Your SlideShare is downloading. ×
0
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
14 hydro landslides_forstudents
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

14 hydro landslides_forstudents

209

Published on

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
209
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
11
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Landscapes,Hydrology, and Mass Movements Interlude F & Chapter 16
  • 2. Outline• Shaping the Earth surface -uplift vs. erosion -describing the surface: relief, contours -factors controlling landscape development• Hydrologic cycle• Mass movements -Basics -Various types -Submarine mass movements• Weakening the surface -Slope stability -Failure surfaces and triggers -Link to plate tectonics -Hazard and prevention Interlude F & Chapter Interlude F & Chapter 16 16
  • 3. Shaping the Earth Surface• Result of competition between uplift and erosion. • Adding or subtracting elevation. • Driven by tectonics: • Uplift- vertical surface motion upwards • Subsidence-vertical motion downwards • Driven by surface processes: • Erosion- surface lowering by mass removal • Deposition- surface rising by mass addition Interlude F & Chapter 16
  • 4. Shaping the Earth Surface Interlude F & Chapter 16
  • 5. Describing the Earth Surface• Relief • Elevation difference between 2 points. Interlude F & Chapter 16
  • 6. Describing the Earth SurfaceContourmaps: Interlude F & Chapter 16
  • 7. Factors Controlling Landscape DevelopmentAgents of transport & erosion• Water, ice windElevation distribution• Relief, slope angleClimate• Mean temp and precipitation amountLife• Ecology/ biota can weaken/stabilize the surfaceExposed material type (substrate)• ErodibilityTime Interlude F & Chapter 16
  • 8. Outline• Shaping the Earth surface -uplift vs. erosion -describing the surface: relief, contours -factors controlling landscape development• Hydrologic cycle• Mass movements -Basics -Various types -Submarine mass movements• Weakening the surface -Slope stability -Failure surfaces and triggers -Link to plate tectonics -Hazard and prevention Interlude F & Chapter Interlude F & Chapter 16 16
  • 9. Hydrologic CycleWater plays major role in surface erosion & deposition.Hydrologic cycle- describes never ending water flow between various reservoirs Interlude F & Chapter 16
  • 10. Hydrologic Cycle Average time spentThe reservoirs: in each reservoir: Interlude F & Chapter 16
  • 11. Extraterrestrial (water) flow!?!?Mars Other? Enceladus (Saturn moon) Interlude F & Chapter 16
  • 12. Outline• Shaping the Earth surface -uplift vs. erosion -describing the surface: relief, contours -factors controlling landscape development• Hydrologic cycle• Mass movements -Basics -Various types -Submarine mass movements• Weakening the surface -Slope stability -Failure surfaces and triggers -Link to plate tectonics -Hazard and prevention Interlude F & Chapter Interlude F & Chapter 16 16
  • 13. Intro to Mass Movements• Most humans consider Earth to be• Earth’s surface, however, is mostly unstable• Due to weathering/erosion/gravity Interlude F & Chapter 16
  • 14. What is a Mass Movement?• Downslope motion of earth materials by gravity• Type of natural hazard • Natural landscape process These hazards can produce catastrophic losses Interlude F & Chapter 16
  • 15. Intro to Mass Movements• Mass movements are important to rock cycle• Initial step in sediment transportation• Significant landscape change agent• All slopes are unstable, they change continously• Mass movements are often Interlude F & Chapter 16
  • 16. Types of Mass WastingClassified based on 4 factors: 1. Material type (rock, regolith (loose debris), snow, ice) 2. Rate of movement (fast, intermediate or slow) 3. Nature of moving mass (cloud, slurry, or distinct blocks) slurry-liquid with suspended soilds 4. Surroundings (subaerial or submarine) Interlude F & Chapter 16
  • 17. Types of Mass WastingCreep, solifluction, rock glaciers (not shown) slumpingFlows (mud) avalanches, falls (rock) Interlude F & Chapter 16
  • 18. Types of Mass WastingCreep –slow downhill movement of regoithDue to expansion and contraction via wetting and drying, freezing and thawingGrain moves: perpendicular to slope upon expansionVerically by gravity upon contraction Interlude F & Chapter 16
  • 19. Types of Mass WastingCreep tilts trees, gravestones, and walls Interlude F & Chapter 16
  • 20. Types of Mass WastingSolifluction –slow downhill movement of tundra melted permafrost slowly flows over deeper, frozen soil generates hillsides with solifluction lobesRock glaciers – mix of rocks fragments and ice rocks added faster than ice accumulationBehave like glacial ice, flowing slowly downhill Interlude F & Chapter 16
  • 21. Types of Mass WastingSlumping – sliding of regolith as coherent blocksSlip occurs along a spoon-shaped failure surfaceVariety of sizes and rates of motionDistinctive features head scarp, bulging toe Interlude F & Chapter 16
  • 22. Types of Mass WastingMud & debris flows – h20 rich mass movementMudflow- slurry of water and fine sedimentDebris flow- mudflow with large rocks Interlude F & Chapter 16
  • 23. Types of Mass WastingLahar – a volanic mud or debris flow volcanic ash from recent/ongoing eruption water from heavy rain or melted glacial ice Interlude F & Chapter 16
  • 24. Types of Mass WastingLandslides – movement down nonvertical slope • Rock slide – consists of rock only • Debris slide – mostly reoglith Movement down failure surface is quick Debris can move 300 km/hr on cushion of air Interlude F & Chapter 16
  • 25. Landslide Case Study• Vaiont Dam disaster – illustrates need to evaluate geology when siting structures • Built in 1960 in a deep gorge in Italian Alps. • Limestone over shale dipped toward valley center. • On 10/9/63, 600 million tons of limestone fell into the reservoir. • A wave crested the dam, destroyed villages, and killed 2,600. Interlude F & Chapter 16
  • 26. Types of Mass WastingAvalanches – turbulent clouds of debris and air • Snow avalanche – over-steepened snow detaches • Debris avalanche – rock and dust fragment • Move up to 250 km/hr on a cushion of air Interlude F & Chapter 16
  • 27. Types of Mass Wasting• Rock & debris falls – vertical freefall • Bedrock/regolith that falls rapidly • Block impact, fragment and keep moving • Talus blocks pile up at slope base Interlude F & Chapter 16
  • 28. Types of Mass WastingSubmarine mass movements.• 3 types – based on degree of disintegration 1. Submarine slumps – coherent blocks break and sip 2. Submarine debris flows – moving material breaks apart 3. Turbidity currents – sediement moves as a turbulent cloud Usually well-perserved Interlude F & Chapter 16
  • 29. Types of Mass WastingSubmarine mass movements. • Gigantic submarine slope failures are widespread • Large than land-based failures • Important process sculpting adjacent land • Create catastrophic tsunamis Interlude F & Chapter 16
  • 30. Outline• Shaping the Earth surface -uplift vs. erosion -describing the surface: relief, contours -factors controlling landscape development• Hydrologic cycle• Mass movements -Basics -Various types -Submarine mass movements• Weakening the surface -Slope stability -Failure surfaces and triggers -Link to plate tectonics -Hazard and prevention Interlude F & Chapter Interlude F & Chapter 16 16
  • 31. Weakening the Surface• Mass movements require earth materials• Fragmentation & weathering. Interlude F & Chapter 16
  • 32. Weakening the Surface• Slope stability is a trade-off between 2 forces: 1. Downslope force – gravitational pull 2. Resisting force – material properties that resist motion• Movement occurs when downslope forces win Interlude F & Chapter 16
  • 33. Slope Stability1. Downslope forces (Fd) = gravityWeight of earth materials2. Resisting forces (Fr) = material strength3. Cohesion friction Interlude F & Chapter 16
  • 34. Slope Stability• Loose material assumes an “angle of repose”.• Maximum stable angle• Due to material propertiesParticle size, shape, surface roughness• Typical repose angles:• Fine sand:35• Coarse sand: 40• Angular pebbles: 45 Interlude F & Chapter 16
  • 35. Failure Surfaces• Weak subsurface layers can initiate motion• Failure surface- types include • Saturated sand/clay layers • Joints parallel to surface • Weak sedimentary bedding (shale) • Metamorphic foliation Interlude F & Chapter 16
  • 36. Failure Triggers• Destabilizing event usually triggers slopes failure• Triggers are natural & anthropogenic: • Shocks or vibration • Changes in slope characteristics • Changes in slope strength Interlude F & Chapter 16
  • 37. Failure Triggers• A triggering event is not necessary for movement • Slope materials slowly weaken over time • Gravity• Result: movements often Interlude F & Chapter 16
  • 38. Failure Triggers• Shocks & vibrations.• Vibrations decrease material friction• On unstable slope, downslope force takes over• Many sources of vibration are common: • Motion of heavy machinery, vehicles Interlude F & Chapter 16
  • 39. Failure Triggers• Vibrations cause saturated sediments to liquefy • Quick clay – pore water slurries clay flakes when shaken • Saturated sand – fluidized by increase in pore pressure Interlude F & Chapter 16
  • 40. Failure Triggers• Changes in characteristics can destabilize a slope • Angle – steepening slope beyond angle of repose • Loading –add weight to top of slope • Water – as rain or via humans Interlude F & Chapter 16
  • 41. Failure Triggers• Changes in slope strength • Weathering – creates weaker regolith • Vegetation – stabilizes slope. Removing it.. • Shows excess water removal • Destroys Interlude F & Chapter 16
  • 42. Link to Plate Tectonics• Tectonic processes influence mass movements • Create uplift – topo and relief leads to steep slopes • Fragment crust – joints and faults ease disintegration • Generate earthquakes – trigger Interlude F & Chapter 16
  • 43. Identifying Slope Hazards• Geologic mapping can identify risk regions• Past failures• Currently unstable slopes: • Cracked and bulging ground • Measureable changes in surveyed land features GPS can detect slow movements Interlude F & Chapter 16
  • 44. Prevention• Action can reduce mass movement hazards • Revegetation – adding plants has 2 positive effects • Removes water • Roots Interlude F & Chapter 16
  • 45. Prevention• Action can reduce mass movements hazards • Slowing or eliminating undercutting- increases stability • Removing erosion agent at slope base • Reducing effect of erosion agent Interlude F & Chapter 16
  • 46. Prevention• Engineered structures. • Rock staples – rods drilled into rock to hold steep face Interlude F & Chapter 16
  • 47. Prevention• Engineered structures. • Avalanche sheds – structures that shunt avalanche snow • Controlled blasting – surgical removal of dangerous rock Interlude F & Chapter 16

×