Evolution of the Rio Grande Valley New Mexico State University 1991 Video furnished by Media Productions, New Mexico State University. Noncommercial use only. For over half a century, scientists have been studying the soils of the Rio Grande River Valley, one of the first desert river valleys to ever be decoded. The knowledge and techniques developed there are used by researchers all over the world as a basis for understanding other desert soils and landscapes. Leland H. Gile, a soil scientist from the Desert Soil Geomorphology Project, demonstrates how the presence of calcium carbonates helps determine the progressive aging of terraces within the river valley. Dr. Greg Mack, a researcher at New Mexico State University, explains why volcanic ash provides another clue to the age and development of area landforms. Learn how scientists used their knowledge of the valley's climate history and the draining of Lake Cabeza de Vaca, together with various soil dating techniques to decode this region. Join geologist, Debbie Caskey, as she turns back time and guides us through the evolution of the Rio Grande Valley.