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Transcript
Soils Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required) To access a customizable version of this book, as well as other interactive content, visit www.ck12.org CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the FlexBook®, CK-12 intends to pioneer the generation and distribution of high-quality educational content that will serve both as core text as well as provide an adaptive environment for learning, powered through the FlexBook Platform®. Copyright © 2014 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated herein by this reference. Complete terms can be found at http://www.ck12.org/terms. Printed: October 16, 2014 www.ck12.org C HAPTER Chapter 1. Soils 1 Soils Lesson 9.2: True or False Name___________________ Class______________ Date________ Write true if the statement is true or false if the statement is false. _____ 1. Without weathering, Earth would have no soils. _____ 2. Most soils consist only of small rock particles and minerals. _____ 3. The average rate of soil formation is about 1 cm/year. _____ 4. Dry conditions produce the thickest soils. _____ 5. The majority of soils in the U.S. are transported soils. _____ 6. Most topsoil consists mainly of clay-sized rock particles. _____ 7. The B horizon contains more organic material than the C horizon. _____ 8. Dead leaves from deciduous trees enrich laterite soils each year. _____ 9. Adding manure to soil reduces the amount of water the soil can hold. _____ 10. No-till farming helps to conserve topsoil. Lesson 9.2: Critical Reading Name___________________ Class______________ Date________ Read this passage based on the text and answer the questions that follow. How Climate and Living Things Affect Soil Formation How well soil forms and what type of soil forms depend on many factors. Climate is the most important factor in soil formation. Living things in soil are also important. The climate of a region includes its rainfall and temperature. Rainfall is an important factor in soil formation because it influences the rate of weathering. More rain means that more rainwater passes through the soil. Chemical weathering occurs when rainwater reacts chemically with rock particles and minerals. High rainfall increases the amount of rock that experiences chemical reactions. High rainfall may also carry away soil minerals and very small rock particles. This exposes new surfaces to weathering, although it also removes nutrients from soil. Temperature is an important factor in soil formation because the rate of chemical weathering increases with higher temperatures. The rate of chemical reactions doubles for every 10 °C increase in temperature. Plants and other living things in soil also grow and multiply more quickly in areas at higher temperatures. Living things affect soil formation in several ways. One way is by increasing the rate of weathering. Plant roots and animals such as earthworms help break up rock particles. Burrowing animals loosen soil, allowing more water to pass through it. After soil organisms die, they add organic matter to soil. Humus forms from the remains of dead plants and animals and is an extremely important part of the soil. Humus coats mineral particles, binding them together into clumps that hold the soil together. This gives the soil its structure and helps it hold water. Soils rich in humus also hold nutrients better and are more fertile for plant growth. 1 www.ck12.org Questions 1. How does the amount of rainfall in an area influence soil formation? 2. Why does chemical weathering occur more quickly in areas with higher temperatures? 3. Describe two ways that living things affect soil formation. Lesson 9.2: Multiple Choice Name___________________ Class______________ Date________ Circle the letter of the correct choice. 1. Factors that influence soil formation in a region include a. b. c. d. average temperature. amount of rainfall. type of bedrock. all of the above 2. How does humus affect soil? a. b. c. d. It prevents soil from holding water. It binds together mineral particles in soil. It reduces the nitrogen content of soil. It makes soil less fertile for plant growth. 3. Which size of rock particles in soil causes soil to hold the most water? a. b. c. d. gravel clay sand silt 4. Which soil horizon is usually darkest in color? a. b. c. d. A B C D 5. What type of soil is usually the most fertile? a. b. c. d. pedalfer pedocal laterite subsoil 6. A soil sample is red in color and contains almost no humus or soluble minerals. Which type of soil is it most likely to be? a. b. c. d. pedalfer pedocal laterite none of the above 7. Practices that help to conserve soil include a. cutting down trees. 2 www.ck12.org Chapter 1. Soils b. building terraces on steep slopes. c. planting the same crops every year. d. two of the above Lesson 9.2: Matching Name___________________ Class______________ Date________ Match each definition with the correct term. Definitions _____ 1. common name for soil horizon B _____ 2. type of soil found in grasslands _____ 3. common name for soil horizon A _____ 4. type of soil found in tropical areas _____ 5. organic material in soil _____ 6. type of soil found in deciduous forests _____ 7. all the layers of a particular soil Terms a. humus b. laterite c. topsoil d. pedocal e. subsoil f. soil profile g. pedalfer Lesson 9.2: Fill in the Blank Name___________________ Class______________ Date________ Fill in the blank with the appropriate term. 1. 2. 3. 4. 5. 6. 7. The most important factor that influences soil formation is __________. Soil that is brought to an area from somewhere else is called __________ soil. Soil that forms in place from the underlying bedrock is called __________ soil. Soil that contains a mixture of clay, sand, and silt is known as __________. An individual layer of soil at a given depth is called a(n) soil __________. The __________ horizon of soil contains the most living things. The __________ horizon of soil consists of partially weathered bedrock. 3 www.ck12.org Lesson 9.2: Critical Writing Name___________________ Class______________ Date________ Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences. Explain how soil can be considered both a renewable and a nonrenewable natural resource. 4