Class 8: Geography 3. Interior of the Earth/Maharashtra state board/Questions and Answers

Class 8: Geography 3. Interior of the Earth/Maharashtra state board/Questions and Answers 

1. Tick [✓] the correct options in the box:

A. There are two layers in the crust.

(a) Inner and outer crust [ ] 

(b) Continental and oceanic crust [ ]

(c) Surface and oceanic crust [ ]

(d) Mantle and core [ ]

Answer:(b) Continental and oceanic crust [✓]

B. Which element is found in both mantle and crust?

(a) Silica [ ]

(b) Magnesium [ ]

(c) Aluminium [ ]

(d) Iron [ ]

Answer:

(b) Magnesium [✓]

C. Which of these minerals are found in the core of the earth?

(a) Iron – magnesium [ ]

(b) Magnesium – nickel [ ]

(c) Aluminium – iron [ ]

(d) Iron – nickel [ ]

Answer:

(d) Iron – nickel [✓]

D. The inner core is in which state?

(a) Gaseous [ ]

(b) Solid [ ]

(c) Liquid [ ]

(d) Semi-solid [ ]

Answer: (a) Gaseous [✓]

E. The outer core is made up of

(a) Iron [ ]

(b) Gold [ ]

(c) Hydrogen [ ]

(d) Oxygen [ ]

Answer: (a) Iron [✓]

F. The layer of the earth on which we live...

(a) Mantle [ ]

(b) Core [ ]

(c) Crust [ ]

(d) Continental crust [ ]

Answer: (d) Continental crust [✓]

Q 2. Tell whether right or wrong. Correct the wrong statement

1. The density of various materials is not the same in the interior of the earth.

Ans. Correct.

2. The core of the earth's interior is made up of hard rocks.

Ans. Incorrect.

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

3. Secondary waves cannot pass through outer core.

Ans. Correct.

4. Continental crust is made up of silica and magnesium.

Ans. Incorrect.

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

Q 3. Answer the following.

1. What are the two parts of the crust? What is the basis of classification?

Ans. (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.

2. Why is the upper mantle called the asthenosphere?

Ans. (1) The upper layer of the mantle is in liquid state.

(2) 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.

(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.

(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.

Q 4. Draw neat diagrams, label them and explain.

 (A) The interior of the earth 

Answer :

 (B) Magnetic pole and equator 

Q 5. Give geographical reasons: 

(A) There is variety in the interior of the earth. OR

There are discontinuities in the interior of the earth.

Ans.

1.There is a difference between the elements, temperatures and the pressure found in the three parts of the interior of the earth, viz. crust, mantle and core.

2.In the interiors of the earth, the transitional areas are found between(a) continental crust and oceanic crust (b) crust and mantle (c) upper mantle and lower mantle (d) mantle and core and € outer core and inner core. Therefore, there are discontinuities in the interior of the earth.

B. There is correlation between the density of metals and their location in the interior of the earth.

Ans.

1.The rocks found in the crust have predominance of the compounds of silicon, aluminium, magnesium, etc. These compounds are lighter in weight. Therefore, they are found in the upper layer of the interior of the earth.

2.The elements like iron, nickel are found in the core of the earth. These elements are heavier in weight. Thus, metals with low density are found in upper level in the interior of the earth and the metals with high density are found in the lower level in the interior of the earth. Thus, there is correlation between the density of metals and their location in the interior of the earth.

C.Mantle is the centre of earthquake and volcanic eruptions.

Ans.

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.

D.The thickness of the crust below the continents is more as compared to oceans.

Ans. (1) The density of the crust below the continents is 2.65 to 2.90 gm / cm³. The density of the crust below the oceans is 2.90 to 3.3 gm / cm³.

(2) As the density of the crust below the continents is comparatively low, it keeps floating on the mantle. It does not subduct into mantle. As its effect, the thickness of the crust below the continents is found to be high.

(3) As the density of the crust below the ocean is comparatively high, it subducts into mantle leading to its low thickness.

Thus, the thickness of the crust below the continents is more as compared to oceans.

E. Earth is protected because of the magnetosphere.

Ans. (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.