• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.1
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• pp.32-42
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• 2002

The late Quaternary deposit of Cheonsu Bay, up to 20 m in thickness above the Jurassic granite basement, consists of two sedimentary units: an upper Holocene mud and sandy mud deposit (Unit M1), and a lower late Pleistocene sand and mud deposit (Unit M2; 'Kanweoldo Deposit&apos). Unit M1 is a typical Holocene tidal-flat deposit of Cheonsu Bay, showing a coarsening upward, retrogradational facies trend. This retrograding facies trend is probably due to a relative low sedimentation rate during Holocene transgression. Overlain unconformably by Unit M1, Unit M2 deposit reaches up to 14 m in thickness and is mainly composed of muddy sediment with yellow to gray color. This unit is characterized by a variety of tide-influenced signatures such as rhythmic bedding, flaser bedding, crab burrow fossil, marine dinoflagellate assemblage and authigenic glauconite mineral, indicating very similar depositional environment to those of Unit M1 deposit. It suggests that Unit M2 was probably accumulated under the tidal-flat environment during a pre-Holocene sea-level highstand. In particular, the uppermost 3-4 m of Unit M2 appears to have undergone subaerial exposure and subsequent weathering during the sea-level lowstand after deposition. Therefore, stratigraphic unconformity between Holocene and late Pleistocene sediments is highlighted by the desiccated and weathered surface of Unit M2.

• Current Research on Agriculture and Life Sciences
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• v.4
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• pp.70-76
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• 1986

The purpose of this study is to offer the basic data of the tidal river development program by grasping the diffusion between the high density-sea water and the low density-fresh water in the tidal river. The tidal range of Hyungsan river which flows at Youngil bay in Pohang was selected to analysis the phenomenon of density current. The results obtained are as follows ; The tide of Youngil bay was one time a day, 0.104m in high tide difference and 0.085m in mean tidy difference. The change of sea level by tide was negligible. The volume of reserved water by sea water was $2,700,000m^3$ and available water of irrigation was $1,200,000m^3$ that salt density is below $750{\mu}{\mho}/cm$ out of total volume. Salt intrusion phenomenon by density current was a little water level change, however, it become a salt wedge type by the much salt invasion during the spring tide and it makes a well-mixed type by the retreating salt wedge during the neap tide. As long as there were some density differences between sea water and fresh water, net upstream flow was existed along the bottom of water way from the estuary to the upstream channel.

• Journal of Environmental Impact Assessment
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• v.33 no.1
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• pp.18-29
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• 2024

The aggravation of coastal erosion due to climate change has recently emerged as a global issue, and the international community is aware of the risk and is applying national consultations and various policies. In the case of coastal countries located in the Mediterranean Sea and the Caribbean Sea, coastal buffer zones and coastal management plans are established at a national level, and the United States is establishing coastal area management plans at the city level. In Korea, coastal erosion management areas are designated and managed to prevent coastal erosion and coastal disasters, but the number of designated areas and policies for coastal land areas are lacking. Therefore, in this study, we study policy cases applied to coastal land to prevent and reduce coastal erosion and coastal disasters through policy status and overseas cases, and seek ways to improve coastal buffer zone policies. As a result of the study, implications were drawn that expansion of the coastal buffer zone for coastal land areas and standards for establishing buffer zones based on scientific analysis are necessary.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.5
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• pp.465-471
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• 2012

To compare the accumulation of paralytic shellfish poison (PSP) in different marine organisms, the occurrence and variation of PSP were surveyed in blue mussel Mytilus edulis, oyster Crassostrea gigas, short neck clam Ruditapes philippinarum, bay scallop Argopecten irradians, and warty sea squirt Styela clava collected from Jinhae Bay, Korea, in 2005 and 2006 year. We also investigated the ability of the blue mussel to detoxify PSP by relaying and depuration (via the water flow or water circulation system). In the marine organisms examined, PSP levels were the highest in blue mussel, followed in order by bay scallop, oyster, short neck clam, and warty sea squirt. Comparing the maximum PSP levels in the bivalve species examined in 2005 and 2006, PSP in blue mussel was 1.6-2.0, 4.0-5.9, and 5.1-6.0 times higher than in bay scallop, oyster, and short neck clam, respectively. Therefore, blue mussel could be useful as a bioindicator for PSP monitoring. With the increasing PSP levels in blue mussel in 2006, the proportion of PSP in its digestive gland increased to 95.1% when the maximum level was detected from the whole tissues of blue mussel on May 29. Subsequently, the PSP proportion in the digestive gland decreased as the PSP level in whole tissue decreased. The detoxification of PSP in blue mussel was greatest with relaying, followed by the water flow, and water circulation systems. Relaying decreased the PSP level below the regulatory limit of $80{\mu}g$/100 g after 2 days in low toxic sample with $124{\mu}g$/100 g, and after 7 days in high toxic sample with $401{\mu}g$/100 g. During depuration in the blue mussel with $401{\mu}g$/100 g via the water flow system, the PSP amounts in the digestive gland decreased by about 50% after 1 day, and about 77% after 7 days. In contrast, the PSP amounts in the soft body, gill, and mantle did not change significantly with depuration.

• Maritime Security
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• v.8 no.1
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• pp.1-39
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• 2024

This study started with the awareness that domestic studies on China's maritime gray zone strategy have been following the analysis results of previous studies, and that only principled positions and directions for countermeasures remain at the 'declarative and conceptual' level. In order to overcome the above problems, the author analyzed the maritime gray zone strategy being developed in the South China Sea, East China Sea, and the West Sea and Ieodo areas, recognizing that China is developing a maritime gray area strategy based on the 'three warfare' that constitutes its own strategic culture. As a result of the analysis, it is predicted that China's maritime gray zone strategy will be more aggressive in order to occupy the West Sea and Ieodo in the future. As a concept of our naval response strategy, The author proposed to 'neutralize' the development effect of 'three warfare', the basis of China's maritime gray zone strategy, to stop the gradual change in the phenomenon induced by China, and to continuously pursue 'return' to a maritime order based on norms and rules. In this study, a 'concrete and systemized' countermeasure to implement this was presented.

• Geophysics and Geophysical Exploration
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• v.11 no.3
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• pp.197-203
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• 2008

A shallow high-resolution seismic reflection survey was carried out at the Mineopo tidal flat on the western coast of Korea. The purpose of the survey was to investigate shallow sedimentary structure of the tidal flat associated with the recent sea level change. A total of 795 shots were generated at 1 m interval from a 5-kg hammer source and recorded on 48 channels of 100 Hz geophones along two mutually perpendicular profiles. The water-saturated ground condition resulted in suppressed ground rolls by significantly decreasing rigidity. In addition, seismic velocities over 1500 m/s provided easy segregation of reflected arrivals from lower velocity noise. As a consequence, seismic sections from the study area show significantly higher resolution and signal to noise ratio than conventional land seismic sections. The tidal flat consists of 5 sedimentary sequences above acoustic basement. The seismic sections reveal the continuous structure of the tidal flat formed in association with sea level rise during the Holocene.

• Korean Journal of Environment and Ecology
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• v.24 no.1
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• pp.26-36
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• 2010

The purpose of this study is to investigate the change and structure of the altitudinal vegetation on the east side of Hallasan National Park, and to accomplish this research, seventeen plots($400m_2$ per zone) were set up along the Seongpanak trail starting from 750m to 1,450m(which was 700m long). These zones, according to the two-way indicator species analysis(TWINSPAN) and ordination analysis(DCA), were divided into six communities: Carpinus tschonoskii-Stryrax japonica community(I), Stryrax japonica-Quercus serrata community(II), Carpinustschonoskii-Q. serrata community(III), Q. mongolica-C tschonoskii community(IV), Acer pseudosieboldianum community(V), and Q. mongolica-Abies koreana community(VI). The findings of my investigation are as follows: the altitudinal vegetation structure of all the investigated zones from 750m to 1,000m above sea level is similar to one another, whereas the same zones from 1,000m to 1,450m above sea level showed dissimilarities among them. That indicates that altitudinal vegetation structure on the east side of Hallasan National Park has changed drastically at the 1,000m areas above sea level, and the forest age of this area is over 50 years.

• Journal of the Korean association of regional geographers
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• v.7 no.2
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• pp.71-81
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• 2001

According to the change of stream power/resisting power relationship due to the crustal movement or the climatic change, most channel landforms which reflect the equilibrium state of fluvial system are eroded and a part of them is remained as a river terrace. In many rivers in Korea are extensively distributed the relatively younger low river terraces. But their accurate formation mechanism is not known. In this paper, the formation processes and the dating of low river terraces distributed in Nakdong River basin will be investigated. Stream power of the downward erosion was revived because the sea level fell down. So stream power was superior to the resisting power under the cool-wet climatic condition during the last glacial period. Thus the river bed was excavated deeply, so that low river terraces were built up. And many incised meander loops were cut during this period. But, when fluvial system did not have equilibrium over all reaches, the last glacial period ended and the sea level initiated to rise rapidly. The headward erosion from the fall of sea level during the last glacial period had kept up to Hagye Fall because of the cutting of incised meander loops. Deeply excavated valleys and abandoned channel of cut-meander in lower reaches of a stream were filled with sediments. Thus the longitudinal profile of the uppermost reaches reflect the last interglacial, the upper reaches the last glacial, and the middle/1ower reaches recent fluvial system. Therefore low river terraces have been formed since the last glacial period.

• The Korean Journal of Quaternary Research
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• v.17 no.1
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• pp.7-16
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• 2003

A 31m-long sediment core (SSDP-102) was taken from the inner shelf (about 40m water-depth) off the northwestern coast of the Korea Strait. Detailed lithofacies and organic-geochemical analyses were performed to establish a high-resolution stratigraphy in the Korea Strait shelf and to reconstruct the paleoenvironmental changes associated with the Holocene marine transgression. The stratigraphic framework of the core was primarily established using 6 AMS $^{14}C$ ages. The sedimentary record of the core SSDP-102 allows for the reconstruction of the paleoenvironmental changes during the last 12.1 ka BP. According to the high-resolution seismic reflection profiles, lithofacies and organic-geochemical data, the core SSDP-102 can be divided into three units (III to I in ascending order) above the acoustic basement. The three units reflect distinct changes of depositional environments resulted from the post-glacial marine transgression. Therefore, it is suggested that three phases of sea-level change have occurred within the inner shelf of the Korea Strait following the Holocene marine transgression. (1) estuarine environments from ca. 12.1 to 6.2 ka BP; (2) near-shore environments with a period of decreased rising of sea level between 6.2 and 5.1 ka BP; (3) near-shore to modem marine environments after 5.1 ka BP. In particular, the present marine conditions influenced by the warm Tsushima Current have been gradually established after ca. 5.1 ka BP.

• Journal of the Korean Geographical Society
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• v.36 no.3
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• pp.217-232
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• 2001

One of the molt debatable Issues on geomorphological study in Korea should be the discussion over the formation process of gent1e slope surfaces on the piedmont area. In this study, the characteristics of spatial distribution and the formation process of geomorphic surfaces were investigated by classifying the alluvial fans as three geomorphic surfaces alluvial the Bulguksa fault-line The fan surfaces, distributed along the west slue of Bulguksa Mts, consists the confluent alluvial fans continuously along the N-S direction The surfaces of Sincheon-Hyomun district juxtaposed to the Ulsan Bay must be infulenced by sea-level chance during the Quaternary Taken together, these observation suggests that the major four factors contributed to the fan formation 1) rather longer freeze-and-thaw cycle during the Glacial period. 2) the steep mountain slope along the west side of Bulguksa Mts.. which had been resulted from the horizont stress of EAst Sea 3)the tectolinear fault system developed by structural movement along the Bulguksa Fault-line valley. and 4) the erosion-labile characteristics of bedrock In this urea which is consisted of the Bulguksa granite and the sedimentary rock formed in Cretaceous period.