Geology

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Author:
FreshW
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115086
Filename:
Geology
Updated:
2011-11-07 02:58:27
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Geology
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Geology Notes
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  1. Branch of geology that studies the shapes,arrangement and interrelationships of rockunits and the forces that cause them.
    Structural Geology
  2. Changes in volume or shape of amaterial
    Deformation
  3. Force applied over an area
    Stress
  4. Tends to change size, shape, or volume
    Stress
  5. Caused by tectonic forces or confining pressure
    Stress
  6. Change in size, shape, or volumein response to stress
    Strain
  7. Compressional, tensional, and shear forces
    Types of Stress
  8. ´╗┐Elastic
    *Deformed object returns to original shape whenstress (force) is removed.
    Types of Strains
  9. Ductile (plastic)
    Deformed object retains new shape when stress(force) is removed
    Types of strain
  10. Brittle
    Deformed object breaks– faults and fractures
    Types of strain
  11. Temporary change in shape and/orvolume of rock due to temporary stress
    Elastic
  12. Permanent change in the shapeand/or volume of rock at high temperatureand high pressure (fold, bend)
    Plastic
  13. Permanent change in theshape and/or volume of rock at lowtemperature and low pressure (break
    Brittle failure
  14. Low temperature
    Brittle
  15. High temperature
    Plastic
  16. Strain rate =
    deformation/time
  17. Fast (Brittle Breaks)
    Brittle, breaks
  18. Slow (Strain Rate)
    Plastic, Flows
  19. Clay, mica, calcite: plastic
    Composition
  20. Quartz, feldspar, olivine: brittle
    Composition
  21. Originally all sedimentary rocks are...
    Horizontal
  22. Tilted and folded fromtheir original horizontal orientation
    Sedimentary rocks
  23. ∩ shaped fold in rocks– The oldest rocks are in the middle– The youngest rocks are in on the outside
    Anticline Fold
  24. ∪ shaped fold in rocks– The oldest rocks are on the outside– The youngest rocks are in the middle
    Syncline Fold
  25. Oldest beds in the core
    Anticlines
  26. Youngest beds in the core
    Synclines
  27. Both limbs same dip
    Symmetric
  28. One limb dips more steeply
    Asymmetric
  29. One limb upside down
    Overturned
  30. Axial plane horizontal
    Recumbent
  31. *Fractures along which no movement hastaken place
    *Most rocks are jointed
    *Very little stress is required
    Joints
  32. Types of fault
    • dip-slip faults
    • *normal faults
    • *reverse faults– includes thrust faults
    • – strike-slip faults
    • – oblique-slip faults
  33. Group of closely spaced mountains or parallelridges
    Mountain Ranges
  34. Chain thousands of kilometers long composed ofmany mountain ranges
    Mountain Belts
  35. The structurally stable portion of a continent
    The Craton
  36. Sediments thicken due to...
    Folding & Faulting
  37. What decreases cohesion?
    Water saturation
  38. Controlling factors of mass wasting
    • Gravity
    • Water
    • Triggering Mechanisms
    • Vegetation
    • Orientation of planes of weakness
    • Climate
  39.  Triggering Mechanisms Examples
    • Shocks
    • – Undercutting
    • – Slope modification
    • – Exceptional precipitation
    • -Human-induced mass movement
    • *Often mismanagement of water
    • *Clearing of forests/land
  40. Slowest type, occurs on almost allslopes
    Creep
  41. Motion takes place throughoutthe mass. Material flows like a fluid
    Debris Flow
  42. – Debris (unconsolidated sediment) flows downhill
    – Can be slow or rapid
    – Often triggered by heavy rains
    – Mass often remains covered by vegetation
    – Forms scarp (steep cut) at upper portion of movement
    Earth Flow
  43. – Slurry of mud+water
    – Fast moving; Speed is function of slope
    – Usually in canyons or gullies
    – Contain large quantities of water
    – More common in arid regions (little or no vegetation)
    Mud Flow
  44. – Fastest of all mass movements
    – steep slopes
    – talus accumulations
    – frost wedging
    – undercutting
    Rock Fall
  45. What should we do about mass movements?
    • – improve safety of existing situations
    • – drainage pipes etc
    • .– reduce slope steepness
    • cut-and-fill
    • Benching
    • Retaining walls
    • Rock bolts
    • Other measures
  46. Single most important geological agent
    • – Erosion
    • – Transport
    • – Deposition
  47. One of our most important natural resources
    • – Drinking water
    • – Irrigation
    • – Brew beer
  48. Where is the water?
    •  1.36 billion km3 Total
    • 97.2% in oceans
    • 2.15% in glaciers and icecaps
    • 0.65% in lakes, streams, groundwater, atmosphere
  49. The study of the waters of the earth;rivers, lakes, groundwater.
    Hydrology
  50. * 85% of water in the atmosphere hasbeen evaporated from the oceans
    *about 80% of precipitation (rainfall,snow etc.) is back into the ocean
    * precipitation on land may be storedtemporarily in lakes, glaciers etc.
    Components of the water cycle
  51. Surface water that flows in a channel
    Mouth
    – End of the stream Oceans Lakes Desert
    *Headwaters
    – Source water area
    *Trunk
    – Main channel of the stream
    Streams
  52. Tree Shaped
    Dendritic
  53. Spokes on a Wheel
    Radial
  54. 90° bends
    Rectangular
  55. Parallel streams withshort tributaries intersecting at90°
    Trellis
  56. Affected by several factors:
    – Velocity
    – Gradient
    – Channel shape & roughness
    – Discharge
    Stream Erosion & Deposition
  57. – Speed, or the distance water travels per unit oftime
    – Controlled by gradient, channel shape andchannel roughness
    – Stream velocity varies depending on positionwithin the channel
    Velocity
  58. Affected by friction against stream bed andbanks, resulting from roughness
    Water Velocity
  59. – Measure of thedownhill slope of thestream bed
    – Generally expressed infeet/mile
    – Stream gradient usuallydecreases downstream
    Gradient
  60. Friction!–
    Stream A flows faster than stream B
    – Rough channel slowswater flow
    Channel shape & roughness
  61. Total volume of water passing a pointper unit time
    – m3/sec or ft3/sec
    = avg width
    x avg depth
    x avg velocity
    Discharge
  62. Increases downstream
    – Addition of water by tributaries
    – Addition of waterfrom groundwater
    Discharge
  63. Streams erode rock and sediment in three ways
    • – Hydraulic action
    • – solution
    • –Abrasion
  64. – Pressure exerted by flowing water can break offrock fragments, roll or slide grains, or lift grains offof the stream bed
    Hydraulic action
  65. – Some rocks and minerals can be dissolved bywater and eroded away
    Solution
  66. – Grinding away of streamchannel by the friction andimpact of the sediment load
    – Most effective erosive process
    – Can form potholes during highwater when water swirls aroundand sand and pebbles scourbowl shaped depressions out ofthe stream bed
    Abrasion
  67. Sediment load is divided into three types:
    • – Bed load
    • – Suspended load
    • – Dissolved load
  68. Large, heavy particles traveling along the streambed
    Bed load
  69. Rolling, sliding or dragginggrain never loses contact with ground
    Traction
  70. Series of short leaps or bounces
    Saltation
  71. Sediment that is small or light enough to be lifted indefinitely by the force of moving water. Sediment is deposited when waterslows down.
    Suspended load
  72. Particles that have been dissolved by water. (Products of chemical weathering, orsolution)
    Dissolved load
  73. As velocity falls
    largest particles settle out
  74. Results in sorting of sediment in riverdeposits, called
    Alluvium
  75. Stream deposits include:
    • – Bars
    • – Braided streams
    • – Meandering streams & point bars
    • – Flood plains
    • – Deltas
    • – Alluvial fans
  76. – A ridge of sediment deposited in the middleor along the banks of a stream
    – Usually sand and gravel
    – Generally formed at the end of a floodingevent, when flood waters recede and slowdown, depositing sediment
    – Bar deposits can sometimes contain placerdeposits- concentrations of heavy particles,such as gold, platinum, other metals orgemstones
    Bars
  77. – A stream heavily loaded with sediment
    – Sediment collects as bar deposits whichseparate the stream into several differentchannels
    Braided Streams
  78. Older, well defined streams tend to developsinuous curves called
    Meanders
  79. – Erosion takesplace along theoutiside of ameander loop
    – Deposition takesplace along theinside of ameander loop =point bar
    – Causes meanderloops to broadenover time
    Meandering streams
  80. – Sediments are deposited as a river floods itsbanks and the water velocity slows.
    – Most sediment is dropped closest to the riverchannel, with progressively less sedimentcarried away from the channel
    Flood plains
  81. – Body of sediment deposited at the mouth of a river due to decrease of velocity of the water
    Deltas
  82. – Long, finger-like sand bodies
    Stream-dominated deltas
    Wave-dominated deltas: seawardmargin of delta consists of islandsreworked by waves
    Deltas
  83. – Large fan or cone shaped pile of sediment that generally forms as a river’s velocity decreases where it emerges from a steep ,narrow canyon onto a flat plain
    Alluvial fans
  84. The most devastating of all geologicagents - exceeded only by plagues, world wars andthe Holocaust in loss of life.
    Floods
  85. Creates narrow canyons
    Downcutting
  86. Broadens the valley by lateral erosion
    Mass wasting
  87. Widens a streamvalley by eroding andundercutting streambanks
    Lateral Erosion
  88. Stream terraces
    •  Step-like landforms found above a stream and its flood plain
    • Erosional remnants of former, higher floodplains

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