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What Is Soil?. Image: T. Loynachan. Soils-1-1. Soil is a layer of unconsolidated material on the Earth’s surface in which plants grow. Image: Louis Maher. Image: Professional Soil Classifiers Assoc. of Alabama. Soils-1-2.
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What Is Soil? Image: T. Loynachan Soils-1-1
Soil is a layer of unconsolidated material on the Earth’s surface in which plants grow. Image: Louis Maher Image: Professional Soil Classifiers Assoc. of Alabama Soils-1-2
Soil is a mixture of mineral grains from the Earth, decomposing organic matter, and voids filled with air or water. Image: Professional Soil Classifiers Assoc. of Alabama Soils-1-3
Soil is the Earth material that links living things (biosphere), air (atmosphere), water (hydrosphere), and the solid Earth (geosphere). Image: Bruce Molnia Soils-1-4
A soil profile is an exposure from the surface downward through a soil to its parent material. Image: Martin Miller Image: NRCS Soils-3-1
Soil profiles generally expose three layers or soil horizons. Image: National Cooperative Soil Survey Soils-3-2
The upper “A” horizon contains organic matter mixed with mineral particles. Percolating water dissolves and removes some mineral constituents from the “A” horizon. Horizon “A” Soils-3-3
Some constituents dissolved from the “A” horizon are deposited below in the “B” horizon. Horizon “A” Horizon “B” Soils-3-4
The “C” horizon is the lower soil layer developed on the underlying parent material. Horizon “A” Horizon “B” Horizon “C” Soils-3-5
A mature soil profile with well developed A, B, and C horizons takes hundreds to thousands of years to develop. Horizon “A” Horizon “B” Horizon “C” Image: NRCS Soils-3-6
Physical weathering breaks rocks into small mineral particles that accumulate on the Earth’s surface. Images: Martin Miller, NRCS Soils-2-2
How Soils Form Image: T. Loynachan Soils-2-1
Chemical weathering dissolves and changes minerals that have accumulated on the Earth’s surface. Images: National Cooperative Soil Survey, University of Nebraska Soils-2-3
Decomposing organic material from plants and animals mixes with accumulated soil minerals. Images: NRCS, Soil Classifiers of Michigan Soils-2-4
Accumulated soil materials contain voids filled with air or water. Image: T. Loynachan Soils-2-5
Continued physical and chemical changes over hundreds to thousands of years produce layers called soil horizons. Image: National Cooperative Soil Survey Soils-2-6