Q.1 What is the average salinity of ocean water?
25 ppt
30 ppt
35 ppt
40 ppt
Explanation - The average salinity of seawater is about 35 parts per thousand (ppt), meaning 35 grams of salts per liter of seawater.
Correct answer is: 35 ppt
Q.2 Which is the largest ocean on Earth?
Atlantic Ocean
Indian Ocean
Pacific Ocean
Arctic Ocean
Explanation - The Pacific Ocean is the largest, covering more than 63 million square miles of Earth's surface.
Correct answer is: Pacific Ocean
Q.3 What is the primary cause of ocean tides?
Winds
Earth’s rotation
Moon’s gravity
Sun’s heat
Explanation - Tides are mainly caused by the gravitational pull of the Moon, with a smaller influence from the Sun.
Correct answer is: Moon’s gravity
Q.4 What is the deepest point in the world’s oceans?
Puerto Rico Trench
Java Trench
Mariana Trench
Tonga Trench
Explanation - The Mariana Trench in the western Pacific Ocean is the deepest part, reaching about 11,000 meters.
Correct answer is: Mariana Trench
Q.5 Which current is known as the 'conveyor belt' of the oceans?
Gulf Stream
Humboldt Current
Thermohaline Circulation
Kuroshio Current
Explanation - Thermohaline circulation moves water around the globe due to differences in temperature and salinity, often called the global conveyor belt.
Correct answer is: Thermohaline Circulation
Q.6 What percentage of Earth’s surface is covered by oceans?
51%
61%
71%
81%
Explanation - Oceans cover about 71% of Earth’s surface, playing a major role in climate and ecosystems.
Correct answer is: 71%
Q.7 Which ocean is the shallowest?
Indian Ocean
Arctic Ocean
Atlantic Ocean
Southern Ocean
Explanation - The Arctic Ocean is the shallowest of all the world’s oceans, with an average depth of about 1,000 meters.
Correct answer is: Arctic Ocean
Q.8 What is upwelling?
Movement of warm surface water
Rising of cold, nutrient-rich water
Warming of surface currents
Evaporation of seawater
Explanation - Upwelling brings cold, nutrient-rich water to the surface, supporting rich marine life and fisheries.
Correct answer is: Rising of cold, nutrient-rich water
Q.9 Which gas is most abundant in seawater?
Carbon dioxide
Oxygen
Nitrogen
Methane
Explanation - Carbon dioxide is the most abundant dissolved gas in seawater, important for marine organisms and buffering pH.
Correct answer is: Carbon dioxide
Q.10 Which ocean current warms Western Europe?
Labrador Current
Humboldt Current
Gulf Stream
Canary Current
Explanation - The Gulf Stream transports warm water from the Gulf of Mexico towards Europe, moderating its climate.
Correct answer is: Gulf Stream
Q.11 What are seamounts?
Underwater volcanoes
Deep-sea trenches
Continental shelves
Ocean ridges
Explanation - Seamounts are underwater mountains formed by volcanic activity, often rising thousands of meters from the seafloor.
Correct answer is: Underwater volcanoes
Q.12 The Great Barrier Reef is located in which ocean?
Atlantic Ocean
Pacific Ocean
Indian Ocean
Arctic Ocean
Explanation - The Great Barrier Reef lies off the northeast coast of Australia in the Pacific Ocean.
Correct answer is: Pacific Ocean
Q.13 Which layer of the ocean is known as the 'sunlight zone'?
Mesopelagic
Epipelagic
Bathypelagic
Abyssopelagic
Explanation - The epipelagic or sunlight zone extends to about 200 meters depth and receives enough light for photosynthesis.
Correct answer is: Epipelagic
Q.14 What is the main driver of surface ocean currents?
Wind
Earthquakes
Salinity differences
Volcanoes
Explanation - Surface currents are driven primarily by global wind patterns, like trade winds and westerlies.
Correct answer is: Wind
Q.15 Which ocean is shrinking due to plate tectonics?
Atlantic Ocean
Indian Ocean
Pacific Ocean
Arctic Ocean
Explanation - The Pacific Ocean is slowly shrinking as subduction zones consume its crust.
Correct answer is: Pacific Ocean
Q.16 What is the average temperature of the deep ocean?
10°C
8°C
4°C
0°C
Explanation - The deep ocean remains cold and stable, with an average temperature of about 4°C.
Correct answer is: 4°C
Q.17 The Sargasso Sea is located in which ocean?
Atlantic Ocean
Pacific Ocean
Indian Ocean
Southern Ocean
Explanation - The Sargasso Sea is a unique region in the Atlantic Ocean defined by surrounding currents, not land.
Correct answer is: Atlantic Ocean
Q.18 Which marine zone is located above the continental shelf?
Oceanic zone
Abyssal zone
Neritic zone
Hadal zone
Explanation - The neritic zone lies over the continental shelf, rich in nutrients and marine life.
Correct answer is: Neritic zone
Q.19 What is bioluminescence in marine organisms?
Absorption of sunlight
Production of light by chemical reactions
Reflection of moonlight
Storage of heat energy
Explanation - Bioluminescence is the ability of organisms to produce light through chemical reactions within their bodies.
Correct answer is: Production of light by chemical reactions
Q.20 What are hydrothermal vents?
Cold water springs
Volcanic gas vents
Hot water springs on ocean floor
Areas of high salinity
Explanation - Hydrothermal vents are hot water springs on the seafloor formed where magma heats seawater, supporting unique ecosystems.
Correct answer is: Hot water springs on ocean floor
Q.21 Which ocean has the most islands?
Indian Ocean
Pacific Ocean
Atlantic Ocean
Arctic Ocean
Explanation - The Pacific Ocean contains thousands of islands, more than any other ocean basin.
Correct answer is: Pacific Ocean
Q.22 What is an estuary?
Deep ocean trench
Where a river meets the sea
Underwater mountain
Salt lake
Explanation - An estuary is a coastal area where freshwater from rivers mixes with saltwater from the ocean.
Correct answer is: Where a river meets the sea
Q.23 Which instrument is used to measure ocean depth?
Barometer
Sonar
Thermometer
Altimeter
Explanation - Sonar (Sound Navigation and Ranging) is used to measure ocean depth by bouncing sound waves off the seafloor.
Correct answer is: Sonar
Q.24 What are tsunamis caused by?
Strong winds
Underwater earthquakes
Heavy rainfall
Ice melting
Explanation - Most tsunamis are generated by undersea earthquakes that displace large volumes of water.
Correct answer is: Underwater earthquakes
Q.25 What percentage of Earth's oxygen comes from the ocean?
10%
30%
50%
70%+
Explanation - Phytoplankton in the ocean produce over 70% of Earth's oxygen through photosynthesis.
Correct answer is: 70%+