Directions: Read the following text carefully and then translate
the underlined segments into Chinese. Your translation should be written neatly
on ANSWER SHEET 2.
The Theory of Continental Drift has had a long and turbulent
history since it was first proposed by Alfred Wegener in 1910. (46)
Vigorously challenged yet widely ignored, the theory had languished for half
a century, primarily due to its lack of a plausible mechanism to support the
proposed drift. With the discovery of sea-floor spreading in the late 1950’s
and early 60’s, the idea was reinvigorated. Plate tectonics is now almost
universally accepted. Many details of the mechanism are to be worked
out. The surface of the Earth is divided into approximately six
large plates, plus a number of smaller ones. The plates are’ bounded by an
interconnected network of ridges, transform faults, and trenches. Ridges,
also called spreading centers, occur where two plates are moving away from each
Other. As the plates separate, hot molten mantle material flows up to fill the
void. (47) The increased heat resulting from this flow reduces the
density of the plates, causing them to float higher, thus elevating the
boundaries by many thousands of feet above the colder surrounding sea floor.
(48) Ridges on the ocean floor form the longest continuous ranges of
mountains on the planet, but. only in a very few places on the Earth do these
mountains rise above the ocean surface. New sea floor is
constantly being created along spreading centers. Obviously somewhere else old
sea floor must be going away. This occurs in trenches, also called subduction
zones. Trenches occur along the boundary between two plates that are moving
towards each other. (49) Where this occurs, one plate is bent downwards at
about a 400 angle and plunges under the other plate’s leading edge, eventually
to melt back into the liquid mantle below. As the subducting plate is heated
back up to mantle temperatures, certain minerals in the plate melt sooner than
others. (50) Minerals that melt at lower temperatures and are lighter than
the surrounding material tend to rise, melting their way up through the
overriding plate to erupt as volcanoes on the ocean floor. As these
volcanoes grow, they rise above the ocean surface to form lines of islands along
the leading edge of the overriding plate. Numerous islands of Micronesia
and Melanesia in the western Pacific were created in this way.