History of the Drift Concept

 

Exercise 1.Before reading the text look at the title. What do you think this text

will tell you.

 

The story of the development of the idea of continental drift is so interesting that it is worth relating1, for there are several important lessons is that landscape can teach us a great deal about earth history, without the necessity to devolve into (to go into details) the stratigraphy below. Another is that scientists are sometimes reluctant (unwilling) to accept the obvious, even with the evidence staring them in the face. Still another is that we occasionally forget those researchers who were the first to formulate important ideas, when those ideas finally become popularly accepted. Some of the earliest protagonists of the concept o f continental drift have been all but forgotten. We ought to remind ourselves of their contributions. Some of them were physical geographers.

It was as long ago as 1619 when Francis Bacon, the great naturalist, remarked that the opposite coasts of the South Atlantic Ocean were so similar and well-matched (corresponded) that they might at one time have been joined. No one paid much attention then, nor in the 19th century when some scholars began to take further note o f the jigsaw-like2 character of the Atlantic and the growing list of similarities on the Ocean’s two sides. Then in 1915 a German scientist named Alfred Wegener published an amazing book for its time, the first systematic statement of the concept that the earth’s continents were once united in a single, vast landmass that broke apart to form the ocean and continents as we know them today. His book, entitled The Origin o f Continents and Oceans, for the first time brought virtually everything that was known to support the idea o f continental drift.

It took a decade before Wegener’s work was translated into English. In many quarters Wegener’s views were not merely criticized - they were ridiculed (laughed at). True, Wegener had assembled an enormous mass of data suggesting that the continents were at one time united. He correlated rock types on opposite sides of the South Atlantic, traced zones o f crustal deformation across the Atlantic, recorded the distribution of fossil life that had required connections across the ocean, interpreted climatic changes common to distant continents. He argued that the jigsaw-like fit of Africa and South America could not be a matter of chance3. But there was one problem:

Wegener could not come up with a plausible explanation for the mechanism of continental drift. How could it happen? What were the forces that propelled the landmasses across the face of the earth, powerful enough to carry the two Americas several thousand miles away from Europe and Africa within, geologically speaking, a comparatively short time? Wegener himself proposed something called “polflucht” - “light from the poles”. He argued that the earth’s gravitational force, somewhat greater at the equator because of the planet’s slight equatorial bulge, would pull the continental landmasses away from the poles. This force might be small at any given moment, but over the time span of million of years its aggregate might be enough, Wegener thought, to cause continental motion. He also suggested that the earth’s rotation had the effects of pushing continents to the west. Thus western North and South America are crumpled up as these landmasses push westward into the Pacific Basin; Madagascar is left behind as Africa moves slowly westward into the Atlantic. Where the surface evidence seemed to contradict4 the concept of westward motion. Wegener proposed that currents in the underlying sima could produce alternate directions of movement.

In 1928, the American Association o f Petroleum Geologists organized a special symposium to consider the Wegener hypothesis. Specialists from all over the world were invited to participate (take part). One of the contributors to the 1928 Symposium was an American, F.B. Taylor, who had proposed a form o f the continental drift independent of Wegener. Like all others seeking to substantiate the hypothesis of drift, Taylor wanted to explain the mechanism, and for his solution he is chiefly remembered. Taylor, viewing the globe and its maldistributed6 continents, suggested that the answer might lie in the relationship between the earth and its satellite, the moon. He theorized that the moon was captured7 by the earth, quite suddenly during the Cretaceous, and that a segment o f crust was dislodged in what is now the vast Pacific Basin. Since then, he thought, the continental landmasses have been moving in directions dictated by the earth’s “refilling” the Pacific gap thus created.

Wegener had given the name Pangaea to the supercontinent that existed prior to the breakup. Actually, the hard evidence for a reassembly came from southern hemisphere, and especially from Africa and South America. An Austrian scientists, E. Suess, gave the name Gondwanaland to the southern group o f connected landmasses (Africa, South America, Australia, Antarctica, and, for reasons we shall discuss later, India as well). The northern group, that is Eurasia and North America, came to the southern continents, from Gondwana (the abbreviated form of Gondwanaland often used), that the major evidence for continental drift soon emerged.

Notes:

1 to be worth relating - стоит того, чтобы рассказать

2 jigsaw - зазубренный

3 a matter o f chance - дело случая, случайность

4 to contradict - противоречить

5 sima - земная кора, сложенная породами из силиция и магния

6 maldistributed - неправильно распределенный

7 to capture – захватывать

 

Exercise 2. Read the first paragraph and give expanded answers to the following

questions.

 

1. Why is it important to know the story o f the development of the idea of

continental drift?

2. What is the difference in meaning between “reluctant” and “willing”?

3. What do you expect the rest o f the text to be about?

 

Exercise 3. Now read about the scientists who contributed to the development of

the drift concept.

 

Exercise 4. Read the text again one paragraph at a time and complete this chart

with ticks (V).

Which of the scientists:	(1) Taylor	(2) E. Suess	(3) Alfred Wegener	(4) Francis Bacon
a)... remarked the similarities of the opposite coasts of the South Atlantic Ocean
b)... published “The Origin of Continents and Oceans”
c)... proposed an independent theory
d)... gave the name Pangaea
e)... gave the name Gondwanaland

 

Exercise 5. a) The text describes that Wegener's views were criticized. What fo r

were they criticized? Write the "comment ” like the example in the table.

Wegener’s views	Comment
1)... suggested that the continents were at one time united	Wegener couldn’t explain the mechanism of continental drift
2)... correlated rock types on opposite sides of the South Atlantic
3)... traced zones of crystal deformation
4)... recorded the distribution of fossil life
5)... interpreted climatic changes common to distant continents

b) What is an American, F. B. Taylor chiefly rememberedfor?

c) What hypothesis o f drift did Taylor propose?