29 March 1996
Vol 271, Issue 5257

About The Cover

Optical micrograph (crossed polarizers) showing parallel dark rods of FeTiO3 (up to 20 micrometers long) that precipitated from solution in the mineral olivine during tectonic transport of a piece of mantle to a location high in the Swiss Alps. These rods formed under high pressure at depths greater than 300 kilometers, indicating profound subduction of continental rocks after the collision of Africa and Europe and their return to the surface carrying this piece of mantle. See page 1841 and News story on page 1811. [Image: L. Dobrzhinetskaya, H. W. Green II, and S. Wang]