Estimating erosion rates

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Estimating erosion rates

• Accumulation of sediment versus time in alluvial
  fans.
• Ratio of cosmogenic isotopic creation rate/unit
  area to concentration/unit volume of sediments.
• Closure age of exposed minerals at surface plus
  increase of temperature with depth.

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Erosion Rate for Cascades 0.05 .25 Km/Ma
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Erosion Rate for Central France 55 m/MA
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1 t/ha/y gt 30 m/Ma
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1 mm/a 1km/Ma
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Summary of Erosion rates

• Himalaya 2-3 m/Ky 2-3 km/Ma
• Eastern edge of Bolivian Altiplano 3 km/Ma
• Cascades 0.3 km/Ma
• Massif Central 50 m/Ma
• Atacama Desert (Chile/Peru) 0.5 m/Ma
• Central Australia 0.5 m/Ma

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Question If erosion can flatten mountain
topography in only a few million years, why are
there mountains at all?
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Question If erosion can flatten mountain
topography in only a few million years, why are
there mountains at all? Answer Uplift is
continuous Implication Earth is a dynamic
planet
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W b(AP)½
Should actually be discharge Area x
precipitation
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