GWD2-Q6/Q9

notidgen

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.

 

 

--------------------------------------------------------------------------------

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

答案是b，我选的d，为什么d错，有谁能帮我解释哈？谢拉～

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.

答案是d，我选的a，为啥错啊～

[此贴子已经被作者于2008-8-19 12:25:36编辑过]

phenixfish

同问~~

112358don

有没有牛人解答下呢，我马上要考试了，可是这道题很不解

shiwenpp

同问Q9，A为什么错啊？？？

cappuccino202

A.    They have confirmed researchers’ doubts regarding the theory that convection within the mantle can lift or lower Earth’s surface vertically.（这个猜测是前面提出的，而此处until recently geophysicists were skeptical of its ability to lift or lower the planet’s surface vertically. 证明了可以lift，不是lift or lower）

ashely91

原文说Dispelling researchers’ initial doubts 推翻研究者的疑问 而A是confirmed  researchers’ doubts 所以错了吧。。。。可是为什么E错额？我选的E