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Rapid Soil Production and Weathering in the Southern Alps, New Zealand

Science  07 Feb 2014:
Vol. 343, Issue 6171, pp. 637-640
DOI: 10.1126/science.1244908

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Weathering Heights

The production of soil is the result of chemical weathering of rocks and minerals. In regions where tectonic uplift brings fresh material to Earth's surface, erosion and weathering can accelerate. Using chemical tracers, Larsen et al. (p. 637, published online 16 January; see the Perspective by Heimsath) measured soil production rates of over 2 millimeters per year in New Zealand's Southern Alps, which are some of the fastest uplifting mountains in the world. Because chemical weathering consumes CO2, these rapid rates may over time influence global climate.

Abstract

Evaluating conflicting theories about the influence of mountains on carbon dioxide cycling and climate requires understanding weathering fluxes from tectonically uplifting landscapes. The lack of soil production and weathering rate measurements in Earth’s most rapidly uplifting mountains has made it difficult to determine whether weathering rates increase or decline in response to rapid erosion. Beryllium-10 concentrations in soils from the western Southern Alps, New Zealand, demonstrate that soil is produced from bedrock more rapidly than previously recognized, at rates up to 2.5 millimeters per year. Weathering intensity data further indicate that soil chemical denudation rates increase proportionally with erosion rates. These high weathering rates support the view that mountains play a key role in global-scale chemical weathering and thus have potentially important implications for the global carbon cycle.

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