Internal Structure of Earth - Practice Test 5

Attempt the quiz above first, then review every question with its correct answer and a short explanation below.

1. Q1.The Mohorovicic discontinuity is roughly at a depth of:

   • A.30-50 km✓ Correct Answer
   • B.2900 km
   • C.5000 km
   • D.10 km

   Explanation: It marks the base of the crust, typically 30-50 km under continents.

2. Q2.Which gas is released during volcanic eruptions contributing to atmosphere?

   • A.Water Vapor and CO2✓ Correct Answer
   • B.Oxygen
   • C.Ozone
   • D.Neon

   Explanation: Volcanoes emit mostly water vapor, CO2, and SO2.

3. Q3.Granite is an example of:

   • A.Intrusive Igneous Rock✓ Correct Answer
   • B.Extrusive Igneous Rock
   • C.Sedimentary Rock
   • D.Metamorphic Rock

   Explanation: Granite forms from cooling magma inside the crust (Continental Crust).

4. Q4.Basalt is an example of:

   • A.Extrusive Igneous Rock✓ Correct Answer
   • B.Intrusive Igneous Rock
   • C.Sedimentary Rock
   • D.Metamorphic Rock

   Explanation: Basalt forms from lava cooling on the surface (Oceanic Crust).

5. Q5.The study of earthquakes is called:

   • A.Seismology✓ Correct Answer
   • B.Volcanology
   • C.Geology
   • D.Tectonics

   Explanation: Seismology is the specific scientific study of earthquakes.

6. Q6.The crust and the uppermost mantle together form:

   • A.Lithosphere✓ Correct Answer
   • B.Asthenosphere
   • C.Mesosphere
   • D.Barysphere

   Explanation: Lithosphere is the rigid outer layer.

7. Q7.Which discontinuity is located at a depth of 2900 km?

   • A.Gutenberg✓ Correct Answer
   • B.Moho
   • C.Conrad
   • D.Lehmann

   Explanation: The Gutenberg discontinuity marks the Mantle-Core boundary.

8. Q8.The temperature at the Moho discontinuity is approx:

   • A.200-400°C✓ Correct Answer
   • B.1000°C
   • C.5000°C
   • D.0°C

   Explanation: It ranges roughly depending on location but is generally several hundred degrees.

9. Q9.Which part of the Earth is responsible for Earth's gravity?

   • A.Mass of the entire Earth✓ Correct Answer
   • B.Core only
   • C.Crust only
   • D.Atmosphere

   Explanation: Gravity depends on the total mass, though the core contributes significantly due to density.

10. Q10.Diamonds are formed in the:

    • A.Mantle✓ Correct Answer
    • B.Crust
    • C.Core
    • D.Atmosphere

    Explanation: Diamonds form under high pressure in the upper mantle and are brought up by volcanic pipes.

11. Q11.Which seismic waves cause the ground to shake vertically and horizontally?

    • A.Surface waves (Rayleigh/Love)✓ Correct Answer
    • B.P-waves
    • C.S-waves
    • D.Sound waves

    Explanation: Surface waves cause the complex rolling and shaking motion.

12. Q12.The deepest hole drilled by humans (Kola Superdeep Borehole) reached:

    • A.12 km✓ Correct Answer
    • B.50 km
    • C.100 km
    • D.6000 km

    Explanation: It reached about 12 km depth, barely scratching the crust.

13. Q13.The interior of the Earth is investigated using:

    • A.Direct observation (drilling)
    • B.Indirect methods (Seismic waves, Gravity, Magnetism)✓ Correct Answer
    • C.Satellite imaging
    • D.Telescopes

    Explanation: We rely mostly on indirect evidence since we cannot drill deep enough.

14. Q14.The term 'Nife' was used by:

    • A.Edward Suess✓ Correct Answer
    • B.Wegener
    • C.Daly
    • D.Pratt

    Explanation: Suess classified layers chemically as Sial, Sima, and Nife.

15. Q15.Which element is the second most abundant in the Earth's Crust?

    • A.Silicon✓ Correct Answer
    • B.Oxygen
    • C.Aluminum
    • D.Iron

    Explanation: Silicon (~27.7%) is second to Oxygen.

16. Q16.The crust is thinnest under:

    • A.Oceans✓ Correct Answer
    • B.Mountains
    • C.Plateaus
    • D.Deserts

    Explanation: Oceanic crust is typically 5-10 km thick.

17. Q17.The crust is thickest under:

    • A.High Mountain Ranges (e.g. Himalayas)✓ Correct Answer
    • B.Oceans
    • C.Plains
    • D.Valleys

    Explanation: Continental crust thickens under mountains (isostasy), reaching up to 70 km.

18. Q18.Convection currents that drive plate tectonics occur in the:

    • A.Mantle✓ Correct Answer
    • B.Crust
    • C.Inner Core
    • D.Outer Core

    Explanation: Heat from the core creates currents in the mantle.

19. Q19.Which seismic wave is purely longitudinal?

    • A.P-waves✓ Correct Answer
    • B.S-waves
    • C.Love waves
    • D.Rayleigh waves

    Explanation: P-waves are longitudinal (compressional).

20. Q20.The Earth's core is composed mainly of:

    • A.Iron and Nickel✓ Correct Answer
    • B.Silica and Alumina
    • C.Silica and Magnesium
    • D.Iron and Magnesium

    Explanation: Iron and Nickel (Nife) dominate the core.