Transcript Geomorphic Processes: Endogenic and Exogenic

Geomorphic Processes:
II. Exogenous
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
 Endogenous (Endogenic) vs.Exogenous (Exogenic)
Processes
 Rock Cycle 
A. Endogenous Processes
Endogenous 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. 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
2. Aggradation Processes
a. Deposition – fluvial, eolian, glacial, coastal
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
 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
 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
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
La Conchita Landslide, January 10, 2005
Monterey Park Debris Flow, 1980
PCH near Pacific Palisades, November 1956
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.
• 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,.
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