Abstract
To clarify formation mechanism of the beach rock, a recently forming beach rock was observed by viewpoints of ecology and civil engineering in the field, and solidification test of the coral grit was conducted in the laboratory. At the field survey of Yoshiwara shore in Ishigaki Island, a modern artifact in the beach rock was observed. This phenomenon was considered that this beach rock is relatively new formation and it continued in the formation process. Adhesion of green algae and cyanobacterium was observed on the beach rock surface. Cement materials including Ca, Mg and Si were detected by SEM-EDX observation.
In the indoor experiment, periodic change of the organic matter acidization and alkalinization which linked ebb and flow was determined. As a new finding, eluviation and crystallization of Ca were deeply related to the beach rock formation.