[O-11] Senior high school student poster presentations

[O11-P02] The study on drifted pumice in Suruga Prefecture,Japan "Identification of the origin of dark brown pumice"

*Tomoki Fujishima¹, *Kotaro Hikawa¹, *Ryoma Takeuchi¹, Rikuto Iida¹, Eri Shinmura¹ (1.Shizuoka Prefectural Iwata Minami High School)

Keywords:Pumice, Drifted pumice, Iwo island , Dark brown

The aim of our study is focus on the origin of the dark brawn pumice drifting to Shizuoka Enshu-nada sea and Suruga Bay and elucidated that it was caused by the eruption Iwo-island south side offing on October 30, 2023 by examining these pumice since May 11, 2024. We collected and analyzed the information based on the identification method of the Tephra layer(Machida・Arai, 2003). We examined five items "mineral composition, all rock chemical composition, the chemical composition of a refractive index, the volanic glass of the form, the chemical composition of the volcanic glass. In addition, the refractive index of the volcanic glass of Iwo-island pumice is 1.520-1.525. As a result, the origin of the dark brown pumice cast ashore in Enshu-nada Sea, Suruga Bay was proved to be Iwo-island. We will classify Iwo-island pumice with a color, and examine them at the rock・mineral level every kind,and find the cause of the difference of the color.