This set covers the relief of the ocean floor, the temperature and salinity of sea water, ocean currents, tides and ocean-atmosphere events like El Nino. Oceanography links physical geography with climate and fisheries and is a steady area for UPSC Prelims questions.
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
- Continental shelf, trenches and mid-ocean ridges
- Coral reefs and atolls
- Salinity of oceans and seas
- Ocean temperature and the thermocline
- Warm and cold ocean currents
- Tides, El Nino and the Indian Ocean Dipole
UPSC Geography MCQs with answers and explanations
Q1. The continental shelf is best described as:
a) the shallow, gently sloping extension of a continent under the sea
b) the deepest part of the ocean floor
c) a steep slope leading down to the abyssal plain
d) an underwater volcanic mountain
Q2. Which is the deepest known point in the world's oceans?
a) Puerto Rico Trench
b) Challenger Deep in the Mariana Trench
c) Java (Sunda) Trench
d) Tonga Trench
Q3. Mid-oceanic ridges are formed at:
a) convergent plate boundaries
b) transform plate boundaries
c) divergent plate boundaries
d) the centres of continental plates
Q4. Atolls are:
a) volcanic islands with no coral growth
b) long sandbars parallel to the coast
c) chains of underwater mountains
d) ring-shaped coral reefs enclosing a lagoon
Q5. Salinity of ocean water is usually expressed as:
a) grams of salt per litre of fresh water
b) parts per thousand of dissolved salts
c) percentage of sodium only
d) the pH value of sea water
Q6. Which of the following water bodies has the lowest salinity?
a) Red Sea
b) Mediterranean Sea
c) Baltic Sea
d) Persian Gulf
Q7. Which statement about ocean temperature is correct?
a) Temperature generally increases with depth
b) Surface temperature is the same at all latitudes
c) The thermocline is a layer of constant temperature
d) The thermocline is a layer where temperature falls rapidly with depth
Q8. The Gulf Stream is a:
a) warm current in the North Atlantic Ocean
b) cold current off the coast of Peru
c) cold current in the North Pacific Ocean
d) warm current in the Indian Ocean
Q9. Which of the following is a cold ocean current?
a) Kuroshio Current
b) Brazil Current
c) Humboldt (Peru) Current
d) Agulhas Current
Q10. In tropical and subtropical latitudes, cold ocean currents are generally found along the:
a) eastern coasts of continents
b) equator only
c) centres of the ocean basins
d) western coasts of continents
Q11. The meeting of the warm Gulf Stream and the cold Labrador Current near Newfoundland creates:
a) dense fog and one of the richest fishing grounds in the world
b) a large coral reef system
c) a hot coastal desert
d) a monsoon climate
Q12. Spring tides occur when:
a) the Sun and the Moon are at right angles to the Earth
b) the Sun, the Moon and the Earth are in a straight line, at new moon and full moon
c) the Moon is at its farthest point from the Earth
d) the Earth is at its farthest point from the Sun
Q13. Which place records one of the highest tidal ranges in the world?
a) Gulf of Mannar
b) Mediterranean coast of Italy
c) Baltic Sea coast
d) Bay of Fundy, Canada
Q14. El Nino refers to:
a) unusual cooling of surface waters off Peru
b) abnormal warming of surface waters in the central and eastern equatorial Pacific
c) a cold local wind in South America
d) a hurricane in the Atlantic Ocean
Q15. A positive Indian Ocean Dipole (IOD) event involves:
a) warmer eastern Indian Ocean near Indonesia than the western part
b) a sharp rise in salinity across the Bay of Bengal
c) warmer western Indian Ocean near Africa than the eastern part
d) freezing of surface waters in the southern Indian Ocean
Quick revision notes
- The ocean floor has four main divisions: continental shelf, continental slope, deep sea plain and ocean deeps or trenches.
- The Challenger Deep in the Mariana Trench is the deepest known point in the oceans, at nearly 11 km.
- Average ocean salinity is about 35 parts per thousand, higher where evaporation is high and lower where river inflow is large.
- In low and middle latitudes, warm currents flow along east coasts and cold currents along west coasts of continents.
- Spring tides occur at new moon and full moon, and neap tides occur at the first and last quarter of the Moon.
- El Nino is the warming of the central and eastern equatorial Pacific and is often associated with weak Indian monsoons.
Frequently asked questions
What causes ocean currents?
Ocean currents are driven mainly by planetary winds, differences in water density due to temperature and salinity, and the Coriolis force. The shape of coastlines and the ocean floor also guides their paths.
Why are cold current regions often rich fishing grounds?
Cold currents and upwelling bring nutrient-rich water from the depths to the surface. These nutrients support plankton, which forms the base of the food chain for large fish populations.
What is the difference between El Nino and La Nina?
El Nino is the abnormal warming of the central and eastern equatorial Pacific, while La Nina is its unusual cooling. La Nina is often linked to normal or above-normal monsoon rainfall in India.
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