Researchers led by a team from the Chinese Academy of Sciences have found extensive evidence of two giant tears in the Arabian Plate underneath southeastern Iran, according to a study published in Nature Geoscience, ScienceAlert reported. The ruptures mark a rare visible transition between oceanic subduction and continental collision—processes that normally unfold separately across millions of years.
The discovery matters because it captures the final stages of the Neo-Tethys Ocean’s disappearance, part of the Wilson Cycle that describes how oceans form, expand, and vanish as tectonic plates move. Geologists rarely observe both tearing modes simultaneously in the same region.
The Two Tears Form Where Rock Types Collide
One tear runs horizontally where the Zagros collision zone meets the Makran subduction zone. The other is a smaller vertical tear closer to the surface by the Makran Trench. The horizontal rupture stems from a density mismatch: the oceanic slab, made of heavier, thinner basalt that was once part of the ancient Neo-Tethys Ocean, subducts beneath a neighboring plate, while the continental rock—thicker but less dense, with granite-like composition—resists subduction and forms mountains instead.
Seismic Stations Mapped the Ruptures Between 2017 and 2018
To detect the activity, researchers used a network of 69 seismic monitoring stations to record vibrations from distant earthquakes between March 2017 and September 2018. The recordings revealed that in the Makran subduction zone, oceanic lithosphere has continuously subducted to depths of at least 450 km, while in the Zagros collision zone to the west, continental lithosphere has subducted no deeper than 300 km.
The Tears Have Been Progressing for Millions of Years
Study models indicate the ruptures have been advancing for several million years. The researchers write that while the two tears initiated independently, the intervening continental-oceanic boundary segment is progressively consumed as tearing advances, and this linkage is expected to eventually drive coalescence of the two tears.
Magma Fills the Gaps as the Tears May Eventually Meet
Hot magma is already filling some of the gaps caused by the ruptures, and researchers are now examining how the tears and their possible merging might affect volcanic activity in the region. The study notes that the coexistence of these two tearing modes provides a rare snapshot of the short-lived early transition from oceanic subduction to continental collision.
Questions About the Arabian Plate Ruptures
Unlike the horizontal rupture, which stems from rock density differences, the vertical tear probably initiated at the junction between the Makran Trench and a transform boundary and has propagated southward as the continental plate advances northward.
The horizontal tear in the Makran subduction zone has pushed oceanic lithosphere to at least 450 km deep, while the Zagros collision zone shows continental lithosphere subducting no deeper than 300 km.
Hot magma is already filling some of the gaps caused by the ruptures, but how the tears and their possible coalescence will affect volcanic activity in the region remains an open question for researchers.
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