Oceans: Floor, Temperature & Salinity – NDA Geography PYQs

NDA 2025-II

Q. 1. Which of the following statements is/are correct?

1. Oceanic trenches are very significant in the study of plate movements.

2. Oceanic trenches are associated with active volcanoes and strong earthquakes.

Select the answer using the code given below:

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. Oceanic trenches form at subduction zones where one tectonic plate dives beneath another. The study of trenches provides critical evidence about plate movements, subduction rates, and the dynamics of plate tectonics. Statement 2: Correct. Subduction zones (where trenches form) are among the most seismically and volcanically active regions on Earth. The Ring of Fire: which contains most of the world’s major trenches: is responsible for about 90% of the world’s earthquakes and 75% of its active volcanoes. Concept Tested: Oceanic trenches: formed at subduction zones; significant for plate tectonics study; associated with earthquakes and volcanoes

NDA 2021-II

Q. 2. Which one of the following factors does not affect the distribution of groundwater?

(a) Amount of precipitation

(b) Rate of evaporation

(c) Ability of the ground surface to allow water to infiltrate

(d) Distance from the sea

Answer: (d) Distance from the sea

Explanation: Groundwater distribution is influenced by: (a) Amount of precipitation: more rain → more water available to infiltrate into the ground ✓. (b) Rate of evaporation: high evaporation reduces water available for infiltration; affects soil moisture ✓. (c) Infiltration capacity: rocky or impervious surfaces prevent infiltration; sandy soils allow more ✓. (d) Distance from the sea: does NOT significantly affect groundwater distribution. Groundwater is replenished by local precipitation and infiltration, not directly by proximity to the sea. Coastal aquifers may face saltwater intrusion, but this is a different issue from distribution. Distance from the sea does not control whether groundwater is present or abundant. Concept Tested: Groundwater distribution: controlled by precipitation, evaporation, and infiltration; NOT by distance from the sea

NDA 2017-II

Q. 3. Mariana Trench is located in the ocean floor of:

(a) Southern Atlantic Ocean

(b) Western Pacific Ocean

(c) Eastern Pacific Ocean

(d) Northern Atlantic Ocean

Answer: (b) Western Pacific Ocean

Explanation: The Mariana Trench is located in the western Pacific Ocean, east of the Mariana Islands. It is the deepest known point on Earth. The Challenger Deep, within the Mariana Trench, reaches approximately 11,034 metres (about 36,000 feet) below sea level. It was formed by the subduction of the Pacific Plate beneath the Mariana Plate. The immense depth is a result of the old, dense oceanic crust being forced downward at this subduction zone. Concept Tested: Mariana Trench: deepest point on Earth (Challenger Deep, ~11,034 m); western Pacific Ocean

NDA 2010-II

Q. 4. Which one of the following is the correct sequence of the four stages of water movement in a hydrological cycle?

(a) Evaporation: Condensation: Precipitation: Infiltration

(b) Evaporation: Precipitation: Condensation: Infiltration

(c) Infiltration: Evaporation: Condensation: Precipitation

(d) Condensation: Precipitation: Evaporation: Infiltration

Answer: (a) Evaporation: Condensation: Precipitation: Infiltration

Explanation: The hydrological (water) cycle is the continuous movement of water through the environment: 1. Evaporation: water from oceans, lakes, and rivers evaporates into the atmosphere as water vapour (solar energy drives this). 2. Condensation: water vapour cools as it rises and condenses into tiny water droplets, forming clouds. 3. Precipitation: water falls from clouds as rain, snow, sleet, or hail. 4. Infiltration: precipitation that reaches the ground either runs off into rivers or infiltrates into the soil, eventually replenishing groundwater. Concept Tested: Hydrological cycle sequence: Evaporation → Condensation → Precipitation → Infiltration

★ JOVIK Exam Insight The Hydrological (Water) Cycle for NDA: Evaporation (from oceans, lakes, soil, vegetation/transpiration) → Water vapour rises. Condensation (cools at altitude, forms clouds) → Clouds form. Precipitation (rain, snow, hail) → Falls to Earth. Infiltration + Surface runoff → Water enters soil/groundwater or rivers → Returns to ocean. Total water on Earth is constant: it just cycles through different forms and reservoirs.

NDA 2008-II

Q. 5. Sunda Trench lies in:

(a) Atlantic Ocean

(b) Pacific Ocean

(c) Indian Ocean

(d) Antarctic Ocean

Answer: (c) Indian Ocean

Explanation: The Sunda Trench (also known as the Java Trench) is the deepest point in the Indian Ocean, located south of Java and Sumatra (Indonesia). It reaches a maximum depth of approximately 7,258 metres. It is formed by the subduction of the Indo-Australian Plate beneath the Eurasian Plate: part of the Sunda subduction zone. This makes it seismically and volcanically active. The 2004 Indian Ocean tsunami (Sumatra earthquake) originated near this trench. Concept Tested: Sunda Trench (Java Trench): deepest point in the Indian Ocean; south of Java and Sumatra

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