Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

H (Human Geosciences ) » H-GM Geomorphology

[H-GM04] Geomorphology

Wed. May 29, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Tsuyoshi Hattanji(Faculty of Life and Environmental Sciences, University of Tsukuba), Masayuki Seto(Fukushima Future Center for Regional Revitalization, Fukushima University)

[HGM04-P13] Marine erosional landforms along the southern coast of Yonaguni Island, Ryukyus

*Hayate Kimura1, Kensaku Urata2, HASEGAWA Hitoshi3, Toshihiko Ichihara4, Atsushi Suzuki5, Nobuyuki Hori6, Hironobu Kan2 (1.Graduate school of integrated sciences for global society, 2.Graduate School of Integrated Sciences for Global Society, Kyushu University, 3.Kokushikan University, 4.Sedimentary Environments Research, 5.Geological Survey of Japan National Institute of Advanced Industrial Science and Technology (AIST), 6.Department of Geography, Nara University)

Keywords:SfM-MVS, Photogrammetry, Sea cliff, Shore platform, Yaeyama Group, Ryukyu Limestone

Yonaguni Island is located at the westernmost of Japan, where marine erosional landform is widely seen. However, high sea cliffs refuse the investigator’s approach. We created three-dimensional models by taking photographs from drone. The coastal area of Yonaguni Island is composed of the Middle Miocene sedimentary rocks of the Yaeyama Group and Pleistocene limestone of the Ryukyu Group. We observed characteristic erosional landforms which varies depending on geology along the southern coast of Yonaguni Island.
We surveyed 6 areas where locate the east and south coasts in Yonaguni Island. Photogrammetric surveys were carried out using DJI Phantom 4 Pro. We installed a GCP at accessible places. PhotoScan Professional was used as SfM-MVS software to create terrain models.
Coastal landforms are largely different depending on geological structure. In the limestone coast, collapsed areas of several hundred meters wide are formed. These collapses seem to originate from the unconsolidated layer of unconformity below the limestone or the detrital layer in the limestone. In the coast of sedimentary rocks, coastal landform varies with sedimentary facies. Shore platform is formed at the base of cliff which composed of layers of sandstone and shale. On the other hand, large boulders are distributed at the base of cliff composed of massive sandstone without layers.