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This site is maintained by the MARGINS Office. Please share your comments and suggestions with us.
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Browse MARGINS-related
awards in reverse chronological order after start
date (most recent first):
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Quantifying how Climate Affects Long-Term Rates of Weathering, Erosion,
and Soil Development
| MARGINS Focus Area |
Source-to-Sink |
| NSF Org |
EAR |
| Latest Amendment Date |
August 30, 2000 |
| Award Number |
0000999 |
| Award Instrument |
Standard Grant |
| Program Manager |
H. Richard Lane
EAR DIVISION OF EARTH SCIENCES
GEO DIRECTORATE FOR GEOSCIENCES |
| Start Date |
September 1, 2000 |
| Expires |
August 31, 2002 (Estimated) |
| Expected Total Amount |
$275,000 (Estimated) |
| Investigator |
James W. Kirchner
(Principal Investigator current) |
| Sponsor |
U of Cal Berkeley
Berkeley, CA 94720 |
| NSF Program |
1571 GEOLOGY & PALEONTOLOGY |
| Field Application |
0000099 Other Applications NEC |
| Abstract |
Physical erosion and chemical weathering are interdependent processes
that sculpt mountainous landscapes, regulate the composition of
soils, deliver sediment and solutes to aquatic habitats, and, over
long timescales, help regulate global climate. Until recently, long-term
rates of erosion and chemical weathering have been difficult to
measure. As a result there is presently no clear consensus about
how erosion and weathering affect the evolution of landscapes, soils,
aquatic habitats, and climate. Recent advances now permit long-term
average rates of physical erosion and chemical weathering to be
inferred from the chemical composition of eroding sediment in watersheds.
The concentrations of cosmogenic nuclides (26Al and 10Be) can be
used to measure long-term rates of erosion. Chemical weathering
rates can be inferred from erosion rates by comparing the concentrations
of insoluble elements (such as Zr and Nb) in rocks and soils, which
reflect the fraction of erosion that is accounted for by chemical
weathering. This project will measure how chemical weathering rates
vary with climate and physical erosion rates. Preliminary results
show that climatic effects on weathering rates are small compared
to erosional effects. However, the climatic effects are measurable,
when the effects of erosion are explicitly accounted for. To expand
on these results, six sites have been selected that span a wide
range of climates (4 to 24 C in temperature; 10 to 420 cm/yr in
precipitation). To minimize effects of variations in bedrock weathering
susceptibility, this study will focus exclusively on granitic bedrock.
At each of the six sites, 5 small watersheds will be selected, and
samples of stream sediment, bedrock, and hillslope soils will be
collected for analysis. Cosmogenic nuclide concentrations in the
stream sediment will be used to measure long-term erosion rates.
The fraction of erosion that is accounted for by chemical weathering
than will be inferred by comparing the bulk chemical composition
of soil and bedrock. This project will quantify how long-term rates
of weathering and erosion vary with climate while, for the first
time, explicitly measuring how chemical weathering and physical
erosion interrelate. These results should contribute to better models
of nutrient cycles and long-term climatic evolution, more accurate
assessments of sediment and solute delivery to aquatic ecosystems,
and a more quantitative understanding of soil development and landform
evolution. |
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