1. The hydrosphere refers to—
a) Earth’s land surface
b) Earth’s gaseous envelope
c) All water on Earth (surface, underground, atmospheric)
d) Earth’s crust only
Answer: c) All water on Earth (surface, underground, atmospheric)
Explanation: Hydrosphere includes oceans, rivers, lakes, glaciers, groundwater, and water vapor.
2. What percentage of Earth’s surface is covered by water?
a) 51%
b) 61%
c) 71%
d) 81%
Answer: c) 71%
Explanation: About 71% of Earth’s surface is covered by water.
3. Approximately what percentage of Earth’s water is in the oceans?
a) 77%
b) 87%
c) 97%
d) 99%
Answer: c) 97%
Explanation: Oceans contain about 97% of total water, but it is saline.
4. Freshwater makes up what percentage of Earth’s total water?
a) 1%
b) 2.5–3%
c) 5%
d) 10%
Answer: b) 2.5–3%
Explanation: Only ~2.5–3% of Earth’s water is freshwater.
5. The largest reservoir of freshwater on Earth is—
a) Rivers
b) Lakes
c) Glaciers and ice caps
d) Groundwater
Answer: c) Glaciers and ice caps
Explanation: About 69% of freshwater is locked in ice caps and glaciers.
6. The second-largest reservoir of freshwater is—
a) Rivers
b) Groundwater
c) Atmosphere
d) Lakes
Answer: b) Groundwater
Explanation: Groundwater accounts for ~30% of freshwater supply.
7. The process of water circulating between atmosphere, land, and oceans is called—
a) Hydrological cycle
b) Rock cycle
c) Carbon cycle
d) Evapotranspiration
Answer: a) Hydrological cycle
Explanation: The water cycle describes continuous movement of water on Earth.
8. The largest ocean on Earth is—
a) Atlantic Ocean
b) Indian Ocean
c) Pacific Ocean
d) Arctic Ocean
Answer: c) Pacific Ocean
Explanation: Pacific Ocean covers ~165 million sq. km, the largest on Earth.
9. Which is the second-largest ocean in the world?
a) Indian Ocean
b) Atlantic Ocean
c) Southern Ocean
d) Arctic Ocean
Answer: b) Atlantic Ocean
Explanation: The Atlantic Ocean is the second-largest, covering ~106 million sq. km.
10. The smallest ocean in the world is—
a) Arctic Ocean
b) Southern Ocean
c) Indian Ocean
d) Atlantic Ocean
Answer: a) Arctic Ocean
Explanation: Arctic Ocean covers ~15 million sq. km, smallest and shallowest.
11. The Indian Ocean is bounded on the north by—
a) Europe
b) Asia
c) Antarctica
d) Africa
Answer: b) Asia
Explanation: Indian Ocean lies south of Asia, west of Australia, and east of Africa.
12. The average depth of the oceans is about—
a) 1 km
b) 2 km
c) 3.7 km
d) 5 km
Answer: c) 3.7 km
Explanation: Average depth of oceans is about 3,700 m.
13. The deepest part of the world’s oceans is—
a) Java Trench
b) Tonga Trench
c) Mariana Trench
d) Puerto Rico Trench
Answer: c) Mariana Trench
Explanation: Mariana Trench in the Pacific is ~11,034 m deep.
14. Ocean water salinity is measured in—
a) mg/L
b) g/kg
c) Parts per thousand (ppt)
d) ppm
Answer: c) Parts per thousand (ppt)
Explanation: Salinity is usually expressed as ppt (‰).
15. The average salinity of ocean water is about—
a) 25‰
b) 30‰
c) 35‰
d) 40‰
Answer: c) 35‰
Explanation: Ocean water contains ~35 grams of salt per kg of water.
16. The most abundant salt in seawater is—
a) Magnesium chloride
b) Sodium chloride
c) Potassium sulfate
d) Calcium carbonate
Answer: b) Sodium chloride
Explanation: NaCl makes up ~77% of dissolved salts.
17. Which ocean current is warm?
a) Labrador Current
b) California Current
c) Kuroshio Current
d) Peru Current
Answer: c) Kuroshio Current
Explanation: Kuroshio (Japan Current) is a warm ocean current in the Pacific.
18. Which ocean current is cold?
a) Gulf Stream
b) Brazil Current
c) Peru Current
d) North Atlantic Drift
Answer: c) Peru Current
Explanation: Peru (Humboldt) Current is a cold current along South America.
19. The Gulf Stream flows in which ocean?
a) Indian Ocean
b) Pacific Ocean
c) Atlantic Ocean
d) Arctic Ocean
Answer: c) Atlantic Ocean
Explanation: Gulf Stream is a warm ocean current in the North Atlantic.
20. The ocean current off the coast of California is—
a) Warm current
b) Cold current
c) Tidal current
d) None
Answer: b) Cold current
Explanation: California Current is a cold current flowing southward.
21. The tides are caused mainly by—
a) Earth’s rotation
b) Wind action
c) Gravitational pull of the Moon and Sun
d) Ocean currents
Answer: c) Gravitational pull of the Moon and Sun
Explanation: Tides are the periodic rise and fall of sea level due to celestial gravity.
22. The highest tides occur during—
a) Quarter moon
b) Half moon
c) New moon and full moon
d) Eclipse
Answer: c) New moon and full moon
Explanation: Spring tides occur when Earth, Moon, and Sun align.
23. The lowest tides occur during—
a) Quarter moon
b) Half moon
c) New moon
d) Full moon
Answer: a) Quarter moon
Explanation: Neap tides occur when Moon and Sun are at right angles.
24. Tsunamis are usually caused by—
a) Wind
b) Earthquakes under the sea
c) Tides
d) Currents
Answer: b) Earthquakes under the sea
Explanation: Seismic activity on the ocean floor displaces water, causing tsunamis.
25. The vertical movement of cold, nutrient-rich water from deep oceans to the surface is called—
a) Upwelling
b) Downwelling
c) Salinity gradient
d) Convection
Answer: a) Upwelling
Explanation: Upwelling increases marine productivity by bringing nutrients to surface waters.
26. The horizontal movement of ocean water is called—
a) Tide
b) Current
c) Wave
d) Drift
Answer: b) Current
Explanation: Ocean currents are horizontal movements of seawater caused by wind, Coriolis force, and salinity differences.
27. The rhythmic rise and fall of ocean water twice a day is called—
a) Waves
b) Tsunami
c) Tides
d) Currents
Answer: c) Tides
Explanation: Tides are periodic vertical movements of ocean water due to Moon and Sun’s gravity.
28. Which ocean current is also called the “warm blanket of Europe”?
a) Kuroshio Current
b) Gulf Stream
c) Labrador Current
d) Canary Current
Answer: b) Gulf Stream
Explanation: Gulf Stream keeps northwestern Europe warmer than other regions at similar latitude.
29. The movement of seawater from the surface to the deeper layers is known as—
a) Downwelling
b) Upwelling
c) Drift
d) Tidal bore
Answer: a) Downwelling
Explanation: Downwelling carries oxygen-rich surface water into deep oceans.
30. The El Niño phenomenon is associated with which ocean?
a) Atlantic Ocean
b) Indian Ocean
c) Pacific Ocean
d) Arctic Ocean
Answer: c) Pacific Ocean
Explanation: El Niño is warming of central/eastern Pacific Ocean, affecting global climate.
31. Which ocean phenomenon is opposite to El Niño?
a) La Niña
b) Walker circulation
c) Monsoon
d) Upwelling
Answer: a) La Niña
Explanation: La Niña refers to unusual cooling of eastern Pacific waters.
32. The longest ocean current in the world is—
a) Gulf Stream
b) West Wind Drift (Antarctic Circumpolar Current)
c) Peru Current
d) North Equatorial Current
Answer: b) West Wind Drift (Antarctic Circumpolar Current)
Explanation: It flows endlessly around Antarctica, the world’s longest current.
33. The most saline water body on Earth is—
a) Dead Sea
b) Caspian Sea
c) Lake Van
d) Great Salt Lake
Answer: a) Dead Sea
Explanation: Dead Sea has ~300–350‰ salinity, one of the saltiest water bodies.
34. The largest freshwater lake (by surface area) in the world is—
a) Lake Baikal
b) Lake Victoria
c) Lake Superior
d) Lake Tanganyika
Answer: c) Lake Superior
Explanation: Lake Superior in North America is the largest freshwater lake by surface area.
35. The deepest freshwater lake in the world is—
a) Lake Tanganyika
b) Lake Superior
c) Lake Baikal
d) Lake Victoria
Answer: c) Lake Baikal
Explanation: Lake Baikal in Russia is ~1642 m deep, the deepest freshwater lake.
36. Which river carries the maximum water discharge in the world?
a) Nile
b) Amazon
c) Mississippi
d) Congo
Answer: b) Amazon
Explanation: Amazon River discharges ~209,000 m³/s, highest in the world.
37. The longest river in the world is—
a) Nile
b) Amazon
c) Mississippi
d) Yangtze
Answer: a) Nile
Explanation: Nile (6,650 km) is slightly longer than Amazon (6,400 km).
38. Which river is known as “Sorrow of Bihar”?
a) Yamuna
b) Kosi
c) Gandak
d) Ghaghara
Answer: b) Kosi
Explanation: Kosi causes frequent floods in Bihar, earning the name “Sorrow of Bihar.”
39. Which river forms the largest delta in the world?
a) Amazon
b) Ganga–Brahmaputra
c) Nile
d) Mississippi
Answer: b) Ganga–Brahmaputra
Explanation: The Sundarbans delta is the largest in the world (~100,000 sq km).
40. Which Indian river is west-flowing and forms an estuary?
a) Ganga
b) Narmada
c) Brahmaputra
d) Godavari
Answer: b) Narmada
Explanation: Narmada flows into Arabian Sea, forming an estuary instead of a delta.
41. Which is the largest river island in the world, located in the Brahmaputra River?
a) Divar
b) Majuli
c) Srirangam
d) Bhavani
Answer: b) Majuli
Explanation: Majuli in Assam is the world’s largest river island.
42. The highest waterfall in the world is—
a) Niagara Falls
b) Angel Falls
c) Victoria Falls
d) Tugela Falls
Answer: b) Angel Falls
Explanation: Angel Falls in Venezuela plunges 979 m, highest in the world.
43. The highest waterfall in India is—
a) Jog Falls
b) Nohkalikai Falls
c) Kunchikal Falls
d) Chitrakote Falls
Answer: c) Kunchikal Falls
Explanation: Kunchikal Falls in Karnataka (455 m) is the tallest waterfall in India.
44. Which ocean current is responsible for bringing warm water to Western Europe?
a) Labrador Current
b) Gulf Stream
c) Benguela Current
d) Peru Current
Answer: b) Gulf Stream
Explanation: Gulf Stream and North Atlantic Drift warm Western Europe.
45. Which ocean is called the “Ring of Fire” due to intense seismic activity?
a) Atlantic Ocean
b) Pacific Ocean
c) Indian Ocean
d) Arctic Ocean
Answer: b) Pacific Ocean
Explanation: Pacific Ocean has many volcanoes and earthquake zones, forming a “Ring of Fire.”
46. Which is the saltiest major ocean?
a) Atlantic Ocean
b) Pacific Ocean
c) Indian Ocean
d) Arctic Ocean
Answer: a) Atlantic Ocean
Explanation: Higher evaporation and lower inflow of rivers make Atlantic more saline.
47. The ocean current flowing around Antarctica in clockwise direction is—
a) Gulf Stream
b) Labrador Current
c) West Wind Drift
d) Brazil Current
Answer: c) West Wind Drift
Explanation: Antarctic Circumpolar Current flows clockwise around Antarctica.
48. Which current is known as the “Japan Current”?
a) Kuroshio Current
b) Oyashio Current
c) California Current
d) Peru Current
Answer: a) Kuroshio Current
Explanation: Kuroshio is a warm current along east coast of Japan.
49. Which is the largest gulf in the world?
a) Gulf of Mexico
b) Persian Gulf
c) Gulf of Alaska
d) Gulf of Aden
Answer: a) Gulf of Mexico
Explanation: The Gulf of Mexico (~1.6 million sq km) is the largest gulf in the world.
50. Which is the largest bay in the world?
a) Bay of Bengal
b) Hudson Bay
c) Bay of Biscay
d) Chesapeake Bay
Answer: a) Bay of Bengal
Explanation: Bay of Bengal is the largest bay in the world (~2.17 million sq km).
51. Which is the largest sea in the world?
a) Arabian Sea
b) South China Sea
c) Mediterranean Sea
d) Caribbean Sea
Answer: b) South China Sea
Explanation: South China Sea (~3.5 million sq km) is the largest marginal sea.
52. Which is the largest inland sea in the world?
a) Red Sea
b) Caspian Sea
c) Black Sea
d) Dead Sea
Answer: b) Caspian Sea
Explanation: Caspian Sea is the world’s largest inland water body (~371,000 sq km).
53. The Aral Sea is shrinking mainly due to—
a) Climate change
b) River diversion for irrigation
c) High evaporation
d) Pollution
Answer: b) River diversion for irrigation
Explanation: Diversion of Amu Darya and Syr Darya caused drastic shrinkage.
54. Which is the saltiest large lake in the world?
a) Dead Sea
b) Great Salt Lake (Utah)
c) Lake Assal (Djibouti)
d) Lake Urmia (Iran)
Answer: c) Lake Assal (Djibouti)
Explanation: Lake Assal has salinity above 340‰, even saltier than Dead Sea.
55. The process by which groundwater naturally comes to the surface is called—
a) Artesian spring
b) Seepage
c) Geyser eruption
d) All of these
Answer: d) All of these
Explanation: Groundwater appears as springs, seepages, or geysers.
56. Which is the world’s longest glacier outside polar regions?
a) Siachen Glacier
b) Lambert Glacier
c) Fedchenko Glacier
d) Baltoro Glacier
Answer: c) Fedchenko Glacier
Explanation: Fedchenko Glacier in Tajikistan (~77 km long) is the longest non-polar glacier.
57. Which is the longest glacier in India?
a) Siachen Glacier
b) Gangotri Glacier
c) Baltoro Glacier
d) Pindari Glacier
Answer: a) Siachen Glacier
Explanation: Siachen (76 km) is the longest glacier in India and second-longest outside poles.
58. Which ocean has the widest continental shelf?
a) Atlantic Ocean
b) Indian Ocean
c) Arctic Ocean
d) Pacific Ocean
Answer: c) Arctic Ocean
Explanation: Arctic Ocean has broad continental shelves, especially in Siberia.
59. Ocean salinity is highest in—
a) Equatorial regions
b) Subtropical high-pressure zones
c) Polar regions
d) Estuaries
Answer: b) Subtropical high-pressure zones
Explanation: High evaporation and little rainfall increase salinity near 20°–30° latitudes.
60. Ocean salinity is lowest in—
a) Equatorial regions
b) Subtropical zones
c) Polar regions
d) Desert coasts
Answer: c) Polar regions
Explanation: Melting ice and low evaporation make polar waters less saline.
61. Which current flows along the west coast of South America?
a) Gulf Stream
b) Kuroshio Current
c) Peru (Humboldt) Current
d) Canary Current
Answer: c) Peru (Humboldt) Current
Explanation: Cold Peru Current flows northward along South America’s west coast.
62. Which current flows along the east coast of North America?
a) Labrador Current
b) Gulf Stream
c) California Current
d) Peru Current
Answer: b) Gulf Stream
Explanation: Warm Gulf Stream flows northward along North America’s east coast.
63. Which current flows along the east coast of Africa?
a) Mozambique Current
b) Peru Current
c) Canary Current
d) Labrador Current
Answer: a) Mozambique Current
Explanation: Mozambique Current is a warm current in the Indian Ocean.
64. Which current flows along the west coast of Africa?
a) Canary Current
b) Mozambique Current
c) Kuroshio Current
d) Brazil Current
Answer: a) Canary Current
Explanation: Cold Canary Current flows southward along northwest Africa.
65. Which current is also called the “Alaskan Current”?
a) Oyashio Current
b) North Pacific Current
c) Kuroshio Current
d) Alaska Current
Answer: d) Alaska Current
Explanation: Alaska Current is a warm current flowing along Alaska.
66. The Japan Current is also known as—
a) Oyashio Current
b) Kuroshio Current
c) Canary Current
d) Peru Current
Answer: b) Kuroshio Current
Explanation: Kuroshio is called Japan Current, a warm current in the Pacific.
67. Which current merges with Gulf Stream to form the North Atlantic Drift?
a) Labrador Current
b) Brazil Current
c) Canary Current
d) Florida Current
Answer: d) Florida Current
Explanation: Florida Current combines with Gulf Stream to form the North Atlantic Drift.
68. Which is the largest warm current in the world?
a) Brazil Current
b) Gulf Stream
c) Kuroshio Current
d) Agulhas Current
Answer: b) Gulf Stream
Explanation: Gulf Stream transports the largest volume of warm water.
69. Which is the largest cold current in the world?
a) Labrador Current
b) Oyashio Current
c) West Wind Drift
d) Peru Current
Answer: c) West Wind Drift
Explanation: Antarctic Circumpolar Current is the largest cold current.
70. The Mediterranean Sea has higher salinity due to—
a) High evaporation and less river inflow
b) High rainfall
c) Melting glaciers
d) Ocean currents
Answer: a) High evaporation and less river inflow
Explanation: Evaporation is high, and river inflow is low in the Mediterranean.
71. Which type of tide occurs when the Sun, Moon, and Earth are in a straight line?
a) Neap tide
b) Spring tide
c) Diurnal tide
d) Mixed tide
Answer: b) Spring tide
Explanation: Spring tides (highest tides) occur at new moon and full moon.
72. Which type of tide occurs when the Sun and Moon are at right angles to Earth?
a) Neap tide
b) Spring tide
c) Diurnal tide
d) Mixed tide
Answer: a) Neap tide
Explanation: Neap tides are the lowest tides, during quarter moon phases.
73. A tidal bore is—
a) A tsunami
b) A steep wave of incoming tide in rivers
c) A cyclone surge
d) A type of ocean current
Answer: b) A steep wave of incoming tide in rivers
Explanation: Tidal bore occurs in rivers with narrow estuaries, e.g., Hooghly.
74. Which ocean has the maximum number of tsunamis?
a) Atlantic Ocean
b) Pacific Ocean
c) Indian Ocean
d) Arctic Ocean
Answer: b) Pacific Ocean
Explanation: Pacific “Ring of Fire” makes it prone to earthquakes and tsunamis.
75. The Sargasso Sea is located in—
a) Indian Ocean
b) South China Sea
c) North Atlantic Ocean
d) Pacific Ocean
Answer: c) North Atlantic Ocean
Explanation: Sargasso Sea is bounded by ocean currents and contains floating Sargassum weeds.
76. The world’s largest ocean trench is—
a) Java Trench
b) Puerto Rico Trench
c) Mariana Trench
d) Tonga Trench
Answer: c) Mariana Trench
Explanation: Mariana Trench (~11,034 m) in the Pacific is the deepest ocean trench.
77. Which is the longest river in India?
a) Ganga
b) Godavari
c) Brahmaputra
d) Narmada
Answer: a) Ganga
Explanation: Ganga (2,525 km) is the longest river flowing entirely in India.
78. Which is the largest river system in India by volume of water discharge?
a) Godavari
b) Ganga
c) Brahmaputra
d) Indus
Answer: c) Brahmaputra
Explanation: Brahmaputra carries the maximum water discharge in India.
79. Which is the longest river in the world?
a) Amazon
b) Nile
c) Yangtze
d) Mississippi
Answer: b) Nile
Explanation: Nile (~6,650 km) is considered the longest, though Amazon rivals it in length.
80. Which river forms the Sunderbans delta?
a) Ganga
b) Brahmaputra
c) Both (a) and (b)
d) Hooghly
Answer: c) Both (a) and (b)
Explanation: Ganga and Brahmaputra together form the world’s largest delta.
81. Which is the largest river basin in India?
a) Ganga Basin
b) Godavari Basin
c) Krishna Basin
d) Indus Basin
Answer: a) Ganga Basin
Explanation: Ganga Basin is the largest in India, covering ~8.6 lakh sq km.
82. The main cause of ocean currents is—
a) Gravity
b) Earth’s rotation and wind systems
c) Tides
d) Earthquakes
Answer: b) Earth’s rotation and wind systems
Explanation: Winds, Coriolis effect, and density differences drive currents.
83. The Labrador Current is a—
a) Warm current
b) Cold current
c) Tidal current
d) Counter current
Answer: b) Cold current
Explanation: Labrador is a cold current flowing south along Canada’s coast.
84. The Brazil Current is—
a) Warm current
b) Cold current
c) Tidal bore
d) None
Answer: a) Warm current
Explanation: Brazil Current is a warm ocean current in the South Atlantic.
85. Which sea has the lowest salinity?
a) Baltic Sea
b) Red Sea
c) Arabian Sea
d) Mediterranean Sea
Answer: a) Baltic Sea
Explanation: Due to river inflow and low evaporation, Baltic Sea has lowest salinity (~8–10‰).
86. The highest salinity is found in—
a) Red Sea
b) Arabian Sea
c) Mediterranean Sea
d) Dead Sea
Answer: d) Dead Sea
Explanation: Dead Sea’s salinity is ~300–350‰, highest among large water bodies.
87. Which current brings cold water along the western coast of Africa?
a) Canary Current
b) Agulhas Current
c) Brazil Current
d) Gulf Stream
Answer: a) Canary Current
Explanation: Canary Current is a cold current flowing southward.
88. Which current is warm and flows along the east coast of Africa?
a) Mozambique Current
b) Canary Current
c) Labrador Current
d) Peru Current
Answer: a) Mozambique Current
Explanation: Warm Mozambique Current flows in the Indian Ocean along Africa.
89. Which Indian lake is the largest brackish water lagoon in Asia?
a) Wular Lake
b) Chilika Lake
c) Loktak Lake
d) Sambhar Lake
Answer: b) Chilika Lake
Explanation: Chilika Lake in Odisha is Asia’s largest brackish water lagoon.
90. Which is the largest freshwater lake in India?
a) Vembanad
b) Wular
c) Dal
d) Loktak
Answer: b) Wular
Explanation: Wular Lake in Jammu & Kashmir is India’s largest freshwater lake.
91. Loktak Lake, famous for floating islands (phumdis), is in—
a) Assam
b) Manipur
c) Kerala
d) Odisha
Answer: b) Manipur
Explanation: Loktak Lake is the largest freshwater lake in northeast India.
92. Sambhar Lake, India’s largest inland salt lake, is in—
a) Rajasthan
b) Gujarat
c) Maharashtra
d) Andhra Pradesh
Answer: a) Rajasthan
Explanation: Sambhar Lake in Rajasthan is India’s largest saltwater lake.
93. Vembanad Lake, India’s longest lake, is located in—
a) Tamil Nadu
b) Kerala
c) Karnataka
d) Andhra Pradesh
Answer: b) Kerala
Explanation: Vembanad is Kerala’s longest lake and part of its backwaters.
94. Pulicat Lake, India’s second largest lagoon, is located in—
a) Odisha
b) Tamil Nadu & Andhra Pradesh
c) Gujarat
d) Kerala
Answer: b) Tamil Nadu & Andhra Pradesh
Explanation: Pulicat Lake lies across Tamil Nadu and Andhra Pradesh coast.
95. Which sea has the highest salinity among large seas?
a) Red Sea
b) Mediterranean Sea
c) Black Sea
d) Arabian Sea
Answer: a) Red Sea
Explanation: Red Sea has very high salinity (~40‰) due to evaporation.
96. Which Indian river is known as “Dakshin Ganga”?
a) Krishna
b) Godavari
c) Narmada
d) Kaveri
Answer: b) Godavari
Explanation: Godavari, the longest peninsular river, is called “Dakshin Ganga.”
97. Which ocean current is responsible for the deserts of Chile and Peru?
a) Gulf Stream
b) Peru (Humboldt) Current
c) Labrador Current
d) Canary Current
Answer: b) Peru (Humboldt) Current
Explanation: Cold Peru Current reduces rainfall, creating Atacama Desert.
98. Which current influences the climate of Japan?
a) Oyashio and Kuroshio Currents
b) California and Peru Currents
c) Canary and Labrador Currents
d) Gulf Stream and Brazil Currents
Answer: a) Oyashio and Kuroshio Currents
Explanation: Warm Kuroshio and cold Oyashio currents meet off Japan, affecting climate and fisheries.
99. Which is the largest island in the world?
a) Greenland
b) New Guinea
c) Borneo
d) Madagascar
Answer: a) Greenland
Explanation: Greenland (~2.16 million sq km) is the world’s largest island.
100. Which is the largest island in India?
a) Majuli
b) Middle Andaman
c) Great Nicobar
d) Rameswaram
Answer: c) Great Nicobar
Explanation: Great Nicobar (~1,045 sq km) is the largest island of India.