Questions: 3. What are the four main causes of weathering?

The four main causes of weathering are:

1. Physical (Mechanical) Weathering: This type of weathering occurs when physical forces break down rocks into smaller pieces without changing their chemical composition. Examples include:

   • Frost Wedging: Water seeps into cracks in rocks, freezes, and expands, causing the rock to break apart.
   • Thermal Expansion: Repeated heating and cooling of rocks cause them to expand and contract, leading to fractures.
   • Abrasion: Rocks and sediments grind against each other, wearing down surfaces.

2. Chemical Weathering: This process involves the chemical alteration of minerals within rocks, leading to their breakdown. Examples include:

   • Hydrolysis: Water reacts with minerals to form new minerals and soluble salts.
   • Oxidation: Oxygen reacts with minerals, especially those containing iron, to form oxides, such as rust.
   • Carbonation: Carbon dioxide in water forms carbonic acid, which reacts with minerals like calcium carbonate in limestone, leading to dissolution.

3. Biological Weathering: This type of weathering is caused by the actions of living organisms. Examples include:

   • Root Expansion: Plant roots grow into cracks in rocks, exerting pressure and causing the rocks to break apart.
   • Lichen and Moss Growth: These organisms produce acids that chemically break down rock surfaces.

4. Human Activity: Human actions can accelerate weathering processes. Examples include:

   • Construction and Mining: These activities expose rocks to the elements, increasing their rate of weathering.
   • Pollution: Emissions from industrial activities can lead to acid rain, which chemically weathers rocks.

In summary, the four main causes of weathering are physical (mechanical) weathering, chemical weathering, biological weathering, and human activity. Each of these processes contributes to the breakdown and alteration of rocks and minerals on Earth's surface.