STUDY GUIDE Weathering

NAME

Chapter 6

DATE

STUDY GUIDE

Weathering

Use the words to fill in the blanks of the paragraphs.

plants freezing climate

pieces chemical desert

moisture oxidation mechanical

ice wedging temperatures cracks

CLASS

acids minerals reacting

Text Pages 148?155

carbonic acid

Weathering is the breaking of rocks into

. There are two main types

of weathering.

weathering involves breaking rocks without changing

their chemical composition. In

, water trapped in rocks freezes and

expands, forcing the rocks apart.

can also cause mechanical weathering.

As their roots grow and put pressure on rocks,

widen and rock

fragments may fall off.

weathering involves water, air, and other

substances'

with the minerals in the rocks. When metal is

exposed to water and oxygen,

occurs and rust forms.

in plant roots and mosses can also react with the

in rocks. Water and carbon dioxide combine to form

, which reacts with minerals such as calcite in limestone. How rapidly

weathering occurs in an area depends on the

. Chemical weathering

happens more slowly in

areas due to a lack of

. Low

in polar regions keep chemical

weathering to a minimum there. Whenever

and thawing alternate,

mechanical weathering becomes an important form of weathering.

26

Copyright ? Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

NAME

Chapter 6

DATE

CLASS

Text Pages 148?155

REINFORCEMENT

Weathering

Weathering includes mechanical weathering and chemical weathering. Mechanical weathering is any process that breaks up rock without changing its chemical composition. Chemical weathering is any process in which water, air, or other substances react with the minerals in the rock and change the chemical composition of the rock.

Decide if the following descriptions are examples of mechanical weathering or chemical weathering. Write the word "mechanical" or "chemical" in the blank at the left.

1. Mosses growing on the surface of rocks, producing pits in the rocks

2. The wedging of tree roots along natural joints in granite outcrops

3. Limestone dissolved by carbonic acid

4. The oxidation of minerals that contain iron

5. Animal burrows dug in rock that let in water and air

6. Repeated freezing and thawing of water that cracks rock

7. The action of water, salt, and air on car fenders and panels

8. Acids from plant roots which break up rocks

9. Formation of potholes in streets during severe winters

10. Lifted sections of sidewalk along tree-lined streets

11. A small rock falling from a cliff

12. Feldspar mixing with acidic groundwater and producing clay minerals

13. Halite in rocks dissolving in water

14. Decaying plants dissolving some of the minerals in rocks

15. Tree roots cracking the concrete foundation of a house

26

Copyright ? Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

NAME

Chapter 6

DATE

CLASS

Text Pages 156?163

STUDY GUIDE

Soil

Use the terms in the box to complete the sentences. Use the information in your textbook.

soil horizons topsoil evolve soil profile

humus composition parent bottom water

A horizon below top leaching

1.

is a mixture of sediments of weathered rock and organic matter.

2. Decaying plant and animal matter is called

.

3. Due to weathering, different layers, or

, of soil form.

4. Soil generally has three layers, and these make up a

.

5. The A horizon is the .

layer and is also known as

6. The B horizon is the layer

the A horizon.

7. The C horizon is the weathered rock but no humus.

layer in a soil profile; it contains partly

8. Below the bottom horizon is

rock.

9. You can tell that the

is the most fully evolved soil layer because it

has more humus and smaller rock fragments than the other layers.

10.

moving downward through the horizons dissolves and carries

minerals into lower horizons by the process of

.

11. The thickness of the soil layers and their

depend on the climate, slope

of the land, and the type of rock in an area and how long the soil has been evolving.

12. Soil horizons

more slowly in an area that has little rainfall

because chemical weathering occurs slowly in a dry climate.

Copyright ? Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

27

NAME

Chapter 6

DATE

CLASS

Text Pages 156?163

REINFORCEMENT

Soil

Use the diagram of a soil profile to answer Questions 1?5 on the lines provided. Then answer Questions 6 and 7.

A horizon: organic matter, roots, worms, insects and other living organisms

B horizon: some roots and other living organisms, materials leached by water from the A horizon

C horizon: materials leached by water from the B horizon, partly weathered rock fragments

Solid Rock

1. Which soil layer contains the most humus?

2. How far into the soil do plant roots extend?

3. Where in this soil profile are worms and insects breaking down organic matter in the soil?

4. Where in this soil profile is solid rock being weathered into soil?

5. What is the name of the process by which water carries materials from the upper horizons down to the lower levels?

6. What factors in an area help determine the type of soil--the thickness of the layers and their composition?

7. Choose a factor from Question 6 and explain how it can affect the soil in an area.

Copyright ? Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

27

NAME

Chapter 6

DATE

CLASS

Text Pages 164?169

STUDY GUIDE

Land Use and Soil Loss

Match the items in Column I with the terms in Column II. Write the letter of the correct term in the blank at the left.

Column I

Column II

1. Practice of leaving plant stalks in the field 2. Mechanical turning and loosening of the soil 3. Trees and plants in tropical regions 4. Desert formation

a. plowing b. rain forest c. strip cropping d. desertification e. no-till farming

5. Practice of alternating crops that cover the ground with crops that leave the land exposed

Decide whether each of the following statements is true or false. Write the word "true" or "false" in the blank. If the statement is false, rewrite it so that it is true.

6. Soil loss is particularly severe in the tropics.

7. Plants are important to soil, because without them, soil evolution stops and no new soil develops.

8. Desertification is a slow process that affects very little land each year.

9. In dry areas, farmers minimize soil erosion by plowing under the natural vegetation.

10. Soil can easily recover the nutrients that crops use up.

28

Copyright ? Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

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