Mass WastingPowerPoint Presentation1. Rock Fall (Rapid movement) material breaks free from a vertical wall or very steep slopeSlide 4Slide 52. SLIDES – (Rapid movement) a single, intact mass of rock, soil, or unconsolidated sediment becomes detached and moves rapidly downslopeSlide 7Slide 83. Slumps (Slow to Rapid movement)Slide 10Slide 114. Flows (Rapid movement)Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Earthflows – Quick claysSlide 23Slide 245. Creep (Slow movement)Slide 26Slide 27Slide 286. Solifluction (Slow movement)Slide 30Slide 31Slide 327. Complex movementsSlide 34Causes and triggers of mass movementSlide 36Slide 37Other means to prevent mass wastingSlide 39Slide 40Slide 41Oceans and Coastal processesQuestions to ponder:Waves, Beaches and coastal ProcessesSlide 45Slide 46Slide 47Tides - Large wavelength waves caused by gravitational pullSlide 49Slide 50Slide 51Slide 52Slide 53Wave Refraction, Longshore currents and Rip CurrentsSlide 55Slide 56Evolution of erosional featuresSlide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Slide 66Slide 67Slide 68Spits a finger-like ridge of sand that develops parallel to the shoreline and projects from the mainland into open waterSlide 70Barrier IslandsSlide 72Slide 73Slide 74Slide 75Slide 76Groins, Jetties and seawallsJetties: disrupt natural sediment flowSeawalls and BreakwatersSlide 80Slide 81Slide 82Slide 83Slide 84Slide 85Slide 86Slide 87Lower Sea level creates undersea canyonsSlide 89Slide 90Mass WastingMass WastingLecture28Lecture281. Rock Fall (Rapid movementRapid movement)material breaks free from a vertical wall or very steep slopeTALUSVery rapid movements; Talus builds up at base of slopes2. SLIDES – (Rapid movementRapid movement) a single, i ntact mass of rock, soil, or unconsolidated sediment becomes detached and moves rapidly downslopeMaterial moves down The Dip of the rocksRock Slide along I-40In the Pigeon River GorgeNear NC/TN borderDip of rocks is the slide plane3. Slumps (Slow toSlow to Rapid movementRapid movement)a downward and outwardmovement of an Intact Mass of unconsolidated materialalong a curved surfaceSmall slump along a road bedLarge slump in CaliforniaWith Debris flow4. Flows (Rapid movementRapid movement)•a mixture of mostly unconsolidatedunconsolidated particles that moves downslope like a viscous fluid•Materials behave as a fluid•Several subcategories:•Mudflows (lahars); Earthflows•DEBRIS FLOWSDEBRIS FLOWS: a slurry of water and particles larger than mud. Can include vegetation, structures as well as geologic materialMudflows•Debris flows consisting of silt and clay sized particles–Usually associated with heavy rain–High water content - up to 30%–Usually follow stream valleysLahars•Volcanic debris flows–Common is loose pyroclastic material–Rain or melting snow saturates soil and rock–Explosive eruptions and associated earthquakes can be triggers–Very fast flowing - up to 150 km/hrMt. St. Helens - laharDebris Flows•Mixtures of water, mud and rock–Liquified soil flows downhill•Up to 50 km/hr–Water lubricates mass of soil and rock–Large boulders, buildings etc. may be carried by viscous fluidEarthflows – Quick clays•Problem in high latitude regions•Clays can become mobilized and flow•Generally susceptible during earthquakes and other seismic events1964 Alaskan earthquake5. Creep (Slow movementSlow movement)•Very common form of mass wasting•Extremely slow movement of soil and regolith - 1 to 10 mm/yr•Combination of factors cause creep–Heaving of soil - expansion & contraction is the primary cause•Wet-dry cycles•Freeze-thaw cycles6. Solifluction (Slow movementSlow movement)•Creep that occurs in permafrost–Melting of soil water occurs from the surface down–Permafrost prevents downward percolation–Surface soils become saturated and begin to flow–Also can “pluck” and move cobble7. Complex movements•In many instances, a variety of mass movement styles can occur in a single event•Example: A rock side can be initiated, and move as a mass, yet later break up during movement to become a debris flow•Thus, the nature of the movement can change with distance from the event sourceCauses and triggers of mass movementCAUSESCAUSES• Underlying Geology–Dipping beds; fractures; easily weathered rocks• Water–Adds mass; increases pore pressure; reduces friction• Weather-Climate• Slope Modifications• DeforestationCauses and triggers of mass movementTRIGGERSTRIGGERS• Volcanic Eruptions• Earthquakes Blasting• Freeze - Thaw• Precipitation – Water•Back-to-Back Storms• Slope ModificationsPreventing mass movementKnow the materialCompositionWater content and drainageEvidence of previous movementConsult risk mapsOther means to prevent mass wasting•Enhance or add vegetation–Vegetation removes water; enhances stability of unconsolidated materials•Develop and enforce applicable building regulations–Be conscious of adding too much mass; proper water drainage; septic•Avoid constructionRemove water – drain pipesDecrease slopeBuild retaining wallsSecure slopesUnfortunately, we Spend 50 times more money on repairs than we do towards prevention!Oceans and Coastal Oceans and Coastal processesprocessesLecture 28&29Lecture 28&29Chap 14Chap 14414-435414-435Questions to ponder:•How do waves form? •How does the energy of waves relate to wavelength and water depth?•What are the parts of a beach? How is sediment distributed to beaches?•Why are barrier islands dynamic?•What causes sea level variationsWaves, Beaches and coastal Processes•How waves form and function•Features of erosion and deposition•Beaches•Barrier Islands•Types of coasts•The effects of sea level changesWaves•Wave motion–Motion is clockwise rotation in direction of wave movement–Wavelength - distance between wave crests–Wave period - time between passage of successive waves–Wave base - depth at which orbital motion dies out, = 1/2 wavelengthTides - Large wavelength waves caused by gravitational pullWind-driven waves transmit mostOf the ocean wave energyWaves•Waves produce little or no forward motion of water – energy is moved•Breakers–Waves break as wave base (orbitals) touch bottom–Wave crest moves forward of base–Wave breaks & swash washes up the beach face, backwash flow downWave Refraction, Longshore currents and Rip CurrentsWave approaches Wave approaches shore at