Download Homework Due Friday, January 15, 2016 The Plate Tectonic Theory

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Homework Due Friday, January 15, 2016
The Plate Tectonic Theory
As you may have discovered, Earth is not just an ordinary planet in the solar system. Much like peeling an
onion, Earth’s layers reveal answers to some interesting mysteries that have baffled scientists for years. Earth’s
crust, the outermost layer, is not entirely one piece but instead is broken into sections which resemble an
oversized jigsaw puzzle. These giant sections, known as plates, are always on the move, creeping along at a
snail’s pace. It is almost as if the plates float on top of the mantle, the layer of Earth that is composed of
partially melted rock.
Have you ever put together a puzzle? The interlocking pieces must fit together perfectly in order to form a
picture. Approximately 100 years ago, a German scientist named Alfred Wegener discovered something
fascinating about a map of Earth. He realized that the continents seem to fit together like the pieces of a jigsaw
puzzle forming a giant piece of land called Pangaea, which existed over 250 million years ago. Over time, the
tectonic plates of which Pangaea consisted slowly drifted apart. These plates are now in their current positions
on Earth, making up the seven continents as we know them.
Earth’s plates are continually being created or recycled. By studying the ocean floor, oceanographers have
discovered mountainous ridges along the bottom of the ocean. These ridges appear to be where two plates have
started to move apart, allowing molten rock from the underlying mantle to ooze out and fill the space created by
the plates’ movement. Plate tectonic theory has also helped scientists explain another amazing Earth landform:
the deep ocean trenches. These deep ocean trenches are areas where plates are being recycled. As plates come
together, one plate may ride on top of the other, while the crust of the lower plate is slowly forced back down
into Earth’s mantle where it becomes molten rock again. This type of area, known as a subduction zone, forms
when continental land masses collide with ocean plates, or when two ocean plates collide together.
Movement of the plates not only causes trenches and ridges on the ocean floor, but it can also form mountains
on land. When two continental plates push together, there is so much force that the plates buckle, forming
massive mountain ranges. The friction during crustal movement can sometimes cause earthquakes and
tsunamis.
The plates on Earth’s crust have the power to change Earth’s surface features in many ways. Having previously
been pieced together in a giant landmass, they slowly moved apart to their current locations. The plates will
continue to move, forming new rocks and recycling the old. In another 250 million years, as the tectonic plates
continue to creep along, imagine how a map of Earth might look.
1. What analogy does the author use to describe how Earth’s continents fit together?
A The plates on Earth form a picture like a jigsaw puzzle does.
B The mountains and volcanoes on Earth are pieced together.
C The plates on Earth fit together like the pieces of a jigsaw puzzle.
D The plates on Earth are slowly drifting apart.
2. Which of the following best describes Pangaea?
A The seven continents that we know now
B An area on Earth that contains a ring of volcanoes
C A giant landmass that existed over 250 million years ago
D The process by which plates move
3. How is Earth’s crust recycled?
A Earth’s crust is not recycled, only created.
B As molten rock seeps out of weak spots in the crust, volcanoes are formed.
C When plates slide past each other, creating friction, an earthquake forms.
As new crust is created, old crust is forced down deep inside Earth’s mantle where it becomes
D molten rock again.
4. Scientists predict that in another 250 million years, the continents will be located in different positions.
How is this possible?
A The tectonic plates on Earth are continually moving at a slow rate.
B The gravity on Earth causes the continents to move around.
C Scientist think that the continents will move back into the shape of Pangaea again.
D All of the above.
5. The diagram below illustrates a type of plate boundary. Which crustal feature is most likely to form at
this type of boundary?
A Trench
B Ridges
C Tsunami
D Earthquake
Use the following words to summarize what you have learned about Plate Tectonics. Summary must be at least 5-6
sentences long and in complete sentences.
(Alfred Wegener, fossil evidence, Pangaea, puzzle pieces, Theory of Continental Drift, Theory of Plate Tectonics,
convection currents, magma, mantle, crust, plate boundaries, transform, divergent, convergent, sea floor spreading, midocean ridges, rift valley, mountains, trenches, volcanoes, earthquakes, subduction zone)
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