Characteristics of Kikai caldera volcanic product revealed by seafloor drilling samples

Abstract

Kikai Caldera volcano has repeatedly erupted in large scale eruptions such as the Kikai Akahoya eruption 7,300 years ago and the Kikai Tozurahara eruption 95,000 years ago, and detailed eruption history can be studied by combining seafloor and on-land surveys.In this study, core samples were collected by the SCORE program of CHIKYU based on the subsurface structure revealed by seismic reflection surveys of large eruptive ejecta on the seafloor, which are still largely unknown.The chemical composition of the volcanic glass was analyzed and compared with subaerial deposits, and it was found that the two large-scale eruptive ejecta are thickly deposited on the seafloor as well, and that the Kikai Akahoya product is divided into two units on the seafloor as well.In addition, the chemical compositional characteristics of volcanic glass in piston core samples from a wide area around the Kikai caldera suggest that the Kikai Akahoya product may have become less accessible to distant sites as the eruption progressed.