Lecture Notes: Weathering, Erosion, and Deposition

Introduction

• Weathering, Erosion, and Deposition are key geological processes:
  • Weathering: Breaking down and changing rocks due to environmental exposure.
  • Erosion: Transporting weathered sediments from one location to another.
  • Deposition: Dropping off sediments at a new location.

Weathering

• Definition: The process of breaking down rocks into smaller pieces or changing them due to environmental factors.
• Types of Weathering:
  • Physical/Mechanical Weathering: Breakdown of rocks without changing their composition.
  • Chemical Weathering: Rocks are chemically altered due to reactions with substances like water or air.

Physical/Mechanical Weathering

• Characteristics: Changes size and shape without altering composition.
• Examples:
  • Frost Action/Ice Wedging: Water seeps into cracks, freezes, expands, and breaks rocks.
  • Exfoliation: Temperature changes cause rocks to expand and contract, leading to peeling and cracking.
  • Abrasion: Grinding of rock against rock, wind, water, or glaciers.
  • Root Wedging: Plant roots grow into cracks, breaking rocks apart.

Chemical Weathering

• Characteristics: Alters the chemical composition of rocks.
• Examples:
  • Oxidation: Formation of rust when iron reacts with oxygen in air or water.
  • Carbonation: Carbonic acid in water dissolves rocks like limestone, forming caves and sinkholes.

Erosion

• Definition: Transportation of sediments weathered from rocks.
• Example: Ocean currents moving fragments of granite from one location to another.

Deposition

• Definition: The dropping off of sediments at a new location.
• Example: Depositing of granite pieces onto a distant coastline.

Factors Affecting Weathering

1. Climate:
   • Hot and dry areas see less weathering.
   • Hot and wet climates increase chemical weathering.
   • Cold climates favor frost action.
2. Hardness of Rock:
   • Softer rocks weather faster than harder rocks.
3. Surface Area:
   • More exposed surface area leads to faster weathering.

Conclusion

• Overview of the processes of weathering, erosion, and deposition.
• Noted factors that influence the rate and type of weathering.
• Preview of upcoming content on erosion, transportation, and deposition processes.