Q1: 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
Ans: (c)
(ii) Polar fleeing force relates to:
(a) Revolution of the Earth
(b) Gravitation
(c) Rotation of the earth
(d) Tides
Ans: (c)
(iii) Which one of the following is not a minor plate?
(a) Nazca
(b) Arabia
(c) Philippines
(d) Antarctica
Ans: (d)
(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.
Ans: (c)
(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
Ans: (d)
Q2: Answer the following questions in about 30 words.
(i) What were the forces suggested by Wegener for the movement of the continents?
Ans: 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?
Ans: 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?
Ans: The difference:
(iv) What was the location of the Indian landmass during the formation of the Deccan Traps?Ans: 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. At that time, Indian landmass was located in the south of the equator.
Q3: Answer the following questions in about 150 words.
(i) What are the evidences in support of the continental drift theory?
Ans: The evidences in support of the continental drift theory are:
(ii) Bring about the basic difference between the drift theory and Plate tectonics.
Ans:
(iii) What were the major post-drift discoveries that rejuvenated the interest of scientists in the study of distribution of oceans and continents?
Ans: 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.
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1. How are oceans and continents distributed on Earth's surface? |
2. What factors influence the distribution of oceans and continents? |
3. Why are most of the Earth's landmasses located in the Northern Hemisphere? |
4. How do oceans and continents interact with each other? |
5. How does the distribution of oceans and continents impact the Earth's climate? |
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