EES 1030 Lecture 5 Outline of Last Lecture I. Lecture 4: Volcanoes and other Igneous ActivityII. Nature of Volcanic EruptionsIII. Types of Volcanic DepositsIV. Basaltic lava flow typesV. Basaltic VolcanoesVI. Pyroclastic MaterialVII. Intermediate-Rhyolitic VolcanoesVIII. Mt. St. Helens 1980IX. Pyroclastic Falls & FlowsX. Lahars: Volcanic mud flowsXI. Volcanoes and ClimateXII. Intrusive Igneous ActivityXIII. Hydrothermal SystemsOutline of Current Lecture XIV.Lecture 5: Weathering & SoilXV. Breakdown of Rocks at Earth’s SurfaceXVI. Earth’s External ProcessesXVII. Two Types of Weathering ProcessXVIII. Mechanical WeatheringXIX. Chemical WeatheringXX. Chemical Weathering: Acid RainXXI. Chemical Weathering: HydrolisisXXII. Chemical Weathering: OxidationXXIII. Chemical Weathering: ProductsCurrent LectureBreakdown of Rocks at Earth’s SurfaceGeneral process is called weathering.Earth’s External ProcessesWeathering: physical/mechanical breakdown (disintegration) and chemical alteration (decomposition) ofrock at Earth’s surface.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Erosion: Physical removal of material by mobile agents. Ex: water, wind, ice, gravity. Exposes fresh unaltered rock to weathering.Lead to formation of sedimentary rocks.Release important nutrient elements into surface waters.Two Types of Weathering Process:Mechanical weathering: (disintegration) breaks rocks into smaller pieces without changing their chemicalcomposition.Chemical weathering: (decomposition) chemical reactions between rock and minerals and air + water.1. Form new minerals.2. Release ions into solution.1) Frost Wedging: Water expands by 9% when frozen. Exerts immense pressure (several million lbs./sq. ft.) Daily freeze-thaw cycles especially in mountain areas.2) Root Wedging3) Salt Wedging: evaporation of water rich in dissolved species will lead to growth of crystals in cracks. Exerts force.4) Thermal Expansion: large daily temperature changes cause thermal strain (expansion and contraction)5) Unloading: uplift & erosion reduces pressureDissolution: promoted by acidic waterHydrolysis: reaction of mineral with water. Hydrogen ion attacks and replaces other ions.Oxidation: exposure to atmospheric oxygen.Acidic Water: corrosive to minerals.Chemical Weathering: Acid RainBurning of fossil fuels produces sulfur dioxide and nitrogen oxides: these gases react with rain water to form sulfuric acid and nitric acid:  environmental damageChemical Weathering: HydrolysisHydrogen ions replace other cations in mineral structure, producing new minerals.Example: Hydrolysis of feldspar to clay minerals.Solid Potassium Feldspar + acidic water  solid residual Kaolinite clay + solution containing dissolved potassium ions, Bicarbonate ions and silica.Chemical Weathering: OxidationIron released from ferromagnesian silicates. Example: Olivine, Pyroxene, Amphibole and Biotite MicaChemical Weathering: ProductsPlacer Deposits: resistant economic minerals. Examples: Gold, diamonds. Released from rock during weathering but resistant (like quartz)Rates of Chemical WeatheringSurface area: same volume of rock, but smaller particles have greater total surface areaRock type: Rocks containing calcite (marble and limestone) readily dissolve in weakly acidic solutions  cavesRock type: Silicate minerals weather in the same order as their order of crystallization. High- T minerals: less stable at Earth’s surface.Climate: what is important? Temperature and MoistureChemical weathering is most effective in areas of warm, moist