[讨论]TTGWD2-6

Q6 to Q9:

       Scientists generally credit

            violent
collisions between

            tectonic
plates, the mobile

Line     fragments
of Earth’s rocky

  (5)     outer shell, with sculpting

the planet’s surface, as, for

example, when what is now

the Indian subcontinent col-

lided with Asia,
producing

 (10)   the
Himalayan
            Mountains.

However, plate tectonics

cannot fully explain certain

massive surface features,

such as the “superswell”

 (15)    of southern Africa, a
vast

plateau over 1,000 miles

across and nearly a mile

high.  Geologic evidence

shows that southern African

 (20)    has been slowly rising for

            the past
100 million years,

            yet it has
not experienced

a tectonic collision for

nearly 400 million years.

 (25)   The
explanation may be in

Earth’s mantle, the layer of

rock underlying the tectonic

plates and extending down

over 1,800 miles to the outer

 (30)    edge of Earth’s iron core.

    
Since the early twentieth

century, geophysicists have

            understood
that the mantle

churns and roils like a thick

 (35)    soup. 
The relative low

density of the hottest rock

makes that material buoyant,

so it slowly ascends, while

cooler, denser rock sinks

 (40)    until heat escaping the mol-

ten core warms it enough to

make it rise again.  While

this process of convection

was known to enable the

 (45)    horizontal movement of tec-

tonic plates, until recently

geophysicists were skeptical

of its ability to lift or lower the

planet’s surface vertically.

 (50)    However, recent technolog-

ical advances have allowed

geophysicists to make three-

dimensional “snapshots”

of the mantle by measuring

 (55)   vibrations,
or seismic waves,

set in motion by earthquakes

originating in the planet’s

outer shell and recording

the time it takes for them to

 (60)   travel
from an earthquake’s

epicenter to a particular

recording station at the

surface.  Because geo-

physicists know that seismic

 (65)    waves become sluggish in

hot, low-density rock, and

speed up in colder, denser

regions, they can now infer

the temperatures and den-

 (70)   sities
in a given segment of

the interior.  By compiling

a map of seismic velocities

from thousands of earth-

quakes across the globe,

 (75)   they
can also begin to map

temperatures and densities

throughout the mantle.  These

methods have revealed some

unexpectedly immense for-

 (80)    mations in the deepest parts

of the mantle; the largest

of these is a buoyant mass

of hot rock directly below

Africa’s
southern tip.  Dis-

 (85)   pelling
researchers’ initial

doubts, computer models

have confirmed that this

formation is buoyant enough

to rise slowly within the mantle

 (90)   and
strong enough to push

Africa
upward as it rises.

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Q6:     

The passage is primarily concerned with

1. describing
        a traditional explanation for the vertical movement of Earth’s surface
2. discussing
        recent geophysical research that may explain certain features of Earth’s
        surface that were previously difficult to account for
3. combining
        elements of several theories in order to develop a plausible explanation
        for a poorly understood feature of Earth’s surface
4. providing
        new evidence in support of a long-standing belief about how certain of
        Earth’s massive surface features were created
5. questioning
        the implications of geophysicists’ recent findings regarding the
        composition and density of Earth’s mantle

Answer:

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Q7:     

The passage suggests that geophysicists can now infer the
characteristics in a given segment of the mantle by doing which of the
following?

1. Observing
        how long it takes for seismic waves to travel from an earthquake’s
        epicenter to a particular surface location and applying knowledge of how
        rock temperature and density affect the velocity of those waves
2. Analyzing
        the results of studies linking the formation of some of Earth’s surface
        features with the violent collisions of tectonic plates and inferring the
        causes of the information of other features from those results
3. Recording
        data about earthquakes throughout the world and correlating the relative
        force and duration of those earthquakes with information about their
        geological environment
4. Comparing
        data about earthquakes that occur in southern Africa’s
        superswell with data about other types of seismic events that occur there
5. Using
        computer models to estimate the length of time it would take for a
        hypothetical landmass 1,000 miles across to rise one mile vertically

Answer:

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Q8:

In line 10, the author mentions the Himalayan
            Mountains most likely in order to

1. highlight
        certain similarities between the southern African superswell and other
        massive features on Earth’s surface
2. identify
        a feature of Earth’s surface that predates the origins of the southern
        African superswell
3. provide
        an example of a feature of Earth’s surface that can explained by plate
        tectonics
4. suggest
        that geophysicists are correct in attributing the sculpting of Earth’s
        surface to violent collisions between tectonic plates
5. give
        an example of a feature of Earth’s surface that scientists are unable to
        explain fully

Answer:

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Q9:     

According to the passage, the computer models referred to in
line 86 have had which of the following effects?

1. They
        have confirmed researchers’ doubts regarding the theory that convection
        within the mantle can lift or lower Earth’s surface vertically.
2. They
        have cast doubt on the validity of plate-tectonics theory as an
        explanation for the sculpting of Earth’s mountain ranges.
3. They
        have proved geophysicists’ theory that the behavior of seismic waves in
        Earth’s mantle is related to the temperature of the rock through which
        they are traveling.
4. They
        have convinced formerly skeptical researchers that rock formations deep in
        Earth’s mantle below southern Africa could have
        created the superswell.
5. They
        have confirmed researchers’ speculation that masses of hot rock are
        buoyant enough to rise to the upper part of Earth’s mantle.

Answer:

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until recently

geophysicists were skeptical

of its ability to lift or lower the

            planet’s surface vertically

6. The belief is not long-standing. So B is better.

9题models confirm的不是researchers' speculation 吧,因为前面提到researchers 只有doubts没有speculation的具体内容,confirm的内容是this formation is buoyant enough to rise slowly within the mantle and strong enough to push Africa upward as it rises

不要被confirm迷惑了,开始我也选成E了