Landscape scale linkages in critical zone evolution

The character of the critical zone reflects the effects of weathering and erosion over time. Weathering processes push a weathering front into fresh rock and continually modify material within the critical zone, generating saprolite and soils, while erosion processes mobilize regolith and remove mass. These processes respond to climate, but also to boundary conditions that may be set by processes occurring elsewhere. We use the Boulder Creek Critical Zone Observatory (BcCZO) to illustrate landscape scale linkages driving critical zone evolution through feedbacks that work both upstream and downstream. We focus on: (1) downstream transfer of sediment and water; and (2) changes in river base-level. The essential point is that regions are linked by transfers of mass and by boundary conditions set by external processes. These linkages result in lags in evolution of critical zone profiles in distant parts of watersheds to drivers such as climate and erosion. Thus, history influences the character of the critical zone.