Geological Processes on Earth

Geological Processes on Earth

• Geological processes describe the natural forces that shape a planet's physical makeup.
• These processes are studied by geologists and earth scientists to understand the planet's history, locate resources, and predict events like earthquakes, tsunamis, and volcanic eruptions.
• Key processes include: Plate Tectonics, Weathering, Erosion, and Sedimentation.
• Processes are categorized as exogenous (external) and endogenous (internal).

Exogenous Processes (External)

• Occur near the Earth's surface.
• Primarily driven by gravity, water, wind, and organisms.
• Exogenous processes often have a destructive aspect reshaping landscapes and ecosystems.
• In extreme cases, they can wipe out most organisms in an area.
• Examples include weathering, erosion, and mass movement.

Types of Exogenous Processes

• Weathering: The disintegration of rocks, soil, and minerals. This occurs through contact with Earth's systems without movement.
  • Physical Weathering: Breakdown of rocks without a change in composition. Examples include thermal and pressure change, wind and waves, freeze and thaw.
    • Thermal and pressure change: Rocks breaking due to alternating hot and cold temperatures. Expansion when heated and contraction when cooled causes cracking and breakdown.
    • Wind and Waves: Wind carrying sand particles that erode rock surfaces; waves chipping and cracking rocks along shorelines.
    • Freeze-thaw: Water seeps into cracks in rocks, freezes, and expands, widening the cracks causing eventual breakdown.
    • Frost Wedging: Water freezing and expanding in cracks within rocks causing them to break.
    • Salt Wedging: Dissolved salts crystallize and expand in the fissures in rocks causing them to break.
    • Ex: Soil cracks due to extreme heat and drought, wind erosion, waves eroding coastlines.
  • Chemical Weathering: Decomposition of rocks due to chemical reactions between minerals in rocks and the environment. The environment can include water and gases in the atmosphere.
    • Oxidation: Reaction of a substance with oxygen.
    • Hydrolysis: Chemical breakdown of a substance when combined with water.
    • Acid Rain: Corrodes or deteriorates metal and stone causing a change in their properties.
    • Ex: Chemical weathering is key to the formation of caves as water reacts with limestone.
• Erosion: Movement of weathered rock (snow, soil, sand, and pebbles) to a new location. Erosion always follows weathering to complete material transfer.
  • Examples include wind erosion, flowing water erosion, glacial erosion, and waves erosion.
• Mass Movement (Mass Wasting): Bulk movements of soil, sand, and rock debris downslope in response to gravity. This includes various processes like slope movement, subsidence and sinking. Include rapid events like landslides and debris flows or gradual movements like soil creep.
  • Debris Flow: Large amounts of sediment, predominantly rocks, falling down a slope without necessarily needing water.
  • Mudflow: Combined soil and water flowing down a slope, usually occurring near water sources.
  • Slump: Slow movement of soil along curved surfaces.

Endogenous Processes (Internal)

• Occur deep inside the Earth, often due to plate tectonics, volcanic activity, etc.
• Not directly covered in the notes.