Earth's Dynamic Processes: Weathering, Transport, and Landforms

Geological Processes: Weathering, Transport, and Landforms

Physical Weathering

• Frost Wedging (Gelifracció)

  Occurs when water enters cracks and fissures in rocks, then freezes and expands, causing the rock to break apart.

• Thermal Stress (Termoclàstia)

  The process where rocks expand when heated and contract when cooled. Repeated cycles cause outer layers to peel off due to differential expansion.

• Unloading (Descompressió)

  The reduction in pressure experienced by rocks that formed under high pressure deep within the Earth. As overlying material is removed, the rock expands and fractures.

Chemical Weathering

• Oxidation

  Oxygen from the air or dissolved in water reacts with certain minerals, especially those containing iron, leading to their breakdown.

• Dissolution

  Affects minerals that are soluble in water, such as some carbonates, sulfates, and chlorides, dissolving them away.

• Carbonation

  The reaction of certain minerals with carbonic acid (formed when carbon dioxide dissolves in water), leading to their dissolution.

• Hydrolysis

  The alteration of minerals through reaction with hydrogen (H+) and hydroxyl (OH-) ions from water.

Biological Weathering

• Biological Weathering (Met. Biològica)

  Mechanical rupture or chemical alteration of rocks caused by the actions of living organisms.

Geological Transport and Sedimentation

Sediment Transport Mechanisms

• Bedload Transport (In Contact with the Bottom)

  When the fluid (e.g., water or wind) is unable to keep clasts (sediment particles) in suspension, these clasts move along the bottom by rolling (traction), dragging (bedload), or bouncing (saltation).

• Suspended & Dissolved Load Transport

  When fine clasts are suspended within the fluid, or if soluble materials are transported dissolved within the fluid (solution), or by flotation.

Sedimentation

• Sedimentation

  The accumulation of materials carried by a geological agent (e.g., water, wind, ice).

Aeolian Processes (Wind-Related)

• Aeolian Deflation

  Wind removes finer materials, leaving behind larger, coarser particles, which creates a stony desert pavement known as a 'reg'.

• Aeolian Abrasion

  Wind carrying sand particles polishes and erodes rock surfaces, primarily affecting the lower parts of rocks.

• Aeolian Transport and Sedimentation

  • Loess Deposits

    Accumulations of wind-transported silt and dust. They cover vast areas, especially in peripheral desert regions.

  • Dunes

    Accumulations of sand that can take various forms, such as crescent-shaped (barchans) or sinuous ridges parallel to the wind direction. They are characteristic features of sand deserts, also known as 'ergs'.

Geological Landforms

Fluvial Landforms (River-Related)

• V-shaped Valleys

  Formed by rivers that are highly erosive, cutting a deep, narrow channel, resulting in a V-shaped cross-section.

• Flat-bottomed Valleys / Meandering Valleys

  Formed by rivers that lose erosive force as their gradient decreases. The river develops S-shaped bends (meanders), depositing sediments on the inside of the curves, gradually creating a wider, flatter valley floor.

Glacial Landforms

• U-shaped Valleys

  Wide, deep valleys with a rounded profile, created by glacial erosion.

• Over-excavated Zones / Glacial Basins

  Depressions produced by glacial ice. When the glacier retreats, these over-excavated zones often fill with water, forming lakes or tarns.

Karst Landforms

• Karst Topography (Modelat Càrstic)

  Landforms created by the dissolution of soluble rocks, typically limestone. Features include dissolution sinkholes, collapse dolines (when cave roofs fall), horizontal galleries, vertical shafts (avencs), and subterranean caves.