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Earth Science
SCIENCE DETECTIVEe A1
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35--Plate Tectonics: Mountains, Volcanoes, and Earthquakes
A ÿEarth's entire crust, which includes the
continents and ocean basins, is constantly
moving. 2Parts of the crust slowly move into,
under, or away from each other. 3The drift of the
continents is so slow (about 1.5 inches per year)
that it is not noticeable unless it's viewed over
millions of years.
'B 4Have you ever put together a jigsaw puzzle?
5Think of the continents as large pieces of a
puzzle. 6Do they all fit together? 71ook closely at
their coastlines.
PANGEA
mantle. ÿ4What causes these plates to move?
15Heat from deep in the Earth's interior causes
the rock in the mantle to become hotter and
rise upward.. ÿ6Then it squeezes between the
edges of two plates, or plate boundaries. ÿTThis
forces the,plates apart. ÿSThis process constantly
pushes the plates farther and farther apart.
' .-ÿ
E ÿgPlaces where plates move apart are called
divergent boundaries. 2°This type of plate
movement is responsible for seafloor spreading,
which is how the Mid-Atlantic Ridge and .East
Pacific Rise were formed.
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F 2ÿAt convergent boundaries, the plates are
actually moving toward each other, causing a
collision. =When there is a continent on both
sides of the plates, the collision causes the crust
to crumble, fold, tilt, or lift, forming mountains.
23The Himalayan Mountains formed along a .
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convergent boundary. 24Volcanoes are also
found at convergent boundaries. 2SAs one plate
slides under another, hot rock material in the
upper mantle melts and becomes magma. 261t
can then erupt through cracks, producing volcanic
C Bin 1912, Alfred Wegener, a German scientist,
wrote a book called The Origins of Continents
and Oceans, where he explained how Earth's
continents had fit together at one time as
one gigantic continent. 9He called this huge
continent Pangea, which means "all lands."• ÿ°His
hypothesis is now known as continental drift.
D ÿEarth's crust and outer mantle form the
lithosphere. ÿ2The lithosphere is broken into
pieces called tectonic plates. ÿ3The tectonic
plates' float on the lower portion of the Earth's
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mountains.
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G ÿTThe San Andreas fault is a famous example
of a transform fault boundary. =SFaults are
huge cracks in the Earth's crust, *%his type of
boundary Occurs when plates slide past each
other in different directions without moving
up or down. 3°Sometimes the motion is very
gradual and occasionally it is very sudden. 31An
earthquake is the rigorous shaking, of the Earth
due to sudden plate movements.
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SCIENCE DETECTIVE® A1
,
Earth Science
For each statement, circle T for true and F for
false. If the statement is false, replace the
bold word(s) to make the statement true.
Then write the number of the sentence(s)
that best supports your answer.
ao T F The Earth's crust is always
Write the numbers of the sentences that
best support your answer.
5. Refer to the lesson to explain Pangea.
moving. __
b. T F The tectonic plates float On
the lower portion of the Earth's crust.
Write the nu. mbers of the sentences that
best support your answer.
co T F Divergent boundaries are
responsible for seafloor spreading.
,
What are earthquakes and how are they
formed?
do T F Volcanoes are formed at
transform fault boundaries°
.
The place where Earth's plates move apart
is called a(n)
Write the numbers of the sentence that best
supports your answer. __
a. transform fault.
b° divergent boundary.
• c. convergent boundary.
d. ocean plate.
Wi'ite the number of the sentence that best
supports your answer.
.
Most earthquakes are caused by
a, magma cooling on the side of a
volcano.
bÿ
C°
Earth's plates spreading apart.
Earth's plates sliding past each other.
d. lava.
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Write the number of the sentence that best
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supports your answer.
,.
1ÿ."
,
Apply what you have read from the lesson to
describe three ways that plates interact with
each other.
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108 '
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