The Hawaiian islands are the surface manifestation of a so-called mantle plume. According to one idea, these plumes are recycled slabs of material that was originally created at mid-ocean ridges and then subducted deep into the mantle. An analysis of osmium isotope ratios in Hawaiian lavas not only supports the idea but — contentiously — concludes that the slab material is little distorted despite having undergone a billion years of mantle convection.
