Earthquakes & Volcanoes – NDA Geography PYQs

NDA 2024-II

Q. 1. Which of the following are extrusive volcanic features?

1. Lava plains

2. Volcanic mountains

3. Laccolith

Select the answer using the code given below:

(a) 1, 2 and 3

(b) 1 and 2 only

(c) 2 and 3 only

(d) 1 and 3 only

Answer: (b) 1 and 2 only

Explanation: Extrusive volcanic features are formed at or on the Earth’s surface when magma/lava erupts. Lava plains (1): formed by the extensive flow of fluid basaltic lava over large areas. Extrusive . Volcanic mountains (2): formed by accumulation of lava and pyroclastic material on the surface. Extrusive . Laccolith (3): formed when magma intrudes UNDERGROUND between rock layers, creating a dome-shaped body without reaching the surface. Intrusive: NOT extrusive. Concept Tested: Extrusive features: Lava plains and Volcanic mountains (formed at surface); Laccolith is intrusive (underground)

Q. 2. Consider the following statements about Primary (P) waves of earthquakes:

1. They are compressional waves.

2. They cannot travel through liquids.

3. They are the fastest seismic waves.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

Answer: (c) 1 and 3 only

Explanation: Statement 1 (P-waves are compressional): Correct. P-waves are longitudinal/compressional waves that move particles back and forth in the direction of wave propagation, like sound waves. Statement 2 (P-waves cannot travel through liquids): Incorrect. P-waves CAN travel through liquids (and gases). This is why P-waves pass through Earth’s liquid outer core and are detected on the far side of Earth. It is S-waves that cannot travel through liquids. Statement 3 (P-waves are the fastest seismic waves): Correct. P-waves travel at approximately 6–13 km/s (depending on the medium): faster than S-waves (~3.5–7 km/s) and surface waves. Concept Tested: P-waves: compressional (correct) and fastest (correct); they CAN travel through liquids (Statement 2 is wrong)

NDA 2024-I

Q. 3. Consider the following:

1. Compressional stress

2. Tension stress

3. Shear stress

Which of the above can produce earthquakes?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 only

(d) 1, 2 and 3

Answer: (d) 1, 2 and 3

Explanation: All three types of stress can produce earthquakes: Compressional stress (1): when rocks are squeezed together (converging plates). This creates thrust/reverse faults and fold-and-thrust belts: associated with earthquakes. Tension stress (2): when rocks are pulled apart (diverging plates). This creates normal faults along rift zones: associated with earthquakes. Shear stress (3): when rocks slide past each other horizontally (transform boundaries). This creates strike-slip faults (e.g., San Andreas Fault): associated with earthquakes. Concept Tested: All three stress types (compressional, tension, shear) can produce earthquakes at different plate boundary types

Q. 4. Which one of the following is the most destructive tsunami?

(a) Tsunamis with very short wavelengths

(b) Tsunamis with very high frequency

(c) Tsunamis with very long wavelengths

(d) Tsunamis with very high amplitude in the open ocean

Answer: (c) Tsunamis with very long wavelengths

Explanation: Tsunamis with very long wavelengths are the most destructive. In the open ocean, tsunamis have extremely long wavelengths (hundreds of kilometres) and travel fast but with low amplitude (barely noticeable). As they approach the coast (where the ocean becomes shallower), the wavelength compresses, the wave slows, and the amplitude increases dramatically: producing the destructive wall of water. The energy of a tsunami is proportional to its wavelength and period: longer wavelength tsunamis carry more energy and cause more flooding when they reach the shore. Concept Tested: Most destructive tsunamis: those with long wavelengths; energy increases as they hit shallow coastal water

NDA 2023-I

Q. 5. Match List I (Intrusive Volcanic Feature) with List II (Description) and select the correct answer:

List I (Intrusive Feature)	List II (Description)
A. Batholith	1. A large dome-shaped intrusion with a level base
B. Laccolith	2. A lens-shaped body occupying the core of a syncline or anticline
C. Lopolith	3. Saucer-shaped, concave at the top
D. Phacolith	4. Large igneous body reaching the base of the crust

Codes:

(a) A-1, B-2, C-3, D-4

(b) A-4, B-2, C-3, D-1

(c) A-4, B-1, C-3, D-2

(d) A-2, B-1, C-3, D-4

Answer: (c) A-4, B-1, C-3, D-2

Explanation: Batholith (A) → Large igneous body reaching the base of the crust (4). Batholiths are the largest intrusive bodies, extending deep into the crust and covering vast areas. Example: the Sierra Nevada batholith. Laccolith (B) → Large dome-shaped intrusion with a level base (1). Magma pushes up the overlying strata forming a dome shape but has a flat base. Lopolith (C) → Saucer-shaped, concave at the top (3). The opposite of a laccolith: the intruded magma causes the overlying and underlying strata to sag downward. Phacolith (D) → Lens-shaped body occupying the core of a syncline or anticline (2). Magma intrudes into the fold structures. Concept Tested: Intrusive volcanic features: Batholith (largest), Laccolith (dome), Lopolith (saucer), Phacolith (lens at fold core)

★ JOVIK Exam Insight Intrusive volcanic features for NDA: Batholith: largest; reaches base of crust; irregular; exposed by erosion. Laccolith: dome-shaped; flat base; pushes up overlying rocks. Lopolith: saucer-shaped; concave; sags underlying strata. Phacolith: lens-shaped; found in anticline/syncline cores. Sill: horizontal tabular intrusion parallel to rock layers. Dyke: vertical or near-vertical tabular intrusion cutting across rock layers. Boss: small, roughly circular intrusion.

NDA 2022-I

Q. 6. Consider the following statements about P-waves and S-waves:

1. P-waves move faster than S-waves.

2. P-waves can pass through all three states of matter.

3. S-waves can pass through all three states of matter.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3 only

(c) 1 and 2 only

(d) 1, 2 and 3

Answer: (c) 1 and 2 only

Explanation: Statement 1: Correct. P-waves (Primary waves) arrive first at recording stations because they travel faster than S-waves. Statement 2: Correct. P-waves are compressional waves that can travel through solid, liquid, AND gas (all three states of matter). They pass through Earth’s liquid outer core. Statement 3: Incorrect. S-waves are shear waves that can ONLY travel through solid material. They CANNOT pass through liquids or gases. This is why S-waves are blocked by Earth’s liquid outer core. Concept Tested: P-waves travel through all states of matter; S-waves travel ONLY through solids: both key seismology facts

NDA 2021-II

Q. 7. The Richter scale is a/an:

(a) arithmetic scale

(b) exponential scale

(c) linear scale

(d) logarithmic scale

Answer: (d) logarithmic scale

Explanation: The Richter scale (developed by Charles F. Richter in 1935) is a logarithmic scale used to measure the magnitude of earthquakes. Each whole number increase represents a 10-fold increase in the amplitude of seismic waves: and approximately 31.6 times more energy released. So a magnitude 7.0 earthquake is 10 times more powerful in terms of ground motion amplitude than a magnitude 6.0, and about 1,000 times more powerful than a magnitude 5.0. Concept Tested: Richter scale: logarithmic (base 10); each unit = 10× ground motion amplitude; ~31.6× more energy

NDA 2019-II

Q. 8. Consider the following statements:

1. The Epicentre is the point from which earthquake waves originate.

2. S-waves cannot pass through the liquid outer core of the Earth.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (b) 2 only

Explanation: Statement 1: Incorrect. The Epicentre is the point on Earth’s surface directly above where the earthquake originates. The point where the earthquake actually originates (underground) is called the Focus (Hypocentre). Statement 2: Correct. S-waves (shear waves) can only travel through solid material. Since Earth’s outer core is liquid, S-waves cannot pass through it. This creates a “shadow zone” where no S-waves are detected on the opposite side of the Earth: key evidence that the outer core is liquid. Concept Tested: Epicentre = surface point above focus (not origin); S-waves cannot pass through liquid outer core

NDA 2019-I

Q. 9. Which one of the following is an intrusive volcanic feature?

(a) Geyser

(b) Hot Spring

(c) Laccolith

(d) Lava plain

Answer: (c) Laccolith

Explanation: Intrusive volcanic features (also called plutonic features) are formed when magma solidifies underground without reaching the surface. Laccolith: magma intruded between rock layers, forming a dome-shaped mass that pushes overlying strata upward. It is a classic intrusive feature. Geyser: water heated by underground magma erupts periodically at the surface: this is an extrusive/volcanic surface feature (hydrothermal). Hot Spring: also a surface hydrothermal feature. Lava plain: formed by lava flowing over the surface: extrusive. Concept Tested: Laccolith: intrusive volcanic feature (magma solidified underground); Geysers and hot springs are surface/extrusive features

NDA 2017-I

Q. 10. The focus of an earthquake is also known as:

(a) Epicentre

(b) Hypocentre

(c) Isobath

(d) Isohypse

Answer: (b) Hypocentre

Explanation: The Focus (Hypocentre) is the point inside the Earth where the earthquake actually begins: the origin point of seismic energy release. It can be shallow (0–70 km), intermediate (70–300 km), or deep (300–700 km). The Epicentre is the point on the Earth’s surface directly above the focus. The epicentre experiences the most intense shaking. Isobath: contour lines of equal depth in the ocean. Isohypse: contour lines of equal elevation on land. Concept Tested: Focus = Hypocentre: origin point of earthquake inside the Earth; Epicentre is on the surface above it

NDA 2014-I

Q. 11. Which type of volcano has gentle slopes and erupts with great fluidity?

(a) Shield volcano

(b) Composite volcano

(c) Cinder cone volcano

(d) Super volcano

Answer: (a) Shield volcano

Explanation: Shield volcanoes have broad, gently sloping flanks (like a warrior’s shield laid flat). They erupt with highly fluid, low-viscosity basaltic lava that flows easily over long distances. The gentle slope results from the lava’s low viscosity: it spreads out before solidifying. Examples: Mauna Loa and Mauna Kea in Hawaii. Composite/Strato volcanoes have steep sides and erupt more viscous (silica-rich) lava explosively. Cinder cones are steep-sided, small, and built from pyroclastic debris. Concept Tested: Shield volcano: gentle slopes, highly fluid basaltic lava, low viscosity eruptions (e.g., Hawaiian volcanoes)

★ JOVIK Exam Insight Volcano types for NDA: Shield volcano: broad, gentle slopes; basaltic (low viscosity) lava; non-explosive (e.g., Mauna Loa, Hawaii). Composite/Strato volcano: steep, cone-shaped; alternating lava and ash layers; explosive (e.g., Vesuvius, Fuji). Cinder cone: steep, small; pyroclastic debris only; short eruptions. Caldera: collapsed volcanic crater; can form super-volcanoes (e.g., Yellowstone).

NDA 2013-II

Q. 12. Consider the following:

1. Seismographs can record both vertical and horizontal movements of the ground.

2. Seismographs can record P-waves and S-waves separately.

3. Seismographs can provide date and time of occurrence of an earthquake.

Which of the above is/are correct?

(a) 1 only

(b) 2 only

(c) 1 and 2 only

(d) 1, 2 and 3

Answer: (d) 1, 2 and 3

Explanation: All three statements are correct: Statement 1: Correct. Modern seismographs record both vertical (up-down) and horizontal (side-to-side) ground movements using separate sensors. Statement 2: Correct. Since P-waves travel faster than S-waves, they arrive at the seismograph first and are recorded separately. The time difference between P and S wave arrivals helps determine the distance to the earthquake epicentre. Statement 3: Correct. Seismographs have precise timing mechanisms and record the exact date and time of each wave arrival. Concept Tested: Seismograph capabilities: records vertical and horizontal movement, P and S waves, and date/time of earthquake

NDA 2012-I

Q. 13. Consider the following statements:

1. P-waves are longitudinal waves.

2. S-waves are transverse waves.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. P-waves (Primary waves) are longitudinal/compressional waves. They cause particles in the rock to vibrate in the same direction as the wave is travelling (back-and-forth, like sound waves). Statement 2: Correct. S-waves (Secondary waves) are transverse waves. They cause particles to vibrate perpendicular to the direction of wave travel (side-to-side, like waves on a string). This is why S-waves cannot travel through fluids: fluids cannot sustain shear stress. Concept Tested: P-waves are longitudinal (compressional); S-waves are transverse (shear): both statements correct

NDA 2011-I

Q. 14. Consider the following:

1. Earthquakes

2. Blasting in mines

3. Explosion of chemical and nuclear devices

Seismograph is used to detect vibrations of which of the above?

(a) 1 only

(b) 1 and 2 only

(c) 2 and 3 only

(d) 1, 2 and 3

Answer: (d) 1, 2 and 3

Explanation: A seismograph records ground vibrations (seismic waves) from any source: not just natural earthquakes. Earthquakes (1): the primary natural source of seismic waves detected by seismographs. Blasting in mines (2): also generates seismic waves that seismographs can detect and record. Explosion of chemical and nuclear devices (3): these produce seismic waves that travel through Earth’s crust, and seismographs are used by international monitoring organisations (like the CTBTO) to detect nuclear tests. All three generate detectable ground vibrations. Concept Tested: Seismograph detects vibrations from earthquakes, mine blasting, AND chemical/nuclear explosions

NDA 2010-II

Q. 15. Consider the following statements about tsunamis:

1. A tsunami is a seismic sea wave.

2. They are caused by earthquakes which occur on the ocean floor.

3. Tsunamis travel at 300 miles per hour in the open ocean.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1, 2 and 3

(d) 1 and 3 only

Answer: (c) 1, 2 and 3

Explanation: Statement 1: Correct. A tsunami is a seismic sea wave: ocean waves generated by seismic events. Statement 2: Correct. Tsunamis are typically caused by underwater (submarine) earthquakes on the ocean floor. They can also be caused by underwater landslides and volcanic eruptions. Statement 3: Approximately correct. Tsunamis travel at speeds of approximately 500–800 km/h (about 300–500 mph) in the open ocean. 300 mph (approximately 480 km/h) is within the lower range of this estimate and is accepted as correct in this NDA context. Concept Tested: Tsunamis: seismic sea waves caused by underwater earthquakes; travel at ~300 mph in open ocean

NDA 2010-I

Q. 16. Isoseismal lines on a map refer to the lines:

(a) Along which the intensity of earthquakes is the same

(b) Along which the frequency of earthquakes is the same

(c) Joining points of the same earthquake magnitude

(d) Connecting the focus and epicentre of an earthquake

Answer: (a) Along which the intensity of earthquakes is the same

Explanation: Isoseismal lines are contour lines drawn on a map connecting points that experienced the same INTENSITY of earthquake shaking. They look like concentric circles around the epicentre, with the highest intensity (innermost circle) at or near the epicentre. Isoseismal lines are used in seismology to map the distribution of earthquake effects across a region. Note: Intensity measures the effect felt at a given location (using the Modified Mercalli Intensity scale); Magnitude measures the energy released at the source (using the Richter or moment magnitude scale). Concept Tested: Isoseismal lines: connect points of equal earthquake intensity (not magnitude or frequency)

NDA 2009-I

Q. 17. Consider the following statements:

1. Secondary (S) waves can only travel through solids.

2. Primary (P) waves travel faster than secondary (S) waves.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. Secondary (S) waves, also called shear waves, can only travel through solid material. They cannot travel through liquids or gases. This is why S-waves cannot pass through Earth’s liquid outer core: a key piece of evidence for the core’s composition. Statement 2: Correct. Primary (P) waves are compressional waves that travel faster than S-waves. P-waves arrive first at seismograph stations (hence “Primary”), followed by the slower S-waves (“Secondary”). Concept Tested: Seismic waves: S-waves travel only through solids; P-waves travel faster than S-waves

★ JOVIK Exam Insight Seismic wave comparison for NDA: P-waves (Primary): Fastest; compressional (push-pull); travel through solids, liquids, and gases. S-waves (Secondary): Slower; shear (side-to-side); travel ONLY through solids (not liquids). L-waves (Love/Rayleigh surface waves): Slowest; travel along Earth’s surface; cause most damage. Key: S-waves cannot pass through Earth’s liquid outer core: this is how scientists know the outer core is liquid.

NDA 2008-I

Q. 18. Which one among the following is the correct definition of an earthquake?

(a) A place inside the Earth where the earthquake starts is called the earthquake

(b) Vibrations produced in the Earth’s crust due to sudden release of energy is called earthquake

(c) Vibrations produced on the Earth’s surface due to the movement of lithospheric plates is called earthquake

(d) A point on the surface of the Earth where Earthquake waves are produced is called earthquake

Answer: (b) Vibrations produced in the Earth’s crust due to sudden release of energy is called earthquake

Explanation: An earthquake is defined as the vibrations in Earth’s crust produced by the sudden release of energy: usually caused by the movement, fracturing, or slipping of rocks along fault planes. Option (a) describes the Focus (Hypocentre): the point inside the Earth where the earthquake originates. Option (c) is partially correct but too narrow: earthquakes can also be caused by volcanic activity, underground explosions, and collapsing mines, not just plate movement. Option (d) describes the Epicentre: the point on the Earth’s surface directly above the focus. Concept Tested: Earthquake definition: sudden release of energy causing vibrations in Earth’s crust

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