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

• Economic and Environmental Geology
• /
• v.48 no.4
• /
• pp.273-285
• /
• 2015

The extensive hydrothermal deposits have been found, for the first time, on the western TA25 seamount caldera in the Tonga arc. The seafloor hydrothermal vents are active and immature, emitting the transparent fluids of which temperatures range from $150^{\circ}C$ to $242^{\circ}C$ (average=$203^{\circ}C$). The recovered hydrothermal sulfides are mainly composed of sphalerite, pyrite, marcasite, galena, chalcopyrite, covellite, tennantite, enargite and sulfates such as barite, gypsum/anhydrite. Predominant sphalerite categorize it into Zn-rich hydrothermal ore body. Zn-rich sulfide ores have minor enargite, indicating that mineralization occurred in high sulfidation environment. The proportion and FeS content of sphalerite increase from outside to inside of the hydrothermal ores, respectively. In particular, sphalerite has a great silver content (up to ~10 wt.%). Chalcopyrite is more frequently observed in mound than in the chimney, implying mineralization temperature in the mound is higher than in the chimney. Homogenization temperatures and salinities from fluid inclusions in barite at the mound range from $148^{\circ}C$ to $341^{\circ}C$ (average=$213^{\circ}C$) and 0.4 to 3.6 equiv. wt.% NaCl, respectively. Homogenization temperatures suggest that sulfides in the mound mineralized at a higher temperature (${\geq}200^{\circ}C$) than in the chimney.

• The Journal of the Petrological Society of Korea
• /
• v.26 no.3
• /
• pp.221-234
• /
• 2017

The Baengnokdam, the summit crater of Mt. Halla, is one of the representative geosites of World Natural Heritage and Global Geopark in Jeju Island. The crater is marked by two distinctive volcanic lithofacies that comprise: 1) a trachytic lava dome to the west of the crater and 2) trachybasaltic lava flow units covering the gentle eastern slope of the mountain. This study focuses on understanding the formative process of this peculiar volcanic lithofacies association at the summit of Mt. Halla through field observation and optically stimulated luminescence (OSL) dating of the sediments underlying the craterforming volcanics. The trachyte dome to the west of the crater is subdivided into 3 facies units that include: 1) the trachyte breccias originating from initial dome collapse, 2) the trachyte lava-flow unit and 3) the domal main body. On the other side, the trachybasalt is subdivided into 2 facies units that include: 1) the spatter and scoria deposit from the early explosive eruption and 2) lava-flow unit from the later effusion eruption. Quartz OSL dating on the sediments underlying the trachyte breccias and the trachybasaltic lava-flow unit reveals ages of ca. 37 ka and ca. 21 ka, respectively. The results point toward that the Baengnokdam summit crater was formed by eruption of trachybasaltic magma at about 19~21 ka after the trachyte dome formed later than 37 ka.

• Geophysics and Geophysical Exploration
• /
• v.12 no.1
• /
• pp.1-7
• /
• 2009

Airborne electromagnetics (AEM) is a useful tool for investigating volcanic structures because it can survey large and inaccessible areas. Disadvantages include lower accuracy and limited depth of investigation. The Grounded Electrical Source Airborne Transient Electromagnetic(GREATEM)survey system was developed to increase the depth of investigation possible using AEM. The method was tested in a survey at Mount Bandai in north-eastern Japan. Mount Bandai is an andesitic stratovolcano that rises 1819m above sea level. An eruption in July 1888 left a hoof-shaped collapsed wall in its northern crater and avalanche debris at its base. Previous surveys of Mount Bandai allow for comparisons of data on its structure and collapse mechanism as obtained by GREATEM and other geophysical methods. The results show resistive structures in recent volcanic cones and conductive structures in the collapsed-crater area. Conductive areas around the collapsed wall correspond to an alteration zone resulting from hydrothermal activity, supporting the contention that a major cause of the collapse associated with the 1888 eruption was hydrothermal alteration that structurally weakened the interior of the volcanic edifice.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.497-500
• /
• 2007

탄성파 코다 파는 두 수진기에서 기록된 탄성파 자료의 상호상관으로부터 두 신호에 대한 순간응답을 구하고 이로부터 지층정보를 구하는데 이용된다. 여기에서는 인공합성 탄성파 자료와 가스 하이드레이트 현장자료에 적용하여 상호상관 모음도와 가상음원 모음도 (virtual source)를 구하고자 하였다. 인공합성자료는 해저면 탄성파 탐사법 (ocean bottom seismic)을 모델로 이용하여 인공합성 탄성파 단면도를 제작하였으며, 탄성파 코다 파를 살펴보기 위해 인공 OBS 자료 중 첫 번째 트레이스를 가상음원으로 정하고 모든 음원 모음도와 상호상관으로 가상응원 단면도를 제작하였다. 현장자료 적용으로는 해저면 기인 고진폭 반사파인 BSR (bottom simulating reflection)을 포함하고 있는 자료를 선정하여 상호상관 단면도와 가상음원 단면도를 제작하였다. 중합단면도상에 나타난 가스 분출지역은 상호상관 단면도에서도 나타났으며, 중합단면도상 BSR부분은 vs 단면도에서 강한 반사파를 보여줌을 알 수 있었다.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.18 no.4
• /
• pp.86-91
• /
• 2010

New Design configurations of the fighter aircraft igloo diffuser were studied based on the closed ventilation type in contrast to the conventional open distribution type. To validate the enhanced and safe performance, the exhaust flow patterns of the two igloo diffuser types were simulated by both experimental and computational approaches as design tools. Flow visualizations were conducted to investigate the exhaust flow patterns in experimental approach. In addition, the commercial code called Fluent was used to calculate flow field properties. Computational simulations provided detailed parametric studies that significantly reduced the amount of experimentation necessary to alter the design parameters of the existing fighter igloo diffuser. The closed ventilation type of the igloo diffuser was shown the better results.

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

• Economic and Environmental Geology
• /
• v.54 no.2
• /
• pp.187-197
• /
• 2021

The Hyeongjeseom (Islet) is an erosional remnant of volcano which is located about 2 km northeast of sea shore of the Songaksan tuff ring, and is composed of volcaniclastic deposit, agglomerate and scoria deposit, ponded lava, aa lava flows, reworked deposit and beach deposit in ascending order from the base. The volcano is formed by volcaniclastic deposits and lava flows that recorded a transition from initial phreatomagmatic to magmatic explosions followed by lava effusion. It is interpreted that the outcropped volcaniclastic deposit may be a remaining portion of outer ring of a tuff cone. A bomb and a ponded lava yield geochemically basaltic trachyandesite compositions (SiO2 51.3 wt%, Na2O+K2O 6.0 wt%) and belong to olivine basalt with scarce (<5 %) phenocrysts of olivine, petrographically. By incremental heating Ar-Ar dating method, the plateau age of lava flow in the Heongjesom is 9.2±3.6(2σ) ka, implying that the volcanism of Heongjeseom may have occurred earlier than the Songaksan tuff ring which erupted ca. 3.7 ka. It still remains a task to find a volcano which matches with a historical record of volcanic activity that occurred a thousand years ago.

• Korean Journal of Remote Sensing
• /
• v.21 no.2
• /
• pp.99-111
• /
• 2005

A fuzzy logic based data integration was applied for geothermal potential mapping in Jeju Island. Several data sets, such as geological map, the density of drainage system, the distribution density of cinder cones, density of lineaments, aerial survey map for total magnetic intensity and total gamma ray, were collected as thematic map for the integration. Fuzzy membership function for all thematic maps were compared to the locations of the spa, which were used as ground-truth control points. The older geology, the lower density of drainage, cinder cones and lineaments, and the lower intensity of magnetic and gamma ray were showed the higher fuzzy membership function values, respectively. After integrating all thematic maps, the results of gamma operator with the gamma value of 0.75 was the highest success rate, and new geothermal potential zone is prospected in western north part of Jeju Island.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.512-512
• /
• 2017

날로 심각해지는 해수 오염, 유류사고, 해파리에 의한 인명피해 및 발전소의 경제적 피해사고, 해양 쓰레기 등과 같은 해양 환경 문제가 발생하고 있다. 이러한 해양환경문제를 해결하기위해 생물학적 방법과 물리적 방법이 있으나 생물학적 방법은 개체군과 종류의 변화로 그 적용이 어려운 실정이고, 물리적 방법은 지속적인 제거를 위한 비용적인 문제와 인부 및 자원봉사자의 안전문제가 발생한다. 따라서 에어버블을 이용한 각종 친환경적 방법이 주목받고 있다. 본 연구에서는 에어버블 차단막의 차단율을 증가시키기 위해 현장조건 내에서 에어버블의 거동특성에 대한 실험을 하였다. 실험을 위해 회류식 개수로 에어버블 거동실험장치를 제작하였다. 실험장치는 길이 8.1m, 높이 1.2m, 폭 0.7m이며, 두께 10mm의 투명 아크릴를 사용하여 에어버블의 거동을 관찰 할 수 있게하였다. 대형펌프를 사용하여 물이 회류함을 통해 흐름유속을 만들어 현장조건을 고려하였다. 에어버블을 분사하기 위해 압축공기 저장탱크와 연결된 분사구가 있으며, 노즐의 크기(0.5mm~1.0mm)로 분사량을 조절하고 분사압은 별도의 조절장치를 이용하여 0~5bar 범위의 분사압 조절을 가능하게 하였다. 초고속 카메라와 3축유속계를 사용하여 에어버블의 이동경로, 유속 및 에어버블의 거동을 측정하였다. 실험을 통한 구간별 에어버블의 거동 분석 결과, 상승속도는 분사구에서 분출되는 구간인 0~0.8m 에서는 상승속도가 증가하고, 0.8~1.2m구간에서는 속도가 다시 상승하는 경향을 확인하였다. 이는 수표면에 가까워질수록 수압이 작아져서 에어버블의 크기가 커짐에 따라 부력이 커짐으로 판단된다. 같은 이유로 분사량이 많을수록 상승속도도 같이 증가되는 것으로 나타났다. 유속에 따른 거동은 유속을 0.1m/s~0.5m/s로 조정하여 유속별 에어버블이 수표면까지 도달하는 거리, 속도 및 이동경로를 분석하였다. 유속과 에어버블이 수표면까지 도달하는 거리는 비례하여 증가하는 것을 확인하였다. 실험결과를 바탕으로 조건에 따른 에어버블 거동 경험식을 도출하였다. 본 실험은 회류식 개수로 에어버블 거동실험장치를 활용하여 에어버블 거동 경험식을 제시하였으며, 이를 바탕으로 에어버블 차단막 기술 개발을 위한 기초자료로 이용될 수 있을 것이다.