WEATHERING

I. Introduction

II. Types of Weathering A. Mechanical/Physical B. Chemical

Mechanical/Physical 1. Thermal Expansion and Contraction

2. Ice Wedging/Frost Action Water expands 9% when it freezes 30,000 psi

3. Exfoliation

6/19/2018

4. Action of Organisms

Biological “Critters” Burrowing animals Humans

II B. Chemical Weathering 1. Factors: A. Type of Rock or Mineral

B. Amount of Surface Area

C. Presence of Moisture

D. Effects of Organisms

E. Air and Water Pollution Sulfur = acid rain

II B. Chemical Weathering 2. Mechanisms of Chemical Weathering

A. Solution“the dissolving of a rock” CO2 + H2O = H2CO3 Carbon Carbonic Acid Dioxide

A. Solution“the dissolving of a rock”  CO2 + H2O = H2CO3 Carbon Carbonic Acid Dioxide H2CO3 + CaCO3 = Ca+ + 2HCO3- Carbonic Limestone Bicarbonate Acid

A. Solution“the dissolving of a rock” More recently…..   2SO2 + 2H2O + O2 = 2H2SO4

A. Solution“the dissolving of a rock” More recently…..   2SO2 + 2H2O + O2 = 2H2SO4 Sulfur Sulfuric Dioxide Acid

B. Hydration “chemically adding water to a rock” CaSO4 + 2 H2O = CaSO4 * 2 H20 Anhydrite Gypsum

C. Hydrolysis “converting a silicate mineral into a clay via water” 2KAlSi3O8 + 2 H2CO3 + H20 = Orthoclase Carbonic Acid Water   Al2Si2O5(OH)4 + 2K+ + 2HCO3- + 4 SiO2 Kaolinite Bicarbonate Quartz

D. Oxidation: “process of rusting; the taking away of electrons” Fe2+ >>>> Fe3+ Ferrous Ferric (dark) (red)

D. Oxidation: “process of rusting; the taking away of electrons” Fe2+ >>>> Fe3+ Ferrous Ferric (dark) (red) 4Fe2+ + 3O2 = 2Fe2O3 iron hematite ore

III. Rates of Weathering A. Climate

III. Rates of Weathering A. Climate B. Rock Structure, Size, Composition