The hard, rigid plates that form the outermost portion of the Earth are about 100
kilometers thick. These plates include both the Earth's crust and
the upper mantle.
The rocks of the crust are
composed mostly of minerals with light elements, like
Line aluminum and sodium, while the mantle contains some heavier
elements, like iron and
(5) magnesium. Together, the crust and upper mantle that form the
surface plates are called
the lithosphere. This rigid layer floats on the denser material of
the lower mantle the
way a wooden raft floats on a pond. The plates are supported by a
weak, plastic layer
of the lower mantle called the asthenosphere. Also like a raft on
a pond, the
lithospheric plates are carried along by slow currents in this
more fluid layer beneath
(10) them.
With an understanding of plate
tectonics, geologists have put together a new history
for the Earth's surface. About 200 million years ago, the plates
at the Earth's surface
formed a “supercontinent” called
Pangaea. When this supercontinent started to tear
apart because of plate movement, Pangaea first broke into two
large continental masses
(15) with a newly formed sea that grew between the land areas as the
depression filled with
water. The southern one ― which included the modern
continents of South America,
Africa, Australia, and Antarctica ― is called Gondwanaland. The
northern one ― with
North America, Europe, and Asia ― is called Laurasia. North
America tore away from
Europe about 180 million years ago, forming the northern Atlantic
Ocean.
(20) Some of the lithospheric plates
carry ocean floor and others carry land masses or a combination of the two types. The movement of the lithospheric
plates is responsible
for earthquakes, volcanoes, and the Earth's largest mountain
ranges. Current
understanding of the interaction between different plates explains
why these occur
where they do. For example, the edge of the Pacific Ocean has been
called the “Ring
(25) of Fire” because so many volcanic eruptions and earthquakes happen
there. Before the
1960's, geologists could not explain why active volcanoes and
strong earthquakes
were concentrated in that region. The theory of plate tectonics
gave them an answer.
Questions
9. With which of the following topics is the passage mainly
concerned?
(A) The contributions of the
theory of plate tectonics to geological knowledge
(B) The mineral composition of
the Earth's crust
(C) The location of the Earth's
major plates
(D) The methods used by
scientists to measure plate movement
10. According to the passage, the lithospheric plates are given
support by the
(A) upper mantle
(B) ocean floor
(C) crust
(D) asthenosphere
11. The author compares the relationship between the lithosphere
and the
asthenosphere to which of the
following?
(A) Lava flowing from a volcano
(B) A boat floating on the
water
(C) A fish swimming in a pond
(D) The erosion of rocks by
running water
12. The word“one”in line 16 refers to
(A) movements
(B) masses
(C) sea
(D) depression
13. According to the passage, the northern Atlantic Ocean was
formed when
(A) Pangaea was
created
(B) plate movement ceased
(C) Gondwanaland collided with
Pangaea
(D) parts of Laurasia separated from each
other
14. The word “carry” in line 20 could best
be replaced by
(A) damage
(B) squeeze
(C) connect
(D) support
15. In line 27, the word “concentrated” is closest in meaning to
which of the following?
(A) Allowed
(B) Clustered
(C) Exploded
(D) Strengthened
16. Which of the following can be inferred about the theory of plate
tectonics?
(A) It is no longer of great
interest to geologists.
(B) It was first proposed in
the 1960's.
(C) It fails to explain why
earthquakes occur.
(D) It refutes the theory of
the existence of a supercontinent.
17. The paragraph following the passage most probably discusses
(A) why certain geological
events happen where they do
(B) how geological occurrences
have changed over the years
(C) the most unusual geological
developments in the Earth's history
(D) the latest innovations in
geological measurement
Please tally your
answer with the below provided answers and then comment here how much you got!
Answers
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