Geomorphic Processes: II. Exogenous

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Geomorphic ProcessesII. Exogenous

• II. Gradation Processes
• Weathering, Mass Wasting, Erosion,
  Transportation
• and Deposition

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• Geomorphic Processes
• Physical processes which create and modify
  landforms on the surface of the earth
• Endogenous (Endogenic) vs.Exogenous (Exogenic)
  Processes
• Rock Cycle ?

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A. Endogenous Processes

• Endogenous Processes are large-scale landform
  building and transforming processes
• they create relief.
• 1. Igneous Processes
• Volcanism Volcanic eruptions ? Volcanoes
• Plutonism Igneous intrusions
• Tectonic Processes (Also called Diastrophism)
• Folding anticlines, synclines, mountains
• Faulting rift valleys, graben, escarpments
• Lateral Faulting strike-slip faults
• Earthquakes ? evidence of present-day tectonic
  activity

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B. Exogenous Processes

• Also called Gradational Processes, they comprise
  degradation and aggradation they modify relief
• a continuum of processes Weathering ? Mass
  Wasting ? Erosion ? Transportation ? Deposition
• these processes are carried through by
  Geomorphic Agents gravity, flowing water
  (rivers), moving ice (glaciers), waves and tides
  (oceans and lakes), wind, plants, organisms,
  animals and humans
• 1. Degradation Processes ? Also called
  Denudation Processes
• a. Weathering , b. Mass Wasting and c.
  Erosion and Transportation
• Aggradation Processes
• a. Deposition fluvial, eolian, glacial,
  coastal

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Degradation ProcessesWeathering, Mass
Wasting,Erosion and Transportation
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Relationship Weathering Mass Wasting Erosion and
Transportation Together, these processes
are responsible for Denudation of Earths surface
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WEATHERING

• Weathering is disintegration and decomposition of
  rocks in situ no transportation involved ?
  produces regolith
• More precisely, it involves the mechanical or
  physical disintegration and/or chemical
  decomposition that fragments rock masses into
  smaller components that amass on-site, before
  being moved by gravity or transported by other
  agents
• The processes begin in microscopic spaces,
  cracks, joints, faults, fractures, lava vesicles
  and other rock cavities
• Types of Weathering 1) Physical or Mechanical
  Weathering,
• 2) Chemical Weathering, and 3) Biological
  Weathering

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• Physical or Mechanical Weathering
• Disintegration and decay of rocks via weather
  elements high temperatures, extreme cold and
  freeze-thaw cycles
• No change in chemical composition of rocks
• Exfoliation due to thermal expansion/contracti
  on and/or release of pressure when buried rocks
  are uplifted and exposed
• e.g., Exfoliation Dome (Stone Mountain, GA) and
  Exfoliation Sheets (Sierra Nevada)
• Frost Wedging
• Salt Wedging

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• Chemical Weathering
• ? decomposes rocks through a chemical change in
  its minerals

Oxidation important in iron-rich rocks
reddish coloration like rust Hydrolysis
igneous rocks have much silica which readily
combines with water Carbonation and Solution
carbon dioxide dissolved in water reacts with
carbonate rocks to create a soluble product
(calcium bicarbonate)
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Biological Weathering

• plants and animals contribute to weathering.
• Roots physically break or wedge rock
• Lichens (algae and fungi living as single unit),
  remove minerals and weaken rock by releasing
  acids
• Burrowing animals can increase weathering.

Lichens
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Talus Cones in the Canadian Rockies
Talus pieces of rock at bottom of a rock fall
Landslides Can cause much destruction
A msssive 300-ton boulder blocks a road in
Southern California
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La Conchita Landslide, January 10, 2005
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Monterey Park Debris Flow, 1980
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PCH near Pacific Palisades, November 1956
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EROSION and TRANSPORTATION

• Various Geomorphic Agents, associated
  Processes,
• and resulting Erosional Features
• Flowing Water Fluvial Morphology
• Humid regions
• Perennial streams and entrenched
• channels, rapids, waterfalls, plunge
• pools, potholes, meandering streams,
• bank erosion, oxbow lakes, etc.

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• Wind Eolian Landscapes
• deflation hollows, ventifacts, yardang, etc
• Tides and Waves Coastal Morphology
• Sea cliffs, sea caves, sea arches, sea stacks,
  wave-cut beaches, etc..
• Moving Ice Glacial Morphology
• glacial troughs (U-shaped valleys), hanging
  valleys, glacial lakes,.

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DEPOSITION

• Various geomorphic agents, associated processes
  and resulting Depositional Features
• Fluvial Humid regions Braided streams, sand
  bars, floodplains (alluvium deposits), natural
  
• levees, distributaries, deltas
• Arid regions Alluvial fans, bajadas,
• piedmont alluvial plains, playas,
• playa lakes, Salinas (salt flats)
• Eolian Sand dunes (Barchans, Parabolic,
  Transverse,
• Longitudinal, Star), and sand sheets
• Coastal Sea beaches and coral reefs
• Glacial Alpine Glacial drifts, tills,
  moraines (lateral, medial, end,
  terminal, recessional, and ground)
• Continental Till plains, outwash plains,
  drumlins, eskers, kames, erratic