Question 1

Q1: (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 Weg...

Accepted Answer

(c) Abraham Ortelius Explanation: According to the source text, "From the known records of the history of science, it was Abraham Ortelius, a Dutch map maker, who first proposed such a possibility as early as 1596."

Question 2

Q2: (ii) Polar fleeing force relates to: (a) Revolution of the Earth (b) Gravitation (c) Rotation of the earth (d) Tides

Accepted Answer

(c) Rotation of the earth Explanation: The text states, "The polar-fleeing force relates to the rotation of the earth. You are aware of the fact that the earth is not a perfect sphere; it has a bulge at the equator. This bulge is due to the rotation of the earth."

Question 3

Q3: (iii) Which one of the following is not a minor plate? (a) Nazca (b) Arabia (c) Philippines (d) Antarctica

Accepted Answer

(d) Antarctica Explanation: The chapter lists Antarctica as one of the seven major plates: "Antarctica and the surrounding oceanic plate". Nazca, Arabia, and Philippines are listed under the important minor plates.

Question 4

Q4: (iv) Which one of the following facts was not considered by those while discussing the concept of sea floor spreading? (a) Volcanic activity along the...

Accepted Answer

(c) Distribution of fossils in different continents. Explanation: The distribution of fossils was a key piece of evidence used by Alfred Wegener to support his theory of Continental Drift. The concept of sea floor spreading was developed later based on evidence from ocean floor mapping, such as volc...

Question 5

Q5: (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) Di...

Accepted Answer

(d) Continent-continent convergence Explanation: The text explicitly states, "The subduction zone along the Himalayas forms the northern plate boundary in the form of continent-continent convergence."

Question 6

Q1: (i) What were the forces suggested by Wegener for the movement of the continents?

Accepted Answer

Alfred Wegener suggested two forces responsible for continental drift. The first was the pole-fleeing force, which he related to the rotation of the Earth causing a bulge at the equator. The second was the tidal force, caused by the gravitational attraction of the sun and the moon.

Question 7

Q2: (ii) How are the convectional currents in the mantle initiated and maintained?

Accepted Answer

Convectional currents in the mantle are initiated by thermal differences caused by radioactive elements within the Earth's interior. Hot, less dense material from the mantle rises, spreads, cools, and then sinks back down. This continuous circular flow, or convection cell, is maintained by the const...

Question 8

Q3: (iii) What is the major difference between the transform boundary and the convergent or divergent boundaries of plates?

Accepted Answer

The major difference is that at transform boundaries, the Earth's crust is neither created nor destroyed; the plates simply slide horizontally past each other. In contrast, at divergent boundaries new crust is generated, and at convergent boundaries, the crust is destroyed as one plate subducts unde...

Question 9

Q4: (iv) What was the location of the Indian landmass during the formation of the Deccan Traps?

Accepted Answer

During the formation of the Deccan Traps, which began around 60 million years ago, the Indian subcontinent was located close to the equator. This was during its long northward journey after breaking away from Gondwanaland and before its collision with the Eurasian plate.

Question 10

Q1: (i) What are the evidences in support of the continental drift theory?

Accepted Answer

Alfred Wegener provided several pieces of evidence to support his theory of continental drift. These are:    The Matching of Continents (Jig-Saw-Fit): The coastlines of Africa and South America show a remarkable and unmistakable match, suggesting they were once joined. This fit is even more perfect...

Question 11

Q2: (ii) Bring about the basic difference between the drift theory and Plate tectonics.

Accepted Answer

The basic differences between Alfred Wegener's Continental Drift Theory and the modern theory of Plate Tectonics are fundamental in terms of both mechanism and scope.    What Moves: Wegener's theory proposed that the continents (sial) moved or plowed through the oceanic crust (sima). In contrast, th...

Question 12

Q3: (iii) What were the major post-drift discoveries that rejuvenated the interest of scientists in the study of distribution of oceans and continents?

Accepted Answer

After Wegener's theory was initially dismissed, several major discoveries, particularly in the post-World War II era, revived scientific interest in the mobility of continents and oceans. These discoveries provided a new evidence base that led to the development of Plate Tectonics.    Mapping of the...

NCERT Solutions