When deciphering the history and future of landscape morphology, we focus on the evolution of ground surface elevation. A convenient unit to study this particular problem is the volume per area per time, which is often the unit that is used to present physical and total denudation rates. This unit, however, needs to be combined with the bulk density of rocks, sediments, and soils when the question is directed to the processes affecting the compositions of these materials that are involved in morphologic evolution of landscapes. Most notably, chemical weathering belongs to this group of processes. Though often ignored, the unit conversion from the elevation to mass changes also reveals the volumetric changes associated with chemical weathering (e.g., collapse or dilation). This is because significant differences in the bulk densities of soils, sediments, saprolites, and bedrocks can occur in association with chemical weathering and physical disturbance. Therefore, connecting the ground surface elevation changes to the volumetric changes of weathering profiles may help us better understand the production of porosities and fractures in weathering profiles, which are in turn critical controls over water pathways and residence time. Furthermore, the morphologic evolution of landscapes could be appreciated from the perspective of the soil’s mineral surface reactivity, when we follow the evolution of minerals’ specific surface area as the minerals transit from their bedrock sources, becoming part of an upland soil, moving downslope into depositional lands, and eventually entering a fluvial networks that link the lands with ocean. In other words, minerals’ reactivity to the surrounding geochemical environments and the minerals’ capacity to complex organic matter on their surface may significantly depend on their transport processes and pathways (ie., geomorphic processes). Therefore, some of the challenges in integrating geomorphology with its sister disciplines such as (bio)geochemistry, environmental chemistry, hydrology, and carbon cycle could be well characterized in the efforts to convert the units of key variables from volumes to masses to surface areas. To illustrate this proposal, we present data from the actively eroding hillslopes in the Feather River, Sierra Nevada, CA, Piedmont soils from PA, and forest soils in northern Minnesota.
Kyungsoo Yoo, St. Paul, Minnesota, USA, 55108-6028
Yoo, K., A.K. Aufdenkampe, B.A. Weinman, S.M. Mudd, C. Chen. (2010): Extending the Interdisciplinary Interfaces of Geomorphology by Changing the Units of Key Variables: From Volumes to Masses to Areas . Abstract EP43A-0749. AGU Fall Meeting, San Francisco, CA, December 13-17..