Submarine terraces of the Dokdo volcano in the Ulleung Basin, the East Sea (Sea of Japan), based on detailed bathymetry and seafloor image survey using multi-beam echosounder

Abstract

The Dokdo volcano is situated in the northeastern part of the Ulleung Basin in the East Sea and comprised of very small islets and a large submerged volcanic edifice. In order to investigate the detailed bathymetry and morphologic characteristics around the volcanos underwater guyot type summit, we carried out multi-beam surveys and analyzed the data. The bathymetry and topographic data around the islets of the volcano show uneven seabed and irregular undulations from costal line to ~30 m in water depth, indicating the effects of partial erosions and taluses formation due to waves, currents and weathering. The area from ~30 m to ~80 m depth shows gentle rises and falls, with a modest slope. Below ~80 m, the bathymetry gradually transitions to a relatively flat undulation with a smooth slope, extending to offshore areas. The bathymetry and the seafloor image from backscattering data show that there are small islets of the Dokdo volcano and a rocky sea bottom elongated from the islets, probably originating from residual parts of the eroded and collapsed main crater of the volcano. Submarine terraces have been reported around continental margins and islands throughout the world. Interestingly, the seabed was found to have stepped slopes, formed mainly due to wave activity and erosion. These topographic features (stepped slopes) are interpreted to be wave-cut submarine terraces rather than bcteristics around the volcanos underwater guyot type summit, we carried out multi-beam surveys and analyzed the data. The bathymetry and topographic data around the islets of the volcano show uneven seabed and irregular undulations from costal line to ~30 m in water depth, indicating the effects of partial erosions and taluses formation due to waves, currents and weathering. The area from ~30 m to ~80 m depth shows gentle rises and falls, with a modest slope. Below ~80 m, the bathymetry gradually transitions to a relatively flat undulation with a smooth slope, extending to offshore areas. The bathymetry and the seafloor image from backscattering data show that there are small islets of the Dokdo volcano and a rocky sea bottom elongated from the islets, probably originating from residual parts of the eroded and collapsed main crater of the volcano. Submarine terraces have been reported around continental margins and islands throughout the world. Interestingly, the seabed was found to have stepped slopes, formed mainly due to wave activity and erosion. These topographic features (stepped slopes) are interpreted to be wave-cut submarine terraces rather than b