Lesson 5
Forces That
Build the Land
Mount Whitney, California
You have probably seen mountains, such as
these in California, in pictures. You may have
even visited one. Why do mountains form?
How do they get their shapes?
344
ENGAGE
ESS.32 Demonstrate the results of constructive and destructive forces using models or
illustrations (ESS-M-A7)
A
Also covers PS.12
Materials
How do mountains form?
Purpose
What happens when rock in Earth’s crust moves?
Make a model to demonstrate the results of
pressure on layers of rock in Earth’s crust.
Procedure
• modeling clay, 3
colors
Make a Model Make three clay layers, each a
different color, 15 cm square, and 1 cm thick. Pile
the layers like a sandwich, and gently push on
the top so that the layers stick together. Place
the layers in the center of the waxed paper.
• metric ruler
• sheet of waxed
paper
• 2 hardcover
books (of similar
thicknesses)
Observe Place two books so that the spines
touch opposite ends of the clay. Slowly and
firmly push the books toward each other.
Describe what happened. Flatten the clay.
Observe Use the knife to cut a “fault” across
• plastic knife
Step
the clay at a 45° angle. Place the books so that
the spines touch opposite ends of the clay.
Slowly push the books toward each other again.
Describe what happened. Flatten the clay.
Observe Move the books to the other sides of the
clay. Slowly push the books in opposite directions
along the “fault.” Draw a picture of the layers.
Draw Conclusions
Step
Interpret Data Your model represents forces on
layers of Earth’s crust. Which step modeled the
formation of layers uplifted along a fault? Which
step modeled folded mountains? Which step
modeled movement without uplift? Explain
your answers.
Explore
More
How could you manipulate your model to demonstrate
a fault where the layers on top of the fault move down
and the others move up? On which side would the
mountain form? Explain.
SI.13 Identify patterns in data to explain natural events (SI-M-A4) SI.14 Develop models to
illustrate or explain conclusions reached through investigation (SI-M-A5)
A
Also
covers SI.12, SI.15, SI.22
345
EXPLORE
What forces change Earth’s crust?
▶ Essential Question
How do forces change
Earth? ESS.32
▶ Vocabulary
fault, p. 346
earthquake, p. 348
focus, p. 348
aftershock, p. 348
seismic wave, p. 349
epicenter, p. 349
volcano, p. 352
vent, p. 352
▶ Reading Skill
Infer
Clues
What I
Know
What I
Infer
▶ Technology
e-Glossary and e-Review online
at www.macmillanmh.com
The forces that move continents can also change
the continents’ shapes. The continents are on top of
large pieces of Earth’s crust called tectonic plates.
These plates slide past each other at transform
boundaries, and the pieces of rock rub together. This
force, called shearing, works like the blades of a
pair of scissors and causes the rock to break. Plates
collide at convergent boundaries. The force of this
collision, called compression, squeezes the rock. At
divergent boundaries, plates separate as new crust
forms between them. The force of this separation is
called tension. Tension makes the crust longer and
thinner. When force exceeds the rock’s strength, the
rock breaks, forming a fault. A fault is a break or
a crack in the rock of the lithosphere along which
movements take place. Faults are usually located
along the boundaries between tectonic plates.
Three Kinds of Faults
Forces cause different kinds of faults. Shearing
forms strike-slip faults. Tension produces normal
faults. In a normal fault, the rock above the fault
moves down. Look at the diagram on the next page.
Can you determine how this lengthens the rock
layers? Compression produces reverse faults. In a
reverse fault, the rock above the fault moves up.
The Teton Range in Wyoming is
made of fault-block mountains.
346
EXPLAIN
Types of Faults
A strike-slip fault is produced at a
transform boundary. The plates slide past
each other without moving up or down.
Slabs of rock move past each other in
different directions. The San Andreas
Fault is an example of a strike-slip fault.
A reverse fault is produced at a
convergent boundary. The plates push
together. Rock above the fault surface
moves upward. The Himalayas in central
Asia were formed at a reverse fault.
A normal fault is produced at a divergent
boundary. The plates pull apart. Rock
above the fault surface moves down. The
Sierra Nevada in California were formed
at a normal fault.
Read a Diagram
Uplifted Landforms
Mountains form where plates push
against each other. Sometimes the
plates compress rock. Mountains that
are made up mostly of rock layers that
were folded by being squeezed together
are folded mountains. At other times,
the rock breaks. Mountains that are
made by huge, tilted blocks of rock
separated from the surrounding rock
by faults are fault-block mountains.
A large area of high, flat land that
was formed by the movement of Earth’s
crust is called a plateau. The Colorado
Plateau formed when rock layers were
pushed upward. The Colorado River
cut through part of that region and
eventually formed the Grand Canyon.
How does a reverse fault
differ from a strike-slip
fault?
Clue: The arrows illustrate
the plates’ movement.
Quick Check
Infer Why are faults often produced
along plate boundaries?
Critical Thinking Why do some
mountains form as folded mountains
and others form as fault-block
mountains?
347
EXPLAIN
Earthquake Locations
ARCTIC OCEAN
PACIFIC
OCEAN
INDIAN
OCEAN
ATLANTIC
OCEAN
Major earthquake
Read a Map
Tectonic plate
Along which ocean coastline do earthquakes tend to
occur closest to the shore?
Clue: Where are most of the earthquake icons located?
What are earthquakes?
Stretching a rubber band takes
energy. When you stretch it past the
breaking point, it snaps. This releases
the energy you put into stretching it.
This rubber-band model helps
explain an earthquake. An earthquake
is a sudden shaking of Earth’s crust.
Most earthquakes occur when the
ground near a plate boundary shifts
and changes position. Forces at plate
boundaries stretch, push, and bend
large sections of rock. Energy can build
up in the rock for years or even decades.
When the rock breaks or slips, energy is
released, and Earth’s crust moves.
348
EXPLAIN
SI.18
Earthquakes can also occur away
from plate boundaries. Here the
condition of rocks and soil may cause
movements and shifting that can
produce earthquakes.
The point below the surface of
Earth where an earthquake begins
is called the focus. Many smaller
earthquakes, called aftershocks,
can follow a major earthquake.
Aftershocks can be almost as strong
as the original earthquake. They can
continue for days, weeks, or months
after the first earthquake.
“Moonquakes” (earthquakes on the Moon) are far less
frequent than those on Earth and are not as strong.
Earthquake Waves
The sudden movement of an
earthquake causes rock to vibrate.
A vibration that travels through Earth
and is produced by an earthquake
or a volcanic eruption is called a
seismic (SIZE•mik) wave. Seismic waves
spread out in all directions from an
earthquake’s focus. The location on
the surface directly above the focus is
called the epicenter (E•pih•sen•tur).
People located at or near the epicenter
are the first to feel the earthquake.
Making Mountains SI.14, SI.21
Make a Model Place a sheet of
aluminum foil on a flat surface
such as a desk or a table. Arrange
rocks and pebbles on the foil to
represent various landforms.
Experiment Press your hands
down flat on the edges of the foil.
Slowly slide your hands closer
together. Watch the surface of the
foil for any changes.
Observe What happens to the foil
surface as your hands move? What
happens to the rock and pebble
“landforms”?
Quick Check
Infer Why do most earthquakes
occur near or along a fault?
Infer What
would happen
if you moved
your hands
faster or at
different
angles?
Critical Thinking Do all
earthquakes occur at plate
boundaries? How do you know?
Focus and Epicenter
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where the strongest shocks
are felt and the greatest
damage usually occurs.
349
EXPLAIN
How destructive is an earthquake?
In October 2005, an earthquake
caused great damage to parts of
Pakistan and India. Where will the
next major earthquake happen? How
powerful can earthquakes be?
Magnitude is the measure of the
energy released during an earthquake.
The strength of an earthquake can
be measured in several ways. One
measure is magnitude, and another
is the extent of damage that an
earthquake does to an area.
Two Measures of Earthquakes
The Richter (RIK•tur) scale is a
set of numbers used to describe an
earthquake’s magnitude on a scale of
1 to 10. An increase of 1 on the Richter
scale means a tenfold increase in an
earthquake’s magnitude.
The strength of an earthquake can
also be measured by its intensity, or the
strength as it is felt on Earth’s surface.
The Mercalli (mer•KAH•lee) scale
rates what people near the epicenter
feel and observe when an earthquake
occurs. It is based on observed effects,
not on mathematics. Because of this
difference, the Mercalli scale is less
reliable than the Richter scale.
Tsunamis
In December 2004, an earthquake
in the Indian Ocean launched a
tsunami (su•NAH•mee), a series of
huge waves caused by an earthquake
or a volcanic eruption beneath the
ocean floor. The tsunami broke over
the coasts of several nations. It caused
extensive damage and loss of life.
Water in a tsunami moves away
from the epicenter of the earthquake
in all directions. Tsunamis have long
wavelengths and low amplitudes, or
wave heights. The speed of a tsunami
depends on the depth of the water.
How a Tsunami Moves across the Ocean
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350
EXPLAIN
Summary of the Richter Scale
Magnitude
Description
1–2+
recorded on local seismographs but
not generally felt
3–4+
often felt, no damage
Summary of the Mercalli Scale
Intensity
Description
II
felt by people at rest or in places
more favorable to sensing tremors
IV
felt indoors and outdoors; similar to
vibrations of passing trucks; windows,
doors, and dishes rattle
VI
felt by almost everyone, walking
is unsteady, pictures fall off walls,
furniture may move or fall over
VIII
walls may collapse, monuments may
fall
5+
widely felt, slight damage near
epicenter
6+
damage to poorly constructed
buildings and other structures within
tens of kilometers of epicenter
7+
“major” earthquake, serious damage
within up to 100 km (60 mi) of
epicenter
X
8+
“great” earthquake, great destruction
and loss of life in areas more than 100
km (60 mi) from epicenter
most buildings are destroyed, large
landslides occur, train tracks are bent
slightly
XII
nearly total damage, objects are
thrown into the air, some landforms
are moved
9+
“rare great” earthquake, major
damage over a large region more
than 1,000 km (600 mi) from
epicenter
In the open ocean, tsunamis move
at speeds of 500–1,000 km/h
(300–600 mph). However, a tsunami
slows down as it approaches a shore.
The length of each wave decreases, but
the height increases. The water piles
up, and it is often pulled away from
the coastline as the tsunami approaches
land. Finally, the tsunami crashes onto
the shore as a giant wall of water.
Fortunately, most earthquakes do not
cause tsunamis.
Earthquake-Safety Steps
• Assemble an emergency kit
with a flashlight, a radio,
and first-aid supplies.
• Make an emergency escape
plan for moving away from
dangerous surroundings.
• If you live in an area that
could be hit by a tsunami,
know the route to higher
elevations farther inland.
• If an earthquake strikes, stay
away from windows.
Protecting against
Earthquake Hazards
People cannot prevent earthquakes.
However, we can help protect ourselves
against the damage they can cause.
For example, scientists design some
buildings in earthquake-prone areas
with “shock absorbers” to minimize
the damage caused by seismic waves.
Also, many highways in these areas are
supported by special reinforced columns
to help prevent collapse.
Quick Check
Infer During an earthquake, a
refrigerator moves, and pictures
fall off the wall. How strong is the
earthquake?
Critical Thinking Why is it useful
to have two scales for measuring
earthquakes?
351
EXPLAIN
How do volcanoes form?
A volcano is an opening in Earth’s
crust through which lava flows. As one
crustal plate moves under another, the
rock in the mantle and lower crust melts
and becomes magma. Melting rock
produces gases that mix with magma.
Over time, the gas-filled magma rises,
because it is less dense than the solid
rock around it. Rising magma can build
up in a weak part of overlying rock,
forming a magma chamber. Magma
chambers are the reservoirs from which
volcanic materials erupt.
When magma reaches the surface,
it erupts through a central opening
called a vent. Recall that once magma
reaches the surface, it is called lava.
After an eruption, lava cools and
hardens, forming a mound. After many
eruptions, this mound can grow. A
crater is the space around the vent at
the top of a volcano.
Some volcanoes are located in the
middle of a plate. Scientists believe
these volcanoes form over a hot spot, a
very hot part of the mantle. As a plate
moves over a hot spot, rising plumes of
magma break through. The Hawaiian
Islands were formed as the Pacific Plate
moved over a hot spot.
Most volcanic eruptions, like most
earthquakes, occur along the boundaries
between shifting plates. Volcanoes and
earthquakes change the surface of Earth
in ways that we can see immediately.
How Volcanoes Form
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352
EXPLAIN
Volcanoes are vents in
Earth’s crust through
which magma, gases,
and other materials are
forced out.
Types of Volcanoes
Three main kinds of landforms are
produced by volcanic eruptions. One kind
is a cinder cone volcano, a landform mainly
made up of small rock particles, or cinders. As
erupting lava shoots into the air, it breaks into
small pieces. These fragments cool and harden
as they fall back to the ground. The fragments
pile around the vent, forming a cone with
steep sides.
A second kind of volcanic landform is
a shield volcano, a landform made up of
many layers of rock. As fluid lava flows out
to the surface from a vent, it spreads out in
all directions, cools, and hardens into rock.
Successive layers of lava rock build up to form
a volcano with broad, gently sloping sides that
resemble a shield carried by ancient warriors.
The third kind of volcanic landform is a
composite volcano, a landform made up of
layers of thick lava flows alternating with
layers of ash, cinders, and rocks. These layers
form a symmetrical cone with steep sides that
are concave, or curving inward.
Sometimes a volcano’s crater collapses into
the vent. This forms a wide crater called a
caldera (kal•DER•uh).
cinder cone
▲ Mount Capulin in New
Mexico, a cinder cone
volcano
shield volcano
▲ Hawaii’s Mauna Loa,
a shield volcano
Volcanoes that have erupted recently
are active volcanoes. Some volcanoes are
dormant, or sleeping. They have not erupted
for a long time, but they have erupted in
recorded history. If a volcano has never been
observed erupting, it is said to be extinct.
Quick Check
Infer Why do shield volcanoes take a long
time to form?
Critical Thinking Why do volcanoes at
hot spots eventually become extinct?
composite cone
▲ Italy’s Stromboli,
a composite volcano
353
EXPLAIN
(t) Dr. John D. Cunningham/Visuals Unlimited
Volcanic Landforms
dike
laccolith
batholith
Volcanoes differ
in the kinds of materials
they eject, in the intensity and frequency
of eruptions, and in the types of landforms that result.
What are other volcanic landforms?
A string of island volcanoes, or
an island arc, can form where one
oceanic plate is driven under another.
Part of the sinking plate melts, and
magma moves up through the crust
along a line parallel to where the
plates meet. The Aleutian Islands and
the Philippine Islands are volcanic
island arcs. Where plates move apart,
volcanoes can form at gaps along the
plates’ edges. These volcanic landforms
are called rift volcanoes.
Magma can affect many land
features. When magma rises, it pushes
against rock layers above it. This can
form a large, dome-shaped structure.
Weathering and erosion can then strip
away the warped layers, exposing the
volcanic rock beneath. The Black Hills
of South Dakota are dome mountains.
If magma hardens in vertical cracks
across horizontal layers, a dike forms.
354
EXPLAIN
When the rocks around a dike are
worn away, the dike looks like a long
ridge. When magma hardens between
horizontal layers of rock, a flat sill is
formed. Sometimes, a sill’s magma is
thick and does not spread out very far
horizontally. Instead, it pushes upward.
This forms a dome-shaped laccolith
(LA•kuh•lith). The largest and deepest
magma formation is a batholith
(BA•thuh•lith). Batholiths are large
pockets of magma that reach deep into
the crust.
Quick Check
Infer Why do so many island
chains and island arcs form
in the Pacific Ocean?
Critical Thinking What is the
relationship between active
volcanoes and earthquakes?
Visual Summary
Faults are breaks or
cracks in rock that
normally form at plate
boundaries.
Earthquakes usually
occur at plate
boundaries. There
are different ways
of measuring an
earthquake’s strength.
Volcanoes form when
magma breaks through
the crust.
Think, Talk, and Write
Vocabulary The point on Earth’s
surface directly above an earthquake’s
focus is called the
.
Infer Why do most earthquakes and
volcanic eruptions occur along plate
boundaries?
Clues
What I
Know
What I
Infer
Critical Thinking Why might seismic
waves from the same earthquake
damage one area more than another?
Test Prep Which is not a part of
a volcano?
magma chamber
vent
crater
inner core
A
B
C
D
Make a
Study Guide
Test Prep Which of the following does
not cause an earthquake?
A lava moving to the top of a volcano
B water penetrating Earth’s surface
C motion along breaks in Earth’s crust
D high temperatures in Earth’s inner core
Make a trifold
book. Use the
labels shown.
Complete the
phrases, and
include a sketch
that summarizes
each example of
Earth’s forces.
Essential Question How do forces
change Earth?
Writing Link
Math Link
Explanatory Writing
Calculate Volcanoes
Write an essay identifying the time
frames over which natural events,
such as mountain formation, volcanic
eruption, and earthquakes, occur.
Explain why the time frames differ.
Alaska has about 40 active volcanoes,
or about 8 percent of all the active
volcanoes on Earth. Calculate how many
active volcanoes Earth has.
-Review Summaries and quizzes online at www.macmillanmh.com
355
EVALUATE
What happens before a volcano
erupts? First, magma moves into
the magma chamber beneath the
volcano. Then, the magma starts to
rise to the surface. As the magma
moves, it causes small earthquakes.
The chance of an eruption increases
as these earthquakes occur closer
to the surface. Scientists use
seismometers to detect this activity.
Scientists also look at the
type of earthquake. Short-period
earthquakes happen as magma
breaks through rock on its way to
the surface. This tells scientists that
the amount of magma near the
surface is increasing. Long-period
earthquakes tell scientists that there
is an ongoing movement of magma
beneath the surface. This may mean
that magma is flowing and moving
toward the surface.
Mount St. Augustine,
Augustine Island, Alaska
Explanatory Writing
A good explanation
▶ develops the main idea
with facts and supporting
details;
▶ lists what happens in an
organized and logical way;
▶ uses time-order words to
make the description clear.
356
EXTEND
Write About It
Explanatory Writing What are the
differences between short-period and
long-period earthquakes? Research these
earthquakes. Write an explanatory essay
with details that support your main idea.
-Journal Research and write about it
online at www.macmillanmh.com
ELA.22 Develop grade-appropriate paragraphs and multiparagraph compositions
using the various modes … (ELA-2-M4)
Estimate Quotients
Forces within and on Earth
change the shape of the land. The
Teton Mountains of Wyoming have
risen about 0.1143 centimeters every
year. Although the highest peak
is just over 2,250 meters above
the lowest part of the valley, the
mountains have actually uplifted
10,700 m.
Using this information, you can
calculate the range of time over
which the Teton Mountains grew.
Divide 10,700 m (1,070,000 cm) by
0.1143 cm to get your answer.
Instead of using long division to
get an exact answer, you can make
an estimate. Use numbers that are
close to the ones in the problem but
are easier to divide.
▶ You can use comparable numbers
to estimate 1,070,000 cm ÷
0.1143 cm/year. What numbers
close to these are easier to divide?
▶ 1,000,000 is close to 1,070,000.
0.1143 is between 0.1 and 0.2, but
much closer to 0.1
▶ Therefore,
1,000,000 ÷ 0.1 = 10,000,000
1,000,000 ÷ 0.2 = 5,000,000
▶ Since 0.1 is much closer to 0.1143
than 0.2 is, the age of the Teton
Mountains is a little less than
10,000,000 years old.
Solve It
Mountains erode at an average
rate of about 1.8 m per year.
Estimate how long it would take a
mountain that is 2,500 m high to
erode away completely.
E
ESS.38
Estimate the range of time over which natural events occur (e.g.,
lightning in seconds, mountain formation over millions of years) (ESS-M-B3)
357
EXTEND
UNIT 6 Review
DOK 1
Visual Summary
Fill each blank with the best term
from the list.
Lesson 1 Rocks and
minerals are used for many
different things.
atmosphere, p. 324
earthquake, p. 348
erosion, p. 334
Lesson 2 Soil is a
natural resource made
of a mixture of nonliving
material and once-living
things.
Lesson 3 Air and water
are resources that support
life on Earth.
hydrosphere, p. 320
igneous rock, p. 300
metamorphic rock,
p. 300
mineral, p. 296
soil, p. 310
volcano, p. 352
weathering, p. 332
1. Magma flows through an opening
in Earth’s crust called a(n)
.
ESS.32
2. The breakdown of rocks and other
materials is called
.
ESS.32
Lesson 4 Weathering and
erosion change the shape
of Earth’s surface.
Lesson 5 Many landforms
result from changes and
movements in Earth’s
crust.
3. As lava or magma cools, a(n)
is formed.
ESS.31
4. A solid natural material made from
nonliving substances in the ground is
a(n)
.
ESS.31
5. Glaciers, wind, and water can cause
.
ESS.32
6. All water on Earth is part of its
.
ESS.34
Make a
Study Guide
7. The layer of gases that surround
Earth is called the
.
Put your lesson study guides together
as shown. Attach the Lesson 5 study
guide to the back. Use this unit study
guide to review what you have learned.
ESS.35
8. A sudden shaking of Earth’s crust is
called a(n)
.
ESS.32
9. Heat and pressure are needed in
order to form a(n)
.
ESS.31
10. A mixture of bits of rock and onceliving plants and animals is called
.
ESS.30
358
-Glossary Words and definitions online at www.macmillanmh.com
DOK 2–3
Answer each of the following.
11. Which are formed by the wind?
A sandbars
B meanders
C dunes
D barrier islands
ESS.33
12. Which is an example of chemical
weathering?
A Tree roots break apart rock.
B Acidic water dissolves limestone to
form a cave.
C Water freezes and breaks rock.
D A glacier carves a river valley.
ESS.32
13. Look at the rocks shown below. Which
statement is correct?
marble
sandstone
16. Communicate Define the term
atmosphere. Describe each layer of
Earth’s atmosphere.
ESS.35
17. Make a Model Create a model to show
how forces change Earth’s surface.
ESS.32
18. Use Numbers Mountain formation
takes millions of years; other natural
events happen in seconds. Research
a natural event, such as earthquakes,
volcano eruptions, or lightning. Estimate
the time it takes for this event to occur.
ESS.38
19. Infer Discuss why photographs of your
family on a beach might look entirely
different from year to year, even if they
were taken in the same spot.
ESS.33
20. How do Earth’s lithosphere,
hydrosphere, and atmosphere
compare?
ESS.32, ESS.34, ESS.35
A The igneous rock could become a
sedimentary rock through pressure
and heat.
B The sedimentary rock could become
a metamorphic rock through erosion
and deposition.
C The metamorphic rock could
become an igneous rock through
melting and cooling.
D The igneous rock could become a
metamorphic rock through erosion
and deposition.
ESS.31
14. Compare and Contrast List different
types of soil. Use reference materials
to find out what kinds of materials are
found in each type of soil.
ESS.30
15. True or False Oceans, mountains, and
streams make up Earth’s hydrosphere.
Is this statement true or false? Explain.
ESS.34
DOK 4
Erosion or Weathering?
Observe rock formations, buildings, and
statues in your neighborhood.
What to Do
1. Find evidence of erosion or
weathering. Record details about
what you saw.
2. Make a list of examples of erosion and
weathering.
Analyze Your Results
Explain which type of weathering or
erosion you think has taken place and
the reasons for your decisions.
ESS.32, ESS.33
-Review Summaries and quizzes online at www.macmillanmh.com
359
1
Study the table below.
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How much of Earth’s freshwater is
in liquid form?
A. 97 percent
B. 2.3 percent
A copper penny has a hardness of
3. Which minerals would a copper
penny most likely scratch?
A. topaz and talc
B. apatite and diamond
C. gypsum and talc
D. feldspar and quartz
ESS.31
2 The diagram below shows different
layers of soil. In which layer will you
most likely find the most nutrientrich soil?
C. 0.6 percent
D. 0.1 percent
ESS.34
4 Which statement defines the word
atmosphere?
A. A layer of gases that surrounds
Earth’s core.
B. All of Earth’s liquid and solid
water.
C. A layer of gases and other
particles that surrounds Earth.
D. A part of Earth’s crust and the
top of the mantle.
ESS.35
5 An experiment shows that waves
can erode beaches. Which
conclusion can you draw from this
observation?
A. Sand dissolves in water.
A. 1
B. 2
C. 3
D. 4
ESS.30
360
B. Only salt water causes erosion.
C. Over time, beaches change
shape.
D. All beaches erode at the same
rate.
ESS.33
6 Which most likely caused the split
in the rock below?
8 Which strategy will be most
effective in preventing soil erosion
on the hill pictured below?
A. a large animal
B. gravity
C. chemical weathering
A. adding more soil to the hill
D. freezing water
ESS.32
B. running water down the hill
7 Which of the following best
describes how a composite volcano
is created?
A. Erupting lava shoots into the air
and breaks into small pieces,
which harden and pile up into a
cone with steep sides.
C. planting more trees on the hill
D. increasing the steepness of the
hill
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9 How long does it most likely take
for an earthquake to occur?
A. centuries
B. Flowing lava spreads out in all
directions, creating a broad,
gently sloping landform with
many layers.
B. seconds
C. months
D. years
C. Thick lava flows alternate with
layers of ash, cinders, and rocks,
making a symmetrical cone with
concave sides.
ESS.38
D. Thin, fast-flowing lava sprays out
of the ground, burning away soil
around it to create a steep cone
surrounded by a trench.
ESS.32
Question
Review
Question
Review
1
p. 297
6
p. 332
2
p. 311
7
p. 353
3
p. 322
8
p. 334
4
p. 324
9
pp. 348–349
5
pp. 337, 338–339
361