In Reality a Closed System 4.6 Ga After Formation! [From Press et al., 2004, Understanding Earth, 4th Edition]
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
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
Weathering of Rock Mechanical Ice wedging/frost action Exfoliation Vegetation Chemical Dissolution Hydrolysis Oxidation
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.
Climate - temperature, rainfall Bedrock Mineralogy Bedrock Structure/Faults/Fractures Topography Influences on Weathering & Soil Production
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
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
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
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
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]
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.