Geomorphology and Landform Processes

Geomorphology
  • Definition: The study of landforms and their evolution.
  • Focus: Examines form-process relationships involving mass and energy interactions in identifiable locations and landforms.
  • Landscape: Considered the sum (and more) of landforms and processes.
  • Processes Covered: Includes weathering and mass wasting.
  • Major Subdisciplines:
    • Fluvial
    • Aeolian
    • Coastal
    • Glacial
    • Floodplain
    • Tectonic
    • Groundwater
    • Storm
    • Engineering
    • Human
Importance of Geomorphology
  • Helps to explain:
    • Landscape evolution and future changes.
    • Soil variations within landscapes.
Fluvial Processes and Landforms
  • Fluvial Landforms: Formed primarily through processes of running water, including erosion, transport, and deposition of sediment.
  • Classification:
    • Erosional: Resulting from water eroding landscapes.
    • Depositional: Resulting from sediment being deposited by water.
  • Processes Involved:
    • Overland Flow: Hillslope processes affecting erosion.
    • Streamflow: River processes affecting erosion and sediment transport.
Key Concepts and Diagrams
  • Hjulström Diagram: Relates river energy, sediment size, and the dominant processes occurring in the streamflow.
  • River Long Profiles: Flow profiles observed from the headwaters to the sea showing varying processes (erosion, transport, deposition).
  • River Plan Forms: Features of floodplains, including meandering rivers and oxbow lakes.
Erosion, Transport, and Deposition

  1. Erosion Methods:

    • Hydraulic Action: Water flow creates pressure in bank cavities causing erosion.
    • Abrasion: Sediments wear down stream banks and beds through collision.
    • Attrition: Sediments collide and chip into smaller, rounded pieces.
    • Corrosion/Dissolution: Acidic water dissolves certain rock types, such as limestone.

  2. Transport of Sediments:

    • Occurs when water energy (volume and velocity) is sufficient to carry sediments.
    • Types of Load:
      • Dissolved Load: Minerals in solution.
      • Suspended Load: Smaller particles held in suspension by turbulence.
      • Bed Load: Larger particles that roll or slide along the riverbed.

  3. Deposition of Sediments: Happens when river energy decreases, causing sediments to settle out of the water.

    • General Outcomes:
      • Aggradation: Increased sediment deposition.
      • Degradation: Erosion of streambed sediment.
River Profiles
  • Upper Course: Characterized by vertical erosion, steep gradient, predominance of erosion processes.
  • Middle Course: Transition between erosion and deposition with a decreasing gradient.
  • Lower Course: Predominantly deposition and alluvial landscapes, with meandering rivers.
Human Impact on Rivers
  • Rivers are essential for:
    • Water sources, food production, settlements, transport, and trade.
  • River Delta Formation: Occurs where sediments accumulate at the river mouth leading to the formation of landforms like deltas.
    • Process: River slows down, splits into distributaries, and builds delta from sediment layer accumulation.
Aeolian Processes
  • Definition: Wind-driven processes affecting soil and landscape formation.
  • Impact on Landscapes:
    • Erosion, transport, and deposition of soil.
    • Formation of aeolian landforms such as dunes.
  • Types of Dunes:
    • Longitudinal, Barchan, Star, Transverse, Parabolic.
  • Aeolian Conditions: Most active during dry conditions and periods of low vegetation, affecting soil fertility.
Summary of Impacts
  • Erosion: Soil top-quality loss due to fine material removal by wind.
  • Human Activities: Dust storms and health impacts related to wind erosion.
Final Notes
  • Fluvial and aeolian processes are critical in landscape development and human influence on natural systems.