Here's a breakdown of what it means:
* Unweathered bedrock: This means the rock has not been broken down or altered by weathering processes like rain, wind, or ice.
* Parent material: The D horizon is the source of the minerals and other components that make up the soil layers above it.
* Underlying layer: The D horizon is the deepest layer of the soil profile, sitting below the C horizon (which is partially weathered bedrock).
Key Points about the D horizon:
* Not always present: The D horizon isn't always visible or easily accessible, as it may be buried deep underground.
* Varying composition: The D horizon can be composed of different types of rock, such as granite, limestone, or sandstone.
* Important for soil formation: The D horizon's composition and properties play a significant role in determining the characteristics of the soil layers above it.
Examples of D horizons:
* A large granite boulder sitting deep beneath the soil.
* A layer of limestone that has not been weathered and broken down.
* A layer of sandstone that is still solid and intact.
In summary, the D horizon is the unweathered bedrock that serves as the source material for soil formation.
