Basalt alteration: Weathering processes, landscapes and oceans
Intervenant : Louis A. Derry
Critical Zone Observatories Program
Institut de Physique du Globe de Paris
Subaerial basalt weathering is quantitatively important in global geochemical cycles. A recent compilation of catchment scale weathering rates shows significant temperature dependence when active volcanic systems are excluded, as they often have contributions from hydrothermal activity. At local scales reactive transport modeling provides some insight into the processes that control basalt weathering. A study of a chronosequence in Hawaii suggest that partially saturated conditions, high soil pCO2, and organic acids are necessary to explain the development of observed weathering patterns over time. At the landscape scale, a characteristic of basaltic landscapes is the delayed development of a stream drainage network. A nascent approach that attempts to couple weathering and soil mechanical behavior shows some promise for explaining the transition to a dissected landscape, which leads to strong hydrologic and geomorphic feedback.