Dupal area, while those from the Jeongog with 5 ppb gold and more are plotted in the Dupal area and those with less than 5 ppb gold in the non-Dupal area, in the Ba/Nb-La/Nb, Zr/Nb-Ba/Nb diagrams. It shows that samples from the Jeju and Guryongpo with high gold content are plotted in the within-plate, while those with low gold content are plotted in the arc-related area, and those from the Jeongog are scattered in the $TiO_2-Al_2O_3$, $Zr/A1_2O_3-TiO_2/Al_2O_3$ diagrams.

• Economic and Environmental Geology
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• v.27 no.4
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• pp.411-420
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• 1994

Euiseong sub-basin, one of three sub-basins in Kyungsang basin, consists of various sedimentary and igneous rocks of Cretaceous age. Kusandong tuff and Yucheon volcanic rocks from the sub-basin were collected for the anisotropy of magnetic susceptibility (AMS) study. Maximum directions of the AMS for Kusandong tuff and Yucheon volcanic rocks are used to detect possible source areas. Although the dispersion of the maximum directions of the AMS, mainly due to low susceptibility and/or low percent anisotropy of individual specimens, is rather large, it is possible to reveal several source areas for the volcanic rocks. Areas near the Keumseongsan and Hwasan, calderas in the study area, are identified as source areas for Yucheon volcanic rocks, while the western part of Sunamsan, another collapsed caldera in Euiseong sub-basin, is inferred to be the source area for Kusandong tuff. However, it is not possible to determine detailed source areas for groups of Yucheon volcanic rocks of different lithologies, because of poor degree of convergence of the maximum directions of the AMS results from the volcanic rocks. It is also concluded that several episodic volcanic activities centered at Keumseongsan and Hwasan calderas were responsible for the formation of Yucheon volcanic rocks in Euseong area.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.117-129
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• 1988

The purpose of this study is to determine the stratigraphy of the volcanic rocks in the Chilpo-Weolpo area, the north of Pohang basin, based on field survey and lithological properties of the rocks. The volcanic pile(Chilpo tuff) overlies the Cretaceous sedimentary formation and is unconformably overlain by the Miocene Yeonil Group. The Chilpo tuff comprises a thick sequence(>200m) of pyroclastic flow deposits. Five members are distinguished, each representing separate flow units, comprising none(or weakly) to densely welded rhyolite tuff. The Chilpo tuff consists of, in ascending order, greenish weakly welded tuff, volcanic conglomerate, alternation of tuff breccias and fine tuffs, greenish none to densely welded tuff and red-brownish densely to weakly welded vitric tuff. This study revealed that the volcanic rocks in this area were formed by 4 volcanic stages. On the basis of K-Ar age($44.7{\pm}1.1\;Ma$) and lithologic data, geological age of the Chilpo tuff may be Eocene.

• Journal of the Korean association of regional geographers
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• v.17 no.3
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• pp.348-356
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• 2011

Someday Mt. Baekdu could erupt by records of orogeny activity until today. This study is to predict influence area of lava flow and volcanic ash by simulation of volcanic eruption in the Mt. Baekdu. Simulation for eruption applied to supposing 7 grade of volcanic explosivity index, season from fall to spring. As a simulation results, lava flewed down into slope of China and volcanic ash diffused over the North Korea. Volcanic ash spreads to Ulneung area after nine hours. It was predicted that 61 cities and villages out of 27 administrative districts of Si-Gun were affected by volcanic ash in North Korea and an immense volume of volcanic ash was blown into farm lands, city areas and forests. This results expected to utilize information for disaster preparation of North Korea and joint research with South-North Korea and China.

• Korean Journal of Remote Sensing
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• v.34 no.6_4
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• pp.1519-1529
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• 2018

The volcanic ash can spread out over hundreds of kilometers in case of large volcanic eruption. The deposition of volcanic ash may induce damages in urban area and transportation facilities. In order to respond volcanic hazard, it is necessary to estimate efficiently the diffusion area of volcanic ash. The purpose of this study is to compare in-situ volcanic deposition and satellite images of the volcanic eruption case. In this study, we used Near-Infrared (NIR) channels 7 and 8 of Geostationary Ocean Color Imager (GOCI) images for Mt. Aso eruption in 16:40 (UTC) on October 7, 2016. To estimate deposit area clearly, we applied Principal Component Analysis (PCA) and a series of morphology filtering (Eroded, Opening, Dilation, and Closing), respectively. In addition, we compared the field data from the Japan Meteorological Agency (JMA) report about Aso volcano eruption in 2016. From the results, we could extract volcanic ash deposition area of about $380km^2$. In the traditional method, ash deposition area was estimated by human activity such as direct measurement and hearsay evidence, which are inefficient and time consuming effort. Our results inferred that satellite imagery is one of the powerful tools for surface change mapping in case of large volcanic eruption.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E2
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• pp.69-77
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• 2006

Combined gas and aerosol measurements at a downwind area of the volcanic plume would be essential for helping to access the impact of the volcanic eruption on the local ecosystem and residents. An intensive and the fine time resolution measurement of $SO_2$, sulfate and PM2.5 was made to estimate their distribution in the Kanto area of Japan during the Miyakejima volcanic eruption period. In Tokyo, the 1 hr average $SO_2$ concentration observed before the eruption was 23.9 ppbv, while that of after eruption was 140.4 ppbv. In the Saitama Prefecture, the average concentration of $SO_2$ marked in the present study was two times higher than the average before the volcanic eruption. The PM2.5 mass concentrations in Sitama ranged from 3.8 to $136{\mu}g\;m^{-3}$. Sulfate accounts for $4.4{\sim}39.6%$ of PM2.5 in Sitama. The good correlationship between the concentrations of $SO_2$ and sulfate was obtained. The results of the VAFTAD and HYSPLIT models indicate that $SO_2$, sulfate, and PM2.5 measured in the present study would be expected to be significantly affected by the Miyakejima volcanic plume.

• Journal of the Korean earth science society
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• v.33 no.7
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• pp.627-636
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• 2012

In the Obongri-Goseong area of Gangwondo, South Korea, there are six densely distributed volcanic edifices i.e., Duibaejae, Oeumsan, Galmibong, 249 m height, 166 m height, and 102 m height, and two other volcanic edifices including Goseongsan and Unbongsan volcanic edifice that are separately located from a distance. A previously undiscovered 249m volcanic edifice in Obongri was found in this investigation, and the six volcanic edifices distributed in Obongri will be referred to as the Obongri volcanic edifice group. Volcanic edifices in this area were interpreted by other researchers as being volcanic plug, plug dome, and cylindrical volcanic pipe type edifices. The aim of this study is to investigate the aspect of volcanic activity in the Obongri-Goseong area and the formation of volcanic edifices by examining of the shape of volcanic edifices, stratigraphy, and characterization of volcanic products. All the volcanic edifices in the area are composed of basaltic rocks on the Mesozoic granite basement, and the prevalence of the dome shape increased towards the upper part of the mountain. Three volcanic edifices (Duibaejae, 166 m height, 102 m height) include intercalated pyroclastic deposits between the basaltic rocks and the basement. The pyroclastic deposit in the Duibaejae volcanic edifice is composed of quartz, feldspar, granite fragments originated from the basement, and scoria fragments originated from the volcanic eruption. In addition to angular olivine, plagioclase, and pyroxene xenocrysts, all the basaltic rocks contained mantle xenolith, gabbroic xenolith originated from the lower crust, and granitic xenolith originated from the basement. This fact indicates that magma rapidly rose to the surface and that the volcanic activity was explosive. It is also interpreted that, as the basaltic magma became highly viscous due to the large amount of xenocrysts, the erupted magma formed a dome structure on the surface. The original dome structure was then severely eroded out leaving a plug dome formation on the basement.

• The Journal of the Petrological Society of Korea
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• v.2 no.2
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• pp.156-166
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• 1993

The volcanic stratigraphy and geochemistry of the Cretaceous volcanic rocks in the southern part of the Pusan showed that the volcanic rocks of the study area consist of alternating pyroclastic rocks and andesitic lavas, apparently constituting a thick volcanic sequence of a stratovolcano. The andesitic rocks contain augite, plagioclase, and hornblende as phenocrysts. Matrix minerals are augite, magnetite, hornblende, apatite. Mafic minerals, such as chlorite, epidote, sericite, and iron oxides occur as alteration products. Dacitic volcanic breccia and rhyolitic welded ash-flow tuff locally overlie the andesitic rocks. The rocks reported in the previous studies as andesitic breccia and andesite plot in the field of basalt, basaltic andesite, andesite, dacite and rhyolite, based on their chemical compositions. The volcanic rocks of the study area belong to the calc-alkaline series, and the andesitic rocks which are predominant in the area plot to the field of orogenic andesite.

• Economic and Environmental Geology
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• v.14 no.1
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• pp.35-49
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• 1981

The studied area is largely occupied by thick piles of the late Cretaceous volcanic rocks of the Yucheon group, which is northeastern border part of the vast volcanic region in the Yucheon basin. The Yucheon group overlies the Geoncheonri Formation and is intruded by granitic and dioritic stocks and dykes. The group can be devided into two parts; the lower is Jusasan andesitic rocks which was called as Jusasan Porphyrite Formation by Tadeiwa in 1929, and the upper is Unmunsa rhyolitic rocks. The volcanic pile consists mainly of various tuffs such as tuff breccia, lapilli tuff, coarse to fine tuff and tuffaceous sediments, and interlayered flows, which range from basaltic andesite to rhyolite in their lithology. The results of petrochemical and volcanostratigraphic studies on the Jusasan andesitic socks suggest that the volcanic rocks were derived from two cyclic evolutions of magmatic fractionation. Systematic study of 5226 joints from the area reveals two sets of steep joints striking $N20^{\circ}-40^{\circ}E$ and $N40^{\circ}-70^{\circ}W$, are dominant and coincide with the fault pattern developed in the area. Three defferent maximum principal stress axes were recognized from conjugate shear joints, which are trending east-west, north-northwest, and north-northeast.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.77-85
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• 2013

The aim of this study is to investigate strength and water purification characteristics of effective microorganism-applied volcanic ash block using flexural strength test and water quality analysis. The specimens were prepared with volcanic ash from Mt. Baekdusan and Mt. Hallasan, and cement as the ratios of 3.5:1, 4.0:1, 4.5:1, 5.0:1 with and without metakaolin. Flexural strength degraded with increasing of the amount of volcanic ash, and increased with addition of metakaolin as a binder. Based on these results, the optimal ratio for fabricating volcanic ash-cement mixture block is determined as 3.5:1 with metakaolin. Furthermore, from water quality analysis on contaminated water, removal ability of effective microorganism-applied volcanic ash-cement mixture block and caged volcanic ash block against T-N, T-P and SS was highly evaluated because of adsorption due to the large specific surface area of volcanic ash. Hence, volcanic ash-cement mixture block and caged volcanic ash block possibly contribute to water purification.