HR: 1340h
AN: H43D-0518    [Abstracts]
TI: The control of salt flat topography by water-mediated halite transport - A case study at the salar de Uyuni, Bolivia
AU: * Borsa, A A
EM: aborsa@ucsd.edu
AF: Scripps Instution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92037 United States
AU: Bills, B G
EM: bbills@ucsd.edu
AF: NASA Goddard Space Flight Center, GSFC Planetary Dynamics Laboratory, Greenbelt, MD 20771 United States
AU: Minster, J
EM: jbminster@ucsd.edu
AF: Scripps Instution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92037 United States
AB: The salar de Uyuni is a massive salt flat in the Bolivian Altiplano that is periodically inundated by a shallow lake during the rainy season and whose water table never drops far beneath the salt surface. Using available gravity data, we have confirmed that the entire salar surface lies within several centimeters of the equipotential surface to which the water table conforms. This close correlation appears to be due to the control of salar topography by the water-mediated salt transport. The salar surface is almost pure halite (sodium chloride), which forms a tough crust that resists mechanical erosion by wind. Halite is readily transported in aqueous solution, however, which means that water plays a critical role in the evolution of the salar surface. Dissolved salt is transported by the flow of surface and subsurface water until it is precipitated by evaporation, with complicating effects due to spatial and temporal variation in dissolution rates, saturation state, evaporation, and wind and Coriolis forcing on overland flow. We separately consider the effect of salt transport for groundwater, surface runoff and rainwater, focusing most of our attention on direct precipitation because of its large associated water flux. We develop a coupled overland-flow/salt-transport model to show how the action of rain alone is sufficient to preserve the equipotential shape of the salar surface despite constant non-equilibrium forcing due to tectonics and isostatic rebound.
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 1824 Geomorphology: general (1625)
DE: 1850 Overland flow
SC: Hydrology [H]
MN: Fall Meeting 2005