Exploring weathering and regolith transport controls on Critical Zone development with models and natural experiments

Evidence for climatic and hillslope‐aspect controls on vadose zone hydrology and implications for saprolite weathering

“…Larger water fluxes through model hillslopes after a large, sustained recharge pulse may help explain differences in soil depth and weathering intensity between the north‐ and south‐facing slopes observed at Gordon Gulch. The north‐facing slope has deeper soil, more weathered saprolite, and greater depth to fresh rock compared to the south‐facing slope (Befus et al ., ; Anderson et al ., ; Kelly, ). Sustained elevated water content on hillslopes following a concentrated recharge pulse suggests that more chemical weathering may occur on hillslopes with a seasonal snow pack compared to hillslopes with intermittent snow.…”

“…The depth to the weathered bedrock and the thickness of saprolite is greater on the north‐facing slope of Gordon Gulch than on the south‐facing slope. Soil is also thicker on the north‐facing slope and the underlying saprolite appears more intensely weathered (Anderson et al ., ). Experiments to determine the tensile strength of rock cores recovered from 1–2 m depth on the north‐ and south‐facing slopes show that rock is weaker and presumably more weathered on the north‐facing slope than on the south‐facing slope (Kelly, ).…”

Unsteady late Pleistocene incision of streams bounding the Colorado Front Range from measurements of meteoric and in situ 10Be

“…During glacial times, high rates of either transformation of rock to regolith, or downslope regolith transport, or both could be invoked to explain the high rates at which sediment is delivered to the streams that flow onto the High Plains. Likely governors of these rates include the density and character of vegetation cover, which in turn can modulate both release of rock from bedrock into soil, and move sediment downhill by root growth and decay; and changes in the thermal regime that control the efficiency of both frost cracking and periglacial hillslope processes such as frost creep and solifluction [ Anderson et al , 2011].…”

“…We emphasize that not all of the streams associated with these surfaces have glaciated headwaters. In these areas, the glacial climates may instead lead to an increase in frost‐cracking and periglacial hillslope processes that in turn lead to enhanced sediment transport rates and higher sediment supply to the range‐bounding basin [ Anderson et al , 2011].…”

How Porosity Increases During Incipient Weathering of Crystalline Silicate Rocks

“…A long history of geochemical research has helped elucidate the macroscale behavior of weathering processes, including quantifi cation of rock weathering rates and soil production and factors that infl uence these rates (e.g., Merrill 1906;Berner 1978;Pavich 1986;Nahon 1991;Blum et al 1994;Drever and Clow 1995;Clow and Drever 1996;Anderson et al 2002Anderson et al , 2011Gaillardet et al 2003;Amundson 2004;Bricker et al 2004;Burke et al 2007;White 2008;Brantley and Lebedeva 2011;Hausrath et al 2011). However, until recently the very earliest pore-scale physical changes associated with incipient weathering were largely unstudied.…”