Stretchy Slabs in Deep Earth
A new paper out in Nature Geoscience, led by Caroline Eakin, suggests that subducting slabs may not be as strong as we think, but instead may be relatively weak and deform easily. When new oceanic plates form at mid-ocean ridges it is thought that they “freeze-in” a certain crystal fabric whereby seismic waves travel faster in the direction of plate spreading. Previously it was assumed that this inherent frozen fabric is preserved within the cold strong slab as it subducts into the deep Earth. New evidence from seismic anisotropy within the subducting Nazca slab beneath South America however shows that this original fabric has long since disappeared and has been replaced by a new fabric. This new fabric appears to be have been induced by stretching as the slab is bent out of shape during subduction.