日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 H (地球人間圏科学) » H-GM 地形学

[H-GM03] Geomorphology

2019年5月29日(水) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:八反地 剛(筑波大学生命環境系)、瀬戸 真之(福島大学うつくしま福島未来支援センター)

[HGM03-P01] Honeycomb Weathering (Tafoni) of Sandstone and Environmental Factors in Yonaguni Island, Okinawa Prefecture, Japan

*尾方 隆幸1 (1.琉球大学島嶼防災研究センター)

キーワード:風化、砂岩、岩石海岸、タフォニ、モンスーン、八重山層群

Sandstone surfaces of Yonaguni Island (westernmost of the Ryukyu Arc) often show a honeycomb structure (tafoni) derived from physical disintegration in relation to salt weathering. Miocene sandstone (Yaeyama Group) is extensively exposed on the island surface, and forms sea cliffs along rocky coasts. The honeycomb structure is especially observed along the coasts where wave splashes produce wetting and drying processes assisted by strong wind and active evaporation. The geometry and density of tafoni seem to be controlled by vertical height from the sea level and horizontal distance of the coast line. Field observations at the rocky coasts of Yonaguni Island suggest that larger holes are developed along the north-faced coasts than the south-faced coasts, which depends mainly on the northeastern monsoon during the winter period.