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NCERT Based MCQ with Explanation:
1. What is the approximate radius of the Earth?
(a) 5,000 km
(b) 6,378 km
(c) 7,000 km
(d) 8,500 km
Explanation: The document states that the Earth's radius is about 6,378 km, which is a key fact used to understand the scale of its interior.
2. Why is it impossible to reach the center of the Earth?
(a) Lack of technology
(b) Extreme heat and pressure
(c) No funding for projects
(d) Absence of oxygen
Explanation: The document explains that no one can reach the Earth's interior due to the extreme conditions, such as high temperature and pressure, which increase with depth.
3. Which layer of the Earth is directly influenced by volcanic eruptions?
(a) Core
(b) Mantle
(c) Crust
(d) Asthenosphere
Explanation: Volcanic eruptions occur on the Earth's surface, which is part of the crust, making it the layer directly affected.
4. What is the primary source of magma during volcanic eruptions?
(a) Crust
(b) Asthenosphere
(c) Outer core
(d) Inner core
Explanation: The document identifies the asthenosphere, the upper portion of the mantle, as the main source of magma that reaches the surface during eruptions.
5. Which of the following is a direct source of information about the Earth's interior?
(a) Seismic waves
(b) Volcanic eruptions
(c) Gravity anomalies
(d) Magnetic surveys
Explanation: Volcanic eruptions provide direct material (magma) from the Earth’s interior for analysis, unlike indirect methods like seismic waves or gravity studies.
6. How deep have gold mines in South Africa reached?
(a) 1-2 km
(b) 3-4 km
(c) 5-6 km
(d) 7-8 km
Explanation: The document mentions that gold mines in South Africa are as deep as 3-4 km, providing surface rocks for study.
7. What is the deepest drill mentioned in the document?
(a) 8 km
(b) 10 km
(c) 12 km
(d) 15 km
Explanation: The deepest drill at Kola, in the Arctic Ocean, has reached a depth of 12 km, as stated in the text.
8. Why is it difficult to determine the depth of magma from volcanic eruptions?
(a) Magma cools too quickly
(b) Lack of instruments
(c) Uncertainty about its source depth
(d) Magma is too dense
Explanation: The document notes that while volcanic eruptions provide magma, ascertaining its exact depth of origin is challenging.
9. Which property increases with depth inside the Earth?
(a) Temperature
(b) Oxygen levels
(c) Light intensity
(d) Water content
Explanation: The text states that temperature increases with increasing depth, a key indirect clue about the Earth's interior.
10. What do scientists use to estimate conditions at different depths of the Earth?
(a) Meteorite composition
(b) Rate of change of temperature and pressure
(c) Surface rock samples
(d) Ocean currents
Explanation: The document explains that scientists estimate interior conditions by analyzing the rate of change of temperature, pressure, and density with depth.
NCERT Science MCQ, Class-1011. Why are meteors considered an indirect source of information about the Earth’s interior?
(a) They are too small to analyze
(b) Their material is not from Earth’s interior
(c) They are only found in space
(d) They melt upon entry
Explanation: Meteors provide indirect information because their material is similar to Earth’s but not directly from its interior.
12. Where is the gravitational force greater on Earth’s surface?
(a) Equator
(b) Poles
(c) Mountains
(d) Oceans
Explanation: The document states that gravitational force is greater near the poles due to the shorter distance to the Earth’s center compared to the equator.
13. What is a gravity anomaly?
(a) A sudden drop in temperature
(b) Difference between expected and observed gravity values
(c) A volcanic eruption
(d) A seismic wave pattern
Explanation: Gravity anomalies are differences in gravity readings from expected values, indicating uneven mass distribution in the crust.
14. Which indirect source provides information about magnetic materials in the crust?
(a) Seismic activity
(b) Magnetic surveys
(c) Volcanic eruptions
(d) Gravity measurements
Explanation: Magnetic surveys reveal the distribution of magnetic materials in the Earth’s crustal portion, as noted in the text.
15. What natural event is caused by the release of energy along a fault?
(a) Volcanic eruption
(b) Earthquake
(c) Tsunami
(d) Avalanche
Explanation: The document defines an earthquake as the shaking of the Earth due to energy release along a fault.
16. What is the point where earthquake energy is released called?
(a) Epicenter
(b) Hypocenter
(c) Fault line
(d) Seismograph
Explanation: The hypocenter, or focus, is the point where the energy is released, as described in the text.
17. Which point on the surface is nearest to the earthquake focus?
(a) Fault
(b) Epicenter
(c) Shadow zone
(d) Seismograph
Explanation: The epicenter is the surface point directly above the focus, as explained in the document.
18. In which Earth layer do all natural earthquakes occur?
(a) Mantle
(b) Core
(c) Lithosphere
(d) Asthenosphere
Explanation: The text specifies that all natural earthquakes take place in the lithosphere, which extends up to 200 km deep.
19. What instrument records earthquake waves?
(a) Thermometer
(b) Seismograph
(c) Barometer
(d) Magnetometer
Explanation: A seismograph is the instrument that records earthquake waves reaching the surface, as mentioned in the document.
20. How many main types of earthquake waves are there?
(a) One
(b) Two
(c) Three
(d) Four
Explanation: The document identifies two main types of earthquake waves: body waves and surface waves.
21. Which type of earthquake wave travels through the body of the Earth?
(a) Surface waves
(b) Body waves
(c) P-waves only
(d) S-waves only
22. What generates surface waves during an earthquake?
(a) Body waves interacting with surface rocks
(b) Volcanic activity
(c) Gravity anomalies
(d) Fault movement
23. Which type of wave arrives first at the surface during an earthquake?
(a) S-waves
(b) P-waves
(c) Surface waves
(d) Gravity waves
24. Which earthquake wave is similar to sound waves?
(a) S-waves
(b) P-waves
(c) Surface waves
(d) Seismic waves
25. Which earthquake wave can only travel through solid materials?
(a) P-waves
(b) S-waves
(c) Surface waves
(d) Body waves
26. Why are S-waves important for understanding the Earth’s interior?
(a) They travel the fastest
(b) They only travel through solids
(c) They cause the most damage
(d) They are the most common
27. Which earthquake waves are the most destructive?
(a) P-waves
(b) S-waves
(c) Surface waves
(d) Body waves
28. How do P-waves affect the material they pass through?
(a) Create troughs and crests
(b) Stretch and squeeze the material
(c) Move perpendicular to the wave
(d) Cause explosions
29. What is the direction of vibration for S-waves?
(a) Parallel to the wave
(b) Perpendicular in the vertical plane
(c) Circular motion
(d) Random direction
30. What is a shadow zone in the context of earthquake waves?
(a) An area with no seismic activity
(b) A region where certain waves are not detected
(c) A zone of high destruction
(d) A volcanic region
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