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Geomorphic Processes: II. Exogenous

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

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Geomorphic Processes: II. Exogenous

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

  2. Geomorphic Processes: • Physical processes which create and modify landformson the surface of the earth • Endogenous (Endogenic) vs.Exogenous (Exogenic) Processes • Rock Cycle 

  3. Endogenous Processes are large-scale landform building and transforming processes • – they createrelief. • 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 A. Endogenous Processes

  4. Also calledGradational Processes, they comprise degradation and aggradation– they modifyrelief • 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 B. Exogenous Processes

  5. Degradation Processes:Weathering, Mass Wasting,Erosion and Transportation

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

  7. WEATHERING • Weathering is disintegration and decomposition of rocks insitu – 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 inmicroscopic 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

  8. 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

  9. 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)

  10. 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

  11. 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

  12. La Conchita Landslide, January 10, 2005

  13. Monterey Park Debris Flow, 1980

  14. PCH near Pacific Palisades, November 1956

  15. EROSION and TRANSPORTATION • – Various Geomorphic Agents, associated Processes, • and resultingErosional Features • Flowing Water –Fluvial Morphology • Humid regions: • Perennial streams and entrenched • channels, rapids, waterfalls, plunge • pools, potholes, meandering streams, • bank erosion, oxbow lakes, etc.

  16. 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,.

  17. – 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 DEPOSITION

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