Recent studies have shown that unusual rock compositions within oceanic plates, resulting from past geological activity, affect how these plates move and at what speed as they sink into the Earth's mantle.
Within the depth range of 410 to 660 kilometers exists the mantle transition zone (MTZ), an essential area functioning as a checkpoint for substances moving into Earth’s deep mantle. Significant amounts of basaltic rock found in the MTZ can lead to subducting slabs—which move under other tectonic plates—to either slow down or become stuck inside this layer rather than continuing downward into the lower mantle. Despite previous findings of basalt reserves within the MTZ, the source of these deposits has stayed ambiguous.
A global group of seismologists, headed by researchers from the University of Southampton (who have since moved to the Woods Hole Oceanographic Institution), presented findings indicating an unusually thick mantle transition zone. This thickness could solely be accounted for by a substantial amount of basaltic rocks, implying that specific areas might contain complete oceanic plates measuring around 100 kilometers in thickness composed largely of basalt.
The findings, published in the journal Nature This offers deeper insight into plate subduction, a process that sends surface materials and volatile components back into Earth’s depths, thereby maintaining long-term climate steadiness, atmospheric equilibrium, and planetary livability for billions of years.
As part of the VoiLA (Volatiles in the Lesser Antilles) initiative, the group installed 34 underwater seismic sensors below the Lesser Antilles archipelago.
“This marks the initial extensive underwater seismic study carried out at an Atlantic subduction zone,” stated Dr. Catherine Rychert, who previously served as an Associate Professor at the University of Southampton and presently works at the Woods Hole Oceanographic Institution. “It was quite astonishing to discover an unusually thick mantle transition zone underneath the Antilles, measuring about 330 kilometers, making it among the thickest such zones identified globally. Despite the Caribbean’s reputation for sunny weather and sandy shores, it can now boast prominence within the realm of plate tectonics.”
It’s astonishing to consider that tectonic plates possess something akin to ‘memory,’ which influences their role in driving mantle convection and facilitating the recycling of materials back into the Earth,” stated Dr. Nick Harmon, who transitioned from being an Associate Professor at the University of Southampton to his current position at the Woods Hole Oceanographic Institution.
Dr. Xusong Yang, who was previously a visiting scholar at the University of Southampton and now works at the University of Miami, highlighted: “It would be unwise to ignore the inherent compositional diversity within subducting oceanic plates as this variability could significantly affect how these structures behave in the depths of our planet.”
More information: Xusong Yang and colleagues, Imaging a Basaltic Slab beneath the Lesser Antilles due to Past Tectonic Activity Nature (2025). DOI: 10.1038/s41586-025-08754-0
Furnished by Woods Hole Oceanographic Institution
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