Soil Geomorphology in the United States.

Soil geomorphology (the study of soils on the landscape and soils as indicators of the past) has its origins in both the "state factor approach" to soils (pedology) and in soil stratigraphy (Quaternary geology). The state factor approach had geologic origins in Russia in the 1870s to 1890s with the work of V.V. Dokuchaev, N.M. Sibertsev, and K.D. Glinka. This paradigm took root in the U.S. in the 20th century through the efforts of E.W. Hilgard, G.N. Coffey, and, especially, C.F. Marbut, who also distanced pedology from geology. From the late 1800s into the 1900s, Midwestern glacial geologists, most prominently T.C. Chamberlin, F. Leverett, and M.M. Leighton, recognized buried soils in stratigraphic sequences and used them for correlation and for inferring interglacial stages. By the 1930s and 1940s, H. Jenny formalized the state factor approach to understanding soil genesis, the USDA began soil erosion studies, and J. Thorp and K. Bryan were integrating Quaternary geology and the factors into pedologic research on buried soils and landscape evolution. The WWII years saw unprecedented integration of pedologists, geomorphologists, and Quaternary geologists in the Military Geology Unit of the USGS. In the post-war years, many of these geologists went on to use soils in their stratigraphic and geomorphic research for the USGS (e.g., C.B. Hunt, G.M. Richmond, R. Morrison). Beginning in the 1950s and continuing into the 1970s, the USDA, under the direction of R.V. Ruhe, sponsored a series of landmark studies that expressly teamed pedologists and geomorphologists in a series of soil-geomorphic projects. The USGS and USDA work inspired formalized teaching and research in soil-geomorphology such as P.W. Birkeland's modification of the state factor approach to investigate soils in the past, and USGS research on chronosequences.