(D) Inner core Explanation: The inner core is the innermost layer of the Earth, and it is primarily composed of solid iron and nickel. It is under immense pressure, which keeps it in a solid state despite the high temperatures.

(A) Crust and upper mantle Explanation: The lithosphere is the rigid outer layer of the Earth and is composed of two layers: the crust and the uppermost part of the mantle. These layers together form the solid, brittle outer shell of the Earth.

(C) Outer core Explanation: The Earth's magnetic field is generated by the movement of molten iron and nickel in the outer core. This movement, driven by convection currents, creates electric currents that produce the magnetic field.

(B) Mantle Explanation: The asthenosphere is a partially molten and ductile region located in the upper mantle. It is a relatively soft and weak layer that allows the lithospheric plates to move and slide over it.

(A) P-waves Explanation: P-waves (primary waves) are the fastest seismic waves and can travel through both solids and liquids. They cause particles to move in the same direction as the wave propagation, leading to compressions and rarefactions.

(A) Crust and upper mantle Explanation: The Moho discontinuity, also known as the Mohorovičić discontinuity, is the boundary between the Earth's crust and the underlying uppermost part of the mantle. It represents a significant change in composition and density.

(B) Increase in pressure Explanation: The primary reason for the increase in density with depth in the Earth is the increase in pressure. As you go deeper into the Earth, the weight of the overlying layers causes an increase in pressure, leading to denser materials.

(B) Mantle Explanation: The mantle is the thickest layer of the Earth, extending from the base of the crust to the outer core. It accounts for about 84% of the Earth's volume and is primarily composed of solid rock materials.

(C) Upper mantle and lower mantle Explanation: The transition zone is a region located between the upper mantle and the lower mantle. It is characterized by changes in mineralogy and physical properties due to increasing pressure and temperature with depth.

(D) All of the above Explanation: The Earth's outermost layer, known as the crust, can be composed of different materials depending on the location. It can consist of solid rock, molten lava (in volcanic regions), as well as loose soil and sediments (in areas such as beaches or riverbeds).

(B) Mantle Explanation: The mantle is the layer of the Earth located between the crust and the core. It is composed of solid rock material that undergoes convection currents due to the heat generated by radioactive decay. These convection currents drive the movement of tectonic plates on the Earth's surface.

(C) Surface waves Explanation: Surface waves are seismic waves that travel along the Earth's surface. They cause the most destruction during an earthquake as they produce rolling and shaking motions, which can damage buildings and infrastructure.

(B) Outer core and inner core Explanation: The Gutenberg discontinuity is the boundary between the outer core and the inner core of the Earth. It is characterized by a significant increase in seismic wave velocities, indicating a change in composition and physical properties.

(B) Mantle Explanation: The mantle is primarily composed of silicate minerals rich in iron and magnesium, such as olivine and pyroxene. These minerals contribute to the mantle's density and solid-state behaviour.

(C) Croatia Explanation: The Mohorovičić discontinuity, also known as the Moho, is named after Andrija Mohorovičić, a Croatian seismologist who first identified and studied this boundary between the crust and the mantle.

Internal Structure of The Earth – Important MCQ

16. Which layer of the Earth is responsible for generating volcanic activity?

(A) Crust
(B) Mantle
(C) Outer core
(D) Inner core

(A) Crust
Explanation: Volcanic activity is primarily associated with the Earth’s crust. Magma, formed by the partial melting of rocks in the mantle, rises to the surface through volcanic vents and erupts as lava during volcanic activity.

17. Which seismic waves cannot travel through liquids?

(A) P-waves
(B) S-waves
(C) Surface waves
(D) Love waves

(B) S-waves
Explanation: S-waves (secondary waves) are shear waves that cannot travel through liquids. They move material perpendicular to the direction of wave propagation and require solid material for transmission.

18. What is the main source of heat in the Earth’s interior?

(A) Solar radiation
(B) Geothermal energy
(C) Nuclear reactions
(D) Frictional heating

(C) Nuclear reactions
Explanation: The main source of heat in the Earth’s interior is the energy generated by nuclear reactions, specifically the decay of radioactive isotopes. This heat contributes to the processes like convection and drives plate tectonics.

19. Which layer of the Earth experiences the highest pressure?

(A) Crust
(B) Mantle
(C) Outer core
(D) Inner core

(D) Inner core
Explanation: The inner core experiences the highest pressure of all the layers of the Earth. The tremendous pressure from the weight of the overlying layers keeps the iron-nickel alloy in the inner core solid despite its high temperature.

20. The lithosphere is divided into several large plates. Approximately how many major tectonic plates are there?

(A) 4
(B) 7
(C) 10
(D) 15

(B) 7
Explanation: The lithosphere is divided into approximately 7 major tectonic plates, including the Eurasian Plate, African Plate, Pacific Plate, North American Plate, South American Plate, Australian Plate, and Antarctic Plate. These plates interact with each other at their boundaries and contribute to the Earth’s geologic activity.

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Internal Structure of The Earth – Important MCQ

16. Which layer of the Earth is responsible for generating volcanic activity?

17. Which seismic waves cannot travel through liquids?

18. What is the main source of heat in the Earth’s interior?

19. Which layer of the Earth experiences the highest pressure?

20. The lithosphere is divided into several large plates. Approximately how many major tectonic plates are there?

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