1. 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.

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

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

5. 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

6. 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.

7. 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

8. Anatomy of a Glacier Steve Dutch- Natural and Applied Sciences, University of Wisconsin-Green Bay

9. A Typical Glacial Advance and Retreat

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

11. If Accumulation Exceeds Ablation, the Glacier Advances

12. If Ablation Exceeds Accumulation, the Glacier Retreats

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

14. A Typical Glacial Advance and Retreat

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

16. Maximum extent of Wisconsin Glaciation

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

18. Minnesota Glaciations

19. Minnesota Glaciations

20. 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

21. 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

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

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

24. 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.

25. 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

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

27. Leaching Index for Minnesota LI = Precipitation - Evapotranspiration

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

29. Sandstone Bedrock - a residual parent material
The End
Sandstone Bedrock - a residual parent material