GEOG 1F91 Lecture Notes - Lecture 6: Eramosa Karst, Shear Strength, Slope Stability

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18 Feb 2016
Department
Course
Professor
Lecture 6
Chemical Weathering
Rocks form at depth
Temp/pressure =unstable at surface
Decay of rock forming minerals – h2o temp, o2, mild acids
Vary with climate (temp and moisture)
Chemical Weathering: oxidation
Metals combine with oxygen (water) to form oxides
E.g. rusting Fe --- Fe2O3
Chemical Weathering: pH scale
Measure how acidic/basic a substance is – concentration of H
ions
Scale 0-14- each step = 10x change
E.g. pH of 4 is 10x more acidic than 5
Chemical Weathering: carbonation/ solution
Mineral dissolves into solution
E.g. salt, sugar or cabon dioxide
Carbonation
Water + carbon dioxide= carbonic acid
Dissolve Minerals
Carry away in solution
Chemical weathering: Hydrolysis
Hydrolysis – water added to mineral structure
-Change to new mineral compound
Hydration
Water combines with minerals
Expansion –weakness
Acid deposition
Emissions – SO2 =sulphuric acid NO2= nitric acid
Long distance transport
More than just rain
Wet deposition
Limestone solution by groundwater
Karst landscape (carbonate bedrock)
Acidic rainwater-in:ltrate soluble rock
Enlarge joints- create caves
Karst: sinkholes
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