Geology

Flat Weathering

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Science  25 Jan 2013:
Vol. 339, Issue 6118, pp. 374
DOI: 10.1126/science.339.6118.374-c

Weathering of silicate minerals is a primary sink for atmospheric CO2. Much of the focus of recent research has been on the erosion of mountain belts, but as shown by Willenbring et al., areas of lower relief may be more important in global budgets. These authors compiled measurements of denudation rates based on 10Be concentrations in sediments. 10Be is produced by the bombardment of near-surface minerals by cosmic rays; it builds up in stable landscapes and thus tracks both physical erosion and chemical weathering. The authors compared the denudation rates versus overall landscape slopes across nearly 1000 river basins globally and used these data to extrapolate to other areas. Overall, they calculate that about 5 gigatons of sediments are produced each year. Because most of Earth's surface has modest or lower slopes, even though the denudation rate there is relatively low (<10 mm per 1000 years), these areas contribute most of the sediment to the oceans. Thus, these areas, not mountains, may dominate the long-term drawdown of atmospheric CO2.

Geology 10.1130/G33918.1 (2013).

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