PARENT ROCK

Hard or loose soil-forming rocks. Starting from the zero depth, which is located under the ground, it can reach up to several hundred meters. Loose material such as sand, gravel, volcanic sand and tuff, which are located under the soil or form the geological structure, or hard rock such as limestone, marble, granite, gneiss.

Parent Rock

Definition: A parent rock (also called bedrock or protolith) is the original rock from which soil, sediments, or metamorphic rocks are formed through weathering, erosion, or other geological processes. It serves as the foundation material for soil development and plays a significant role in determining the properties of the resulting soil or rock.

Types of Parent Rock

1. Igneous Rocks:

   • Formed from the cooling and solidification of magma or lava.
   • Examples: Granite, Basalt.
   • Soil Type: Typically forms mineral-rich soils with good drainage, such as sandy or loamy soils.

2. Sedimentary Rocks:

   • Formed from the compression and cementation of sediments (sand, clay, organic matter, etc.).
   • Examples: Limestone, Shale, Sandstone.
   • Soil Type: Can produce calcareous soils (lime-rich) or clayey soils, depending on the rock composition.

3. Metamorphic Rocks:

   • Formed when existing rocks (igneous or sedimentary) are transformed under heat, pressure, or chemical processes.
   • Examples: Marble (from limestone), Schist, Quartzite.
   • Soil Type: Usually forms thin soils that can vary based on the mineral content of the parent rock.

Processes That Form Soil from Parent Rock

1. Weathering:

   • Physical weathering: Breakdown of rock into smaller particles through mechanical forces (e.g., temperature changes, freezing and thawing, wind).
   • Chemical weathering: Alteration of rock minerals through reactions with water, acids, or oxygen.
   • Biological weathering: Actions of organisms (e.g., roots breaking rocks, microbial activity).

2. Erosion and Deposition:Weathered materials from the parent rock are transported by wind, water, or ice and deposited in new locations.

3. Decomposition:Organic matter from plants and animals mixes with weathered rock materials to form fertile soil.

Importance of Parent Rock

1. Soil Composition:

   • Determines the mineral content, texture, and fertility of the soil. For example:
     • Basalt-rich parent rocks create iron- and magnesium-rich soils.
     • Granite forms sandy, acidic soils.

2. Land Use:Soil formed from certain parent rocks may be better suited for agriculture, construction, or other uses.

3. Groundwater Recharge:The porosity and permeability of the parent rock affect water infiltration and aquifer formation.

4. Geological Studies:Understanding parent rock helps in studying the origin and evolution of landscapes.

Examples of Parent Rocks and Derived Soils

Parent Rock	Derived Soil	Characteristics
Granite	Sandy Soil	Drains well, low fertility.
Basalt	Black Soil	Rich in iron, calcium, and magnesium.
Limestone	Calcareous Soil	Alkaline, rich in calcium carbonate.
Shale	Clayey Soil	High water retention, nutrient-rich.
Sandstone	Sandy Soil	Well-draining, poor in nutrients.