Japan Geoscience Union Meeting 2019

Presentation information

[E] Poster

H (Human Geosciences ) » H-GM Geomorphology

[H-GM03] 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)

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

*Takayuki Ogata1 (1.Disaster Prevention Research Center for Island Regions, University of the Ryukyus)

Keywords:weathering, sandstone, rocky coast, tafoni, monsoon, Yaeyama group

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.