1. Chapter 11 - Soil Resources
it’s just dirt!

2. I. Soils: Products of Weathering
Soil  loose surface materials composed of weathered rock and mineral materials with variable amounts of organic matter
can support growth of plants
resting upon bedrock

4. Soils B. Residual vs. Transported Soils
Residual  formed “in situ” via weathering
Transported  formed elsewhere & deposited
alluvial, glacial, wind deposited
Example  loess soils & the Palouse

6. Soils
C. Soil Profile  vertical section of soil from surface to bedrock D. Soil Horizons  layers of soil (in profile) distinguished by color, texture, structure & composition

7. Soil Profile & Horizons

9. Soils E. Color & Texture 1. Color  indications of composition
Higher organics  darker color
Higher iron  redder color
Higher calcium or salts  whitish colors

11. Soils 2. Texture Grain sizes  Sand, silt, clay
often determines physical properties
-looseness/compactibility
-drainage & moisture retention

12. Soil Texture

13. Soils F. Soil Classification  “a pain in the _____!”
Early attempts  Zonal classification based on climate controls, temp. vs. rainfall

14. Classification
“modern” classification  soil science vs. engineering classification
Classified by physical characteristics
14,000 soil “series” now recognized!
Forgetaboutit!

16. II. Soil Resources & Problems
Soil  a renewable resource?
Soil Erosion
U.S. farmlands, 1992 = 2 billion tons
~4.8 tons/acre, average annual loss
~1.6 tons/acre, avg. annual formed
accumulated side effects!

17. Soil Erosion
Styles of erosion
Sheet
Rill
Gullying
Wind

22. Global Soil Erosion

23. II. Soil Resources & Erosion
B. Causes
Natural
Human-related 
Overgrazing & bad agriculture techniques
Deforestation
Recreational activities

27. Case Study: Palouse soil erosion
Palouse region, eastern WA  Go COUGS!
Loess soil  wind blown silt

28. Case Study: Palouse soil erosion
Formed during Pleistocene glaciation
Several hundred feet thick in places
High fertility, important physical properties & agricultural potential
Interesting historical ramifications

29. Palouse soil & erosion issues

30. Palouse soil erosion Up to 25 tons/acre/year erosion
Highest rates  200 tons/acre/year!  steeper slopes
~.17 inches/year  8.5 inches/50 years
*Farm near Thornton, WA  4.5 feet of soil lost in less than 50 years!

31. Palouse soil erosion 20% + of cropland eroded to subsoils 
Decreased yields
Increased fertilizers needed, decreased soil pH (acidifying)
Dirt: The Erosion of Civilizations, 2007, David Montgomery, University of California Press

32. Palouse soil erosion Contributing factors to Palouse erosion?
Intensive mechanized farming  tractor plowing began (1930’s)
Plowing on hillsides
Rain on freshly plowed land  rilling/gullying
Wind storms  age-dated lake cores  4-fold increase in erosion w/modern plowing

33. II. Soil Resources B. Soil Contamination Industrial pollution
Salinization

34. II. Soil Resources & Problems
C. Expansive Soils
expansion upon water saturation
shrink when dried out
$6 billion/year damages
Clay-rich soils
Why is clay the culprit?

37. Expansive Soils Mitigation How to deal with expansive soils?
Hire a geoengineering firm & spend lots of $$$$ fixing the problem after, or…..
Spend less $$$$$ before
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39. II. Soil Resources & Problems
D. Settlement
Non-uniform settling and compaction 
Differential settlement
Soils with strength & cohesion differences
READ  Leaning Tower of Pisa

40. II. Soil Resources & Problems
E. Permafrost
Permanently frozen ground
Northerly, polar latitudes
Freezing depth (winter) exceeds thaw depth (summer)

43. Case Study: The Trans-Alaska Pipeline
Prudhoe Bay (North Slope) oil fields
Discovered 1968 – “world class field”
Remote location, cold water port
No oil tankers! How to get the oil to market?
1300 km (~800 mi) pipeline

44. Trans Alaskan Pipeline
B. Pipeline Route
Prudhoe Bay to Valdez (Prince William Sound)
Inaccessible wilderness
2 mountain ranges, large river crossings
LARGE areas of permafrost

45. Trans Alaskan Pipeline
C. Planning Studies, Designs, & Cost
Prefeasibility studies  mapping & drilling bedrock vs. permafrost
Identified faults  active Denali fault
Permafrost dilemma  oil needs to 65oC in 48” pipeline
*1/2 of pipeline must be above ground  why?

46. Trans Alaskan Pipeline
Above ground design MUST:
Dissipate heat away from ground
Allow for fault movements & earthquakes
Vertical support members (down to 60’) w/heat exchangers & refrigerant
Horizontal beam & jiggle joints for magnitude 8 quake

47. Building on permafrost

51. 2002 Denali Fault Earthquake
7.9 magnitude
Remote section on Denali fault
Movement along fault ~14 feet!
Design specifications withstand quake!