Title Page Photo

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Title Page Photo
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Denudation

• Disintegration, wearing away, and removal of rock
  material
• Involves three activities
• Weathering atmospheric and biotic break down of
  rock
• Mass wasting down slope movement of rock
  material
• Erosion removal, transportation, and deposition
  of rock material
• Results in the lowering of continental surfaces

• Fig. 15-1.

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The Impact of Weathering and Mass Wasting
Processes on the Landscape

• Weathering and mass wasting
• shape Earths surface
• winds, water, debris, organisms, etc.
• ex. Grand Canyon

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• The scarred walls of Grand Canyon of the Colorado
  River are a testament to the awesome forces of
  weathering and mass wasting.

• Fig. 15-2

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Weathering and Rock Openings

• Weathering
• Mechanical weathering
• Chemical weathering
• Openings in Rock

• Fig. 15-3

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• The Importance of Jointing
• Plain of weakness in rock
• Makes rock susceptible to weathering
• Joint versus Fault

• Fig. 15-4

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• Joint System
• Extends great distances (vertically and
  horizontally)
• Master joints

• Fig. 15-5
• Fig. 15-6

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• Mechanical Weathering
• Animation (Mechanical Weathering)
• Physical disintegration of rock
• No change in its chemical composition
• Increases surface area for chemical weathering

• Fig. 15-14

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• Mechanical
• Frost Wedging

• Fig. 15-7 and 15-8

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• Salt Wedging
• Growth of salt crystals in rock openings
• Granular disintegration

• Fig. 15-10

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• Temperature Changes
• Day to night (diurnal) changes
• Winter to summer (seasonal) changes
• Especially effective in high mountain elevations

• Alps, Austria-Italy border (Richard A. Crooker
  photo)

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• Exfoliation
• Curved and concentric sets of joints
• Unloading and pressure release
• Mainly in granite and related intrusive igneous
  rocks

• Fig. 15-11

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• Fig. 15-12. Two large exfoliation domes in
  Yosemite N.P.

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• Fig. 15-13. Exfoliated boulder in Joshua Tree
  N.P.

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• Chemical Weathering
• Chemical alteration of rock minerals
• Enhanced by mechanical weathering
• Rates
• High rates Warm, moist environments wet
  tropics
• Low rates Cold lands and deserts
• Processes
• Oxidation
• Hydrolysis
• Carbonation

• Fig. 15-14

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• Biological Weathering
• Root penetration
• Burrowing animals
• Organic acids
• e.g., from lichens

• Photo 1 Scrub Oak, San Bernardino Mountains, CA
• Photo 2 Termite Mound, Venezuela
• (Richard A. Crooker photos)
• Fig. 15-17. Lichens, Lake District, England.

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• Climate and Weathering
• Moisture is usually more important than
  temperature

• Fig. 15-18

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Mass Wasting

• Animation (Mass Wasting)
• Gravity (downslope) transfer
• Angle of repose
• Steepest angle without downslope transfer of rock
• Accumulation of weathered material
• Soil
• Regolith
• Fragmented rock

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• Rock Fall (Fall)
• Talus cone

• Fig. 15-20 and 15-21

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• Slide
• Animation (Eruptions of Mount St.
  Helens)
• Landslide
• Slope failure
• Heavy rains
• Earthquake

• Geological weakness (jointing)
• Rapid downslope movement
• Large, rigid mass (no fluid flow) of weathered
  rock
• Fig. 15-22

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• Slump
• Weathered debris rotates along a curved plane
• Concave side face upward
• Crescent-shaped scarp face marks the top
• Bulging lobe of water saturated material at the
  base of the slide

• Fig. 15-23

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• Flow
• Water-saturated weathered debris with high clay
  fraction is an important catalyst
• Earth flow
• Relatively rigid, slower moving than the mudflow
  is

• Fig. 15-24

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• Mudflow
• Debris flow
• Arid and semi-arid slopes
• Heavy rains saturate slope causing slope failure
• Fluid flow follows stream network
• Very dangerous

• Fig. 15-25. Caraballeda, Venezuela (1999). Series
  of debris flows devastated this coastal city.

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• Creep
• Slowest moving mass wasting process
• Entire slope is involved
• Particle-by-particle movement
• Conditions
• Freeze-thaw temperature pattern
• Wet-dry precipitation pattern

• Fig. 15-26. Freeze thaw condition

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Activity

• Read Chapter 15
• Observing the landscape
• Walk around campus and determine
• Characteristics of a semi-arid region
• Features and processes in the adjacent
  lands/waters
• List your findings
• Please use objective, value-free observations
• Turn-in summary, list, or proof of participation