With reference to 'Isostasy', which of the following is correct?
- It is the process by which the Earth's magnetic field reverses.
- It refers to the state of gravitational equilibrium between the Earth's crust and mantle.
- It is the theory that the Earth's core is cooling over time.
- It is the chemical weathering of silicate minerals in the mantle.
Explanation: Isostasy explains why mountains have deep 'roots' and why the crust sinks or rises when mass (like ice or sediment) is added or removed, acting like a ship in water.
Consider the following statements regarding the shadow zones of earthquake waves:
1. The shadow zone of S-waves is much larger than that of P-waves.
2. A seismograph located at any distance within 105 degrees from the epicenter records both P and S-waves.
3. The P-wave shadow zone is a continuous zone covering the entire Earth beyond 105 degrees from the epicenter.
Which of the statements given above are correct?
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
- 2 and 3 only
Explanation: Statement 3 is incorrect. The P-wave shadow zone is not continuous; it appears only as a **band between 105° and 145°**. Beyond 145°, P-waves are recorded again. S-waves, however, have a massive, continuous shadow zone beyond 105° because they cannot pass through the liquid core.
Which of the following is the most likely reason the inner core is solid despite having a temperature similar to the Sun's surface?
- The presence of ice-VII at the center of the Earth.
- It is composed of materials with extremely high melting points like Tungsten.
- The Earth's rotation creates a centrifugal force that solidifies the center.
- The intense pressure from the weight of the Earth above it forces atoms together into a solid.
Explanation: Pressure increases the melting point of substances. At the center of the Earth, the pressure is so high (over 3.5 million atmospheres) that it overrides the effect of temperature, keeping the iron solid.
Consider the following statements regarding 'Secondary (S) Waves':
1. They are also known as transverse or shear waves.
2. They vibrate the particles of the medium at right angles to the direction of wave travel.
3. They are responsible for the 'Shadow Zone' beyond 105° from the epicenter.
Which of the statements given above are correct?
- 2 and 3 only
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
Explanation: All statements are correct. S-waves are shear waves that cannot pass through liquids, which creates the massive shadow zone beyond 105 degrees.
Regarding the Earth's 'Outer Core', consider the following statements:
1. It is composed primarily of iron and nickel with some lighter elements like sulfur and oxygen.
2. It is under so much pressure that it remains in a solid-state despite high temperatures.
3. Its convective motion is responsible for the Earth's magnetic field.
Which of the statements given above is/are correct?
- 1 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Explanation: Statement 2 is incorrect; the outer core is liquid. The inner core is the part that remains solid due to intense pressure.
Regarding 'Isostasy', which statement best relates it to the Earth's interior?
- It is the study of seismic wave shadow zones.
- It is the state of gravitational equilibrium between the lithosphere and the asthenosphere.
- It is the process of mountain building in the crust.
- It is the chemical breakdown of rocks in the lower mantle.
Explanation: Isostasy explains how the rigid lithosphere 'floats' on the semi-fluid asthenosphere, adjusting its height based on its thickness and density.
Consider the following statements regarding 'Surface Waves' (Love and Rayleigh):
1. They are the slowest of all seismic waves.
2. They are recorded last on a seismograph.
3. They are confined to the Earth's crust and cause the most structural damage during an earthquake.
Which of the statements given above are correct?
- 1, 2 and 3
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
Explanation: All statements are correct. Surface waves travel along the surface, have the largest amplitudes, and are the primary cause of damage to buildings and infrastructure.
Regarding the 'Lithosphere', which of the following best describes it?
- The thin layer of soil and organic matter on the Earth's surface.
- The combination of the crust and the uppermost solid part of the mantle.
- The layer of the Earth composed entirely of liquid iron.
- The portion of the mantle below the asthenosphere.
Explanation: The lithosphere includes the crust and the top-most rigid layer of the mantle. Its thickness ranges from 10–200 km.
With reference to the Earth's Core, consider the following statements:
1. The outer core is in a solid state while the inner core is in a liquid state.
2. The core is composed of very heavy material, primarily nickel and iron.
3. The boundary between the mantle and the core is located at a depth of 2,900 km.
Which of the statements given above are correct?
- 1 and 2 only
- 1 and 3 only
- 2 and 3 only
- 1, 2 and 3
Explanation: Statement 1 is incorrect. It is the opposite: the outer core is liquid (proven by S-wave behavior) and the inner core is solid due to extreme pressure.
Which of the following best describes the 'Moho Discontinuity'?
- The line separating the solid inner core from the liquid outer core.
- The surface where tectonic plates collide.
- The boundary where the density of rocks increases from ~2.9 g/cm³ to ~3.3 g/cm³.
- The zone where seismic waves slow down abruptly due to melting.
Explanation: The Moho marks the transition from the less dense crustal rocks to the denser mantle rocks. Seismic waves speed up as they cross this boundary into the denser mantle.
Consider the following statements regarding the 'Shadow Zone' of P-waves:
1. It exists because P-waves are refracted by the Earth's liquid outer core.
2. No P-waves are recorded in the zone between 105° and 145° from the epicenter.
3. P-waves that pass through the core are recorded beyond 145°.
Which of the statements given above are correct?
- 1 and 3 only
- 1 and 2 only
- 2 and 3 only
- 1, 2 and 3
Explanation: All statements are correct. The P-wave shadow zone is a result of refraction (bending) as the waves change speed entering and leaving the core.
Which of the following seismic waves are characterized by a 'Push-Pull' motion, compressing and expanding the material they pass through?
- Secondary Waves (S-waves)
- Rayleigh Waves
- Love Waves
- Primary Waves (P-waves)
Explanation: P-waves are longitudinal waves (like sound waves). They vibrate in the direction of propagation, creating cycles of compression and rarefaction in the rock.
Regarding the 'Mantle' of the Earth, which of the following statements is/are correct?
1. It extends from Moho's discontinuity to a depth of 2,900 km.
2. The upper portion of the mantle is called the asthenosphere.
3. The asthenosphere is the main source of magma that finds its way to the surface during volcanic eruptions.
Select the correct answer:
- 1 only
- 1 and 2 only
- 1, 2 and 3
- 2 and 3 only
Explanation: All statements are correct. The mantle begins after the crust (marked by the Moho discontinuity) and contains the plastic, semi-liquid asthenosphere which provides the magma for volcanoes.
With reference to volcanic activity providing information about the interior, which statement is most accurate?
- The chemical composition of lava is identical to that of the continental crust.
- Lava provides a direct sample of the materials present in the asthenosphere.
- Volcanoes only erupt material from the upper 5 km of the crust.
- Magma comes from the solid inner core.
Explanation: Volcanic eruptions bring magma from the upper mantle (asthenosphere) to the surface, allowing scientists to analyze the mantle's chemical composition directly.
Consider the following statements about 'Mantle Plumes':
1. They are upwellings of abnormally hot rock within the Earth's mantle.
2. They are thought to be the cause of volcanic 'hotspots' like Hawaii and Reunion Island.
3. They originate only from the asthenosphere and never from the core-mantle boundary.
Which of the statements given above is/are correct?
- 1 and 2 only
- 2 and 3 only
- 1 only
- 1, 2 and 3
Explanation: Mantle plumes are believed to originate from very deep in the mantle, often at the Core-Mantle Boundary (Gutenberg Discontinuity), making Statement 3 incorrect.
Consider the following statements regarding the 'Shadow Zone' of seismic waves:
1. The existence of the S-wave shadow zone is the primary evidence for the liquid nature of the outer core.
2. The P-wave shadow zone occurs because P-waves are totally reflected at the core-mantle boundary.
3. Seismographs between 105° and 145° from the epicenter record no direct P-waves.
Which of the statements given above is/are correct?
- 2 only
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
Explanation: Statement 2 is incorrect. The P-wave shadow zone exists because P-waves are *refracted* (bent) as they enter the slower-velocity liquid outer core, not because they are totally reflected.
Regarding the Earth's magnetic field, which statement is correct?
- The magnetic poles are fixed and never change position.
- It is a result of the Sial layer rotating faster than the Sima layer.
- It protects the Earth from harmful solar wind and cosmic radiation.
- It is generated by the solid iron in the inner core.
Explanation: The magnetosphere acts as a shield against solar particles. It is generated by the outer core, and the poles actually 'flip' or wander over geological time.
Which of the following provides the most detailed 'map' of the Earth's deep interior for modern scientists?
- Measuring the Earth's circumference
- Seismic Tomography
- Deep-sea drilling projects
- Analysis of volcanic ash
Explanation: Seismic Tomography uses computer processing of thousands of seismic wave records to create 3D images of the Earth's interior, similar to a CT scan for the human body.
Which of the following describes 'Nife'?
- The mineral composition of the upper crust.
- The nickel and iron composition of the Earth's core.
- The process of heat transfer within the mantle.
- The transition zone between the crust and the mantle.
Explanation: Nife is a mnemonic for Nickel (Ni) and Ferrum (Fe/Iron), the primary constituents of the Earth's core, which is responsible for the planet's magnetic field.
Which of the following is the 'Dynamo Effect' primarily associated with?
- The subduction of tectonic plates.
- The generation of Earth's magnetic field.
- The movement of glacier ice.
- The formation of mountain ranges.
Explanation: The Dynamo Effect is the process through which a rotating, convecting, and electrically conducting fluid (the outer core) can maintain a magnetic field over astronomical time scales.
Consider the following statements about the 'Mesosphere' in Earth's interior:
1. It is the solid, rigid part of the mantle below the asthenosphere.
2. It is composed primarily of liquid iron and nickel.
3. It extends from the 660 km depth down to the core-mantle boundary.
Which of the statements given above is/are correct?
- 1 and 3 only
- 1, 2 and 3
- 1 and 2 only
- 2 only
Explanation: The Mesosphere refers to the lower mantle, which is solid. Statement 2 is a description of the outer core, not the mesosphere.
What happens to the temperature as we move from the surface of the Earth to the center?
- It increases at a constant rate.
- It decreases at a constant rate.
- It increases, but the rate of increase decreases with depth.
- It remains constant until the core-mantle boundary.
Explanation: While temperature increases with depth (geothermal gradient), the *rate* of increase is highest in the crust (~25-30°C/km) and becomes much slower in the mantle and core.
Consider the following statements regarding the 'Asthenosphere':
1. It is located immediately below the Mohorovicic discontinuity.
2. It exists in a plastic or semi-fluid state, allowing for the movement of tectonic plates.
3. It is the layer where the velocity of seismic waves increases abruptly.
Which of the statements given above is/are correct?
- 1 and 2 only
- 2 only
- 1, 2 and 3
- 2 and 3 only
Explanation: Statement 1 is incorrect because the 'uppermost solid mantle' lies between the Moho and the asthenosphere. Statement 3 is incorrect; the asthenosphere is the 'Low Velocity Zone' (LVZ) where seismic waves actually slow down due to the partial melting of rocks.
With reference to 'S-wave' shadow zones, why can't S-waves travel through the core?
- S-waves are absorbed by the magnetic field of the inner core.
- S-waves cannot travel through liquid media, and the outer core is liquid.
- The core is too dense for S-waves to penetrate.
- The core's temperature is too high for wave propagation.
Explanation: S-waves are shear waves that require a rigid medium. Because they disappear at the core-mantle boundary, it is the primary evidence that the outer core is liquid.
The 'Moho Discontinuity' marks the boundary between which two layers?
- Sial and Sima
- Hydrosphere and Lithosphere
- Crust and Mantle
- Mantle and Core
Explanation: The Mohorovicic (Moho) discontinuity is the boundary where seismic waves significantly change speed, marking the transition from the crust to the denser mantle.
What happens to the velocity of P-waves when they enter the Core from the Mantle?
- The velocity remains constant.
- The velocity decreases significantly.
- P-waves disappear completely.
- The velocity increases significantly.
Explanation: When P-waves transition from the solid mantle to the liquid outer core, their velocity drops sharply. However, they continue to travel through the liquid, unlike S-waves.
With reference to Earth's volume and mass, which layer accounts for the largest percentage of Earth's total volume?
- Mantle
- Crust
- Inner Core
- Outer Core
Explanation: The Mantle is the largest layer of the Earth, accounting for about 84% of its volume and 67% of its total mass.
With reference to Earthquake waves, consider the following statements:
1. P-waves move faster and are the first to arrive at the surface.
2. S-waves can travel through solid, liquid, and gaseous materials.
3. P-waves create density differences in the material through which they travel by stretching and squeezing.
Which of the statements given above is/are correct?
- 1 and 3 only
- 1 only
- 2 and 3 only
- 1, 2 and 3
Explanation: Statement 2 is incorrect. S-waves (Secondary waves) can only travel through solid materials. This characteristic helped scientists understand that the outer core is liquid.
With reference to 'Geoid', which of the following is correct?
- It is the perfect spherical shape of the Earth.
- It represents the exact boundary between the Mantle and the Core.
- It is the surface of the Earth's gravity field, which is approximately the same as mean sea level.
- It is the layer of the atmosphere where satellites orbit.
Explanation: The Geoid is a model of the figure of the Earth—the surface that the oceans would take under the influence of Earth's gravitation and rotation alone. It reflects the uneven distribution of mass in the Earth's interior.
Regarding the thermal state of the Earth's interior, consider the following statements:
1. Convection is the primary mode of heat transfer in the solid lithosphere.
2. Conduction is the dominant heat transfer mechanism in the mantle.
3. The Earth's internal heat is a combination of primordial heat from formation and heat generated by radioactive decay.
Which of the statements given above is/are correct?
- 3 only
- 1 and 2 only
- 1, 2 and 3
- 2 and 3 only
Explanation: Statements 1 and 2 are swapped. Conduction is the primary mode of heat transfer in the rigid lithosphere/crust, while Convection is the dominant mechanism in the mantle (asthenosphere). Statement 3 correctly identifies the two main sources of Earth's internal energy.
Regarding the Earth's Core, what is the 'Lehmann Discontinuity'?
- The boundary between the crust and the mantle.
- The boundary between the upper mantle and the lower mantle.
- The boundary between the liquid outer core and the solid inner core.
- The boundary where S-waves disappear.
Explanation: The Lehmann Discontinuity, located at a depth of roughly 5,150 km, marks the transition where seismic waves increase in velocity as they move from the liquid outer core into the solid inner core.
With reference to 'Geothermal Gradient', consider the following statements:
1. It refers to the rate of increasing temperature with respect to increasing depth in the Earth's interior.
2. The rate of increase is uniform from the crust to the center of the Earth.
3. At the center of the Earth, temperatures are estimated to be as high as 6000°C.
Which of the statements given above is/are correct?
- 1 only
- 2 and 3 only
- 1, 2 and 3
- 1 and 3 only
Explanation: Statement 2 is incorrect. The rate of temperature increase is not uniform; it is very rapid in the crust but slows down in the deeper layers (mantle and core).
Consider the following statements regarding 'Barysphere':
1. It refers to the innermost layer of the Earth (the core).
2. It is characterized by extremely high temperature and pressure.
3. It is primarily composed of light silicate minerals.
Which of the statements given above is/are correct?
- 1 and 2 only
- 1 only
- 1, 2 and 3
- 2 and 3 only
Explanation: Statement 3 is incorrect. The Barysphere (the core) is composed of heavy minerals like iron and nickel, not light silicates (which are found in the lithosphere).
Consider the following statements about Earth's density:
1. The average density of the entire Earth is approximately 5.5 g/cm³.
2. The density of the crust is significantly higher than that of the core.
3. Density generally increases as we move from the surface towards the center.
Which of the statements given above is/are correct?
- 2 and 3 only
- 1 only
- 1 and 3 only
- 1, 2 and 3
Explanation: Statement 2 is incorrect. The crust is the least dense layer (2.7–3.0 g/cm³), while the core is the most dense (reaching over 13 g/cm³ at the center).
Which part of the Earth's interior is believed to be the source of Earth's magnetic field?
- The liquid Outer Core
- The plastic Asthenosphere
- The magnetic Crust
- The solid Inner Core
Explanation: The convection of molten iron and nickel in the outer core, combined with the Earth's rotation, generates electrical currents that create the magnetic field.
Consider the following statements regarding the 'Lithosphere':
1. Its thickness varies significantly, being much thicker under mountains than under oceans.
2. It is broken into several large and small plates known as tectonic plates.
3. It is entirely composed of the Earth's crust.
Which of the statements given above are correct?
- 2 and 3 only
- 1, 2 and 3
- 1 and 3 only
- 1 and 2 only
Explanation: The lithosphere includes both the crust AND the uppermost solid portion of the mantle. It is not 'entirely' the crust, making Statement 3 incorrect.
Consider the following statements about the 'Mesosphere' in the context of Earth's interior:
1. It is the layer of the mantle below the asthenosphere.
2. It exists in a liquid state due to the extreme temperatures found at those depths.
3. It extends down to the boundary with the outer core.
Which of the statements given above are correct?
- 1, 2 and 3
- 2 and 3 only
- 1 and 3 only
- 1 and 2 only
Explanation: Statement 2 is incorrect. Although the temperature is very high, the Mesosphere (lower mantle) is in a **solid and rigid state** because the immense pressure prevents the rock from melting. Statements 1 and 3 correctly describe its position and extent.
With reference to the sources of information about the interior of the Earth, consider the following statements:
1. Deep ocean drilling and volcanic eruptions are considered direct sources of information.
2. Analysis of properties of matter like temperature, pressure, and density are considered indirect sources.
3. Meteorites are considered a direct source of information because they reach the Earth's surface from space.
Which of the statements given above are correct?
- 1, 2 and 3
- 2 and 3 only
- 1 and 3 only
- 1 and 2 only
Explanation: Statement 3 is incorrect. Meteorites are considered an indirect source of information. Although they reach Earth, they are not part of the Earth's interior; however, they are made of similar materials as the planets and provide clues about the Earth's composition.
With reference to 'Xenoliths', consider the following statements:
1. They are fragments of rock that are brought to the surface by volcanic eruptions.
2. They provide a direct sample of the Earth's mantle or lower crust.
3. They are usually composed of sedimentary rocks formed in the deep ocean.
Which of the statements given above are correct?
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
- 2 and 3 only
Explanation: Xenoliths are 'foreign rocks' trapped in magma. They are typically igneous or metamorphic fragments from the deep interior (like peridotite), not sedimentary rocks, making them vital for studying the mantle's composition.
Consider the following statements regarding the 'Crust' of the Earth:
1. The oceanic crust is thinner and denser as compared to the continental crust.
2. The main mineral constituents of the continental mass are silica and magnesium.
3. The mean thickness of oceanic crust is about 5 km, while that of the continental crust is around 30 km.
Which of the statements given above are correct?
- 1 and 2 only
- 1, 2 and 3
- 1 and 3 only
- 2 and 3 only
Explanation: Statement 2 is incorrect. The main minerals of the continental crust are silica and aluminium (Sial), while the oceanic crust is primarily composed of silica and magnesium (Sima).
The 'Repetti Discontinuity' is the transition zone between which of the following?
- Upper Mantle and Lower Mantle
- Upper Crust and Lower Crust
- Lower Mantle and Outer Core
- Lower Crust and Upper Mantle
Explanation: The Repetti Discontinuity is found at a depth of about 660 km, marking the boundary where the upper mantle transitions into the lower mantle (mesosphere).
Consider the following statements regarding the 'Inner Core':
1. It is solid due to the immense pressure of the overlying layers.
2. It is responsible for the Earth's magnetic field through the 'Dynamo Effect'.
3. It is primarily made of iron and nickel.
Which of the statements given above are correct?
- 2 and 3 only
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
Explanation: Statement 2 is incorrect. While the core as a whole is responsible for magnetism, the 'Dynamo Effect' specifically involves the movement/convection of the *liquid outer core* around the solid inner core.
Which of the following discontinuities separates the Mantle from the Core?
- Gutenberg Discontinuity
- Lehmann Discontinuity
- Conrad Discontinuity
- Repetti Discontinuity
Explanation: The Gutenberg Discontinuity (also known as the Core-Mantle Boundary or CMB) is located at a depth of about 2,900 km and separates the silicate mantle from the metallic core.
Consider the following statements regarding 'Pressure' in the Earth's interior:
1. Pressure increases steadily from the surface to the center of the Earth.
2. The high pressure at the center prevents the inner core from melting despite temperatures exceeding 5000°C.
3. The pressure at the center of the Earth is nearly 3 to 4 million times that of atmospheric pressure at sea level.
Which of the statements given above are correct?
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Explanation: All statements are correct. The weight of overlying rock increases pressure with depth, which raises the melting point of iron, keeping the inner core solid.
With reference to the chemical composition of the Earth as a whole, which of the following elements is most abundant by weight?
- Magnesium
- Iron
- Oxygen
- Silicon
Explanation: For the Earth as a whole, Iron is the most abundant element (approx. 32-35%), followed by Oxygen, Silicon, and Magnesium. However, if considering only the Earth's *Crust*, Oxygen is the most abundant.
Consider the following pairs of Discontinuities and the layers they separate:
1. Mohorovicic Discontinuity: Crust and Mantle
2. Gutenberg Discontinuity: Upper Mantle and Lower Mantle
3. Lehmann Discontinuity: Outer Core and Inner Core
Which of the pairs given above are correctly matched?
- 1, 2 and 3
- 1 and 2 only
- 1 and 3 only
- 2 and 3 only
Explanation: Pair 2 is incorrectly matched. The Gutenberg Discontinuity separates the Mantle from the Core. The Repetti Discontinuity separates the Upper Mantle from the Lower Mantle.
Which layer of the Earth is known as the 'Low Velocity Zone' for seismic waves?
- Asthenosphere
- Continental Crust
- Lower Mantle
- Inner Core
Explanation: The asthenosphere is called the Low Velocity Zone (LVZ) because the semi-molten/plastic nature of the rocks causes seismic waves to slow down as they enter this layer.
Regarding the Earth's 'Mantle', which mineral is considered the most dominant in the upper mantle?
- Olivine
- Calcite
- Quartz
- Feldspar
Explanation: The upper mantle is primarily composed of peridotite, a rock consisting largely of the magnesium-iron silicate mineral known as Olivine.
With reference to 'Gravity Anomaly', consider the following statements:
1. Gravity values are consistent across all latitudes on the Earth's surface.
2. Gravity anomaly refers to the difference between the observed value of gravity and the expected value at a location.
3. It gives us information about the distribution of mass of the material in the Earth's crust.
Which of the statements given above is/are correct?
- 2 and 3 only
- 1, 2 and 3
- 3 only
- 1 only
Explanation: Statement 1 is incorrect. Gravity is greater near the poles and less at the equator due to the distance from the center and the Earth's rotation. Gravity anomalies help geologists find dense mineral deposits.
With reference to 'Endogenic' forces, which of the following is correct?
- They are driven by the energy originating from within the Earth's interior.
- They only affect the oceanic crust.
- They include weathering, erosion, and deposition.
- They are forces that originate from the atmosphere.
Explanation: Endogenic forces (like volcanism and tectonics) are powered by the internal heat of the Earth. Weathering and erosion are 'Exogenic' forces.
Regarding 'Body Waves' and 'Surface Waves', which of the following is correct?
- Surface waves are generally the most damaging as they cause displacement of rocks.
- Surface waves are the first to be recorded on a seismograph.
- Body waves are generated by the interaction of surface waves with the atmosphere.
- Body waves travel only along the surface of the Earth.
Explanation: Body waves (P and S) travel through the interior, while Surface waves (Love and Rayleigh) travel along the crust. Surface waves have high amplitude and cause the most destruction.
With reference to the density of Earth's layers, which of the following is the correct ascending order (lowest to highest)?
- Crust < Mantle < Core
- Core < Mantle < Crust
- Mantle < Crust < Core
- Mantle < Core < Crust
Explanation: Earth underwent gravitational differentiation. The lightest materials (Crust, ~2.7-3.0 g/cm³) stayed on top, followed by the Mantle (~3.4-5.6 g/cm³), and the heaviest materials (Core, ~10-13+ g/cm³) sank to the center.
Consider the following statements about 'Convectional Current Theory':
1. It was proposed by Arthur Holmes in the 1930s.
2. It suggests that convection currents operate in the mantle portion.
3. These currents are generated due to radioactive elements causing thermal differences.
Which of the statements given above are correct?
- 1, 2 and 3
- 1 and 3 only
- 2 and 3 only
- 1 and 2 only
Explanation: Arthur Holmes proposed that thermal convection in the mantle provides the driving force for continental drift (later Plate Tectonics).
With reference to 'Primary (P) Waves', they can travel through:
1. Solids
2. Liquids
3. Gases
Select the correct answer:
- 1 and 2 only
- 2 and 3 only
- 1, 2 and 3
- 1 only
Explanation: P-waves are longitudinal waves (compressional). Much like sound waves, they can propagate through all states of matter, though their velocity changes significantly based on the density and elasticity of the medium.
With reference to the 'Sial' and 'Sima' layers, consider the following statements:
1. Sial is typically associated with the continental crust, while Sima is associated with the oceanic crust.
2. Sial is denser than Sima, which is why continents sit higher.
3. Sial stands for Silica and Aluminium, while Sima stands for Silica and Magnesium.
Which of the statements given above are correct?
- 1 and 3 only
- 2 and 3 only
- 1 and 2 only
- 1, 2 and 3
Explanation: Statement 2 is incorrect. Sial is *less* dense (approx. 2.7 g/cm³) than Sima (approx. 3.0 g/cm³). This density difference is why the denser oceanic crust (Sima) sinks lower into the mantle than the continental crust (Sial).
Consider the following statements regarding the 'Kola Superdeep Borehole':
1. It is the deepest man-made hole on Earth, reaching about 12 km.
2. It successfully reached the mantle-core boundary.
3. It provided direct evidence that the crust becomes hotter with depth.
Which of the statements given above is/are correct?
- 1 only
- 1, 2 and 3
- 2 and 3 only
- 1 and 3 only
Explanation: The Kola Borehole only reached 12.2 km, which is still well within the continental crust (it did not even reach the mantle). It confirmed that temperature increases significantly with depth.
Consider the following statements about the Earth's Magnetic Field (Geodynamo):
1. It is generated by the convection of molten iron and nickel in the outer core.
2. The Coriolis force caused by Earth's rotation plays a critical role in structuring these convective flows.
3. The magnetic north pole always remains fixed at the geographic North Pole.
Which of the statements given above are correct?
- 1 and 3 only
- 1 and 2 only
- 1, 2 and 3
- 2 and 3 only
Explanation: The magnetic poles wander and have historically undergone full reversals (geomagnetic reversals), so Statement 3 is incorrect. The magnetic field is maintained by the movement of conductive fluid in the outer core (Dynamo effect).
Which of the following minerals are most abundant in the 'Mantle'?
- Olivine and Pyroxene
- Iron and Nickel
- Silica and Aluminium
- Gold and Platinum
Explanation: The mantle is composed of peridotite, which consists primarily of the silicate minerals olivine and pyroxene.
The 'Conrad Discontinuity' is generally found within:
- The Mantle
- The Oceanic Crust
- The Continental Crust
- The Outer Core
Explanation: The Conrad Discontinuity is a boundary found only within the continental crust, separating the upper 'granitic' layer from the lower 'basaltic' layer.
Which of the following discontinuities separates the Upper Crust from the Lower Crust?
- Conrad Discontinuity
- Gutenberg Discontinuity
- Repetti Discontinuity
- Mohorovicic Discontinuity
Explanation: The Conrad Discontinuity is the boundary within the crust that separates the sialic upper crust from the more mafic/simatic lower crust.