Erosion

Chapter 1: Introduction

  • Welcome to part 2 of video series about module 9: Exogenic Process.

  • Today's focus: Second type of exogenic process, starting with a review of weathering.

    • Weathering: Breaking down of rocks into smaller particles.

    • Types of Weathering:

      • Mechanical Weathering: Exfoliation, frost wedging, root wedging, salt wedging, thermal expansion.

      • Chemical Weathering: Dissolution, hydrolysis, oxidation, hydration, biological weathering.

  • Moving on to erosion.

    • Erosion Defined: Separation and removal of weathered rocks and soil from its substrate (origin).

    • Erosion vs. Weathering: Weathering is breaking down, whereas erosion is the movement of particles.

    • Transportation: Movement of sediments from source to deposition area.

    • Agents of Erosion: Wind, glacial, and water.

Chapter 2: Process of Wind Erosion

  • Wind Erosion: Occurs in flat, bare, dry, or sandy areas.

    • Examples: Sand dunes, effects of sandstorms in desert areas.

    • Impacts: Loss of soil, dryness, and nutrient depletion.

    • Mechanics of Wind Erosion:

      • Creeping: Larger particles roll along the surface.

      • Saltation: Smaller particles bounce and are displaced.

      • Suspension: Very fine particles are carried aloft by the wind.

    • Formation of Sand Dunes: Wind shapes the dunes through the processes mentioned.

Chapter 3: Types of Erosion

  • Glacial Erosion: Carving and shaping of land beneath glaciers.

    • Movement of glaciers leads to scraping of rock and soil (abrasion).

    • Processes:

      • Plucking: Rocks become detached and are carried away by glaciers.

      • Abrasion: Scraping action of sediments carried by the glacier.

  • Water Erosion: Most common type of erosion, occurs in areas near rivers, coasts, and oceans.

    • Types of Water Erosion:

      • Splash Erosion: Detachment of soil from rain impact.

      • Sheet Erosion: Removal of thin layers of soil.

      • Gully Erosion: Narrow openings carrying excess water, leading to sediment removal.

      • Valley Erosion: Example: Grand Canyon created by continuous water flow.

      • Bank Erosion: Erosion along riverbanks.

      • Coastline Erosion: Water interacting with sediments on beaches.

      • Seaside Cliff Erosion: Rock formations shaped by wave action.

Chapter 4: Process of Erosion

  • Water Erosion: Initiated by rainfall (splash erosion).

    • Splash Erosion: Drops detach soil grains.

    • Sheet Erosion: Better defined flow of water, removing fine soil grains.

    • Gully Erosion: Water flows through narrow openings, transporting sediments.

    • Valley Erosion: Water width increases over time due to sediment transport, shaping valleys.

    • Bank Erosion: Continuous water flow erodes sediment from riverbanks.

Chapter 5: Glacial Erosion Movement

  • Glacial erosion involves two main processes: plucking and abrasion, impacting land beneath glaciers.

    • Glacial movement causes physical reshaping of the landscape, impacting soil and rock.

    • Water Erosion: Most significant type of erosion, can cause various landforms.

    • Movements of Sediments:

      • Suspension: Light sediments carried within the water column.

      • Traction: Heavier materials rolled along the riverbed.

      • Saltation: Sediments bouncing off the riverbed.

      • Solution: Dissolved materials transported with water.

Chapter 6: Conclusion

  • Water erosion effects: Creation of valleys, cliffs, and unique rock formations such as sea stacks.

  • Examples include effects observed in the Philippines with erosion issues in Manila Bay.

  • Final Notes: Differentiate between weathering (on-site breakdown) and erosion (movement away from location).

  • Questions to be posted in module Q&A.