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Lecture 4a Soil Forming Factors

Lecture 4a Soil Forming Factors. * Parent Material * Climate Vegetation Topography Time Soils vary from place to place because the intensity of the factors is different at different locations. Soil Parent Materials.

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Lecture 4a Soil Forming Factors

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  1. Lecture 4aSoil Forming Factors • * Parent Material • * Climate • Vegetation • Topography • Time • Soils vary from place to place because the intensity of the factors is different at different locations.

  2. Soil Parent Materials • Residual - Soil formed from Bedrock. In Minnesota only the following are close enough to the surface to have a soil formed from them: • Sandstone • Limestone • Basalt • Granite

  3. Transported PM Soils Basalt & Gabbro Residual Soils Granite Sandstone Limestone

  4. Transported Parent Materials • Water - Rivers = Alluvium • Wind - eolian = sand or silt (loess) • Gravity = colluvium • Ice = Glacial Drift - all materials transported by ice or as a result of glacial activity alluvium

  5. A. Unsorted Glacial Materials • Glacial Till = unsorted deposits left by the retreating ice - made of : sand, silt ,clay, gravel, boulders, stones and large rocks.Till can be deposited into various shapes • Moraines- ground moraine - gently rolling plain • End moraine - large hill or series of hills • Drumlins - low hill shaped by the ice

  6. Anatomy of a GlacierSteve Dutch- Natural and Applied Sciences,University of Wisconsin-Green Bay

  7. Sorted Parent Materials • Water Outwash - often stratified sand or sand and gravel Lacustrine - lake deposited - silt or clay in texture - fine sediments - flat terrain, former lake bottom Lake Plain Beach Ridge

  8. Wind • Loess - wind blown silt (.05 - .002mm diameter) • Sand - dune sand - wind blown sand (eolian sand)

  9. Dyad – Where have you seen evidence of glaciers …. One for each person.. VIDEO OF GLACIERS

  10. Soil forming Factors • Parent Material • Climate • Vegetation • Topography • Time • Soils vary from place to place because the intensity of the factors is different at different locations.

  11. Soil Forming Factor - Climate • Temperature - Warmer = Faster Cooler = Slower --> Soil Development • Precipitation - higher rainfall = greater leaching • Leaching Zone - determined by location of CaCO3 in the soil profile • Leaching Index = Pcpt. - Evapotranspiration= the amount of effective rainfall that can cause soil leaching

  12. Temperature & Precipitation vs. Clay, Depth to Carbonates & OM

  13. The End Sandstone Bedrock - a residual parent material

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