The correct option is 2 and 3 only.
Explanation
Physical or mechanical weathering refers to the disintegration and breakdown of rocks into smaller fragments without any alteration to their chemical composition. These processes are driven by physical forces acting on the rock mass.
Statement-wise Analysis:
- Statement 1 is Incorrect. Physical weathering processes depend on applied forces such as gravitational forces (overburden pressure, load, and shearing stress), expansion forces (due to temperature changes, crystal growth, or animal activity), and water pressures. They do not depend on chemical interactions. Chemical interactions drive chemical weathering processes such as solution, carbonation, hydration, and oxidation.
- Statement 2 is Correct. The majority of physical weathering processes are driven by thermal expansion and pressure release.
- Thermal Expansion: Repeated heating and cooling (insolation weathering) induce expansion and contraction in rock minerals, creating stress that leads to fracture.
- Pressure Release (Unloading): When overlying materials are removed through erosion, the vertical pressure on the underlying rock decreases. This causes the rock to expand, leading to the formation of joints and fractures parallel to the surface (sheeting).
- Statement 3 is Correct. While individual weathering events may seem minor, these processes are persistent. The repetitive cycle of expansion and contraction (thermal or moisture-related) causes material fatigue. Although the process is slow, it results in significant disintegration and damage to rock formations over geological time.
Key Takeaway:
Physical weathering is the mechanical disintegration of rocks caused primarily by thermal expansion, pressure release (unloading), and frost action, distinct from chemical weathering which involves changes in mineral composition.