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

• Korean Journal of Environmental Biology
• /
• v.39 no.2
• /
• pp.245-257
• /
• 2021

Ulleungdo, a volcanic island, has different climate, soil, and topography characteristics from inland of the Korean Peninsula. Its agriculture also exhibits distinctive features. This study focused on floristic compositions and characteristics of crop lands in Ulleungdo. Flora surveys were conducted for 37 areas three times, one in May of 2016, one in July of 2020, and one in August of 2020. Results showed that vascular plants of crop lands in Ulleungdo included 186 taxa of 53 families, 132 genera, 160 species, 14 varieties, five subspecies, and five hybrids. Asteraceae had the most diverse species (33 taxa), followed by Poaceae (25 taxa), Fabaceae (12 taxa), Polygonaceae (11 taxa), and Liliaceae (nine taxa). The biological type of crop lands in Ulleungdo island was determined to be Th-R₅-D₄-e type. Rare plants were found for nine taxa: Athyrium acutipinnulum Kodama ex Nakai, Sedum takasimense Nakai, Rubus takesimensis Nakai, Dystaenia takesimana (Nakai) Kitag., Ligustrum foliosum Nakai, Aster pseudoglehni Y.Lim, Cirsium nipponicum (Maxim.) Makino, Lilium hansonii Leichtlin ex D.D.T.Moore, and Polygonatum robustum (Korsh.) Nakai. In addition, 45 taxa contained naturalized plants of 13 families, 33 genera, 44 species, and one variety. Urbanization and naturalization indices were 13.9%, and 24.2%, respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.11 no.1
• /
• pp.21-30
• /
• 2006

This study investigated the temperature-salinity spatio-temporal variability around the Ulleung-do Island (UI) by using CTD profiles obtained by the ARGO floats far the period of Oct.,2003 to Aug.,2005. The waterbody in the upper 700 m around the UI could be classified into five water masses, which is consistent to traditional water characteristics in the East Sea. In the upper surface layer, the temperature and salinity in fall season became even lower than those properties in the summer time. The East Sea Intermediate Water (ESIW) characterized by the salinity minimum layer shows the range of potential temperature between 1 to $5^{\circ}C$ and salinity lower than 34.06 psu. The ESIW lies approximately at 265 m depth with average thickness of 175 m. This thickness of the ESIW continues to be relatively uniform regardless of spatio-temporal space. However, the depth of the ESIW shows vertical variation influenced by the Ulleung warm eddy (UWE). Since the UWE lies in the upper layer, the Upper Portion of the Japan Sea Proper. Water (UPJSPW) is also affected to show the vertical variation. The influence extorted by the UWE reached down to 700 m depth in terms of temperature. The CTD profiles obtained with the high sampling rate by ARCO floats over two-year period provided with very useful and detailed informations in investigating the spatio-temporal variability In the study area.

• The Korean Journal of Petroleum Geology
• /
• v.5 no.1_2 s.6
• /
• pp.36-47
• /
• 1997

This study presents multi-variable sequence model for a broader application of sequence concept proposed by Exxon group. The concept of the multi-variable model is based on the fact that internal organization and boundary type of the sequences are determined by three varying factors including 3rd-order cycles of eustasy, and tectonic movement and sediment influx with 2nd-order changes. Instead of Exxon group's systems tracts, this model adopts parasequence sets as the fundamental building blocks of the sequence, because they are descriptive stratigraphic units simply defined by internal stacking pattern, reflecting interactions of accommodation and sediment influx. Seven sequence types which vary in number and type of internal parasequence sets are formulated as associations of four types of accommodation development and three grades of sediment influx. In the southwestern margin of Ulleung Basin, the multi-variable sequence analysis of shelf-slope sequence shows systematic changes in stratal patterns and the numbs, of constituent parasequence sets (i.e. sequence type). These changes are interpreted to reflect temporal and spatial changes in type and rate of tectonic movement and sediment influx, as a result of back-arc opening and closing. During the back-arc opening, rapid subsidence, continuous rise of relative sea level, and high sediment influx gave rise to sequences dominantly of single progradational parasequence set. In the early stage of back-arc closing accompanied by local contractional deformation, different types of sequences contemporaneously formed depending on the spatial changes in tectonically-controlled accommodation and influx rates. During the subsequent slow back-arc subsidence, rise-dominated relative sea-level cycle was coupled with moderate to high sedimentation rate to have resulted in sequences consisting of $2~3$ parasequence sets.

• Journal of Life Science
• /
• v.21 no.2
• /
• pp.279-285
• /
• 2011

The objective of the present study was to evaluate the skin whitening effect of the extracts of 3 herbs, Ligularia fischeri, Solidago virga-aurea and Aruncus dioicus, which were collected from Ullung island. Tyrosinase inhibition activities were 33% in pre-fermented extracts and 45% in post-fermented ones. When tyrosinase activities in B16F10 murine melanoma cells were tested, activities in pre- and post-fermented extracts were 41 and 56.5%, respectively. Thus, the post-fermented extracts might have greater skin whitening effects. The protein expression of MITF, TRP-1, TRP-2, and tyrosinase, which are all skin-whitening related transcription factors, showed that both pre- and post-fermented herbs inhibited protein biosynthesis in B16F10 melanoma cells. Post-fermented herb extracts especially showed a greater decrease of protein expressions. The expression of MITF, a regulatory transcription factor, was also decreased by both extracts but was greater in the post-fermented ones. From the results, it can be concluded that the 3 herb extracts from Ullung island may inhibit melanin biosynthesis by the suppression of MITF activity in a signaling pathway. Results indicate that the post-fermented herbs tested in the present study had skin whitening activities and can be used as functional ingredients for food and cosmetic compositions.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.24 no.2
• /
• pp.351-373
• /
• 2019

The cold eddies around the Ulleung Basin in the East Sea were identified from satellite altimeter sea level data using the Winding-Angle method from 1993 to 2015. Among the cold eddies, the Dokdo Cold Eddies (DCEs), which were formed at the first meandering trough of the East Korea Warm Current (EKWC) and were pinched off to the southwest from the eastward flow, were classified and their migration patterns were analyzed. The vertical structures of water temperature, salinity, and flow velocity near the DCE center were also examined using numerical simulation and observation data provided by the Hybrid Coordinate Ocean Model and the National Institute of Fisheries Science, respectively. A total of 112 DCEs were generated for 23 years. Of these, 39 DCEs migrated westward and arrived off the east coast of Korea. The average travel distance was 250.9 km, the average lifespan was 93 days, and the average travel speed was 3.5 cm/s. The other 73 DCEs had moved to the east or had hovered around the generated location until they disappeared. At 50-100 m depth under the DCE, water temperature and salinity (T < $5^{\circ}C$, S < 34.1) were lower than those of ambient water and isotherms made a dome shape. Current faster than 10 cm/s circulates counterclockwise from the surface to 300 m depth at 38 km away from the center of DCE. After the EKWC separates from the coast, it flows eastward and starts to meander near Ulleungdo. The first trough of the meander in the east of Ulleungdo is pushed deep into the southwest and forms a cold eddy (DCE), which is shed from the meander in the south of Ulleungdo. While a DCE moves westward, it circumvents the Ulleung Warm Eddy (UWE) clockwise and follows U shape path toward the east coast of Korea. When the DCE arrives near the coast, the EKWC separates from the coast at the south of DCE and circumvents the DCE. As the DCE near the coast weakens and extinguishes about 30 days later after the arrival, the EKWC flows northward along the coast recovering its original path. The DCE steadily transports heat and salt from the north to the south, which helps to form a cold water region in the southwest of the Ulleung Basin and brings positive vorticity to change the separation latitude and path of the EKWC. Some of the DCEs moving to the west were merged into a coastal cold eddy to form a wide cold water region in the west of Ulleung Basin and to create a elongated anticlockwise circulation, which separated the UWE in the north from the EKWC in the south.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.6
• /
• pp.587-601
• /
• 2020

The ocean circulation was simulated in the East Sea and Ulleungdo-Dokdo region using ROMS (Regional Ocean Modeling System) model. By adopting the East Sea 3 km model and the HYCOM 9 km data, Ulleungdo 1 km model and Ulleungdo-Dokdo 300 m model were constructed with one-way grid nesting method. During the model development, a correction method was proposed for the distortion of the open boundary data which may be caused by the bathymetry data difference between the mother and child models and the interpolation/extrapolation method. Using this model, a super-high resolution ocean circulation with a horizontal resolution of 300 m near the Ulleungdo and Dokdo region was simulated for year 2018. In spite of applying the same conditions except for the initial and boundary data, the numerical models result indicated significantly different characteristics in the study area. Therefore, these results were compared and verified by using the surface current data estimated by satellites altimeter data and temperature data from NIFS (National Institute of Fisheries Science). They suggest that in general, the improvement of the one-way grid nesting with the HYCOM data on RMSE, Mean Bias, Pattern correlation and Vector correlation is greater in 300 m model than in the 1 km model. However, the nesting results of using East Sea 3 km model showed that simulations of the 1 km model were better than 300 m model. The models better resolved distinct ridge/trough structures of isotherms in the vertical sections of water temperature when using the higher horizontal resolution. Furthermore, Karman vortex street was simulated in Ulleungdo-Dokdo 300 m model due to the terrain effect of th islands that was not shown in the Ulleungdo 1 km model.

• Monthly Newsletter
• /
• s.233
• /
• pp.4-4
• /
• 2007

• 한국석유지질학회:학술대회논문집
• /
• autumn
• /
• pp.47-54
• /
• 2001

• 한국석유지질학회:학술대회논문집
• /
• spring
• /
• pp.24-24
• /
• 2004