Soil is formed from weathered rock and organic matter and varies in composition with depth, forming distinct horizons. It consists of minerals, organic matter, water, and air. The type of soil depends on the parent material and climate, with pedalfer soils found in humid regions, pedocal soils in drier areas, and laterite soils in the tropics. However, human activities like agriculture and construction can accelerate erosion and damage soil formation.

1. 5.2 Soil

2. Regolith
• The layer of rock and mineral fragments that
nearly everywhere covers Earth’s surface

3. Soil
• A combination of mineral and organic
matter, water, and air.

4. Soil Horizon
• A layer of soil that has identifiable
characteristics produced by chemical
weathering and other soil-forming processes

5. Soil Profile
• A vertical section through a soil showing its
succession of horizons and the underlying
parent material.

6. Pedalfer
• Soil of humid regions characterized by the
accumulation of iron oxides and aluminum-
rich clays in the B horizons.

7. pedocal
• Soil associated with drier regions and
characterized by an accumulation of calcium
carbonate in the upper horizons

8. laterite
• A red, highly leached soil type found in the
tropics that is rich in oxides of iron and
aluminum.

9. Key Concept
• Soil is the part of the regolith that supports
the growth of plants

10. Key Concept
• Soil has four major components: mineral
matter, or broken-down rock; organic
matter, or humus, which is the decayed
remains of organisms; water; and air.

11. Key Concept
• The most important factors in soil formation
are parent material, time, climate, and slope.

12. Key Concept
• Soil varies in
composition, texture, structure, and color at
different depths.

13. Key Concept
• Three common types of soil are
pedalfer, pedocal, and laterite.

14. Key Concept
• However, human activities that remove
natural vegetation, such as
farming, logging, and construction, have
greatly accelerated erosion.