Transcript Geomorphic Processes: Endogenic and Exogenic

Geomorphic Processes:
II. Exogenic
II. Gradation Processes –
Weathering, Mass Wasting,
Erosion, Transportation
and Deposition
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 
A. Endogenic Processes
Endogenic Processes are large-scale landform
building and transforming processes
– they create relief.
1. Igneous Processes
a. Volcanism: Volcanic eruptions  Volcanoes
b. Plutonism: Igneous intrusions
2. Tectonic Processes (Also called Diastrophism)
a. Folding: anticlines, synclines, mountains
b. Faulting: rift valleys, graben, escarpments
c. Lateral Faulting: strike-slip faults
Earthquakes  evidence of present-day tectonic activity
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)
2. Aggradation Processes
a. Deposition – fluvial, eolian, glacial, coastal
A Conceptual Model
of
Gradation
(Erosion + Deposition)
Relationship:
Weathering
Mass Wasting
Erosion
and
Transportation
Together,
these processes are
responsible for
Denudation
of Earth’s surface
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
 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
 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
 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)
 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
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
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
Classification of Mass Wasting
Based on
• Speed of Movement
• Kind of Earth Material Involved
• Kind of Motion Involved
Soil Creep 
Classification of Mass Wasting
Based on
Moisture Content
and
Speed of Movement
La Conchita Debris Flow/Earthflow, January 10, 2005
Monterey Park Debris Flow, 1980
Landslide/Earthflow on PCH near Pacific Palisades
November 1956
Slump in Coastal California near San Clemente
January 7, 2011
Massive Slump, PCH, San Pedro, CA, November 20, 2011
Massive Slump, PCH, San Pedro, CA, November 20, 2011
Massive Slump, PCH, San Pedro, CA, November 20, 2011
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.
• 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.
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