SEDIMENT TRANSPORT IN THE MCMURDO DRY VALLEYS, ANTARCTICA

The McMurdo Dry Valleys of Antarctica have a hyper-arid, cold, polar desert climate today, which results in some of the lowest erosion rates on Earth. Previous research suggests that a polar desert climate has persisted in the Dry Valleys for millions of years, and that sediment erosion and transportation rates remained low during this time. Even though the erosion rates are very low, the downslope transportation of sediments is evident in the Dry Valleys. One indication of sediment mobility is the characteristic sediment convergence above and divergence below boulders (0.5-3m in diameter) that are lodged in the hillslope. The downslope movement of material is apparent because the boulder acts as an obstruction to the matrix (silt, sand, pebbles) moving around it, which indicates that the boulder is stationary or moving more slowly than the surrounding debris.

To determine and quantify the processes involved in downslope sediment transportation in the Dry Valleys we use a finite difference sediment transport model based on the local slope dependent transport rate. To guide our modeling effort, we made topographic surveys in the field at ten centimeter increments around boulders with the characteristic build up of material around them. We are exploring the potential role of thermal contraction and expansion in a moisture-free soil as a process that promotes the downslope movement of a matrix.

Very little is known about how a landscape can remain stable for millions of years. Our goal is to understand and determine the processes and rates of sediment transport in a polar desert climate. This will aid us in resolving the apparent contradiction between suggested landscape stability and the observed indicators of the downslope movement of sediments.