For more than a decade, we have been using cosmogenic nuclides to estimate the rate at which bare bedrock surfaces erode. Our work has been focused on quartz-bearing rocks in which 10-Be and 26-Al can be measured. We've sample extensively across climatic gradients in Namibia, Australia, and North America. The Australian rock surfaces are the most stable, perhaps reflecting the long-term tectonic stability of the landscape. The Namibian surfaces are eroding more rapidly at rates similar to those in North America. As a group, the bedrock data indicate that even in arid and hyper arid environments, bedrock landforms are dynamic, changing (if only slowly) over time. Only the Australian surface show a distinct positive relationship between lowest measured erosion rate and mean annual precipitation.

This research has been supported by the National Geographic Society and NSF.

Relevant Publications:

• Bierman, P. (1994) Using in situ cosmogenic isotopes to estimate rates of landscape evolution: A review from the geomorphic perspective. Journal of Geophysical Research (special issue on Tectonics and Topography), 99, B-7, 13,885-13,896.
   
• Bierman, P. and Turner, J. (1995) 10Be and 26Al evidence for exceptionally low rates of bedrock erosion and the likely existence of pre-Pleistocene landforms. Quaternary Research, 44, 378-382 and subsequent comment and reply Quaternary Research, 48, 386-389.
   
• Schroeder, P.A., Nathan D., Melear, N.D., Bierman, P.R., Kashgarian, M., and Caffee, M.W., (2001) Apparent gibbsite growth ages for the regolith in the Georgia Piedmont. Geochimica et Cosmochimica Acta., 65 (3) p 381-386.
   
• Bierman, P. and Caffee, M. (2002) Cosmogenic exposure and erosion history of ancient Australian bedrock landforms. Geological Society of America Bulletin. v. 114; no. 7; p. 787–803; review in Science, v. 297 issue 5579, p. 159.
   
• Bierman, P. and Caffee, M. (2001) Steady state rates of rock surface erosion and sediment production across the hyperarid Namib desert and the Namibian escarpment, southern Africa. American Journal of Science. v. 301, (4-5), p. 326-358.
   
• Bierman, P. R. and Nichols, K.K. (2004) Rock to sediment - Slope to sea with 10Be - Rates of landscape change, Annual Review of Earth Science. v. 32. p. 215–255.