Earth_Science_SHS_10.1_Weathering

Weathering Overview

• Weathering is the natural process of breaking down rocks and minerals on the Earth's surface into smaller particles through environmental factors.

Objectives of Lesson 10.1

• Differentiate between mechanical weathering and chemical weathering.

• Describe how rocks undergo weathering.

• Enumerate factors that contribute to weathering.

Concepts of Weathering

Definition

• Weathering is the process of breaking down rocks found at Earth's surface.

Environmental Factors

• Weathering is influenced by:

  • Rainwater

  • Extreme temperature fluctuations

  • Biological activities.

Types of Weathering

Mechanical Weathering

• Definition: The breaking down of rocks into smaller pieces without altering their chemical composition.

• Factors contributing to Mechanical Weathering:

  • Fluctuating temperatures and pressure.

  • Biological activity.

• Examples: Rocks by the sea change shape due to the force of water during high tide.

Types of Mechanical Weathering

1. Frost Wedging

   • Process: Involves repeated cycles of freezing and thawing of ice.

   • Conditions: Requires moisture, existing cracks, and fluctuating temperatures.

2. Salt Crystal Growth

   • Process: Occurs when seawater enters crevices in rocks, mainly in rocky shorelines and arid regions.

   • Mechanism: Salt crystals expand with temperature increases, widening cracks.

3. Biological Activity

   • Description: Activity of organisms (plants and animals) that reduce the size of rocks, making them more susceptible to chemical weathering.

4. Unloading

   • Process: Erosion or uplift removes thick layers of sediments over buried rocks, reducing pressure and leading to mechanical weathering.

Chemical Weathering

• Definition: process where rock materials are altered into different substances with distinct physical and chemical properties.

Types of Chemical Weathering

1. Dissolution

   • Process: A solid (e.g., halite) dissolves in a liquid (e.g., water).

2. Hydrolysis

   • Process: Water reacts with a mineral resulting in the formation of a new mineral.

3. Oxidation

   • Description: The chemical combination of oxygen with a mineral, forming a different mineral with a higher ionic charge.

Factors Affecting Weathering

• Climate: The amount of moisture and temperature where weathering occurs affects the process.

• Elevation: Higher elevations are more susceptible to weathering due to exposure to environmental factors.

Comparison of Mechanical and Chemical Weathering

Key Points

1. Weathering involves the breakdown of rocks through mechanical and chemical processes.

2. Factors influencing weathering include climate, surface area, topographic relief, and rock composition.

3. Distinction between chemical and mechanical weathering is critical for understanding rock degradation process.