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Module 2 Week 2 Crustal Processes
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Module 2 Week 2 Crustal Processes

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Module 2 Week 2 Crustal Processes Module 2 Week 2 Crustal Processes Presentation Transcript

  • Crustal Processes
  • Overview
    • Orders of relief
      • Topographic regions
    • Crustal Formation
      • Oceanic and Continental crust
      • Displaced terranes
    • Crustal Deformation
      • Folding
      • Faults
      • Landforms
  • Orders of Relief
    • Relief refers to the relative difference in height between objects on the landscape (specifically, the difference in height between the highest and lowest point)
      • Plains: low relief
      • Mountainous areas: high relief
    • Topography : Variation in the relief of the Earth’s surface
    • Orders of Relief : classification of landscape by spatial scale
  • First Order of Relief
    • Continental platforms
      • The above-water landmasses
      • The continental shelves
    • Ocean basins
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  • First order relief: ~ 9000 – 10,000 meters
  • Second Order of Relief
    • On continents:
      • continental masses (Edward’s Plateau)
      • mountain masses (Rocky Mts, Alps, Sierra Nevada)
      • plains (the Great Plains)
      • lowlands (west Siberia)
    • Oceans
      • continental rises and slopes (the slope of the continental shelf)
      • abyssal plains, mid-oceanic ridges, submarine canyons, subduction trenches
  • Third Order of Relief
    • Most detailed order of relief
    • Individual features on the landscape
      • single mountains, valleys, rivers, etc.
      • Mt. St. Helens, Lake Travis, etc.
  • Topographic Regions of the World
    • A classification system of second order features based on relief
    • Six categories
      • Plains
        • Local relief less than 100 meters
      • Hills and Low Tablelands
        • Hills: Relief between 100 and 600 meters
        • Low Tablelands: Elevation less than 1500 meters, relief less than 100 meters (an elevated plain)
      • High Tablelands
        • Elevation greater than 1500 meters, relief less than 300 meters
        • Canyons are often a feature of high table lands
      • Mountains: Relief greater than 600 meters
      • Widely Spaced Mountains
        • Discontinuous or solitary with 600 meter plus relief; intervening spaces have relief less than 150 meters
      • Depressions: Basins surrounded by other features
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  • Crustal Formation
    • Three categories of continental crust
      • Residual mountains and continental cores from past tectonic activity
        • Inactive
        • Continental cores (shields) or the original crust around which the rest of a continent’s crust forms
        • Terranes: migrating pieces of crust that merge with larger continents
          • Much of the west coast is terranes, esp. Alaska, British Columbia and Mountain West
      • Active tectonic features: mountains, folding, faulting
        • New crust formed from seafloor spreading and subduction
      • Volcanic features
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  • Crustal Deformation
    • All rock types experience stress
    • Sources of stress
      • Tectonic forces
      • Gravity
      • Weight of overlying rocks
    • Types of Stress
      • Tension
      • Compression
      • Shear
    • Strain: how rocks respond to stress
      • folding – pliable layers
      • faulting – rigid layers: normal, reverse, and strike-slip
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  • Folding
    • Folding occurs in response to compression
    • Strata folded into a series of anticlines and synclines
      • Anticline
        • Antiform: young > old > young
      • Syncline
        • Synform: old > young > old
    • Domes and Basins
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  • Surface: Antiform Profile: Anticline
  • Surface: Synform Profile: Syncline
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  • Faulting
    • Rock strata fracture when stresses are too great to be compensated for by folding
    • Displacement of strata on either side of fracture is called a fault
      • Normal Fault
        • Hanging wall slips below foot wall
      • Reverse and Thrust Fault
        • Hanging wall raised above foot wall
      • Strike-Slip Fault
    • Faulting occurs in sudden episodes which release energy, triggering earthquakes
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  • Horst and Graben
    • Systems of normal faults producing alternating ridges and valleys
    • Characteristic of the Basin and Range area of the western US.
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