Biological weathering is the breakdown of rocks due to the activities of living organisms, including plants, animals, and microorganisms. It involves both physical and chemical processes.

Processes of Biological Weathering:

 

1. Plant Roots Penetration (Root Wedging)

○ Roots grow into rock cracks and expand as they absorb water.

○ Over time, the pressure from growing roots forces rocks apart.

○ Example: Tree roots breaking concrete sidewalks or rock surfaces.

 

2. Microbial Activity (Organic Acid Secretion)

○ Bacteria, fungi, and lichens produce organic acids that dissolve minerals in rocks.

○ This process helps in soil formation by releasing nutrients.

○ Example: Lichens on rocks secrete acids that dissolve minerals like feldspar.

 

3. Burrowing Animals

○ Animals like earthworms, ants, and rodents disturb rocks by digging and burrowing.

○ This exposes rocks to air and water, speeding up other weathering processes.

○ Example: Termites and moles breaking down soil particles.

 

4. Human Activities

○ Mining, deforestation, and construction break rocks, leading to faster weathering.

○ Roads and buildings accelerate exposure to physical and chemical agents.

○ Example: Quarrying and drilling weaken rock formations.

 

5. Decomposition of Organic Matter

○ Decaying plants and animals release carbon dioxide and acids, which react with rocks.

○ These acids promote chemical weathering by breaking down minerals.

○ Example: Humic acid from decomposing leaves dissolving limestone.