rare earth oxides
These rare-earth oxides are used as tracers to determine which parts of a watershed are eroding. Clockwise from top center: praseodymium, cerium, lanthanum, neodymium, samarium, and gadolinium. Image Number D1115-1. Photo by Peggy Greb, USDA-ARS.
Image Dimensions: 2700 x 1754
Location Taken: USSource:
USDA Agricultural Research Service Image Gallery