CHAPTER 3
LESSON 2
Erosion and Deposition
Landforms Shaped by Water
and Wind
Key Concepts
• What are the stages of
stream development?
• How do water erosion and
deposition change Earth’s
surface?
• How do wind erosion and
deposition change Earth’s
surface?
What do you think? Read the two statements below and decide
whether you agree or disagree with them. Place an A in the Before column
if you agree with the statement or a D if you disagree. After you’ve read
this lesson, reread the statements to see if you have changed your mind.
Before
Statement
After
3. A beach is a landform that does not change
over time.
4. Windblown sediment can cut and polish
exposed rock surfaces.
3TUDY#OACH
Reading Check
1. Identify What are the
two most important agents
of weathering, erosion, and
deposition?
36
Erosion and Deposition
Shaping the Land with Water and Wind
Earth’s surface is constantly changing. Recall that
weathering and erosion are destructive processes that shape
Earth’s surface. These destructive processes often produce
tall, jagged landforms.
Deposition is a constructive process that also shapes
Earth’s surface. Constructive processes often produce flat,
low-lying landforms.
What causes these processes that continually tear down
and build up Earth’s surface? In this lesson, you will read
that water and wind are two of the most important causes of
weathering, erosion, and deposition. Water and wind can
change the shape of landforms. Fast-moving water can
change the shape of rocks, and strong winds can move
sediment great distances.
In the next lesson, you will read about the changes to
Earth’s surface by the downhill movement of rocks and soil.
You will also learn how the movement of glaciers changes
Earth’s surface.
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Make Vocabulary Cards
Make a vocabulary card for
each boldface term in this
lesson. Write each term
on one side of the card.
On the other side, write the
definition and draw a picture
that represents or explains
the term. Use these cards to
review the vocabulary for the
lesson.
Water Erosion and Deposition
Moving water can cause great changes both on and below
Earth’s surface. The shape of the landforms created by water
erosion and deposition depends on the speed of water
movement and the depositional environment.
Water Erosion
Have you ever gone swimming in an ocean? If so, then
you know that moving water can have great energy. Moving
water causes erosion along streams and rivers, at beaches,
and underground.
Make a two-tab book to
organize information about
erosion and deposition by
water and wind.
Erosion and Deposition
Water
Wind
Stream Erosion Streams are active systems that erode land
and transport sediment. Erosion by a stream depends on the
stream’s energy.
Young streams in mountainous areas usually have the
greatest energy. Water flows rapidly downhill where the
mountain slopes are steep. The rushing water often carves
steep, V-shaped valleys. Waterfalls and river rapids are
common in steep mountain streams.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Water in a young stream slows as it reaches gentler slopes
near the base of mountains. The stream is then called a
mature stream. The shape and speed of a mature stream are
different from those of a young stream.
Mature streams flow more slowly through gently sloping
valleys. Slower-moving water erodes the sides of the stream
channel more than it erodes the bottom of the channel.
Curves called meanders develop in the channel. A meander is
a broad, C-shaped curve in a stream. Meanders can make a mature
stream into a large, snake-shaped feature in the land.
A stream moves even slower when it reaches flat land. A
stream flowing through flat land is called an old stream. Over
time, meanders change shape. More erosion occurs on the
outside of bends, where the water flows faster. More
deposition occurs on the inside of bends, where the water
flows slower. Over time, this increases the size of the
meander.
Coastal Erosion Like streams, coastlines are always changing.
Waves and currents along a shore cause erosion of loose sand,
gravel, and rock. A longshore current is a current that flows parallel
to the shoreline. Longshore currents transport sediment from
place to place, continually changing the size and shape of the
beaches. Review how coastal erosion is caused by a longshore
current in the figure on the next page.
Reading Essentials
Reading Check
2. Describe What is the
shape of a valley formed by
a young stream? (Circle the
correct answer.)
a. U-shaped
b. V-shaped
c. S-shaped
Key Concept Check
3. Sequence Describe the
stream development stages.
Erosion and Deposition
37
Erosion by Longshore Currents
Shoreline
Visual Check
Sediment
transport
4. Locate Circle the arrows
on the diagram that show
where the longshore current
flows.
Key Concept Check
5. Explain How does
water erosion change Earth’s
surface?
Longshore currents, shown above, are one cause of
coastal erosion. Coastal erosion also occurs when waves cut
away rocky shorelines. This type of erosion creates sea cliffs.
Sea stacks, sea caves, and sea arches are features that form
when waves erode less-resistant rocks along the shore. Sea
stacks are tall pillars of rock just offshore. Sea arches are rock
bridges that extend from the shore into the sea.
Groundwater Erosion Water beneath Earth’s surface is called
6. Explain How does
water erosion form a cave?
Water Deposition
Flowing water deposits sediment as the water slows. A loss
of speed reduces the amount of energy that the water has to
carry sediment.
Deposition Along Streams Deposition by a stream takes
Key Concept Check
7. Cause and Effect
How does water deposition
change Earth’s surface?
place anywhere along its path where the water’s speed
decreases. Slower-moving water deposits sediment on the
inside curves of meanders. A stream also deposits sediment
when it reaches flat land or a body of water, such as a lake or
an ocean. A delta is a large deposit of sediment that forms where a
stream enters a large body of water.
Deposition Along Coastlines Much of the sand on most
ocean beaches was originally deposited by rivers. Longshore
currents moved the sand along ocean coasts. The sand was
eventually deposited where the currents were slower and had
less energy. Sandy beaches often form at those locations.
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Erosion and Deposition
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Reading Check
groundwater. Flowing groundwater erodes rock and forms
features such as caves. When carbon dioxide in the air mixes
with rainwater, a weak acid forms. Some of this acidic
rainwater seeps through rock and soil into the ground. As the
acidic water passes through layers of limestone, it dissolves
and washes away the limestone, forming a cave.
Groundwater Deposition Weathering and erosion form
caves. But many of the structures inside caves form as the
result of deposition. Stalactites and stalagmites are cave
features that form as dripping groundwater deposits minerals.
Stalactites are icicle-like deposits that hang from cave ceilings.
Stalagmites build up on the cave’s floor.
Land Use Practices
Damage caused by water erosion can be affected by the
ways people use land. Two areas of concern are beaches
along coasts and surface areas within continental interiors.
Beach Erosion Ocean waves can erode beaches by removing
sediment. To reduce this erosion, people sometimes build
structures such as retaining walls and groins. Retaining walls
are structures that are built parallel to a beach. They help to
reduce erosion by waves. Groins are structures that are built at
right angles to a beach. As longshore currents flow along a
beach, groins trap sediment and reduce the effects of
longshore currents.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Some ways people affect beaches are unintended. For
example, people build dams along rivers. The dams are built
to control flooding and for other reasons. Normally, when
rivers reach the ocean, they drop sediment. Dams can stop
sediment from reaching beaches. As a result, beach sand that
is washed out to sea by waves might not be replaced.
Surface Erosion Human activities affect surface erosion in
several ways. Removing vegetation from the land increases
surface erosion. Agricultural production, construction activities,
and cutting trees for lumber and paper production are some of
the reasons that people remove vegetation.
A floodplain is a wide, flat area located next to a river. A
floodplain is usually dry land. However, when a river
overflows its banks, the dry land can become flooded. Heavy
rain or rapid melting of snow can cause a river to flood.
Building homes or businesses within a floodplain can be
risky. However, flooding makes the soil rich, so it is ideal for
farming. One way to reduce flooding on a floodplain is to
build a levee. A levee is a long, low ridge of soil built along a
river. Reducing flooding also reduces the supply of mineralrich soil. When levees break, such as in New Orleans during
Hurricane Katrina in 2005, great flood damage can occur.
Reading Essentials
Reading Check
8. Describe How do
human activities affect water
erosion?
Reading Check
9. State How do levees
affect erosion on a
floodplain?
Erosion and Deposition
39
Wind Erosion and Deposition
The gentle winds that blow leaves around in autumn are
not likely to cause land erosion and deposition. However,
strong or long-lasting winds can greatly change the land.
Wind Erosion
As wind blows, it carries sediment. This sediment cuts
and polishes exposed rock. Abrasion is the grinding away of rock
or other surfaces as particles carried by wind, water, or ice scrape
against them.
Key Concept Check
10. Determine How do
wind erosion and deposition
change Earth’s surface?
Visual Check
11. State What can the
wind cause the dune to do?
Wind Deposition
Two common types of windblown deposits are dunes and
loess (LUHS). A dune is a pile of windblown sand. Dunes form
when wind loses energy and drops the sand it is carrying.
Entire fields of dunes can move over land as wind blows the
sand. The figure below shows how dunes form.
Sand grains
drop down
the
steep face.
Sand grains
blow and bounce
up the dune.
Dune moves
Loess is a crumbly, windblown deposit of silt and clay. One type
of loess forms from rock that was ground up and deposited
by glaciers. When wind picks up this small, fine-grain
sediment and drops it, thick layers of dust called loess form.
Land Use Practices
Reading Check
12. State What are some
ways in which human
activities affect wind erosion
on farmland?
40
Erosion and Deposition
Human activity can contribute to wind erosion. One
example of this takes place when wind blows across
farmlands. Plowed fields and dry, overgrazed pastures leave
topsoil exposed to the wind. Strong winds can remove
topsoil that is not held in place by plants.
One way to reduce the erosion of topsoil by wind is to
leave fields unplowed after the crops are harvested. Farmers
can also plant rows of trees that slow the wind and protect
the farmland.
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Dune Formation
Mini Glossary
abrasion: the grinding away of rock or other surfaces as
loess (LUHS): a crumbly, windblown deposit of silt and clay
particles carried by wind, water, or ice scrape against them
longshore current: a current that flows parallel to the
delta: a large deposit of sediment that forms where a stream
shoreline
enters a large body of water
meander: a broad, C-shaped curve in a stream
dune: a pile of windblown sand
1. Review the terms and their definitions in the Mini Glossary. Write a sentence to compare
and contrast a dune and loess.
2. Use the terms from the Mini Glossary to complete the table. Use each term only once.
Agent of Change
Water
Erosion
Deposition
• Old streams erode the land to form a
• A
forms where a river empties into the
ocean.
.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
• A
erodes sediment along a beach.
Wind
•
happens when sand cuts and polishes
rocks and other surfaces.
• A
is a
large pile of sand deposited by the wind.
•
is a
layer of silt deposited by the wind.
3. Review your vocabulary cards. Write one term and its meaning on the lines below.
What do you think
Reread the statements at the beginning of the
lesson. Fill in the After column with an A if you
agree with the statement or a D if you disagree.
Did you change your mind?
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Log on to ConnectED.mcgraw-hill.com
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lesson’s resources.
END OF
LESSON
Erosion and Deposition
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