The theory of plate tectonics proposes that the earth's lithosphere is divided into ______ major and some minor plates.
- A.7
- B.6
- C.12
- D.16
Correct answer
Explanation
The correct answer is A, seven. Plate tectonics, propounded in 1967, holds that the lithosphere is broken into seven major plates and a number of minor ones that move over the plastic asthenosphere. The seven are the Pacific plate, which is the largest and wholly oceanic, the North American, South American, Eurasian, African, Indo-Australian and Antarctic plates. Option B, six, would be right only if the Indo-Australian plate were left out, and some texts instead split it in two and count eight, but the standard answer taught in school geography is seven. Options C and D, twelve and sixteen, come close to the total number of plates when the minor ones such as Nazca, Cocos, Arabian, Philippine, Caribbean, Juan de Fuca, Scotia, Caroline and Fuji are added to the majors.
Read the full article: Continental Drift and Plate Tectonics: Exam Notes
Practice Questions
View allThe theory of continental drift was propounded by:
- A.Alfred Wegener
- B.Harry Hess
- C.Arthur Holmes
- D.Charles Lyell
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Wegener, a German meteorologist and climatologist, put forward the continental drift theory in 1912 and developed it in his book The Origin of Continents and Oceans; he argued that all the continents once formed a single landmass, Pangaea, which broke up about two hundred million years ago.
Read the full explanation →In Wegener's theory, the single great ocean that surrounded the supercontinent Pangaea was called:
- A.Tethys
- B.Panthalassa
- C.Laurasia
- D.Gondwana
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Wegener held that about two hundred and fifty million years ago all the land of the earth lay together as one mass, Pangaea, and that one enormous ocean, Panthalassa, surrounded it.
Read the full explanation →Which pair of forces did Wegener suggest as the cause of continental drift?
- A.Ridge push and slab pull
- B.Pole-fleeing force and tidal force
- C.Isostasy and gravity
- D.Convection currents and radioactivity
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Wegener attributed the horizontal movement of the continents to the pole-fleeing force, which arises from the rotation of the earth and the bulge of the equator, and to the tidal force, which arises from the attraction of the moon and the sun.
Read the full explanation →The Tethys Sea separated which two landmasses after the break-up of Pangaea?
- A.Laurasia and Gondwanaland
- B.Africa and South America
- C.India and Australia
- D.Antarctica and Australia
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When Pangaea began to break about two hundred million years ago, it parted into a northern mass called Laurasia or Angaraland and a southern mass called Gondwanaland, and the long narrow Tethys Sea lay between the two.
Read the full explanation →The concept of sea floor spreading was given by:
- A.Alfred Wegener
- B.Harry Hess
- C.Alfred Lothar Nazca
- D.Edward Suess
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After the detailed mapping of the ocean floor during and after the Second World War revealed mid-oceanic ridges, deep trenches and a surprisingly thin cover of sediment, Hess proposed in 1961 that molten material rises along the ridge, forms new ocean floor and pushes the older floor away on both…
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