Hauptmenü:
1. Articles. You should read the complete article first before doing the exercise: http://archive.wired.com/science/discoveries/news/2002/04/51969 .
Magma bursts forth as volcanoes in many parts of world, but these superplumes originate so much deeper
that they cross boundary between Earth's upper and lower mantle 400 miles below.
scientists from University of California at Berkeley, report new evidence of plumes in
Friday's issue of journal Science.
Researcher Barbara Romanowicz said earthquake studies until now have emphasized dynamics of
collisions between planet's massive surface plates. When two of them crash together, one slips beneath other
in process called subduction, and earthquakes and volcanoes can follow. "We think
superplumes play important role as well," Romanowicz said.
new study seeks to focus attention on hot material rising upward from base of mantle,
partially molten region that extends about 1,740 miles from Earth's core to its crust, or lithosphere.
" hot material brought under lithosphere by superplumes then spreads out horizontally toward
mid-ocean ridges," Romanowicz explained. ridges are often active volcanic areas.
material heats up region under plates that cover Earth's surface and thus may actively
contribute to their movement.
David Bercovici, professor of geology and geophysics at Yale University, said other indications
of superplumes have been detected, such as variations in Earth's gravity field in those areas. He was
pleased to see plumes identified through seismic measurements.
"It's not hugely surprising to see upwellings at these regions but it's nice to see they are distinct," he said.
Romanowicz and Yuancheng Gung were able to develop images that indicate presence of
uperplumes by measuring movement of seismic waves through Earth.
Romanowicz said they used elastic tomography, process that measures movement of
seismic waves to chart interior of planet, somewhat like CAT scan machine uses X-rays
to look inside person.
She said plumes' temperature has not been determined, but they may be as much as several hundred
degrees hotter than surrounding material.
"We do not know precisely, because images we have are still not very well resolved, and actual
temperature may depend on whether superplumes are like we see them now: wide, thick conduits several
thousand kilometers across, or whether they are composed of several narrower plumes grouped together," she said.
"Generally, it is assumed that only about 10 percent of heat that comes out at surface of Earth
comes from earth's core. This number may thus be underestimated, perhaps as much as by factor of
two," she said.
regions above superplumes tend to bulge upward.
plateaus of southern and eastern Africa are about 1,600 feet higher than most old continental areas
in world, she said. This is referred to as "African superswell."
Also, she said, heat flow from Earth's interior that is measured in wide area of southern
Africa is higher than expected, indicating that unusually large supply of heat must be coming from
underneath.
volcanoes exist in Africa and in southern Atlantic Ocean that could be related to
superplume, in same way that Hawaii and other hotspot volcanoes in southern
Pacific may be related to Pacific superswell, she said.
Copyright © 2002 Associated Press
2. Prepositions. The newspaper article below is taken from "The Daily Mail, 29-
The following prepositions are omitted:
about | into |
at | of |
by | over |
for | to |
from | with |
in | within |
in terms of | without |
You should add the 41 prepositions before you control yourself by hitting the answers button.
3. make and do. Choose the appropriate form of either make or do to complete the given sentences.
3.1. | Are they progress with their computer course? |
3.2. | GBS often business with other companies in Wales. |
3.3. | Did that news really him happy? |
3.4. | The headmaster a really interesting speech on hooliganism yesterday. |
3.5. | She's already been her final exam test for half an hour. |
3.6. | What he told the children wasn't a true. He the story up the very minute he was telling it. |
3.7 | I know it isn't a good situation, but I'll have to the best of it. |
3.8. | She a scene because her father wouldn't let her do it. |
3.9. | Waiter, once and for all, I'd like my steak well , please. |
3.10 | Two thieves were caught by the young police officer whilst an attempt on a local post office. |