In a groundbreaking discovery from Woods Hole, Massachusetts, scientists have unveiled how the ancient tectonic histories of oceanic plates influence their fate as they plunge into the depths of the Earth. New research indicates that distinct rock anomalies within these plates can dramatically affect their speed and trajectory in a critical region known as the mantle transition zone (MTZ) between 410 and 660 kilometers beneath the Earth's surface.

The MTZ acts as a gateway for materials descending into the Earth’s deeper mantle. Strikingly, large concentrations of basalt rock within this zone can halt or slow down subducting plates—those that slip beneath others—rather than allowing them to sink directly into the lower mantle. While basalt reservoirs in the MTZ have been spotted before, their origins had remained largely a mystery.

Led by an international team of seismologists from the University of Southampton and now at the Woods Hole Oceanographic Institution, this research presents evidence of an exceptionally thick MTZ. This finding suggests that certain oceanic slabs can be composed largely of basalt rock, measuring up to 100 kilometers thick!

Published in the prestigious journal Nature, these revelations provide deeper insights into the process of plate subduction, which plays a crucial role in recycling Earth's surface materials and volatile elements. This mechanism is vital for sustaining long-term climate stability and ensuring the planet remains habitable over billions of years.

The study, part of the innovative VoiLA (Volatiles in the Lesser Antilles) project, involved deploying 34 seismometers on the ocean floor beneath the Lesser Antilles.

Dr. Catherine Rychert, a key researcher and former Associate Professor at the University of Southampton, remarked, "This is the first large-scale ocean-bottom seismic experiment in an Atlantic subduction zone. We were astounded to discover a mantle transition zone beneath the Antilles that is approximately 330 kilometers thick—one of the thickest known globally. While the Caribbean is famed for its sun-kissed beaches, it has now carved out a new reputation in the realm of plate tectonics!"

Reflecting on the implications of this research, Dr. Nick Harmon noted, "It's fascinating to think that tectonic plates possess a kind of 'memory' which influences the way they drive mantle convection and reintroduce materials back into the Earth."

Leading author Dr. Xusong Yang, who transitioned from the University of Southampton to the University of Miami, underscored, "The compositional diversity of subducting oceanic slabs is crucial. It could profoundly affect how these slabs behave deep within the Earth’s interior."

This revolutionary experiment was conducted by a collaborative team, including Dr. Kate Rychert and Dr. Nick Harmon, along with Professor Saskia Goes from Imperial College London and Professor Andreas Reitbrock from Karlsruhe Institute of Technology, with funding from the Natural Environment Research Council (NERC) and the European Research Council (ERC).