In a report published in the Sept. 24 issue of Science, current and former graduate students Lowell Miyagi, Waruntorn (Jane) Kanitpanyacharoen, Pamela Kearcher and Kanani Lee (Lowell and Kanani are now at Yale), working with faculty member Rudy Wenk, describe diamond anvil high pressure deformation experiments performed at ALS on the enigmatic mineral phase postperovskite MgSiO3. They observe strong mineral alignment due to intracrystalline dislocation movements that can be captured in inverse pole figures. This alignment, when applied to lowest mantle rheology, predicts fast S-waves to be polarized parallel to the core mantle boundary which is just what seismologists observe. Linking microscopic processes to macroscopic geodynamics provides new insight about the deep earth. Read Press Release from UC Berkeley.