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Skills Worksheet
Concept Review
In the space provided, write the letter of the definition that best matches the term
or phrase.
______ 1. Pangaea
______ 2. lithosphere
______ 3. rift valley
______ 4. sea-floor spreading
a. region along a plate boundary where one
plate moves under another
b. piece of lithosphere with a unique
geologic history
c. crack in the center of a mid-ocean ridge
______ 5. paleomagnetism
d. supercontinent formed about 300 million
years ago
______ 6. terrane
e. residual magnetism of rock
______ 7. mid-ocean ridge
______ 8. subduction zone
______ 9. continental drift
______ 10. convection cell
f. process by which new sea floor forms
g. layer that forms the thin outer shell of Earth
h. cycle in which heated material rises and
cooler material sinks
i. undersea mountain range
j. hypothesis that the continents once formed
a single landmass
In the space provided, write the letter of the answer choice that best completes
each statement or best answers each question.
______ 11. What kind of fossil evidence supported Wegener’s hypothesis?
a. fossils hinting at a land bridge between South America and Africa
b. fossils proving Mesosaurus never lived in Africa
c. plant fossils showing that cold areas used to be tropical
d. sea fossils proving the continents had plowed through the
ocean floor
______ 12. Sea-floor spreading was a key discovery because it showed
a. that mid-ocean ridges exist.
b. how continents move.
c. why some rocks have reversed polarity.
d. that mid-ocean ridges have rifts at the center.
______ 13. Tectonic plates ride on the layer of Earth’s mantle called the
a. lithosphere.
b. oceanic crust.
c. continental crust.
d. asthenosphere.
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Concept Review continued
______ 14. Scientists identify tectonic plate boundaries primarily by studying
a. the outlines of the continents.
b. earthquake data.
c. the Pacific Ring of Fire.
d. active volcanoes.
______ 15. A plate boundary at which two plates slide past each other
horizontally is a
a. divergent boundary.
b. convergent boundary.
c. transform boundary.
d. subduction zone.
______ 16. Convection currents cause movement of tectonic plates by
a. making water in Earth’s core boil.
b. creating ridge push and slab pull.
c. making hot mantle material sink.
d. turning lithosphere to asthenosphere.
______ 17. New, smaller continents may form from larger continents through
a. rifting.
b. accretion.
c. paleomagnetism.
d. subduction.
______ 18. What often forms when large terranes and continents collide?
a. mid-ocean ridges
b. atolls
c. seamounts
d. major mountain chains
______ 19. The movements of the continents
a. discourage the development of unique species.
b. keep climates constant.
c. create fewer mountain ranges.
d. isolate some populations of organisms.
______ 20. One likely result of the supercontinent cycle is that
a. the continents will continue to get further apart.
b. California will move closer to the equator.
c. the Mediterranean Sea will close.
d. the Atlantic Ocean will disappear.
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Skills Worksheet
Critical Thinking
ANALOGIES
In the space provided, write the letter of the pair of terms or phrases that best
complete the analogy shown. An analogy is a relationship between two pairs of
words or phrases written as a:b::c:d. The symbol : is read is to, and the symbol :: is
read as.
______ 1. magma : ocean
lithosphere ::
a. dirt : mud
b. water : ice
c. mineral : rock
d. bark : tree
______ 5. convection : mantle
material ::
a. cloud : rain
b. boiling : water
c. temperature : heat
d. weigh : scale
______ 2. lithosphere : tectonic
plates ::
a. dish : china
b. slice : pie
c. sky : stars
d. mosaic : tiles
______ 6. convergent : divergent ::
a. hot : cold
b. running : walking
c. closing : opening
d. separating : meeting
______ 7. rifting : accretion ::
a. losing : gaining
b. subtracting : deducting
c. walking : running
d. driving : traveling
______ 3. continents : tectonic
plates ::
a. ship : tugboat
b. airplane : sky
c. passengers : bus
d. submarine : ocean
______ 8. Panthalassa : Pangaea ::
a. Lake Michigan :
North America
b. Atlantic : Virginia
c. Asia : Europe
d. Pacific : Hawaii
______ 4. earthquake : plate
boundary ::
a. landslide : mountain
b. flood : desert
c. snow : blizzard
d. cloud : rain
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Critical Thinking continued
INTERPRETING OBSERVATIONS
Read the following passage and answer the questions below.
In the Pacific Ocean lies a boundary between two tectonic plates:
the fast-moving Pacific Plate and the slower-moving Philippine
Plate. The Mariana Trench is located at the boundary of the two
plates. The Mariana Trench is the deepest point in the ocean, with
a depth of nearly 11,000 m below the surface. The Mariana Trench
is located near the Mariana Islands, a group of 15 islands.
9. What kind of plate boundary do you think the passage describes? Explain
your answer.
10. Describe the process that is occurring at the boundary. Explain how you
know.
11. What part do you think slab pull plays in the process at this boundary?
Explain.
12. What kind of landform is the Mariana Islands? Why do you think so?
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Critical Thinking continued
AGREE OR DISAGREE
Agree or disagree with the following statements, and support your answers.
13. Wegener had sufficient evidence to support his hypothesis of continental drift
even without evidence of sea-floor spreading.
14. Plate boundaries are almost always clearly identifiable.
15. North America has a location that makes it free for the most part from earthquakes and volcanoes.
16. Earth’s climate will probably undergo major changes in the next 150 million
years.
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Critical Thinking continued
REFINING CONCEPTS
The statements below challenge you to refine your understanding of concepts covered in the chapter. Think carefully, and answer the questions that follow.
17. An earthquake with a magnitude of at least 7.7 occurred in San Francisco
along the San Andreas Fault in 1906. Afterwards, observers noticed that
roads, fences, and plants that spanned the fault had moved. The objects on
one side of the fault had moved in a different direction from those on the
other side, or been offset. One road had been offset 21 feet. What was the
cause of the quake? Which direction do you think the ground west of the fault
moved? Explain.
18. Japan experiences about 1,500 earthquakes per year. Explain why, based on
its geographical formation and location.
19. Would you expect to find a volcano erupting on the San Andreas Fault?
Explain why or why not.
20. Suppose you wanted to prove that a particular terrane had been scraped onto
the North American plate. What evidence would you search for?
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Skills Worksheet
Graphing Skills
Pie Graphs
A pie graph shows how the parts of something make up the whole. Pie graphs
are frequently created to show data consisting of percentages. For example, you
could create a pie graph to show the percentage of each element that is present
in Earth’s crust.
To make a pie graph, draw a circle to represent the whole or total. Divide the circle into 100 equal sections of 3.6° each. Each section represents 1% of the whole.
To show 40%, shade in 40 consecutive sections. Or use a protractor to measure
the number of degrees that are represented by a percentage of the circle. For
example, 40% would be equal to 40 3 3.6°, or 144°. Mark a section of the circle to
represent each percentage. Then use different colors or designs to shade in each
portion of the circle.
Average Chemical Composition of
the Continental Crust
Silicon
27.7%
Oxygen
46.6%
Aluminum
8.1%
Iron
5.0%
Calcium 3.6%
Sodium 2.8%
Potassium 2.6%
Magnesium 2.1%
Other 1.5%
PRACTICE
Use the pie graph above to answer the following questions.
1. Which two elements together make up over 70% of continental crust? What
percentage of the crust do they make up?
2. Which element named on the graph is present in the smallest amount in the
continental crust? What percentage of the crust does it make up?
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Plate Tectonics
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Graphing Skills continued
3. The continental crust is considered to be rich in iron and magnesium. What
conclusion can you reach about the amounts of these elements that are necessary to enrich a substance? Explain.
4. The table below shows the average chemical composition of the main layer of
oceanic crust. (It does not include the thin surface sediment layer of oceanic
crust.) Use the table to create a pie graph that displays the information.
Average Chemical Composition of Basaltic Layer of Oceanic Crust
Oxygen
45.6%
Silicon
23.0%
Aluminum
9.0%
Calcium
8.4%
Iron
6.7%
Sodium
2.0%
Potassium
0.1%
Others
5.2%
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Skills Worksheet
Math Skills
Scientific Notation and the Rate of Plate Movement
Sometimes scientists who study the geologic history of Earth must work with
very large numbers. For example, Pangaea began breaking up 250 million, or
250,000,000, years ago. Scientific notation is a way of expressing large
numbers such as this without writing the place-holding zeros. A number written in scientific notation is expressed as the product of two factors: a number
between 1 and 10 and a power of ten. For example, the scientific notation for
the number 250,000,000 is 2.5 3 108 .
When you write a number in scientific notation, you first need to identify the
digits that are not place-holding zeros. Place the decimal point after (to the right
of) the leftmost digit. Then find the exponent for the factor of 10 by counting the
number of places that you moved the decimal point.
SAMPLE PROBLEM
In 300 million years, a tectonic plate that moves 4 centimeters per year
will move 1,200,000,000 centimeters. Express this distance in scientific
notation.
SOLUTION
Step 1: Identify the number without the place-holding zeros.
12
Step 2: Place the decimal point after the leftmost digit.
1.2
Step 3: Find the exponent by counting the number of places that you
moved the decimal point in the number.
1,200,000,000 → 1.2
You moved the decimal point nine places to the left. Therefore, the
exponent of 10 is 9.
Step 4: Write the number in scientific notation.
1.2 3 109
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Plate Tectonics
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Math Skills continued
PRACTICE
Using the sample problem as a guide, answer the following questions. Remember
to show your work.
1. Fill in this chart showing years in the supercontinent cycle.
Years
Number Without
Place-Holding 0s
Power of 10
Scientific Notation
Pangaea forms:
300,000,000
years ago
Pangaea splits
in two: 160,000,000
years ago
Continents moving
to their current
positions: 60,000,000
years ago
2. The Nazca plate off the west coast of South America moves an average of
16 cm per year. In 50 million years, it will move 800,000,000 cm. Express this
number in scientific notation.
3. Use the formula rate 5 distance 4 time to work the following problem: The
Pacific plate on which the city of Los Angeles is located is moving northwest
as the plate on which San Francisco is located is moving southeast. The two
cities are moving closer to one another at a rate of about 0.00005 km per year.
The cities are now a distance of about 611 km apart. How many years from
now will the cities meet? Express the answer in scientific notation.
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Plate Tectonics