Weathering and Soil Formation CHAPTER NEW CHAPTER Weathering and Soil Formation the BIG idea Natural forces break rocks apart and form soil, which supports life. 4.1 Mechanical and chemical forces break down rocks. 4.2 Weathering and organic processes form soil. 4.3 Human activities affect soil. CHAPTER OUTLINE

4.1 Mechanical and chemical forces break down rocks. weathering mechanical weathering exfoliation Over time, mechanical weathering breaks a rock into smaller pieces. abrasion chemical weathering SECTION OUTLINE

4.1 Mechanical and chemical forces break down rocks. weathering mechanical weathering exfoliation Chemical weathering affects exposed rock surfaces abrasion chemical weathering SECTION OUTLINE

4.1 weathering Mechanical and chemical forces break down rocks. mechanical weathering The process by which natural forces break down rocks. exfoliation abrasion chemical weathering KEY CONCEPT SUMMARY

mechanical weathering 4.1 Mechanical and chemical forces break down rocks. weathering mechanical weathering mechanical weathering The breakdown of rock into smaller pieces of the same material without any change in its composition. exfoliation abrasion chemical weathering KEY CONCEPT SUMMARY

4.1 exfoliation Mechanical and chemical forces break down rocks. weathering exfoliation mechanical weathering In geology, the process in which layers or sheets of rock gradually break off. exfoliation abrasion chemical weathering KEY CONCEPT SUMMARY

4.1 abrasion Mechanical and chemical forces break down rocks. weathering abrasion mechanical weathering The process of wearing something down by friction. exfoliation abrasion chemical weathering KEY CONCEPT SUMMARY

4.1 Mechanical and chemical forces break down rocks. weathering chemical weathering mechanical weathering The breakdown or decomposition of rock that takes place when minerals change through chemical processes. exfoliation abrasion chemical weathering KEY CONCEPT SUMMARY

Weathering and organic processes form soil. 4.2 Weathering and organic processes form soil. Soil has measurable properties, such as color, texture, pore space, and chemistry. humus soil horizon soil profile Soil is a mixture of weathered rock, organic matter, water, and air. Plants, microorganisms, and animals affect soil characteristics. SECTION OUTLINE

4.2 humus Weathering and organic processes form soil. soil horizon The decayed organic matter in soil. soil profile KEY CONCEPT SUMMARY

4.2 soil horizon Weathering and organic processes form soil. humus soil horizon soil horizon A soil layer with physical and chemical properties that differ from those of soil layers above or below it. soil profile KEY CONCEPT SUMMARY

4.2 soil profile Weathering and organic processes form soil. humus soil profile soil horizon The soil horizons in a specific location; a cross section of soil layers that displays all soil horizons. soil profile KEY CONCEPT SUMMARY

Human activities affect soil. 4.3 Human activities affect soil. Soil is essential to life and takes a long time to form. It is difficult or impossible to replace soil that has been lost. desertification Farming, construction and development, and mining are three human activities that affect soil. Soil Loss SECTION OUTLINE

Human activities affect soil. 4.3 Human activities affect soil. Soil is essential to life and takes a long time to form. It is difficult or impossible to replace soil that has been lost. desertification Soil conservation practices help keep soil from blowing or washing away. Soil Conservation SECTION OUTLINE

4.3 desertification Human activities affect soil. The expansion of desert conditions in areas where the natural plant cover has been destroyed. KEY CONCEPT SUMMARY

4.1 Mechanical and chemical forces break down rocks. I. Mechanical and chemical forces break down rocks. weathering A. Weathering breaks rocks into smaller pieces. mechanical weathering B. Mechanical weathering produces physical changes in rocks. exfoliation abrasion C. Chemical weathering changes the mineral composition of rocks. chemical weathering 1. Dissolving 2. Rusting D. Weathering occurs at different rates. KEY CONCEPT SUMMARY

Weathering and organic processes form soil. 4.2 Weathering and organic processes form soil. II. Weathering and organic processes form soil. humus A. Soil is a mixture of weathered rock particles and other materials. soil horizon 1. Soil Composition soil profile 2. Soil Horizons B. Climate and landforms affect soil. C. The activities of organisms affect soil. D. Properties of soil can be observed and measured. 1. Texture 2. Color 3. Pore Space 4. Chemistry KEY CONCEPT SUMMARY

Human activities affect soil. 4.3 Human activities affect soil. III. Human activities affect soil. desertification A. Soil is a necessary resource. B. Land-use practices can harm soil. 1. Farming 2. Construction and Development 3. Mining C. Soil can be protected and conserved. KEY CONCEPT SUMMARY