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Soils
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Printed: October 16, 2014
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C HAPTER
Chapter 1. Soils
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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.
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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.
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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.
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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.
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