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Slides for Weathering and Soils | EAS 101, Study notes of Environmental Science
Material Type: Notes; Professor: Kirschner; Class: Earth's Dynamic Environment I; Subject: Earth & Atmospheric Sciences; University: Saint Louis University; Term: Unknown 1989;
Typology: Study notes
2009/2010
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Quote of Day
Never let the fear of striking out
get in your way.
George "Babe" Ruth
http://www.baberuth.com/
Babe Ruth led the American League in home runs 12 seasons ,
but he also struck out 16% of the time!
Chapter 6
Weathering and Soils
(from Brady and Weil “The Nature and Properties of Soils”
http://www.dailyweeder.com/wp-content/uploads/fertilizer.jpg
Factors controlling soil formation
- Parent material composition
Some soils create better soils than others; for example, granitic materialcreates good soils while quartz-dominated beach sands create thin, poor soils
controls rate of weathering / soil formation
influences chemistry of soil and soil moisture, and thus the type andabundance of plants (e.g., grapes) that can grow in the soil.
“terra rosa” soil developed from limestoneproduces excellent red wines on LimestoneCoast of South Australia
http://highbank.com.au/photogallery.html
Book on the importance of differentsoils in determining quality / kind ofwine produced in France.
http://images.amazon.com/images/P/1891267221.01.LZZZZZZZ.jpg
- Time
Amount of time for soil formation varies for differentsoils depending on geologic and climatic conditions
With really long times, soils generally become redderdue to relative increase in iron, contain more clays,have lower pH, and fewer nutrients (less fertile)
Average global rate of growth is ~1 cm/180 years
Info and photos from http://www.soils.agri.umn.edu/academics/classes/soil2125/doc/s2chap4.htm
Example
: Different age soils that developed
on sandy material adjacent to Lake Michigan
Layer leached of humus, iron,and enriched in CaCO
Layer enriched inhumus & iron
- Plants and animals
Influence the soil’s physical and chemical properties (e.g., amount ofhumus in soil)
- Topography
Steep slopes often have poorly developed soils
Optimum terrain is a flat-to-undulating upland surface
Poor environment for soil development
Good environment for soil development
Soil profile ¾
Soil forming processes operate fromthe surface downward
¾
Vertical differences are calledhorizons, zones, or layers of soil
O horizon – organic matte
r
A horizon – organic and mineralmatter
High biological activity
E horizon – little organic matter
Zone of eluviation (removalof fine particles) and leaching
B horizon – zone of accumulation
C horizon – partially alteredparent material
Unweathered parent material
Figure 6.
Soil erosion Natural rates of soil erosion depend on
Soil characteristics
Climate - high rainfall promotes erosion
Slope - steeper slopes have higher ratesof erosion
Type of vegetation
In many regions, soil erosion >> soil formation http://www.accessexcellence.org/BF/bf04/sarukhan/slides/saruk_img20.jpg
http://www.iqi.ru/indexes/Soil%20Erosion.jpg
Significant erosion of farmland
Deforestation
Subsequent erosion
http://www.geography.ndo.co.uk/images/forestloss1.gif
http://www.isd77.k12.mn.us/schools/dakota/dust.jpg http://www.mtnbrook.k12.al.us/tech/k6/dustbowl.gifhttp://www.sdcoe.k12.ca.us/score/dust/title.JPG
The “
dustbowl
” of the 1930’s caused great
hardship in the country and was due to 1) poor farming practices that encouragederosion of soil 2) drought conditions It’s effects were compound by the 1929 crashof the stock market and subsequent depression.
Good farming practice 1) contour plowing -
contours inhibit the flow of surface water downhill and thus
reduce the loss of soil downhill.
http://www.uwsp.edu/geo/faculty/ozsvath/images/contour%20plowing.jpg
http://extension.missouri.edu/explore/images/g01653art01.jpg
Good farming practice 3) Vegetative barriers –
densely planted, noncrop
vegetation in fields, along
fields, adjacent to roads and streams slow down water flow and thusinhibit soil loss off of the field.
In the field between corn rows
Along the edge of field
http://plantandsoil.unl.edu/croptechnology2005/UserFiles/Image/siteImages/P36LG.jpg
http://www.oh.nrcs.usda.gov/programs/Lake_Erie_Buffer/images/windbreak_hancock_co.jpg
Good farming practice 4) Windbreaks –
impede the flow of wind across the farm fields
and thus protect the soil from wind erosion.