Silicate weathering: Where have we come in the last 50 years?

In the context of the Geochemical Society’s fiftieth anniversary I shall review how ideas on chemical weathering have evolved and where I think the field is going. The field received a large boost in the 1980s and early 1990s in conjunction with public concern over acid deposition. The objective here was to develop quantitative predictions of how acid neutralization by mineral weathering would respond to different levels of acid deposition from the atmosphere. It led to integrated quantitative models of how various ecosystem processes affect surface water chemistry. There was also extensive laboratory work on mineral dissolution kinetics. We learned a great deal about mineral dissolution mechanisms in laboratory systems but we have been remarkably unsuccessful to date in using laboratory results to model quantitatively weathering processes in the field. In the near future we should see new insights into mineral dissolution mechanisms from atomic-scale imaging and various spectroscopies. In the past decade, the emphasis has been on role of weathering in the global carbon cycle, particularly as a long-term control on the CO2 concentration and hence temperature of the atmosphere. This brings in the role of tectonic uplift, physical erosion, and various ecosystem processes, including human intervention, in CO2 consumption by chemical weathering. New insights are coming from the innovative use of various isotopic systems. Understanding of the role of chemical weathering in environmental processes cannot come from study of weathering processes in isolation. Weathering rates are strongly affected by ecosystem processes, by physical processes, particularly erosion, and by hydrologic processes. We need an integrative approach in order to understand how our planet functions. Does life leave a topographic signature on Earth