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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. Minnesota Glaciation • Ice left Minnesota-Iowa border about 12,000 YBP (years before present) • 40,000 YBP is the oldest glacial till in Minn. That is a soil parent material (SE Mn.) • 10,000 YBP ice left MN-Canadian border • Ice thickness = 1000 to 5000 ft. over the state • There were at least 4 advances of the ice and that complicates the history and the kinds of glacial parent materials. • Glacial till in Minnesota is not all the same.

  6. 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

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

  8. A Typical Glacial Advance and Retreat

  9. As long as Accumulation = Ablation, the Glacier Front Remains Fixed

  10. If Accumulation Exceeds Ablation, the Glacier Advances

  11. If Ablation Exceeds Accumulation, the Glacier Retreats

  12. Eventually, Material Trapped in the Ice Reaches the Terminus

  13. A Typical Glacial Advance and Retreat

  14. Continental Glacier Landforms Steve Dutch -Natural and Applied Sciences,University of Wisconsin-Green Bay

  15. Maximum extent of Wisconsin Glaciation http://geology.isu.edu/Digital_Geology_Idaho/Module12/extent.gif

  16. Minnesota Glaciations – 15,000 B.P.(before present) Superior Lobe advances to near Minnesota River

  17. Minnesota Glaciations

  18. Minnesota Glaciations http://mrbdc.mnsu.edu/mnbasin/flash/glaciers/glaciation_animation.html

  19. Glacial Tills of Minnesota • Superior Lobe Till - red in color, sandy in texture, acid, rocks of granite, basalt, and sandstone • Des Moines Lobe Till - gray or tan in color, loam to clay loam in texture, calcareous (free calcium carbonate present), rocks present- limestone and shale DesMoines Lobe Till Superior Lobe Till

  20. 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

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

  22. Dyad – Where have you seen evidence of glaciers …. One for each person.. VIDEO OF GLACIERS http://dsc.discovery.com/videos/discovery-project-earth-jakobshaven-glacier-retreat.html http://video.google.com/videosearch?q=glacier+melting&hl=en&emb=0&aq=5&oq=glacier+#q=glacier+extent&hl=en&emb=0&start=10 http://video.google.com/videosearch?q=glacier+melting&hl=en&emb=0&aq=f#q=glacier+melting+tourists&hl=en&emb=0

  23. 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.

  24. 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

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

  26. Leaching Index for MinnesotaLI = Precipitation - Evapotranspiration LI

  27. Leaching Index = 0 to 12 in Minnesota CaCo3 Zone LI = 2 LI = 4 LI = 8

  28. The End Sandstone Bedrock - a residual parent material

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