• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.255-258
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• 2003

The purpose of this study is to understand characteristics of stream and spring water and subsurface geologic structure in Seogwipo area. This study area is surrounded by various smaller parasitic volcanic cinder cones, tuff cones, strangely shaped basalt and trachyte rocks, beautiful waterfalls. The geologic structure in study area is classified into the Upper layer(volcanic rocks), Middle layer(SGF), Lower layer(UF), and Basement layer. The groundwater in Seogwipo area is classified into the Upper layer groundwater, Middle layer groundwater, Lower layer groundwater and Basement layer groundwater on the basis of the hydrostratigraphy structure.

• Korean Journal of Hydrosciences
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• v.3
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• pp.1-9
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• 1992

The effects of fractures in rock masses on the groundwater flow and the groundwater flow system in the volcanic rocks are analyzed by GFFP-WT model, which allows more realistic analysis of groundwater system by considering the fractures in rock masses. The evaluation of the effects of fractures in rock masses on the groundwater flow has been carried out in the 2nd Yeonwha and resulted in that the fractures mostly influence flow time because of hydraulic head distribution change. The results of the groundwater flow system analysis in the volcanic rocks are as follows. Most of groundwater once flowed in Lapilli tuff flowed out through Lappilli tuff layer. But only a small fraction of water flowed out through crystal tuff layer.

• Journal of the Mineralogical Society of Korea
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• v.29 no.4
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• pp.239-254
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• 2016

The Hwangto cave is a sea cave which is located near shore in the Taeha-ri, Ulleung Island, being composed of the reddish tuff wall rock, the topic of this study, and the trachyte ceiling rock. The chemical compositions of the red tuff layer are 49.81-63.63% of $SiO_2$, 13.05-24.91% of $Al_2O_3$, 2.67-5.82% of $Fe_2O_3$, 2.87-6.92% of $Na_2O$, 2.37-3.85% of $K_2O$, 0.55-0.81% of $TiO_2$, 0-0.53% of MnO, 0.39-1.75% of MgO, and 0.60-1.40% of CaO with a pH ranging from 4.5 to 8. The reddish tuff are composed of 23.7-39.4% of anorthoclase, 16.9-33.3% of sanidine, 15.8-26.1% of illite, 5.1-9.0% of hematite, 0-3.7% of goethite, 6.9-9.9% of titanium oxide, and 0.9-9.5% of halite in mineral composition. Although it only includes anorthoclase, sanidine, and illite as major minerals, there can be additional vitric minerals that could not detected by the XRD. The mineralogy and textures of the tuff layer indicate that it became reddish due to the formation of amorphous palagonite and the oxidation of the iron as a heat from the trachytic lava affects the underlying tuff to altered. This iron oxides are enriched in the palagonite, or form microcrystalline or amorphous minerals. We thus suggest that the red tuff layer was generated by the combination of the thermal oxidation involved in the trachytic lava flow on the tuff layer, the palagonitization of the matrix of the tuff, and the oxidation of iron-bearing minerals.

• Journal of The Geomorphological Association of Korea
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• v.25 no.1
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• pp.47-65
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• 2018

Frost shattering has traditionally been considered as one of the most effective process in rock weathering. Each slab specimens of five or six rhyolite, basalt and tuff was prepared and put in freeze-thaw cycles and repeated 300 times in the temperature of $-25^{\circ}C$ to $+30^{\circ}C$ and their weathering patterns and products were analyzed by surface observation, particle size, XRD and thin section. As the result, some changes were observed in weathering patterns and weathering products. Rock shattering was more active in waterlogging rather than atmospheric conditions, but there are many differences depending on the type of rock. Rhyolite is hardly weathered by 300 times freeze-thaw cycles and generates the least amount of weathering products. Weathering of Basalt is limited to the surface layer where water can be absorbed, and produces a few amount of platy-shape debris. Tuff are separated by blocky structure which the particles are aggregated along their edges rather than enlarged existing cracks/joins or generated new joints.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.28-35
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• 2004

Driven pile has the excellent bearing characteristics and good economics, so it is known as the comparative piling method. To use the advantages of driven pile fully, it is necessary to perform the proper construction management. Engineers must drive pile to the proper bearing layer with proper blow energy and measure the blow count and penetration per certain depth to analyze the bearing capacity and driveability. In conventional method, these parameters have been measured manually so it was difficult to get good accuracy. After PIR-D(Pile Installation Recorder-Driven Pile) was attached to the driving equipment, the hammer efficiency, blow count and penetration in blow/10cm were measured automatically. In this paper, to givethe rational judgement criteria of bearing layer, driveability, blow/10cm according to pile depth during pile driving, the some relationship between the driving resistance and ground layer distribution was analyzed. The ground investigation during piles (PHC ${\Phi}450,\;{\Phi}400\;&\;Steel\;Pile\;{\Phi}609{\ast}16t$) installation in the marine clay layer in Incheon, the sandy soil layer in Yongin and the tuff layer in Pusan was done. And measuring hammer efficiency not doing recently, we could compare hammer efficiency(Eh) by PIR-D and energy transfer ratio(ETR) by Pile Dynamic Analyzer(PDA).

• Economic and Environmental Geology
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• v.25 no.2
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• pp.101-114
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• 1992

Occurrences of many kaolin-pyrophyllite deposits in the Youngnam area is related to the Late Cretaceous volcanic rocks, which are widely distributed through southern part from Tongnae-Yangsan to Miryang-Wolsung. The mode of occurrence and genesis of the kaolin-pyrophyllite deposits related to the volcanism was studied. This area is covered by andesitic rocks, rhyolite and rhyolitic welded tuff in ascending order. Lower most andesitic part is almost fresh. The altered rocks in the rhyolitic welded tuff can be classified into the following zones: silicified, pyrophyllite-kaolin, and argillic zone from the center part of ore deposit. The clay deposits occur as irregular massive, layer and funnel type about 5~20 m in width and is accompanied by thin diaspore bed outside of ore shoot. The clays chiefly consist of kaolinite, sericite, pyrophyllite, a little amount of diaspore, alunite, dumortierite, corundum and pyrite. The process of kaolinization-pyrophyllitization has a close relation to a local acidic hydrothermal solution originated from granitic rocks. Acidic hydothermal alteration occurrs mainly in the rhyolitic welded tuff. Initial solution containing $H_2S$ and others was oxidized near the surface and formed hydrothermal sulfuric acid solution.

• Journal of the Mineralogical Society of Korea
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• v.13 no.4
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• pp.196-204
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• 2000

We present characteristics of hydrothermal chlorite and its interstratification with 7-$\AA$ mineral phase that occur in the propylitic alteration zone of the Bobae sericite deposit formed in rhyodacitic tuff. Chlorite is found as disseminated fine-grained aggregate or replacement materials of precursor minerals such as Fe-oxides and amphibole. Based on X-ray diffraction(XRD), all chlorites belong to IIb polytype and the (060) reflections averaging $1.53~1.54\AA$ indicate a trioctahedral structure. Chemical compositions of chlorite show that the Fe/(Fe+Mg) values are mostly in the range of 0.44~0.53, and cation deficiencies in octahedral sites range from 0.06 to 0.37. Under scanning electron microscope(SEM) chlorite occurs as well-crystallized aggregates and is subparallely stacked in interstices or between grain boundaries of associated minerals. transmission electron microscopic(TEM) images reveal that chlorite shows regular layers with $14-\AA$ spacings, locally interstratified with $7-\AA$ or $21-\AA$ periodicities. The $21- \AA$ periodicity corresponds to the sum of the $d_{001}$ values of chlorite and $7-\AA$ phase. The chlorite packet coexisting with 7-$\AA$ layers displays abundant defects such as edge dislocations and layer terminations. Selected-area electron diffraction(SAED) indicates that chlorite and $7-\AA$ phase are randomly interstratified in the mixed-layer areas. We propose a lateral change of layers for the polymorphic transition of $7-\AA$ phase to chlorite.e.

• 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.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.399-410
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• 1985

Bentonites from the Janggi Group of the Lower Miocene age from the Geumgwangdong area, Korea, have been studied for mineralogical and genetic characterization. The Janggi Group is subdivided, in ascending order, into the Janggi Conglomerate, the Nuldaeri Tuff, the Geumgwangdong Shale, the Lower Coal-bearing Formation, the Basaltic Tuff, and the Upper Coalbearing Formation. Bentonites occur as thin or thick beds in all sedimentary units of the Janggi Group, except for the Janggi Conglomerate. Significant bentonite deposits are found in the Nuldaeri Tuff, the Lower Coal-bearing Formation and the Basaltic Tuff. Bentonites consist mainly of smectite (mainly montmorillonite), with minor quartz, cristobalite, opal-CT and feldspar. Occasionally, kaolinite, clinoptilolite or gypsum is associated with bentonites. Bentonites were studied by the methods of petrographic microscopy, X-ray diffraction, thermal analysis (DT A and TG), infrared absorption spectroscopic analysis, SEM, intercalation reaction, and chemical analysis. Smectites commonly occur as irregular boxwork-like masses with characteristic curled thin edges, but occasionally as smoothly curved to nearly flat thin flakes. Most of smectites have layer charge of 0.25-0.42, indicating typical montmorillonite. Crystal-chemical relations suggest that Fe is the dominant substituent for Al in the octahedral layer and there are generally no significant substituents for Si in the tetrahedral layer. Ca is the dominant interlayer cation in montmorillonite. Therefore, montmorillonite from the study area is dioctahedral Ca-montmorillonite. Occurrence and fabrics of bentonites suggest that smectites as well as cristobalite, opal-CT and zeolites have been formed diagenetically from tuffaceous materials. The precursor of smectites is trachytic or basaltic tuff. Smectites derived from the former contain relatively more $Al_2O$ a and less $Fe_2O_3$ than those from the latter.

• Economic and Environmental Geology
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• v.43 no.4
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• pp.359-369
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• 2010

This study characterizes aquifer system and hydrogeologic property in the western half of Jeju Island where wells were drilled for regional water supply in three sub-areas (northwestern, western, and southwestern sub-areas). The aquifer system of the northwestern sub-area is largely composed of upper high-permeability layer, upper low-permeability layer, lower high-permeability layer, and lower low-permeability layer. On the other hand, the aquifer systems of the western and southwestern sub-areas are mostly composed of upper low-permeability layer, high-permeability layer, and lower low-permeability layer. Transmissivity and specific capacity decrease in the order of the northwestern, western, and southwestern sub-areas. The relationship between specific capacity and the top surface of tuff is negative with a high correlation coefficient of -0.848, indicating that the tuff acts as the bottom of the aquifer. Groundwater level change due to the 2004 Sumatra earthquake is an average of 23.74 cm in the northwestern sub-area, an average of 9.48 cm in the western sub-area, and none in the southwestern sub-area. Further, it is found that groundwater change due to the earthquake has a positive relationship with transmissivity and specific capacity.