Geomorphic Processes

Geomorphic 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

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

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

1.         Degradation Processes

 Also called Denudation Processes  

a. Weathering ,

b.  Mass Wasting 

c.  Erosion and Transportation

2. Aggradation Processes

a. Deposition – fluvial, eolian, glacial, coastal

Relationship: Weathering Mass Wasting 

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

Ø Types of Weathering:

1) Physical or Mechanical Weathering, 

2) Chemical  Weathering, 

3) Biological Weathering

q 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

q 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)

q 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. Talus Cones in the Canadian Rockies