Soil Formation from Rocks
- Is a gradual process where rocks break down into soil particles over time.
- This natural phenomenon is slow but persistent, particularly when it occurs directly on hard rocks.
A. Types of Soils Based on Rock Origin
a. Sedentary Soils (Form in place)
- Develop directly from underlying bedrock.
- Common on sedimentary rocks (e.g., sandstone, limestone).
- Depth: Shallow in areas with rapid erosion, deeper on stable slopes.
b. Transported Soils (Moved by natural forces)
- Moved by wind, water, ice, or gravity.
- Tend to accumulate away from their rock source.
B. How Rocks Turn into Soil?
a. Physical Weathering (Mechanical Breakdown)
- Temperature changes (expansion/contraction)
- Freeze-thaw cycles (frost wedging)
- Root penetration (biological disruption
b. Chemical Weathering (Mineral Alteration)
- Hydrolysis (feldspar to clay)
- Oxidation (rust formation)
- Carbonation (limestone dissolution)
c. Biological Weathering (Organisms at Work)
- Plant roots crack rocks.
- Microbial activity releases acids.
C. Landforms Shaped by Soil Formation:
a. Pediments: (Gentle, erosion-formed slopes)
- Result from long-term weathering and erosion.
- Covered by a thin soil layer.
b. Plateaus: (Flat-topped highlands)
- Form when water erosion cuts through horizontal rock layers.
c. Mesas: (Medium-sized plateaus)
- Arise from differential erosion where hard rock sits above softer layers.
d. Buttes: (Isolated rock towers)
- Smallest remnants of eroded plateaus.