GEOL 102 1st EditionLecture 5Outline of Last Lecture I. Landscape Evolution TheoriesII. Water and the Hydrologic CycleOutline of Current Lecture I. Hydrologic CycleII. Soils and WeatheringCurrent LectureI. Hydrologic CycleEarth is the only planet with an abundance of liquid water on the surfaceInventory of water in the hydrosphere: 98% in oceans, ice caps and glaciers. . . small amount in lakes, rivers, and groundwater Volume of water in glaciers has changed significantly through geologic historyWhat happens if glaciers and ice caps melt? Where does the water go? OceansWater Cycle1. Evaporation: water bonds break and turn into gas2. Precipitation3. Runof4. Transpiration5. Sublimation: solid to vapor6. Infiltration: groundwaterThese 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.7. Deposition: vapor to liquidGlobal Balance1. Only 9% of water evaporated from oceans is precipitated on land2. In oceans, evaporation exceeds precipitationWater residence timeAverage time that a molecule of water spends in a particular reservoirRivers: 6 days, Atmosphere: 13 days, Lakes: 1.2 years, Groundwater: 143 years, Oceans: 3200 yearsGlobal precipitation patters: the equator receives twice as much solar radiationII. Soils and WeatheringSediments cover 80% of the Earth’s landmassSoils allow for historical artifact preservationWeathering may afect global climate change over long time scalesFood production needs to increase 50% over the next forty years to keep up with the populationgrowthEach Northern American requires .5 hectares of arable land to sustain their diet30% of the world’s farmland has become unusable in the last forty years due to soil erosion The loss of soil resources contributes to the loss of societyThe essence of WeatheringDefinition: breakdown of material at the Earth’s surfaceEarth’s surface is diferent from where rocks come fromEarth’s surface is diferent to rocks: rich in oxygen, lower pressure, lower temperatureMechanical Weathering (or physical weathering)Reduces rock sizeDepends on bedding planes, joints, fractures, faults (discontinuities)Frost wedging: water freezes and expands cracks, occurs at sub-zero temperatures and involves migration of thin water filmsCrystal growth: rock absorbs water with dissolved compounds, water evaporates, crystal grows, and pressure generated can crack rockThermal expansion: enlargement of crystal structures is due to heat, some chemical bonds are weaker than othersMechanical exfoliation: overlying rocks apply pressure, rock expands upon removalBiological disturbance: tree root growth, mammal disturbanceAbrasion: scraping/sculpting by loose particles, glaciers, rivers, and windChemical WeatheringAlters composition of rockTypically occurs through flow of waterNatural rainwater is slightly acidicDissolution: water removes mass in solution, limestone dissolutionCarbonic acid- not produced in the atmosphereKarst topographyHydrolysis: H+ and OH- ions in solution displace mineral ionsVery common weathering reactionFeldspars are altered to clay materials- negatively charges particles enable absorptionOxidation: elements lose electrons when combined with oxygen, ion oxides commonly