ES_Q2_Week_1_Lesson_1

Weathering

  • Definition: The process of breakdown of rocks at the Earth’s surface by water, ice, acids, salts, plants, animals, gravity, and changing temperatures.

Types of Weathering

  • Three Types:

    1. Physical (Mechanical) Weathering

    2. Chemical Weathering

    3. Biological Weathering

A. Physical (Mechanical) Weathering

  • Caused by changing temperatures affecting rocks, leading to breakdown.

  • Assists by water, particularly in areas with little soil and few plants (e.g., mountains, deserts).

  • Occurs through:

    • Repeated freezing and thawing (in tundra or mountainous areas).

    • Expansion and contraction of rock surfaces due to sun exposure (in hot deserts).

Types of Physical Weathering

  1. Abrasion: Rocks are worn down by exposure to water, wind, and gravity.

  2. Freeze-thaw: Water seeps into cracks, freezes, expands, and breaks rocks.

    • Process:

      • Water collects in cracks, freezes overnight, expands, and splits the rock.

      • During the day, ice melts, water deepens the crack, and refreezes at night.

  3. Exfoliation: Development of cracks parallel to the land surface from pressure reduction during uplift and erosion.

    • Occurs in upland areas with coarse crystalline rocks.

    • Process:

      • Pressure decreases as erosion exposes the rock, leading to cracks.

      • Water enters cracks, causing chemical weathering and rock slab detachment.

B. Chemical Weathering

  • Occurs when rainwater reacts with mineral grains to form new minerals (clays) and soluble salts.

  • Most rapid in warm, damp climates.

  • Essential for soil production (e.g., hydrolysis, oxidation).

Types of Chemical Weathering

  1. Carbonation: Carbon dioxide forms weak carbonic acid in rainwater, dissolving limestone and creating caves over time.

  2. Acidification: Pollutants like sulfur dioxide create stronger acids in rainwater, leading to acid rain that damages buildings and monuments.

  3. Hydrolysis: Acidic water reacts with minerals to produce clay and salts; quartz remains unaffected.

  4. Hydration: Water chemically modifies rock structure (e.g., anhydrite to gypsum).

  5. Oxidation: Reaction of oxygen and water with rocks, often rusting iron-rich surfaces.

C. Biological Weathering

  • Weakening of rocks by biological agents (plants and animals).

  • Plant roots create fractures in rocks, leading to breakage.

Classification of Biological Weathering

  1. By Physical Means: Burrowing animals move rock fragments to the surface, enhancing weathering.

  2. By Chemical Compounds: Some organisms produce acids that slow the disintegration of rocks.

Written Work

  • Research on how humans harness Earth’s internal energy for electricity and latest developments in Earth's internal structure.