Lecture Notes: Geomorphology - Transportation and Deposition

Introduction

• Presenter: Dr. Krishnanand
• Topic: Transportation and Deposition as Geomorphological Processes
• Context: Fourth important type of denudation process following weathering, erosion, and mass wasting.

Transportation

• Definition: Movement of particles after they are entrained by erosional agents like water or wind.
• Factors Affecting Transportation:
  • Velocity of Medium: Determines how far a particle can be transported.
  • Surface: Slope angle affects transportation.
  • Particle Characteristics: Weight, size, shape, and surface configuration impact movement.
  • Medium Type: Whether water, air, glaciers, etc.

Transportation Processes

1. Suspension: Particles are suspended in the medium (air, water).
2. Saltation: Particles bounce along the surface.
3. Traction: Rolling or sliding along the surface.
4. Solution: Minerals dissolved in water.
   • Mnemonic: SSTs - Suspension, Saltation, Traction, Solution.

Deposition

• Definition: Process where transported materials are laid down or settled.
• Causes:
  • Loss of velocity and energy by erosional agents.
  • Coarser materials settle first, followed by finer particles.

Processes and Features

• Deposition Sequence: Bhabar (coarse) → Terai → Bangar → Khadar (fine)
• Filled Depressions: Deposition fills surface depressions over time.
• Null Point Hypothesis: Threshold where transportation forces are balanced by gravity and friction, resulting in deposition.

Depositional Landforms

• Agents: Same as erosional agents - running water, glaciers, wind, waves, and groundwater.

Fluvial Depositional Features

• Alluvial Fans: Cone-shaped deposits at the base of slopes.
• Natural Levees: Raised riverbanks from deposition.
• Meanders and Oxbow Lakes: Curves in rivers and cut-off lakes.
• Deltas: Formed from silt and finer materials at river mouths.

Glacial Depositional Features

• Moraines: Deposits left by glaciers (lateral, medial, end).
• Eskers and Kames: Long ridges and mounds from glacial deposits.
• Drumlin: Elongated hills formed from glacial action.

Aeolian Depositional Features

• Sand Dunes: Various types (barkhan, parabolic, transverse, longitudinal).
• Loess Deposits: Fine silt deposits, e.g., in China's Yellow River.

Coastal and Other Depositional Features

• Beach Deposits: Sand dunes and backshore deposits.
• Sandbars: Formations in bays (e.g., spits, baymouth bars).
• Speleothems: Stalactites and stalagmites formed by groundwater action.

Conclusion

• Future Topics: Theories of landforms by Davis, Penck, Elsie King, and others.
• Reminder: Share and subscribe to The Geoecologist for more sessions.