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USGS CMG InfoBank: Soil Horizons

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Comment: 15:35 - 16:19 (00:44)
Source: Annenberg/CPB Resources - Earth Revealed - 15. Weathering and Soils
Keywords: weathering, soil, rock, horizon, "loamy topsoil", "A horizon", "B horizon", "C horizon", humus, plant, rainfall, water, leaching

Our transcription: In essence, soil is a thin layer that rests on bed rock, like a coating of rust on iron.
As the soil matures, it forms into several different layers or "horizons."
The "A" horizon is the loamy top soil the gardeners know so well.
This is where most plant humus is derived.
Rain waters seeps down through this layer and washes or leaches some of the soil materials down to the "B" horizon -- the next layer, where the leached materials accumulate.
The "C" horizon, the bottom most layer is the zone where the underlying bed rock is partly disintegrated and decomposed, but still recognizable.

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Page Last Modified: Thu Oct 31 04:26:52 PDT 2013  (chd)