Compressive stresses in the lithosphere in an opening ocean basin induce mixing and damage in mineral grains, thereby generating vertical weak bands that facilitate the initiation of subduction, a study finds. Plate tectonics is driven by subduction - the sinking of old, cold, heavy lithospheric plates into the Earth's mantle. Subduction often occurs at boundaries between the sea floor and continents, but that is where the lithosphere is strongest and least likely to deform. To address the mystery of how subduction is initiated, David Bercovici and Elvira Mulyukova developed a theoretical model of the lithosphere in an opening ocean basin undergoing simple ridge-push stress, which is compressive in the direction of plate motion. Horizontal compressive stresses cause mineral grains to mix and diminish in size, thereby generating vertical weak bands in the lithosphere. Bands of mixing and weakening occupy a large portion of lithosphere after approximately 100 million years. These weak zones are susceptible to vertical shear and bending associated with subduction initiation. According to the authors, the findings may provide insight into why plate tectonics exists on Earth but not on other planets.
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Article #20-11247: "Evolution and demise of passive margins through grain mixing and damage," by David Bercovici and Elvira Mulyukova.
MEDIA CONTACT: David Bercovici, Yale University, New Haven, CT; tel: 203-432-3168; email: < david.bercovici@yale.edu >
Proceedings of the National Academy of Sciences