An international research group led by Dr. Takayuki Ishii from HPSTAR and Okayama University, Institute for Planetary Materials, has precisely determined the temperature dependence of the high-pressure phase transition pressure of a mantle mineral of pyrope garnet to bridgmanite plus corundum (post-garnet transition) which may well explain the puzzling dynamics of subducting slabs and upwelling plumes observed seismically in the upper part of the lower mantle.