1145962_cover.jpg (IMAGE) Arizona State University Caption Surface topography and bathymetry around South America (top) overlays variable topography on Earth's upper mantle phase transition discontinuities at 410 km (middle) and 660 km (bottom) depth (topography is contoured in 2 km increments). Topography on the discontinuities is used to characterize compositional and thermal heterogeneity within the Earth. In this region, the large depressions are related to subduction processes, whereby cold oceanic lithosphere descends into the mantle. Credit Nicholas Schmerr, Edward Garnero, Arizona State University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.