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Understanding Erosion Rates and Mountain Formation: The Dynamic Nature of Earth

Earth exhibits remarkably few craters despite a similar cratering rate to the Moon, primarily due to geological processes such as erosion. Erosion constantly reshapes landscapes with varying rates across different regions. For example, the Himalayas see rates of 2-3 km/Ma, while areas like the Atacama Desert experience much lower rates at 0.5 m/Ma. Continuous uplift in mountain ranges counteracts erosion, indicating that the Earth is a dynamic planet. This interplay between erosion and uplift is vital in understanding the persistence of mountain topography.

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Understanding Erosion Rates and Mountain Formation: The Dynamic Nature of Earth

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  1. Question: If cratering rate on Earth is same as our Moon, why are their so few craters preserved? Answer: Erosion

  2. Estimating natural 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.

  3. mm/y = m/Ka = Km/Ma Erosion Rate for Cascades ~ 0.05 – .25 Km/Ma

  4. Erosion Rate for Central France: 55 m/MA

  5. 1 t/ha/y => 30 m/Ma

  6. 1 mm/a = 1km/Ma

  7. Summary of Erosion rates • Himalaya: 2-3 m/Ky = 2-3 km/Ma • Eastern edge of Bolivian Altiplano: 3 km/Ma • Cascades: 300 m/Ma • Massif Central (France): 50 m/Ma • Atacama Desert (Chile/Peru): 0.5 m/Ma • Central Australia: 0.5 m/Ma

  8. Question If erosion can flatten mountain topography in only a few million years, why are there mountains at all?

  9. 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

  10. L = cA½ Channel length and drainage area

  11. Streamflow and drainage area… or River basins in Kentucky, USA, from Solyom and Tucker, 2004 Q = 0.0171*A0.9932 R2 = 0.9977

  12. Channel Width: Data from the Clearwater River, Washington State, from Tomkin et al., 2003. Q = 0.1335 * A0.9 W=4.2*A0.42

  13. W = b(AP)½ Should actually be discharge = Area x precipitation

  14. Precip Distance Spatially Variable Precipitation, Ellis, Densmore & Anderson, 1999

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