1. Geomorphic Processes: II. Exogenic
II. Gradation Processes –
Weathering, Mass Wasting, Erosion, Transportation
and Deposition

2. Geomorphic Processes:
Physical processes which create and modify landforms
on the surface of the earth
A. Endogenic (Endogenous) vs. B. Exogenic (Exogenous) Processes
These processes operate in episodic
manner – with earthquakes and
volcanic eruptions causing a
punctuated equilibrium
These processes relate closely
to the Rock Cycle 

3. A. Endogenic Processes
Endogenic 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

4. B. Exogenic Processes Also called Gradational Processes
-- comprise degradation and aggradation
-- they modify relief
A continuum of processes – Weathering  Mass Wasting  Erosion  Transportation  Deposition
Operates through Geomorphic Agents: gravity, flowing water (rivers), moving ice (glaciers), waves and tides (oceans and lakes), wind, chemicals, plants, organisms, animals and humans
1. Degradation Processes  Also called Denudation Processes
a. Weathering , b. Mass Wasting and c. Erosion (+ Transportation)
Aggradation Processes
a. Deposition – fluvial, eolian, glacial, coastal

5. A Conceptual Model of
Gradation
(Erosion + Deposition)

6. Degradation Processes: Weathering, Mass Wasting, Erosion (+ Transportation)

7. Relationship: Weathering Mass Wasting Erosion Denudation and
Transportation
Together,
these processes are
responsible for
Denudation
of Earth’s surface

8. WEATHERING
Weathering is disintegration and decomposition of rocks in situ – no transportation involved  produces regolith → eventually soil and sediments
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

9. Factors affecting Weathering:
(1) Strength and resistance of rocks,
(2) Climate, especially temperature
and humidity regimes,
(3) Slope and relief of the land, and
(4) Type and density of vegetative cover
Types of Weathering:
1) Physical or Mechanical Weathering,
2) Chemical Weathering, and
3) Biological Weathering

10. 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/contraction 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

11. 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)

12. 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

13. MASS WASTING
Process whereby weathered material is moved downslope under the immediate influence of gravity.
However, gravity being a passive force needs a triggering factor to create instability and initiate mass wasting – groundwater, meltwater, rain water and vibrations produced by earthquakes, explosions, heavy trucks and trains, and amount and type of vegetation cover are all potential triggers
Slope Angle and Angle of Repose (the steepest angle that can be assumed by loose fragments on a slope without downslope movement) are strongly related to rates of mass wasting

14. in the Canadian Rockies
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

15. Classification of Mass Wasting
Based on
Speed of Movement
Kind of Earth Material Involved
Kind of Motion Involved
Soil Creep 

16. Classification of Mass Wasting
Based on
Moisture Content
and
Speed of Movement

17. La Conchita Debris Flow/Earthflow, January 10, 2005

18. Monterey Park Debris Flow, 1980

19. Landslide/Earthflow on PCH near Pacific Palisades
November 1956

20. Slump in Coastal California near San Clemente January 7, 2011

21. Massive Slump, PCH, San Pedro, CA, November 20, 2011

22. Massive Slump, PCH, San Pedro, CA, November 20, 2011

24. Massive Slump, PCH, San Pedro, CA, November 20, 2011

25. EROSION ( + 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.
Arid regions:
Intermittent streams (washes, arroyos,
wadis), badlands topography, plateaus,
mesas, buttes, inselbergs, etc.

26. 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
Alpine:
arête, horn (e.g., Matterhorn), col, glacial troughs (U-shaped valleys), hanging valleys, paternoster lakes, fjords;
Continental:
ice-scoured plains, glacial lakes, kettles and kettle lakes.

27. 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