A research group has revealed through seismic wave analysis that the oceanic plate beneath the Ontong Java Plateau—the world’s largest oceanic plateau—was extensively altered by massive volcanic activity during its formation. The study is published in Geophysical Research Letters.

The oceanic plate beneath the Ontong Java Plateau (OJP) has a composite structure consisting of layered structures overlaid by dike swarms. Low seismic velocity anomalies within the plate suggest chemical modification by magma derived from a thermochemical plume. These findings demonstrate that oceanic plates can undergo significant physicochemical modification due to large-scale volcanic activity, contributing to a comprehensive understanding of plate formation processes.

The research was led by Lecturer Azusa Shito of Okayama University of Science, together with Associate Professor Akira Ishikawa of the Institute of Science Tokyo and Professor Masako Yoshikawa of Hiroshima University.