Geology: Exogenic Processes

Exogenic Processes

• Exogenic processes modify the Earth's surface, causing degradation and sculpting the landscape.
• Key types include weathering, erosion, mass movement (mass wasting), deposition, and sedimentation.

Weathering

• Weathering involves the disintegration (physical) and decomposition (chemical) of rocks.
• Types of weathering are classified into physical and chemical categories.

Physical Weathering

• Rocks break into smaller pieces without changing composition through physical weathering.
• Factors causing physical weathering:
  • Thermal and Pressure Change: Rock expands when heated and contracts when cooled, leading to crumbling.
  • Temperature: High temperatures cause expansion, while freezing can also fracture rocks.
  • Frost Wedging: Water enters cracks in rocks, freezes, and expands, causing further breakage.
  • Abrasion: Friction and impact from moving particles like sand and silt shape rocks by wearing down sharp edges.
  • Organic Activity: Plant roots can penetrate cracks and expand, leading to rock breakage.
  • Human Activities: Actions such as digging, quarrying, and deforestation contribute to physical changes in rocks.
  • Burrowing Animals: Animals like rats and rabbits excavate ground, altering soil and rock structures.

Chemical Weathering

• Causes decomposition of rocks through chemical reactions altering rock-forming minerals.
• Factors causing chemical weathering:
  • Dissolution: Rock minerals dissolve in water, altering structure.
  • Hydrolysis: Acidic water breaks down minerals into clay and soluble salts.
  • Carbonation: Carbon dioxide combines with water to form carbonic acid, leading to weathering of limestone and formation of stalactites.
  • Oxidation: Oxygen and water react with minerals (e.g., iron-rich rocks), causing rusting and surface decomposition.

Erosion

• Involves the movement of rock particles by agents such as wind, water, ice, and gravity.
• Agents of erosion: Water, wind, ice, and gravity significantly impact landscape alteration.
• Running Water: The most powerful erosive force, reshaping landscapes by transporting sediments during heavy rains and floods.
• Wind: Carries sand and dust, particularly in arid regions, forming dunes and landscapes via erosion.
• Ice: Glaciers erode landscapes by picking up and transporting materials as they move.

Mass Movement

• Involves the downhill movement of soil and rock debris influenced by gravity.
• Types of mass wasting processes include slump, solifluction, earthflow, mudflow, debris slide, debris flow, rock flow, and soil creep.
• Slump: Sliding of cohesive materials along a curved surface.
• Solifluction: Slow downhill flow of saturated soil.
• Earthflow: Viscous flow of fine-grained materials saturated with water.
• Mudflow: Rapid movement of mud down slopes.
• Debris Slide: Chaotic movement of mixed materials down slopes.
• Debris Flow: Loose materials traveling downhill under gravity.
• Rock Fall: Detachment of rocks from steep cliffs.
• Soil Creep: Gradual, slow movement of soil over time.

This quiz covers the concepts of weathering, erosion, and deposition as exogenic processes. You will learn how these processes occur and identify the agents responsible for them. Test your understanding of how these forces shape and transform Earth's crust.