Английский для бакалавров. Зарубина Л.П - 200 стр.

UptoLike

ВУЗ: 

ТулГУ | Тула

Составители: 

Рубрика: 

200
I. Read the text ‘Nano-technology and Micro-Electro-Mechanical Systems
(MEMS) – Systems of Systems’ and get its central idea.
II. Say which of the facts in the text seems to you the most interesting and new.
III. Find in the text and put down the key words.
IV. Use the key words to retell the text.
Text 4. WANDERING CONTINENTS
Anyone who has looked at a world map must have noticed how snugly the
coastline of Africa and the Americas could be made to fit together, if the intervening
ocean were removed. Modern geophysics has established that all of the Earth's land-
masses were indeed joined together in one supercontinent, Pangaea, hundreds of mil-
lions of years ago, and that this supercontinent was broken apart, with the land
masses drifting to their present positions on the globe.
His idea took many years to become established. Speculations about the fit of
the continents go back to Francis Bacon (1561-1626), but the acknowledged “father”
of the idea of continental drift was the German astronomer and meteorologist Alfred
Wegener, who published the first comprehensive statement of the theory in 1912.
Wegener thought that the continents might move through the thinner crust of the
ocean floor, like icebergs ploughing through the sea, and he gathered a wealth of evi-
dence showing how well the continents could be fitted together like some global jig-
saw puzzle. But the idea of continents moving through the rocks of the sea floor did
not seem feasible, and found little favour until the 1950s, when the development of
new geological techniques provided conclusive evidence that the continents do move.
The key evidence came from magnetic studies of the ocean floors. These
showed that the crust of the Atlantic Ocean floor is arranged symmetrically on either
side of a great ridge of volcanic activity which runs roughly down the center of the
ocean bed. The interpretation of this discovery is that new oceanic crust is being cre-
ated at the mid-ocean ridge, where it wells up through a crack in the Earth’s crust and
is pushing out on either side, steadily widening the Atlantic.
In other parts of the world the reverse happens. The North Pacific, for example,
has no oceanic ridge, but there is a deep trench running down the west of the ocean
floor, next to the Eurasian landmass. There the thin crust of the ocean floor is being
pushed under the continent, back down into the mantle where it melts and is ulti-
mately recycled. The net effect is that there is no change in the surface area of the
Earth — spreading in the Atlantic and at other sites is balanced by contraction of the

Страницы