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 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

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

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

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.

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

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

A Typical Glacial Advance and Retreat

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

If Accumulation Exceeds Ablation, the Glacier Advances

If Ablation Exceeds Accumulation, the Glacier Retreats

Eventually, Material Trapped in the Ice Reaches the Terminus

A Typical Glacial Advance and Retreat

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

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

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

Minnesota Glaciations

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

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

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

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

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

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 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

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

Leaching Index for Minnesota LI = Precipitation - Evapotranspiration

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

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