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Distribution of Oceans and Continents NCERT Solutions - Geography for UPSC CSE

1. Multiple choice questions.


(i) Who amongst the following was the first to consider the possibility of Europe, Africa and America having been located side by side.

(a) Alfred Wegener 

(b) Antonio Pellegrini 

(c) Abraham Ortelius

(d) Edmond Hess

► (c) Abraham Ortelius


(ii) Polar fleeing force relates to:

(a) Revolution of the Earth 

(b) Gravitation 

(c) Rotation of the earth

(d) Tides

► (c) Rotation of the earth


(iii) Which one of the following is not a minor plate?

(a) Nazca 

(b) Arabia 

(c) Philippines

(d) Antarctica

► (d) Antarctica


(iv) Which one of the following facts was not considered by those whilediscussing the concept of sea floor spreading?

(a) Volcanic activity along the mid-oceanic ridges.

(b) Stripes of normal and reverse magnetic field observed in rocks of ocean floor.

(c) Distribution of fossils in different continents.

(d) Age of rocks from the ocean floor.

► (c) Distribution of fossils in different continents.


(v) Which one of the following is the type of plate boundary of the Indian plate along  the Himalayan mountains?

(a) Ocean-continent convergence

(b) Divergent boundary

(c) Transform boundary

(d) Continent-continent convergence

► (d) Continent-continent convergence


2. Answer the following questions in about 30 words.


(i) What were the forces suggested by Wegener for the movement of the continents?


Wegener suggested that the movement responsible for the drifting of the continents was caused by pole-fleeing force and tidal force. The polar-fleeing force relates to the rotation of the earth. The earth is not a perfect sphere; it has a bulge at the equator. This bulge is due to the rotation of the earth. The second force, the tidal force is due to the attraction of the moon and the sun that develops tides in oceanic waters. Wegener believed that these forces would become effective when applied over many million years.


(ii) How are the convectional currents in the mantle initiated and maintained?


The convectional currents in the mantle are generated due to radioactive elements causing
thermal differences in the mantle portion. The hot material rises up from greater depths and comparatively cold material goes down from above. The occurrence of this process repetitively give birth to convectional currents. 


(iii) What is the major difference between the transform boundary and the convergent or divergent boundaries of plates?


Transform Boundary

Convergent Boundary

Divergent Boundary

Where the crust is neither produced nor destroyed as the plates slide horizontally past each other.Where the crust is destroyed as one plate dived under another.Where new crust is generated as the plates pull away from each other.


(iv) What was the location of the Indian landmass during the formation of the Deccan Traps?


The Deccan Traps were formed during the movement of the Indian plate towards the Asiatic plate. This started somewhere around 60 million years ago and continued for a long period of time. At that time, Indian landmass was located in the south of the equator.

3. Answer the following questions in about 150 words.

(i) What are the evidences in support of the continental drift theory?


The evidences in support of the continental drift theory are:

• The Matching of Continents (Jig-Saw-Fit): The shorelines of Africa and South America facing each other have a remarkable and unmistakable match.

• Rocks of Same Age Across the Oceans: The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa. The earliest marine deposits along the coastline of South America and Africa are of the Jurassic age. This suggests that the ocean did not exist prior to that time.

• Tillite: It is the sedimentary rock formed out of deposits of glaciers. The Gondawana system
of sediments from India is known to have its counter parts in six different landmasses of the Southern Hemisphere. The glacial tillite provides unambiguous evidence of palaeoclimates and also of drifting of continents.

• 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. 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.

• 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. The observations that Lemurs occur in India, Madagascar and Africa led some
to consider a contiguous landmass “Lemuria” linking these three landmasses.


(ii) Bring about the basic difference between the drift theory and Plate tectonics.


Drift Theory

Plate tectonics

Drift theory suggested that in the past, there was a super continent called Pangaea. Over time, this super continent split apart to form the seven continents we have today.Plate Tectonics is a theory of global tectonics which proposes that the earth’s lithosphere is divided into seven major and some minor plates.
It only covers the movement of continents. It covers movements of both Continents and Oceans.
The evidences in support of drift theory are Jig-Saw-Fit, Placer Deposits, Distribution of Fossils and others.It is based on scientific analysis of the processes inside the earth’s surface.
It does not give any future prediction.This theory says that all plates shall continue to move in the future period as well.


(iii) What were the major post-drift discoveries that rejuvenated the interest of scientists in the study of distribution of oceans and continents?


A number of post-drift discoveries during the post-war period added new information to geological literature. Particularly, the information collected from the ocean floor mapping provided new dimensions for the study of distribution of oceans and continents.

• All along the midoceanic ridges, volcanic eruptions are common and they bring huge amounts of
lava to the surface in this area.

• The rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties. Rocks closer to the
mid-oceanic ridges are normal polarity and are the youngest. The age of the rocks increases as one moves away from the crest.

• The ocean crust rocks are much younger than the continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 million years old.

• The sediments on the ocean floor are unexpectedly very thin.

• The deep trenches have deep-seated earthquake occurrences while in the midoceanic ridge areas, the quake foci have shallow depths.

The document Distribution of Oceans and Continents NCERT Solutions | Geography for UPSC CSE is a part of the UPSC Course Geography for UPSC CSE.
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FAQs on Distribution of Oceans and Continents NCERT Solutions - Geography for UPSC CSE

1. What is the distribution of oceans and continents?
Ans. The distribution of oceans and continents refers to the arrangement and location of large bodies of water (oceans) and land masses (continents) on the Earth's surface. It determines the overall geography of the planet, including the shape and size of the continents and the depth and extent of the oceans.
2. How are oceans and continents distributed on the Earth?
Ans. Oceans cover about 71% of the Earth's surface and are mainly concentrated in the southern hemisphere. The Pacific Ocean is the largest and covers more area than all the other oceans combined. The Atlantic Ocean is the second-largest, followed by the Indian Ocean, Southern Ocean, and Arctic Ocean. Continents, on the other hand, are large land masses that are primarily located in the northern hemisphere, with Asia being the largest continent, followed by Africa, North America, South America, Antarctica, Europe, and Australia.
3. What are the main factors influencing the distribution of oceans and continents?
Ans. The distribution of oceans and continents is influenced by various factors. Plate tectonics play a significant role, as the movement of tectonic plates can cause the formation of new land masses and the opening or closing of ocean basins. Volcanic activity and earthquakes also contribute to the shaping of the Earth's surface. Additionally, factors such as erosion, weathering, and sea level changes over time can further impact the distribution of oceans and continents.
4. How do oceans and continents affect climate patterns?
Ans. Oceans and continents have a significant influence on climate patterns. Oceans, with their large thermal capacity, act as heat sinks and help regulate temperatures by absorbing and releasing heat over time. They also play a crucial role in the global water cycle, providing moisture for rainfall. Continents, on the other hand, can create barriers that influence the flow of air masses, leading to variations in precipitation and temperature across different regions. The distribution of oceans and continents can result in the formation of ocean currents and wind patterns, further affecting climate on a global scale.
5. What are the implications of the distribution of oceans and continents on human settlements and biodiversity?
Ans. The distribution of oceans and continents has significant implications for human settlements and biodiversity. Coastal areas, where land and sea meet, are often densely populated due to their access to resources and transportation routes. The proximity to oceans also influences economic activities such as fishing, trade, and tourism. The distribution of continents determines the availability of land for agriculture and habitation. In terms of biodiversity, different regions of the world, with their unique oceanic and terrestrial ecosystems, support a wide variety of plant and animal species. The distribution of oceans and continents plays a crucial role in shaping the habitats and biodiversity hotspots on Earth.
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