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(i) The curve of the secondary waves seems to have ended around the depth of 2900 km in figure (A).

(ii) The velocity of the secondary waves is 6 to 8 km/sec around the boundary of the outer core shown in figure (A).

(iii) On the basis of the curve of the secondary waves stopping around the depth of2900 km, it can be concluded that secondary waves do not enter the core.

(iv) The velocity of the primary waves at the time of entering the outer core shown in figure (A) is 8 km/sec.

(v) The following conclusions can be drawn about the intensity of the gravitational force shown in Figure (B) :

1. Gravitational force increases at certain depth from the surface of the earth and then it reduces according to the depth. 

2. At the centre of the earth, the gravitational force is zero.

(a) A and R are correct and A explains(a) A and R are correct and A explains

The top of the cone of a volcanic mountain has a depression known as the crater

1. Weichart – Gutenberg discontinuity

2. seismograph

3. fissure eruption

4. St. Helens USA

5. earthquake

1. The interior of the earth will be very hot. 

2. Huge sized rocks will be present I in the upper layers of the interior of the earth. 

3. Due to extreme heat and pressure, the rocks must be melting in the interior of the earth. 

4. Due to the melting of the rocks, magma will be created in the interior of the earth. 

5. Due to endogenous movements in the interior of the earth, volcanic eruptions will occur on the surface of the earth. 

6. The primary earthquake waves will be travelling through the mantle and the core of the earth. 

7. The secondary earthquake waves will be travelling only through the mantle of the earth. 

8. The temperature in the interior of the earth will get increased with the depth.

9. The highest temperature will be found at the centre of the earth. 

10. The elements like silica, aluminium, magnesium, iron and nickel will be found in the various layers of the interior of the earth.

1. The ozone layer protects the earth from ultraviolet radiation.

2. The earth’s magnetosphere serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer. In this way, the earth is protected because of the magnetosphere.

1. The inner most layer of the earth, called the core has two parts, the outer core and the inner core. 

2. The outer core is rich in iron and is in liquid state.

3. The inner core is made of Nickel and Ferrous which is in solid state. 

4. The central core has very high temperature and pressure

The portion of the Earth’s interior below’ the Crust is called mantle. It extends from 60 km to , 7,900km. The density of this layer ranges from 3.3 to 5.7gm.The mantle is a composition of dense and rigid rocks which have minerals like magnesium and iron.

The mid-continental belt.

Pacific belt is known as the “Ring of Fire”.

Japan, USA, Hawaiian Islands, Philippines, Alaska, New Zealand.

1. The density of the earth goes on increasing from its surface to the centre.

2. The average density of the crust of the earth is approximately 2.98 gm/cm³ . 

3. The average density of the mantle of the earth is approximately 5.7gm/cm³ . 

4. The average density of the outer core of the earth is approximately 9.8 gm/cm³ . 

5. The density of the inner core at the centre of the earth is approximately 13 gm/cm³

The Mid- continental belt.

Correct option is (a) Primary waves

1. Continental crust and the Oceanic crust are the two parts of the crust. 

2. The crust is classified on the basis of whether it lies below the land or the ocean. 

3. The part of the crust lying below the continent is known as the continental crust. 

4. The part of the crust lying below the ocean is known as the oceanic crust.

The important leaders of the assertive nationalist phase were Bal Gangadhar Tilak, Bipin Chandra Pal, Lala Lajpat Rai and Aurobindo Ghosh.

Due to continually increasing pressure towards the center of the Earth and due to presence of heavy substances, the density of earth’s layers also increases.

The earthquake in ordinary language means: The vibration of the earth. Because of the sudden movement of the crustal plates, the sequence of shocks occurring at some point in crust or mantle is called earthquake. Earthquake is a natural phenomenon in which waves emerge due to the release of energy, which spreads in all directions causing destruction.

Origin of earthquake: On the surface, crust is often the source of energy on the edge of fault. The crustal (tectonic) plates move and collides with one another, sometime causing faults at impact sites. When the plates dis – enage, huge amounts of energy are released. The slabs on either side of the fault move in the opposite direction, where the top rocks hold the static with the pressure, and the friction between them keeps them interlocked. In spite of this, due to the tendency of separation, the impact of friction decreases.

As a result, the rock clusters suddenly collapse in opposite directions. As a result, energy waves emerge and become dynamic in all directions. These energy waves reach the surface in different directions, consequently the vibrations begin. Thus, earthquake originates.

Correct option is (d) Inner core

The Earthquake Shadow Zone is a region between 105° and 145° to earthquake’s seismic focus where no seismic wave is recorded.

1. The early nationalists spread political awareness among the people. 

2. The assertive nationalists believed that British rule in India was not a blessing but a curse. 

3. After the partition of Bengal, the assertive nationalists adopted the methods of boycott, swadeshi and national education to achieve the goal of swaraj. 

4. Separate electorates meant that the Muslim voters could elect Muslim representatives. 

5. Gandhi spent about 22 years in South Africa as a practising lawyer.

The sources from which direct information is received about the internal structure of the Earth are called the direct sources of interior of the Earth’s information. These sources include volcanic eruptions, landslides in the geologic areas and the rock formation on earth’s surface, etc.

Humans have no direct means to know the interior structure of the Earth. Human knowledge about the structure of this part is limited to very little depth. Direct knowledge of the structure of the earth can be found only by oil wells, mines to the depth of only 3 to 4 km in most places. It is very minuscule compared to the depth of the center of the Earth (about 6371 km).

By mining activity, we learn that as the depth of the Earth’s surface increases, the temperature and pressure also increase. According to an estimate, the temperature of the inner part of the Earth is approximately 2000°C. Due to such high temperature, it is completely impossible to obtain direct knowledge of the earth’s internal structure.

Therefore, direct study of the interior structure of the Earth is beyond the human capability. With this reason, for obtaining information about the interior part of the earth, man is dependent on indirect sources, like earthquakes, seismic waves, temperature, pressure, meteorites and gravity.

(i) Correct.

(ii) Incorrect. 

Correct statement: The core of the earth’s interior is made up of elements, viz. iron and nickel.

(iii) Correct.

(iv) Incorrect. 

Correct statement: Continental crust is made up of silica and aluminum.

The assertive nationalists had no faith in the constitutional methods followed by the early nationalists. They knew that the British would never concede to the demand for swaraj without a struggle. So they have to adopt a method of active opposition to government Swaraj would have to be achieved through a political, anti-government agitation and with the involvement and support of the masses. The Congress would have to be transformed from a platform for debates among the westernized, Indian intelligentsia into a regiment of freedom fighters-united, determined, confident and willing to make sacrifices.

1. The early nationalists believed in the sense of justice and fair play of the British. True. 

2. The early nationalists presented their grievances to the British in the form of protests and strikes. False. 

3. The political beliefs, aims and methods of the assertive nationalists were the same as those of the early nationalists. False.  

4. The assertive nationalists had no faith in the constitutional methods followed by the early nationalists. True. 

5. Tilak knew that the British would concede to the demand of swaraj easily without any struggle. False.

The temperature at the center of the Earth is more than 2,000°C.

These are associated with the activity of volcanoes and occur as a result of depth explosion of the gases and magma. Such volcanoes are confined to volcanic areas. The intensity of such earthquakes depends on the intensity of volcanic eruption. They are not very destructive e.g. Krakatau (1883) and Katmai (1912).

1. Volcanoes are also grouped according to their periodicity of eruptions such as active, dormant and extinct.

2. These names refer to the state of activity rather than the types of volcanoes

3. Active Valcanoes that erupt frequently are called active volcanoes. Most of the active volcanoes lie in the Pacific Ring of Fire belt which lies along the Pacific coast.

4. Mt. Stromboli in Mediterranean Sea, St.Helens in USA, Pinatubo in Philippines.

5. Dormant volcanoes have shown no sign of activity for many years but they may become active at any time. It is also called Sleeping Volcano

6. Vesuvius mountain of Italy, Mt Fujiyama in Japan, Mt. Krakatoa of Indonesia are famous examples of this types. 

7. Extinct The top of extinct volcanic mountains have been eroded. Mt Popa of Myanmar and Mt. Kilimanjaro and Mt. Kenya of Africa are examples of extinct volcanoes.

The three major layer of the interior of the Earth are the crust, the mantle and the core.

(b) Richter scale

Correct option is (a) Primary

Correct option is (a) Crust

Earthquake is a sudden natural phenomenon. This leads to a great loss of human lives and huge public money. 

Consequences of destructive earthquakes are as follows:

1. Vibration on the earth’s surface. 

2. surface distortion. 

3. landslide and pulsation. 

4. avalanches. 

5. surface displacement. 

6. soil melting. 

7. unilateral inclination of the surface. 

8. the huge loss of public money due to the collapse of buildings. 

9. fire. 

10. the destruction of buildings, roads and other construction works. 

11. heavy loss of property and goods. 

12. Tsunami waves in the coastal areas, (in case of under sea earthquakes) Loss of public money etc.

Correct option is (d) Continental crust

Temperature, pressure and density are the artificial sources of information in geology.

(a) The assertive nationalists had no faith in the British sense of justice and fair play. They believed that the British rule in India was not a blessing but a curse. They were convinced that the British had no honest intentions of introducing reforms for the welfare of the Indians. They realized that the British interests were different and clashed with the Indian interests. India could never grow and progress under British rule. 

(b) The goal of the assertive nationalists was not selfgovernment in ‘gradual’ stages but immediate freedom (Swaraj) from British rule. 

(c) The early nationalists had great faith in the sense of justice and fair play of the British. So they adopted peaceful and constitutional methods. They presented their grievances to the government and waited patiently for the government to pass laws to remove those grievances. They believed that the government would gradually give in to their demands. They promoted unity, spread political awareness among the people and built up a strong public opinion through meetings, lectures and the press. But the assertive nationalists on the other hand, had no faith in the constitutional methods followed by the early nationalists. Twenty years of prayers, petitions, appeals and resolutions and representations had failed to yield any concrete results.

1. The uppermost layer of the interior of the earth is called the crust. Continental crust and the oceanic crust are the two parts of the crust. 

2.The thickness of the continental crust is approximately 16 km to 45 km. On the other hand, the thickness of the oceanic crust is approximately 7 km to 10 km 

3. The density of the continental crust is approximately 2.65 to 2.90 gm/cm. On the other hand, the density of the oceanic crust is approximately 2.65 to 2.90 gm/cm³ .

4. Silica and aluminium are the main elements found in the continental crust. Therefore, it is also called Sial. On the other hand, Silica and Magnesium are the main elements found in the oceanic crust. Therefore, it is also called Sima.

1. The primary earthquake waves travel through the mantle as well as the core of the earth. 

2. While travelling through the core of the earth, the direction of the primary earthquake waves gets altered. 

3. While travelling through the core, the speed of the primary earthquake waves decreases. 

4. The secondary earthquake waves can travel only through the mantle of the earth. These waves get absorbed in the core of the earth.

Thus, these waves cannot travel through the core of the earth.

Correct option is (a) Iron

1. The rocks in the upper 100 to 200 km of the mantle melt due to the heat and the magma is created. 

2. Magma chambers are found in this layer of the earth. 

3. Due to the heat and pressure, the energy waves are created in mantle. These energy waves move in vertical direction and magma comes out on the surface of the earth by volcanic eruptions. Thus, mantle is the centre of earthquake and volcanic eruptions.

1. The chief cause of earthquake is the sudden slipping of the portion of the earth’s crust along fractures or faults.

2. Another cause of earthquake is volcanic activity.

Focus is the vibrations originate in an earthquake.

‘The substance found in liquid and molten form beneath the surface is called the magma.

1. The mantle is located below the crust of the earth. The mantle is divided into the upper mantle and the lower mantle. 

2. The thickness of the mantle is approximately 2870 km. The average density of mantle is approximately 4.5 gm/cm³ . 

3. The rocks in the upper 100 to 200 km of the mantle melt due to the heat and magma is created.

Magma chambers are found in this layer of the earth. Due to the heat and pressure, the energy waves are created in mantle. These energy waves move in vertical direction and magma comes out on the surface of the earth by volcanic eruptions. 

4. These endogenitic movements continuously occur in the upper layer of the mantle. Therefore, the upper layer of the mantle is known as the asthenosphere.

5. The average thickness of mantle is approximately 2870 km. Its average density is approximately 4.5 gm/cm³ . The temperature at the depth of 2400 to 2900 km is around 2200° to 2500° C. The density of the lower mantle is approximately 5.7 gm / cm³

The All India Congress Committe met at Bombay on August 8, 1942 and passed the Quit India Resolution. After the Cripps Mission failed, this great Mass struggle for Independence was launched by the Congress. It was the greatest mass challenge to the British authority. It shook the foundations of the British Rule. Gandhiji declared, “I therefore want freedom immediately, this very night before dawn if it can be had.” He also gave a mantra ‘Do or Die”. He said ‘We shall either free India or die in the attempt.’ The movement was the greatest mass challenge to the British authority. It shook the foundations of the British rule in India and showed the British that the masses had immense capacity to suffer and die for the cause of freedom. The government soon arrested all leaders and declared Congress illegal. The government resorted to stem measures to suppress the movement.

The core is divided into two parts: 

1. External core. 

2. Internal core.

1. The inner core is located below the upper core. 

2. It is located at the depth from 5150 km to 6371 km from the surface of the earth. 

3. The average temperature of the inner core of the earth is around 6000° C. The density of the inner core of the earth is approximately 13.3 gm/cm . 

4. The elements, viz. Iron (Ferrous) and Nickel (Ni) are mainly found in the inner core of the earth. Therefore, it is also called Nife. 

5. The temperature at the centre of the earth is almost equivalent to the surface temperature of the sun.

1. The secondary waves of earthquake can travel only through the solid state of the interior of the earth. 

2. The outer core of the centre of the earth is in liquid state. Therefore, the secondary waves of earthquake cannot travel through the core of the earth.