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Geological Perspectives on Upstate Soils William A. Ranson Department of Earth & Environmental Sciences Furman University.

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Presentation on theme: "Geological Perspectives on Upstate Soils William A. Ranson Department of Earth & Environmental Sciences Furman University."— Presentation transcript:

1 Geological Perspectives on Upstate Soils William A. Ranson Department of Earth & Environmental Sciences Furman University


3 In Reality a Closed System 4.6 Ga After Formation! [From Press et al., 2004, Understanding Earth, 4th Edition]

4 Implications of a Closed System Earth Finite resources No “away” to throw things - all waste remains on Earth A change in one part of the Earth System eventually affects all parts of the Earth system

5 Atmosphere Hydrosphere Geosphere Biosphere

6 Global Commons = Natural Capital

7 Global Commons Clean Air Clean Water Energy Resources Mineral Resources Fertile Soil Biological Diversity

8 Soil A complex medium of: Clay minerals Al-Fe-hydroxides Bedrock fragments Humus Microorganisms Air Water

9 Pangaea at 290 Ma

10 Appalachian cross section


12 Rocks and Minerals of the Upstate: The Raw Materials for Soil Felsic Gneiss - feldspar, quartz, mica (biotite & muscovite), hornblende Schist - muscovite, biotite with minor feldspar and quartz Mafic Amphibolite - hornblende, feldspar Diabase - feldspar and pyroxene





17 Weathering of Rock Mechanical Ice wedging/frost action Exfoliation Vegetation Chemical Dissolution Hydrolysis Oxidation

18 Hydrolysis Feldspar+water+carbonic acid=>Clay+dissolved ions Oxidation Iron silicates+Oxygen=>Iron oxides/hydroxides Lack of glaciation means a thick accumulation of clay minerals and saprolite.

19 Climate - temperature, rainfall Bedrock Mineralogy Bedrock Structure/Faults/Fractures Topography Influences on Weathering & Soil Production

20 Products of Weathering Saprolite - in situ, chemically weathered bedrock; retains the structural features of the rock Soil - a complex medium of clay minerals+ Al-Fe-hydroxides+bedrock fragments+humus+ microorganisms+air+water

21 Photo of saprolite

22 Saprolite!

23 Rock and Mineral Chemistry Gneiss - K, Na, Al, Si minor Fe, Mg Schist - K, Al, Si, minor Na, Fe, Mg Amphibolite - Ca, Fe, Mg, Al, Si, minor Na, K Diabase - Ca, Na, Fe, Mg, Si

24 Soil Horizons


26 Soil pH and Plant Diversity Felsic Rocks with Rich A-Horizon Acidic Soils with pH~5.0-5.3 Lower Plant Diversity Mafic Rocks with Rich A-Horizon Circum Neutral Soils with pH~6.7-6.8 Greater Plant Diversity Mafic Rocks with Depleted A-Horizon Acidic Soils with pH~5.6-5.8 Lower Plant Diversity

27 Threats to Soil Erosion - physical removal by: Running water Wind Ice Bulldozer Degradation - physical or chemical changes to the soil that render it unviable Increased salinity Heavy application of fertilizers/pesticides/herbicides Removal of vegetation and exposure to sun

28 Influences on Erosion in the Upstate Naturally steep slopes and hillsides Hard, relatively impermeable silicate bedrock Temperate, humid climate=>abundant water & clay ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Urbanization=reduced permeable surface area Considerable agriculture Lack of riparian buffers Improper logging practices Road construction Less than optimal land-clearing practices


30 About 5.6 tons/acre/year or ~4 cm/100 years Average Rate of Soil Production in the US ~0.6 cm/100 years Average Loss of Soil in the US [US Soil and Water Conservation Service, 2002]

31 Along the Blue Ridge Escarpment steep slopes combined with hard, relatively impermeable gneisses result in a thin soil profile that is susceptible to mass movement. Mass movement is the slow to rapid down slope movement of soil and/or rock debris under the influence of gravity.

32 Glassy Mountain Development 1984

33 Mature Piedmont landscape

34 Average Annual Transport of Rock & Soil Wind erosion1.0 Glaciers4.3 Mountain building14 Oceanic volcanism30 Humankind42 Water53 Billion Tons [Source: Hooke, 1994]


36 a physical contaminant a chemical contaminant if laden with pesticide, herbicide, or fertilizer residue Eroded Soil

37 Careful land-use planning Better construction practices Better logging practices Riparian buffers for agriculture/grazing Terracing Strip cropping Alley cropping or agroforestry Windbreaks or shelterbelts Gully reclamation Conservation-tillage farming More soil/water conservation education and enforcement Some Obvious Solutions

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