Class 11 Geography: Distribution of Oceans and Continents — Chapter Question Set

(c) Abraham Ortelius — This is the textbook-supported choice for the question.

(c) Rotation of the earth — This is the textbook-supported choice for the question.

(d) Antarctica — This is the textbook-supported choice for the question.

(c) Distribution of fossils in different continents. — This is the textbook-supported choice for the question.

(d) Continent-continent convergence — This is the textbook-supported choice for the question.

d) interior of the earth — The textbook states: In the previous chapter, you have studied the interior of the earth.

c) 29 per cent — The textbook states: You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters.

b) same in the past — The textbook states: The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past.

a) now a well-accepted fact that oceans and cont — The textbook states: Moreover, it is now a well-accepted fact that oceans and continents will not continue to enjoy their present positions in times to come.

d) their positions in the past? — The textbook states: If this is so, the question arises what were their positions in the past?

c) true that the continents and oceans have chan — The textbook states: Even if it is true that the continents and oceans have changed and are changing their positions, you may wonder as to how scientists know this.

b) questions in this chapter — The textbook states: You will find the answers to some of these and related questions in this chapter.

a) RIFT Observe — The textbook states: CONTINENTAL D RIFT Observe the shape of the coastline of the Atlantic Ocean.

d) side of the ocean — The textbook states: You will be surprised by the symmetry of the coastlines on either side of the ocean.

c) Americas — The textbook states: No wonder , many scientists thought of this similarity and considered the possibility of the two Americas, Europe and Africa, to be once joined together.

b) 1596 — The textbook states: From the known records of the history of science, it was Abraham Ortelius, a Dutch map maker, who first pr oposed such a possibility as early as 1596.

a) the three continents together — The textbook states: Antonio Pellegrini drew a map showing the three continents together.

d) 1912 — The textbook states: However, it was Alfred Wegener—a German meteorologist who put forth a comprehensive argument in the form of “the continental drift DISTRIBUTION OF OCEANS AND C ONTINENTS CHAPTER theory” in 1912 .

c) regarding the distribution of the oceans and — The textbook states: This was regarding the distribution of the oceans and the continents.

b) Wegener — The textbook states: According to Wegener, all the continents formed a single continental mass and mega ocean surrounded the same.

a) PANGAEA — The textbook states: The super continent was named PANGAEA, which meant all earth.

d) PANTHALASSA — The textbook states: The mega-ocean was called PANTHALASSA, meaning all water.

c) 200 million — The textbook states: He argued that, around 200 million years ago, the super continent, Pangaea, began to split.

b) Laurasia — The textbook states: Pangaea first broke into two large continental masses as Laurasia and Gondwanaland forming the northern and southern components respectively.

a) Laurasia — The textbook states: Subsequently, Laurasia and Gondwanaland continued to break into various smaller continents that exist today.

d) offered in support of the continental drift — The textbook states: A variety of evidence was offered in support of the continental drift.

c) Support — The textbook states: Evidence in Support of the Continental Drift The Matching of Continents (Jig-Saw-Fit) The shorelines of Africa and South America facing each other have a remarkable and unmistakable match.

b) 1964 — The textbook states: It may be noted that a map produced using a computer programme to find the best fit of the Atlantic margin was presented by Bullard in 1964.

a) tried at 1 — The textbook states: The match was tried at 1,000fathom line instead of the present shoreline.

d) Same Age — The textbook states: Rocks of Same Age A cross the Oceans The radiometric dating methods developed in the recent period have facilitated correlating the rock formation from different continents across the vast ocean.

c) 2,000 million — The textbook states: The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa.

b) South America — The textbook states: The earliest marine deposits along the coastline of South America and Africa are of the Jurassic age.

a) prior to that time — The textbook states: This suggests that the ocean did not exist prior to that time.

d) the sedimentary rock formed out of deposits o — The textbook states: Tillite It is the sedimentary rock formed out of deposits of glaciers.

c) India — The textbook states: The Gondawana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere.

b) extensive and prolonged glaciation — The textbook states: At the base, the system has thick tillite indicating extensive and prolonged glaciation.

a) Africa — The textbook states: Counterparts of this succession are found in Africa, Falkland Island, Madagascar, Antarctica and Australia.

d) Gondawana — The textbook states: Overall resemblance of the Gondawana-type sediments clearly demonstrates that these landmasses had remarkably similar histories.

c) of drifting of continents — The textbook states: The glacial tillite provides unambiguous evidence of palaeoclimates and also of drifting of continents.

b) Ghana — The textbook states: Placer Deposits The occurrence of rich placer deposits of gold in the Ghana coast and the absolute absence of source rock in the region is an amazing fact.

a) Brazil — The textbook states: The gold bearing veins are in Brazil and it is obvious that the gold deposits of the Ghana are derived from the Brazil plateau when the two continents lay side by side.

d) Fossils When — The textbook states: Distribution of Fossils When identical species of plants and animals adapted to living on land or in fresh water are found on either side of the marine barriers, a problem arises regarding accounting for such distribution.

c) Lemurs — The textbook states: The observations that Lemurs occur in India, Madagascar and Africa led some to consider a contiguous landmass ‘Lemuria’ linking these three landmasses.

b) Southern Cape — The textbook states: The skeletons of these are found only in two localities: the Southern Cape province of South Africa and Iraver formations of Brazil.

a) 4,800 km — The textbook states: The two localities are presently 4,800 km apart with an ocean in between them.

d) Drifting Wegener — The textbook states: Force for Drifting Wegener suggested that the movement responsible for the drifting of the continents was caused by pole-fleeing force and tidal force.

c) rotation of the earth — The textbook states: The polar-fleeing force relates to the rotation of the earth.

b) aware of the fact that the earth is not a per — The textbook states: You are aware of the fact that the earth is not a perfect sphere; it has a bulge at the equator.

a) Wegener — The textbook states: The second force that was suggested by Wegener — the tidal force — is due to the attraction of the moon and the sun that develops tides in oceanic waters.

d) over many million years — The textbook states: Wegener believed that these forces would become effective when applied over many million years.

You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters. The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past. Force for Drifting Wegener suggested that the movement responsible for the drifting of the continents was caused by pole-fleeing force and tidal force.

Convectional Current Theory Arthur Holmes in 1930s discussed the possibility of convection currents operating in the mantle portion. These currents are generated due to radioactive elements causing thermal differences in the mantle portion. Holmes argued that there exists a system of such currents in the entire mantle portion.

The theory of plate tectonics proposes that the earth’s lithosphere is divided into seven major and some minor plates. There are three types of plate boundaries: Divergent Boundaries Where new crust is generated as the plates pull away from each other . Transform Boundaries Where the crust is neither produced nor destroyed as the plates slide horizontally past each other.

Rocks of Same Age A cross the Oceans The radiometric dating methods developed in the recent period have facilitated correlating the rock formation from different continents across the vast ocean. The observations that Lemurs occur in India, Madagascar and Africa led some to consider a contiguous landmass ‘Lemuria’ linking these three landmasses. During the movement of the Indian plate towards the Eurasian plate, a major event that occurred was the outpouring of lava and formation of the Deccan T raps.

In the previous chapter, you have studied the interior of the earth.

You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters.

The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past.

Moreover, it is now a well-accepted fact that oceans and continents will not continue to enjoy their present positions in times to come.

If this is so, the question arises what were their positions in the past?

Even if it is true that the continents and oceans have changed and are changing their positions, you may wonder as to how scientists know this.

How have they determined their earlier positions?

You will find the answers to some of these and related questions in this chapter.

CONTINENTAL D RIFT Observe the shape of the coastline of the Atlantic Ocean.

You will be surprised by the symmetry of the coastlines on either side of the ocean.

No wonder , many scientists thought of this similarity and considered the possibility of the two Americas, Europe and Africa, to be once joined together.

From the known records of the history of science, it was Abraham Ortelius, a Dutch map maker, who first pr oposed such a possibility as early as 1596.

Antonio Pellegrini drew a map showing the three continents together.

However, it was Alfred Wegener—a German meteorologist who put forth a comprehensive argument in the form of “the continental drift DISTRIBUTION OF OCEANS AND C ONTINENTS CHAPTER theory” in 1912 .

This was regarding the distribution of the oceans and the continents.

According to Wegener, all the continents formed a single continental mass and mega ocean surrounded the same.

The super continent was named PANGAEA, which meant all earth.

The mega-ocean was called PANTHALASSA, meaning all water.

He argued that, around 200 million years ago, the super continent, Pangaea, began to split.

Pangaea first broke into two large continental masses as Laurasia and Gondwanaland forming the northern and southern components respectively.

Subsequently, Laurasia and Gondwanaland continued to break into various smaller continents that exist today.

However, it was Alfred Wegener—a German meteorologist who put forth a comprehensive argument in the form of “the continental drift DISTRIBUTION OF OCEANS AND C ONTINENTS CHAPTER theory” in 1912 . A variety of evidence was offered in support of the continental drift. Evidence in Support of the Continental Drift The Matching of Continents (Jig-Saw-Fit) The shorelines of Africa and South America facing each other have a remarkable and unmistakable match. Post-drift Studies It is interesting to note that for continental drift, most of the evidence was collected from the continental areas in the form of distribution of flora and fauna or deposits, like tillite. This was an attempt to provide an explanation to the issue of force, on the basis of which contemporary scientists discarded the continental drift theory. available at the tim e Wegener put forth his concept of continental drift. Force for the Plate Movement At the time that Wegener proposed his theory of continental drift, most scientists believed that the earth was a solid, motionless body.

However, it was Alfred Wegener—a German meteorologist who put forth a comprehensive argument in the form of “the continental drift DISTRIBUTION OF OCEANS AND C ONTINENTS CHAPTER theory” in 1912 . A variety of evidence was offered in support of the continental drift. This was an attempt to provide an explanation to the issue of force, on the basis of which contemporary scientists discarded the continental drift theory. Siberia (Emilani, 1992) concept termed Plate Tectonics . The theory of plate tectonics proposes that the earth’s lithosphere is divided into seven major and some minor plates. Force for the Plate Movement At the time that Wegener proposed his theory of continental drift, most scientists believed that the earth was a solid, motionless body. However, concepts of sea floor spreading and the unified theory of plate tectonics have emphasised that both the surface of the earth and the interior are not static and motionless but are dynamic.

Even if it is true that the continents and oceans have changed and are changing their positions, you may wonder as to how scientists know this. However, it was Alfred Wegener—a German meteorologist who put forth a comprehensive argument in the form of “the continental drift DISTRIBUTION OF OCEANS AND C ONTINENTS CHAPTER theory” in 1912 . This was regarding the distribution of the oceans and the continents. Particularly, the information collected from the ocean floor mapping provided new dimensions for the study of distribution of oceans and continents. Expeditions to map the oceanic floor in the post–World War II period provided a detailed picture of the ocean relief and indicated the existence of submerged DISTRIBUTION OF OCEANS AND CONTINENTS 29 mountain ranges as well as deep trenches, mostly located closer to the continent margins. Of these, the deep-oceanic trenches are the areas which are of considerable interest in so far as the distribution of oceans and continents is concerned. PLATE T ECTONICS Since the advent of the concept of sea floor spreading, the interest in the problem of distribution of oceans and continents was revived.

In the previous chapter, you have studied the interior of the earth. In the previous chapter, you have studied the interior of the earth. You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters. The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past.

You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters. In the previous chapter, you have studied the interior of the earth. You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters. The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past. Moreover, it is now a well-accepted fact that oceans and continents will not continue to enjoy their present positions in times to come.

The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past. You know that continents cover 29 per cent of the surface of the earth and the remainder is under oceanic waters. The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past. Moreover, it is now a well-accepted fact that oceans and continents will not continue to enjoy their present positions in times to come. If this is so, the question arises what were their positions in the past?

Moreover, it is now a well-accepted fact that oceans and continents will not continue to enjoy their present positions in times to come. The positions of the continents and the ocean bodies, as we see them in the map, have not been the same in the past. Moreover, it is now a well-accepted fact that oceans and continents will not continue to enjoy their present positions in times to come. If this is so, the question arises what were their positions in the past? Even if it is true that the continents and oceans have changed and are changing their positions, you may wonder as to how scientists know this.