Questions Answers For All Chapters – Geography Class 8
Solutions
Interior of the Earth
Q 1. Tick 9 the correct options in the box
(A) There are two layers in the crust.
(i) Inner and outer crust
(ii) Continental and oceanic crust
(iii) Surface and oceanic crust
(iv) Mantle and Core
Answer: (ii) Continental and oceanic crust
(B) Which element is found in both mantle and crust ?
(i) Silica
(ii) Magnesium
(iii) Aluminium
(iv) Iron
Answer: (i) Silica
(C) Which of these minerals are found in the core of the earth?
(i) Iron-magnesium
(ii) Magnesium-nickel
(iii) Aluminium- Iron
(iv) Iron-nickel
Answer:(iv) Iron-nickel
(D) The inner core is in which state?
(i) Gaseous
(ii) Solid state
(iii) Semi-solid state
Answer: (ii) Solid state
(E) The outer core is made up of
(i) Iron
(ii) Gold
(iii) Hydrogen
(iv) Oxygen
Answer: (i) Iron
(F) The layer of the earth on which we live.
(i) Mantle
(ii) Core
(iii) Crust
(iv) Continental crust
Answer: (iii) Crust
(G) Which seismic waves can travel through liquid medium?
(i) Primary waves
(ii) Secondary Waves
(iii) Surface waves
(iv) Oceanic waves
Answer: (i) Primary waves
Q 2. Tell whether right or wrong. Correct the wrong statement
(A) The density of various materials is not the same in the interior of the earth
Answer: Right
(B) The core of the earth’s interior is made up of hard rock
Answer: Wrong. The core is composed mainly of iron and nickel, with the outer core being liquid and the inner core being solid.
(C) Secondary waves cannot pass through outer core.
Answer: Right
(D) Continental crust is made up of silica and magnesium
Answer: Wrong. The continental crust is made up of silica and aluminum (Sial), while the oceanic crust is made up of silica and magnesium (Sima).
Q3. Answer the following
(A) What are the two parts of the crust? What is the basis of classification?
Answer:
The two parts of the crust are:
- Continental Crust – Composed mainly of silica and aluminum (Sial).
- Oceanic Crust – Composed mainly of silica and magnesium (Sima).
The classification is based on the composition of elements and density.
(B) Why is the upper mantle called the asthenosphere?
Answer:
The upper mantle is called the asthenosphere because it is in a semi-liquid state and contains magma chambers. This layer is responsible for tectonic movements, volcanic eruptions, and earthquakes.
(C) Magnetosphere of the earth is a result of rotation. Explain.
Answer:
The magnetosphere is formed due to the movement of liquid iron in the outer core. The Earth’s rotation creates circular currents (eddy currents) in the molten iron, which generate electric currents. These currents create a magnetic field around the Earth, protecting it from solar winds.
Q4. Draw neat diagrams, label them and explain.
(A) The interior of the earth
consists of three main layers: Crust, Mantle, and Core. The core is divided into the outer core (liquid) and inner core (solid).
(B) Magnetic pole and equator
show the Earth’s magnetic field, generated by the outer core. The magnetic poles are different from the geographic poles.
(Diagrams should include labeled layers of Earth and magnetic field lines.)
Q5. Give geographical reasons:
(A) There is variety in the interior of the earth.
- The temperature, pressure, and composition change at different depths.
- The Earth has different layers: the crust (solid), mantle (semi-solid), and core (solid and liquid).
(B) There is correlation between the density of metals and their location in the interior of the earth.
- Lighter elements (silica, aluminum) are found in the crust.
- Denser elements (iron, nickel) are found in the core.
- Density increases as we go deeper into the Earth.
(C) Mantle is the center of earthquakes and volcanic eruptions.
- The upper mantle (asthenosphere) contains magma that causes volcanic eruptions.
- Earthquakes originate from this layer due to tectonic activity.
(D) The thickness of the crust below the continents is less as compared to oceans.
- The continental crust is thicker (30-40 km), while the oceanic crust is thinner (7-10 km).
- The denser oceanic crust subducts under the lighter continental crust in tectonic processes.
(E) Earth is protected because of the magnetosphere.
- The magnetosphere deflects solar winds and harmful radiation from the Sun.
- It prevents the Earth’s atmosphere from being stripped away.
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