• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1997.11a
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• pp.97-142
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• 1997

The Seoguipo Formation occurs only in a small exposure along the coast of the Seoguipo City, but in the subsurface, underlies tile western part of the Bugcheon-Pyoseon Line in the northeastern part of tile island. The Bugcheon-Pyoseon Line is presumed to be a facies boundary that reflects tile distribution of hyaloclastites resulted from submarine volcanic activity. The Seoguipo Formation is distributed in the subsurface along the part which is lower than 400m in average altitude, and occurs at El. -5.76∼-46.63m in tile southern area, El. -41.89∼-57.97m in the western area, El. -13.15∼-50.59m in the northern area. Therefore, the southern area was uplifted after the deposition of the Seoguipo Formation. In the subsurface, the vertical depth of the volcanic rocks of the Cheju Volcanic Edifice is El. -40.6m in the southern area, El. -111.3m in the western area, El. -81.5m in the northern area and El. -134.7m in the eastern area. The unconsolidated U Formation, which is, overlying the basement and about 70∼250m thickness underlies the whole island. There is a positive correlation between tile groundwater level and the depth of the subsurface distribution of the Seoguipo Formation. Consequently, it is conformed that the subsurface distribution of the Seoguipo Formation plays important role for controlling the characteristics of the reservoir of tile groundwater in Cheju Island.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.19-36
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• 1983

The study revealed that the sequence of volcanism in Ulrung island can be classified into 5 stages, and the volcanic history is summerized as follow: 1st stage: Eruption of basaltic agglomerates, tuffs and lavas, 2nd stage: Eruption of trachytic and trachyandesitic agglomerates and tuffs, 3rd stage: Eruption of trachyte lavas and their lapilli tuffs, 4th stage: Eruption of trachyte lavas and nepheline phonolites, 5th stage: Eruption of pumice, trachytic ash and lapilli, and plutonic ejecta (fragments of alkali gabbro, monzonite and alkali feldspar syenite) and a subsequent caldera formation. Finally, a small scale eruption of leucite bearing trachyandesite lava in the caldera. Several evidences show that there have been long erosional intervals between the 1st and 2nd stages and between the 4th and 5th stages. A K-Ar age for trachybasalt lava of the 1st stage was determined to be 1.8 Ma, and a $C^{14}$ age, 9300Y. (Machida, 1981) is available for these volcanic events. Therefore, it is considered that volcanic activity of the island above sea level began at least in early Pleistocene, and continued to until 9300 years ago exploding large amount of pumice, prior to pouring out of leucite bearing trachyandesite from the inner caldera. Using solidification index (SI) of Kuno, microscopic texture and mineral composition as criteria of the classification, the volcanic rocks are classified into alkali basalt, trachybasalt, trachyandesite, trachyte and phonolite. These are mostly prophyritic in texture. Main constituent minerals of alkali basalt and trachybasalt are plagioclase, olivine, Ti-augite and magnetite. Principal minerals of trachyandesite are plagioclase, anorthoclase, clinopyroxenes, kaersutite, biotite and magnetite. Trachyte and phonolite consist mainly of anorthoclase, clinopyroxene and magnetite, showing typical trachytic texture in groundmass. In solidification index, alkali basalt ranges from 39 to 27, trachybasalt 17 to 14, trachyandesite 12 to 9 and trachyte 8.15 to 0.72. A trend of compositional variation showing a typical alkali volcanic rock series is revealed on $SiO_2$-oxides and SI-oxides diagrams. In $SiO_2$-total alkali diagram, alkali lime index and An-Ab'-Or diagram, the samples fall into the fields of potassic series of the alkali volcanic rock series, whereas in A-F-M diagram show a trend toward the alkali enrichment with a curve approaching toward the iron apex. In particular, trachybasalt lavas in this island have higher total iron contents which is comparable to alkali rocks in other areas, e. g. as Gough and Tristan volcanic islands located near the Mid-Oceanic ridge in South Atlantic Ocean.

• Journal of the speleological society of Korea
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• no.5
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• pp.66-69
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• 1997

The island of S.Miguel is part of the Azores, an archipelago composed of nine volcanic islands situated between the european and american continents. Aligned in a general WNW -ESE trend, between latitudes 37$^{\circ}$ -40$^{\circ}$ N and longitude 25$^{\circ}$ -31$^{\circ}$ W, the Azores islands show a very special geotectonic setting, at the triple junction of the Eurasian, African and North American lithospheric plates.(omitted)

• Korean Journal of Environmental Agriculture
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• v.24 no.4
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• pp.364-369
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• 2005

In Jeju island, the southernmost island of Korea, the field soils are mostly consisted of volcanic and non-volcanic soils. Animal manures of 0, 50, 100, and 150 MT/ha were treated to analyse the humus content changes by application amounts and the soil types. The results are as follows; Humus distribution type was A in the most of the volcanic soils while a few soils was type B, and it was possible to confirm that the humus process has occurred in the soils. Most of the non-volcanic soils was Rp and B type, therefore, the humus content change pattern was different from the volcanic soils. The nitrate-nitrogen content and the humus content showed positive correlation of $R^2=0.5263$ in the volcanic soils, while that of non-volcanic soils was $R^2=0.524$. The carbon content and the humus content showed positive correlation of $R^2=0.469$ in the volcanic soils, while that of non-volcanic soils was $R^2=0.550$.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.205-217
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• 2024

This study evaluated the physical characteristics and quality of volcanic rocks distributed in the Jeju Island-Ulleung Island area as aggregate resources. The main rocks in the Jeju Island area include conglomerate, volcanic rock, and volcanic rock. Conglomerate is composed of yellow-red or gray heterogeneous sedimentary rock, conglomerate, and encapsulated conglomerate in a state between lavas. Volcanic rocks are classified according to their chemical composition into basalt, trachybasalt, basaltic trachytic andesite, trachytic andesite, and trachyte. By stratigraphy, from bottom to top, Seogwipo Formation, trachyte andesite, trachybasalt (I), basalt (I), trachybasalt (II), basalt (II), trachybasalt (III, IV), trachyte, trachybasalt (V, VI), basalt (III), and trachybasalt (VII, VIII). The bedrock of the Ulleung Island is composed of basalt, trachyte, trachytic basalt, and trachytic andesite, and some phonolite and tuffaceous clastic volcanic sedimentary rock. Aggregate quality evaluation factors of these rocks included soundness, resistance to abrasion, absorption rate, absolute dry density and alkali aggregate reactivity. Most volcanic rock quality results in the study area were found to satisfy aggregate quality standards, and differences in physical properties and quality were observed depending on the area. Resistance to abrasion and absolute dry density have similar distribution ranges, but Ulleung Island showed better soundness and Jeju Island showed better absorption rate. Overall, Jeju Island showed better quality as aggregate. In addition, the alkaline aggregate reactivity test results showed that harmless aggregates existed in both area, but Ulleungdo volcanic rock was found to be more advantageous than Jeju Island volcanic rock. Aggregate quality testing is typically performed simply for each gravel, but even similar rocks can vary depending on their geological origin and mineral composition. Therefore, when evaluating and analyzing aggregate resources, it will be possible to use them more efficiently if the petrological-mineralological research is performed together.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.499-510
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• 2015

Artificial accelerated weathering test evaluated rocks from near the circuit road of Ulleungdo island, approximately 120 km from east of the Korean Peninsula. The tests subjected rock specimens to conditions based on the climate of the island. The specimens (such as basaltic breccia, trachyte, volcanic breccia) were preliminarily classified using a TAS diagram (XRF data) and based on the constituent minerals (XRD data); they were further classified by weathering degree according to their absorption ratios. During the artificial accelerated weathering, the absorption ratio of most of the specimens increased, but the point-load strength did not decrease in most cases, except for the volcanic breccia. The greater initial absorption ratio of trachyte rock specimen in comparison with the other specimens led to a greater increase of its absorption ratio during the artificial accelerated weathering test. The volcanic breccia specimens showed the greatest increase of absorption ratio and the biggest reduction ratio of the point- load strength during the tests. These results could aid prediction of the weathering rate of rocks in Ulleungdo island subjected to weathering processes; trachyte which appears to accelerate with time, and volcanic breccia whose mechanical strength can largely decrease in a relative short period of time. Proper measures therefore appear necessary for the prevention of natural disaster such as rock fall and landslide around the circuit road.

• Journal of the Mineralogical Society of Korea
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• v.1 no.1
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• pp.40-47
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• 1988

Mineralogy of sand, silt and clay fractions from the five chronosequence soils of Jeju Island is studied with the X-ray, TEM and SEM techniques. Soils of Songag and Donghong situated at lower elevations are generally developed on relatively of ash or alluvial deposits and contain mainly ferromagnesian minerals and feldspars, with some quartz, mica and volcanic glass. Crystalline minerals are dominant in the clay fraction; halloysite and vermiculite are abundant but small amounts of allophane are present. Clay migration results in well developed ferrigargillan, Soils of Pyeongdae and Heugag located at higher elevations are developed on relatively young volcanic ash with some contamination of continental aeolian dust probably containing quartz which may be come from acid ash shower. The absence of clay illuivation is due to the dominance of allophane. This clay mineral is associated with some gibbsite, imogolite and halloysite.

• The Journal of the Petrological Society of Korea
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• v.27 no.3
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• pp.121-138
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• 2018

We have examined the petrotectonic setting and magmatic evolution from petrochemical characteristics of major and trace elements for the Cretaceous volcanic rocks in and around the Mireukdo Island. The volcanic rocks, can be devided into Jusasan, Unmunsa, Yokji and Saryang subgroups on the ascending order, are classified as basalt, basaltic andesite, andesite, dacite and rhyolite on TAS diagram. Petrochemical data show that the rocks are calc-alkaline series, and suggest that erupted earlier medium-K series and later high-K series. The volcanic rocks provide a case in which the calc-alkaline magma are formed, not only from separate protoliths, but following separate paths from source to surface. Earlier and later subgroups take different paths to the surface respectively, and are emplaced in the shallow crust as a series of discrete magma chambers through the volcanic processes. After emplacement, each chamber evolves indepently through fractional crystallization with a little assimilation of wall rock. The volcanic rocks have close petrotectonic affinities with orogenic suite and subduction-related volcanic arc. The rhyolitic magma can be derived from calc-alkaline andesitic magma by fractional crystallization with crustal assimilation, which may be derived from a partial melt of peridotite in the upper mantle.

• Geosciences Journal
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• v.22 no.6
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• pp.1069-1080
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• 2018

The Alaskan Aleutian Islands form one of the world's largest volcanic island chains. The islands are exposed to both direct and indirect damage from continuous volcanic eruptions. Surface deformation is mostly observed before volcanic eruption, but with some volcanoes, such as Ontake Volcano, deformations cannot be detected. In this study, we analyzed volcanic eruptions in the Alaskan Aleutian Islands, which is a region of frequent volcanic eruptions. Based on our results, we predicted the type of eruption that would occur on Baekdusan Volcano according to the presence or absence of surface deformation. For this purpose, 10 sites were selected from areas where recent volcanic activity had occurred in the Aleutian Islands. Additionally, Advanced Land Observing Satellite Phased Array-type L-band Synthetic Aperture Radar (ALOS-PALSAR) and European Remote Sensing (ERS)-1/2 satellite data were obtained from 10 experimental sites. Based on the radar satellite data, the volcanic surface deformations were identified, and the characteristics of the volcanic eruption were quantitatively calculated by determining the presence of surface deformation. The results of this study should facilitate the process of correlation between volcanic eruption and surface deformation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.1
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• pp.39-51
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• 1999

This study has an object to evaluate runoff characteristics with ILLUDAS model and SWMM owing to each rainfall distribution type of Huff's quartile and each rainfall duration time of 30 ,60, 120 and 180 minutes. As a result of this study, Type-Ⅰ Extreme (TIE) rainfall distribution pattern with Huff's 2nd quartile is adequate for Cheju volcanic island . To decide optimal rain fall duration , time of concentration and critical duration should be compared and analyzed each other. In this study, 30 and 120 miniutes were suggeste to iptiaml duration time of A and B study basins. It is concluded that the magnitude of peak runoff discharge is maximum with Huff's 4th quartile, and that of total runoff volume is maximum with Huff's 4th quartile for ILLUDAS model and with Huff's 1st quartile for SWMM. As rainfall duration time increasing is increasing . Also in case of total runoff volume, volumen by SWMM is less than by ILLUDAS model as to variation ratio of total runoff volume in A and B study basin. Therefore, the resulots of this study canb e sued as basic data in determining adequate rainfoal duration time and rainfall distribution type and used for urban drainage systems analysis and design at small urbanization catchment is Cheju volcanic island.