This set covers the structure of the Earth's interior, the main rock types and the theories that explain how continents and oceans move. These are foundational topics in physical geography and form the base for questions on volcanoes, earthquakes and landforms in UPSC Prelims.
How to practise: read each question and tap the option you think is correct. You will see right away whether you got it, along with a short explanation, and your score is tracked at the bottom of the screen. This set has 15 questions.
Topics covered in this set
- Layers of the Earth and major discontinuities
- Seismic waves and shadow zones
- Composition of crust, mantle and core
- Igneous, sedimentary and metamorphic rocks
- Continental drift and sea-floor spreading
- Plate boundaries and their landforms
UPSC Geography MCQs with answers and explanations
Q1. The Mohorovicic (Moho) discontinuity separates which two layers of the Earth?
a) Crust and mantle
b) Upper mantle and lower mantle
c) Mantle and outer core
d) Outer core and inner core
Q2. The S-wave shadow zone on the Earth's surface exists mainly because S-waves:
a) travel faster than P-waves
b) cannot pass through the liquid outer core
c) are completely reflected by the crust
d) travel only along the Earth's surface
Q3. The asthenosphere, a weak and partly molten zone that is a main source of magma, lies in the:
a) lower crust
b) outer core
c) upper mantle
d) lower mantle
Q4. The Earth's core is believed to be composed mainly of:
a) silicon and aluminium
b) silicon and magnesium
c) calcium and sodium
d) nickel and iron
Q5. Which element is the most abundant in the Earth's crust by weight?
a) Silicon
b) Oxygen
c) Aluminium
d) Iron
Q6. Marble is a metamorphic rock formed from which original rock?
a) Granite
b) Shale
c) Limestone
d) Sandstone
Q7. Which of the following is an extrusive (volcanic) igneous rock?
a) Granite
b) Gabbro
c) Diorite
d) Basalt
Q8. Which of the following statements about sedimentary rocks is correct?
a) They are formed in layers and may contain fossils
b) They form directly from cooling magma
c) They form only under extreme heat and pressure
d) They make up most of the volume of the Earth's crust
Q9. The theory of continental drift was proposed by:
a) Harry Hess
b) Arthur Holmes
c) Alfred Wegener
d) W. J. Morgan
Q10. Which observation supports the concept of sea-floor spreading?
a) Oceanic crust is older than one billion years everywhere
b) Sediments are thickest at the mid-ocean ridges
c) Volcanic activity is absent along mid-ocean ridges
d) Rocks become older with increasing distance from the mid-ocean ridge
Q11. When an oceanic plate converges with a continental plate, the usual result is:
a) subduction of the oceanic plate and formation of a deep trench
b) formation of a mid-ocean ridge
c) creation of a rift valley
d) the continental plate sinking beneath the oceanic plate
Q12. The San Andreas Fault in California is an example of a:
a) divergent boundary
b) transform boundary
c) oceanic-oceanic convergent boundary
d) hotspot
Q13. The Himalayas were formed mainly by the collision of which plates?
a) Pacific and Eurasian plates
b) African and Eurasian plates
c) Indian and Arabian plates
d) Indian and Eurasian plates
Q14. The East African Rift Valley is an example of which type of plate boundary?
a) Convergent boundary
b) Divergent boundary on land
c) Transform boundary
d) Subduction zone
Q15. Which of the following correctly describes the Earth's inner core?
a) It is liquid and made mostly of silicates
b) It is the least dense layer of the Earth
c) It is solid despite very high temperature, because of immense pressure
d) It lies directly below the crust
Quick revision notes
- The Earth has three main layers: crust, mantle and core, separated by the Moho and Gutenberg discontinuities.
- P-waves pass through solids and liquids, while S-waves pass only through solids, which shows the outer core is liquid.
- The crust is mainly oxygen and silicon, while the core is mainly nickel and iron (NIFE).
- Igneous rocks form from magma, sedimentary rocks from deposited sediments, and metamorphic rocks from changes under heat and pressure.
- Wegener's continental drift was later explained by Hess's sea-floor spreading and the plate tectonics theory.
- Divergent boundaries create crust, convergent boundaries destroy or crumple it, and transform boundaries neither create nor destroy it.
Frequently asked questions
How do scientists know about the Earth's interior if no one has reached it?
Most knowledge comes from indirect sources, mainly the behaviour of seismic waves from earthquakes. Changes in their speed and direction, and the shadow zones where they are not recorded, reveal the layers and their states.
What is the difference between the lithosphere and the asthenosphere?
The lithosphere is the rigid outer shell made of the crust and the uppermost mantle, and it is broken into plates. The asthenosphere below it is weak and partly molten, allowing the plates to move.
Why do fold mountains like the Himalayas have few volcanoes?
They form from collision of two continental plates, which are both light and do not sink deep into the mantle. Without subduction, little magma is produced, so volcanic activity is limited.
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