Q1. Consider the following statements:
- Shallow earthquakes are generally less devastating compared to deeper earthquakes, because Shallow earthquakes carry less energy when they emerge on the surface.
- The seismic waves of deeper earthquakes move radially upwards to the surface.
- The earthquake magnitude scale gives a measure of the energy released by the seismic waves.
How many of the statements given above is/are correct?
(a) Only one
(b) Only two
(c) All three
(d) None
Ans: (b)
Explanation:
- Shallow earthquakes are generally more devastating because they carry greater energy when they emerge on the surface. Deeper earthquakes lose much of their energy by the time they come to the surface. The deeper quakes spread farther — the seismic waves move radially upwards to the surface — even as they lose energy while travelling greater distances, and hence cause less damage.
- The earthquake magnitude scale gives a measure of the energy released, although the reading in itself is not of energy. Rather, it takes into account amplitude or ‘size’ of the seismic waves released, and variations in distance between various seismographs and the earthquake epicenter. Thus, it is a dimensionless number — with no physical units.
Q2. Which of the following statements is NOT correct about the Earthquake?
(a) The seismograph provides information regarding time, location and magnitude of the earthquake.
(b) The seismographs located beyond 145’ from the epicenter record the arrival of P-waves only.
(c) At a seismic station the first waves to arrive are surface waves.
(d) The intensity of an earthquake is measured by the Mercalli scale.
Ans:(c)
Explanation:
- Seismic waves are the vibrations from earthquakes that travel through the Earth; they are recorded on instruments called seismographs. Seismographs record a zig-zag trace that shows the varying amplitude of ground oscillations beneath the instrument. Sensitive seismographs, which greatly magnify these ground motions, can detect strong earthquakes from sources anywhere in the world. The time, location, and magnitude of an earthquake can be determined from the data recorded by seismograph stations.
- S waves shadow zone extend from 105⁰. P wave shadow zone extends between 105⁰ to 145⁰. Beyond 145⁰ only P waves are received
- At seismic station first waves to arrive are P waves. Then S waves and in the last the surface waves.
Q3. Consider the following statements about earthquakes:
- All natural earthquakes take place in the lithosphere.
- The denser the material, the lower is the velocity of the earthquake waves.
- The surface waves are more destructive.
How many of the statements given above is/are correct?
(a) Only one
(b) Only two
(c) All three
(d) None
Ans: (b)
Explanation:
- All natural earthquakes take place in the lithosphere.
- Earthquake waves are basically of two types — body waves and surface waves. Body waves are generated due to the release of energy at the focus and move in all directions travelling through the body of the earth. The body waves interact with the surface rocks and generate new set of waves called surface waves. These waves move along the surface. The velocity of waves changes as
- they travel through materials with different densities. The denser the material, the higher is the velocity.
- The surface waves are the last to report on seismograph. These waves are more destructive. They cause displacement of rocks, and hence, the collapse of structures occurs.
Q4. The Mid-Atlantic Ridge is a divergent plate boundary. Which of the following statements is TRUE about the Mid-Atlantic Ridge?
(a) It is a long, underwater mountain range that runs down the middle of the Atlantic Ocean.
(b) It is the site of new oceanic crust formation.
(c) The rocks on the ridge are getting older as they move away from the ridge.
(d) All of the above.
Ans: (d)
Explanation:
- The correct answer is (D) All of the above. The Mid-Atlantic Ridge is a long, underwater mountain range that runs down the middle of the Atlantic Ocean. It is the site of new oceanic crust formation, as magma rises from the mantle and cools to form new rock. The rocks on the ridge are getting older as they move away from the ridge, because they are being carried away from the source of new crust formation.
Q5. Consider the following statements about Central Bureau of Investigation:
- It operates under the jurisdiction of the Ministry of Home Affairs.
- It is exempted from the provisions of the Right to Information Act.
- It is India’s officially designated single point of contact for liaison with the Interpol.
How many of the statements given above is/are correct?
(a) Only one
(b) Only two
(c) All three
(d) None
Ans: (b)
Explanation:
- The Central Bureau of Investigation (CBI) is the premier investigating agency of India.
- It operates under the jurisdiction of the Ministry of Personnel, Public Grievances and Pensions.
- CBI is exempted from the provisions of the Right to Information Act.
- CBI is India’s officially designated single point of contact for liaison with the Interpol.
