Chapter 11 - Soil Resources it’s just dirt!

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

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

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

Soil Profile & Horizons

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

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

Soil Texture

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

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

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!

Soil Erosion Styles of erosion Sheet Rill Gullying Wind

Global Soil Erosion

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

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

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

Palouse soil & erosion issues

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!

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

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

II. Soil Resources B. Soil Contamination Industrial pollution Salinization

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?

Expansive Soils Mitigation How to deal with expansive soils? Hire a geoengineering firm & spend lots of $$$$ fixing the problem after, or….. Spend less $$$$$ before http://web.mst.edu/~rogersda/umrcourses/ge 341/

II. Soil Resources & Problems D. Settlement Non-uniform settling and compaction  Differential settlement Soils with strength & cohesion differences READ  Leaning Tower of Pisa

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

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

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

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 flow @ 65oC in 48” pipeline *1/2 of pipeline must be above ground  why?

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

Building on permafrost

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