Oceanography and Hydrology

In the midst of ocean, garbage patches develop due to collection of marine waste brought together by ocean currents. These are dubbed as gyres. The Great Eastern Garbage Patch in the Pacific Ocean is the size of Rajasthan and Maharashtra combined.

This term refers to the collection of minute or microscopic organisms that inhabit the surface layer of a body of water.

Salinity of 24.7 parts per thousand has been considered as the upper limit to demarcate ‘brackish water.

Arabian sea shows higher salinity due to high evaporation and low influx of rivers.

Salt is separated from sea water by the process of evaporation. The sea water is a liquid. Hence, it changes into vapours and vaporizes whereas salt being a solid does not. Thus, we get salt from sea water by the process of evaporation.

Atoll is a low island found in the tropical oceans consisting of coral reefs surrounding a central depression. It may be a part of the sea (lagoon), or sometimes form enclosing body of fresh, brackish, or highly saline water.

Sonar sends vibrations deep inside the sea, they touch the ground and return back and the time they take in returning back, helps in calculating the depth of the sea.

Correct. The process through which evaporated water is converted back to water is called condensation. The water vapor present starts to condense to form tiny water droplets, these droplets float in the air and form cloud and fog and rain . The whole process is called water cycle.

Correct. A variety of salts, like sodium chloride, calcium, magnesium, and potassium are present in saline water.

Of all water on Earth, about 97.5% is saline ocean water unsuitable for drinking or irrigation without desalination. Only about 2.5% is freshwater, and most of that is locked in glaciers or groundwater. This makes approximately 97% of ocean water unusable for direct human consumption.

The meaning of Option 3 is undersea.

The part of the ocean in which photosynthesis does not occur, is called aphotic zone.

In the ocean the microscopic plant occupies the upper layers, which is called pelagic zone.

Ocean acidification is the decrease in the pH and increase in acidity of the Earth's oceans caused by the uptake of anthropogenic carbon dioxide (CO₂) from the atmosphere. About a quarter of the carbon dioxide in the atmosphere goes into the oceans, where it forms carbonic acid. Statement 1 is wrong as ocean acidification allows sound to propagate, further increasing ocean noise and impacting animals that use sound for echolocation or communication. Statement 2 is wrong because when ocean pH falls, the concentration of carbonate ions get under saturated and structures made of calcium carbonate become vulnerable to dissolution. Species like shellfish and pteropods experience dissolution when exposed to elevated CO₂. Hence, option '4' is correct.

A peninsula is a landform surrounded by water on three sides and connected to mainland on the fourth. India itself is a peninsula (Deccan Peninsula). A strait is a narrow water passage, while a delta is formed by river deposition at a river's mouth.