A study on comparison and analysis of detailed bathymetry in the southern nearshores of the Dongdo and the Seodo of Dokdo, in the East Sea

Abstract

We analyze precise seabed geomorphology and conditions for comparing the nearshore areas of the Dongdo(East Islet) and the Seodo(West Islet) using detailed bathymetry data and seafloor backscattering images, in Dokdo, the East Sea. As a result of bathymetry survey, the southern area of the Dongdo(~50 m) is deeper than the Seodo(~30 m) in the water depth. The survey areas consist of extended bedrocks from land of the Dongdo and the Seodo. The underwater rock region of the Seodo is larger than the Dongdo. In spite of similar extended rocks features from islets, there are some distinctive seabed characteristics between the southern nearshore areas of the Dongdo and the Seodo. The Talus-shaped seafloor environmentformed by gravel and underwater rocks originating from the land of the Dongdo occurs up to about 15 m depth. And the boundary line between extended bedrocks and seabottom is unclear in the southern nearshore of the Dongdo. On the other hand, the southern coast of the Seodo is characterized by relatively large scale underwater rocks and evenly distributed sediments, which clearly distinguish the boundary between extended bedrocks and seafloor. This is because the tuff layers exposed to the coastal cliffs of the Dongdo are weak against weathering and erosion. It is considered that there are more influences of the clastic sediments carried from the land of the Dongdo compared with the Seodo. Particularly, the land