1. What Is Soil? Soils-1-1 Image: T. Loynachan

2. Soil is a layer of unconsolidated material on the Earth’s surface in which plants grow. Soils-1-2 Image: Louis Maher Image: Professional Soil Classifiers Assoc. of Alabama

3. Soil is a mixture of mineral grains from the Earth, decomposing organic matter, and voids filled with air or water. Soils-1-3 Image: Professional Soil Classifiers Assoc. of Alabama

4. Soil is the Earth material that links living things (biosphere), air (atmosphere), water (hydrosphere), and the solid Earth (geosphere). Soils-1-4 Image: Bruce Molnia

5. A soil profile is an exposure from the surface downward through a soil to its parent material. Soils-3-1 Image: NRCS Image: Martin Miller

6. Soil profiles generally expose three layers or soil horizons. Soils-3-2 Image: National Cooperative Soil Survey

7. 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

8. Some constituents dissolved from the “A” horizon are deposited below in the “B” horizon. Horizon “A” Horizon “B” Soils-3-4

9. The “C” horizon is the lower soil layer developed on the underlying parent material. Horizon “A” Horizon “B” Horizon “C” Soils-3-5

10. 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” Soils-3-6 Image: NRCS

11. Physical weathering breaks rocks into small mineral particles that accumulate on the Earth’s surface. Soils-2-2 Images: Martin Miller, NRCS

12. How Soils Form Soils-2-1 Image: T. Loynachan

13. Chemical weathering dissolves and changes minerals that have accumulated on the Earth’s surface. Soils-2-3 Images: National Cooperative Soil Survey, University of Nebraska

14. Decomposing organic material from plants and animals mixes with accumulated soil minerals. Soils-2-4 Images: NRCS, Soil Classifiers of Michigan

15. Accumulated soil materials contain voids filled with air or water. Soils-2-5 Image: T. Loynachan

16. Continued physical and chemical changes over hundreds to thousands of years produce layers called soil horizons. Soils-2-6 Image: National Cooperative Soil Survey