Scientists have found that Earth's largest volcanic outpouring more than 100 million years ago altered the structure and chemistry of the oceanic plate below the Ontong Java Plateau. Seismic data revealed networks of vertical magma channels and signs of chemical change in the rock. The findings were published in Geophysical Research Letters.
A research team led by Azusa Shito of Okayama University of Science examined the plate using Po and So seismic waves recorded by ocean bottom seismometers. The waves showed horizontal layers crossed by dike swarms, which are vertical intrusions formed when magma forced through cracks and cooled.
The team also measured unusually slow wave speeds. This indicated that magma from a thermochemical plume did not simply pass through the plate but chemically modified the surrounding mantle rock through a process called refertilization.
The Ontong Java Plateau formed 110 to 120 million years ago in the western Pacific Ocean. It is the largest oceanic plateau on Earth and resulted from the biggest known volcanic event in the planet's history.
The study suggests that such massive eruptions can reshape oceanic plates by creating extensive intrusion networks and altering their composition. The work involved researchers from Okayama University of Science, the Institute of Science Tokyo, and Hiroshima University.