NSSS7.2

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=7.2 Soil Formation and Composition=

Vocabulary

 * Soil**: Weathered and loose material on the Earth's surface in which plants can grow in.
 * Bedrock**: The bedrock is the solid block of rock beneath the soil.
 * Humus**: A very dark-colored substance that forms when animals and plants decay.
 * Loam:** Soil that is made out of equal amounts of clay, sand, and silt.
 * Soil Horizon**: A soil layer that differs in color and texture from the layers that are above the soil or below the soil.
 * Topsoil**: Crumbly, dark brown soil that is a mixture of humus, clay, and other materials.
 * Subsoil**: A soil layer that consists of clay and other particles washed down from the soil horizon.
 * Litter**: A loose layer that forms when plants shed their leaves.
 * Decomposers**: Organisms that break the remains of dead organisms into smaller pieces and then digest them with chemicals.