The concept of geomorphic processes and their role in shaping landscapes

Geomorphic processes are natural mechanisms that alter the Earth's surface, creating and modifying landforms over time. These processes are fundamental in shaping landscapes through the breakdown, removal, and movement of rock and soil materials.

Types and mechanisms of weathering

Weathering is the process by which rocks are broken down into smaller pieces without being transported. It occurs through physical, chemical, or biological means.

Categories of weathering

• Mechanical weathering - Involves the physical disintegration of rocks without altering their chemical makeup.
  • Freeze-thaw weathering - Happens in areas where temperatures fluctuate around 0°C. Water seeps into cracks in rocks like basalt, freezes and expands, exerting pressure on the rock walls. When it thaws, the pressure is released. Repeated cycles enlarge cracks, eventually causing fragments to break off.
  • Salt weathering - Occurs in coastal or arid regions where salt water enters rock cracks. As the water evaporates, salt crystals form and grow, applying pressure that splits the rock apart.
• Chemical weathering - Breaks down rocks by altering their chemical composition.
  • Carbonation weathering - Takes place in warm, wet climates. Rainwater absorbs carbon dioxide from the atmosphere, creating a mild carbonic acid. This acid reacts with rocks containing calcium carbonate, such as chalk, dissolving them over time.
• Biological weathering - Involves living organisms contributing to rock breakdown.
  • Root action - Plant roots, especially from trees, grow into rock fissures, exerting force as they expand, which pries the rock apart.

Processes of erosion in coastal and river environments

Erosion is the wearing away and removal of rock and soil material by natural agents like water and wind. It is a critical geomorphic process in both coastal and river settings.

Mechanisms of erosion

• Hydraulic action - The sheer force of water dislodges material.
  • In coastal areas, waves strike cliffs, compressing air in cracks, which forces the rock apart over time.
  • In rivers, the water's power directly removes particles from the channel bed and banks.
• Abrasion - Eroded particles carried by water act as abrasives.
  • These particles grind against cliffs, sea beds, or river channels, scraping away small fragments and smoothing surfaces. This is the dominant form of erosion in river systems.
• Attrition - Particles in water collide with each other.
  • Repeated impacts break them into smaller pieces and round off sharp edges. In rivers, particle size decreases from source to mouth due to this process.
• Solution - A chemical process where water dissolves rock.
  • Both river and sea water, made slightly acidic by dissolved carbon dioxide, react with certain rocks like marble and travertine, dissolving them into the water.

The nature and causes of mass movement

Mass movement refers to the transfer of material down a slope when gravitational forces exceed the forces holding the material in place. It plays a significant role in landscape change, particularly in coastal areas where it can lead to rapid retreat of cliffs.

Types of mass movement

• Slides - Material moves in a straight line down the slope.
• Slumps - Material shifts with a rotational motion.

Factors contributing to mass movement

• Water content - Saturated material is heavier and acts as a lubricant, reducing friction and increasing the likelihood of movement.
• Slope undercutting - Erosion at the base of a slope, often by waves or rivers, destabilises the material above, making mass movement more probable.