Indian Ocean – Relief and Strategic Importance
Short Questions
1. What is the average depth of the Indian Ocean?
Answer: The average depth of the Indian Ocean is approximately 4,000 meters.
2. Which ocean is named after a country?
Answer: The Indian Ocean is named after India.
3. What is the continental shelf?
Answer: It is the submerged portion of continents under oceanic water, hosting gulfs, seas, and bays.
4. Name one mid-oceanic ridge in the Indian Ocean.
Answer: The Mid-Indian Oceanic Ridge.
5. Why is the Ninety East Ridge so named?
Answer: It is named for its proximity to the 90°E longitude.
6. Which is the largest island in the Arabian Sea?
Answer: Madagascar is the largest island in the Arabian Sea.
7. Name one ocean basin in the Indian Ocean.
Answer: The Ganga Basin.
8. What is the deepest trench in the Indian Ocean?
Answer: The Java/Sunda Trench, with a depth of 7,450 meters.
9. Why is salinity lower in the Bay of Bengal?
Answer: It is lower due to freshwater inflow from rivers like the Ganga and heavy monsoon rainfall.
10. What drives ocean currents in the northern Indian Ocean?
Answer: Seasonal monsoon winds drive the ocean currents.
11. Name a cold current in the Indian Ocean.
Answer: The West Australian Current.
12. What is the Strait of Hormuz known for?
Answer: It is a key route for 30% of global oil exports.
13. What are poly-metallic nodules?
Answer: They are mineral deposits on abyssal plains containing nickel, copper, manganese, and cobalt.
14. Why is India’s location in the Indian Ocean strategic?
Answer: Its central position facilitates control over key maritime trade and energy routes.
15. What is the primary economic activity of Maldives in the Indian Ocean?
Answer: Marine tourism and the marine ecosystem drive the economy of the Maldives.
Long Questions
1. Explain the variation in the width of the continental shelf in the Indian Ocean.
Answer: The continental shelf in the Indian Ocean varies widely, being extensive along the western coast of India due to significant sediment deposition from terrestrial erosion. In contrast, it is narrower along the eastern coast of India, eastern Africa, Madagascar, and Indonesia (about 160 km) due to limited sediment supply. These variations are influenced by coastal geomorphology and the volume of riverine sediment input.
2. Why is the eastern coastal part of the Indian Ocean seismically active?
Answer: The eastern coastal part of the Indian Ocean is seismically active due to its location along the converging boundary between the Indo-Australian and Pacific plates. This tectonic interaction causes frequent earthquakes and volcanic activity, particularly around features like the Java/Sunda Trench. The subduction process in this region makes it prone to significant geological disturbances.
3. Describe the formation of a gyre in the Southern Indian Ocean.
Answer: A gyre in the Southern Indian Ocean is formed by the South Equatorial Current flowing east to west under easterlies and the West Wind Drift moving west to east under westerlies. The circulation is completed by the Mozambique-Agulhas currents in the west and the West Australian Current in the east. This large-scale oceanic circulation is driven by wind patterns and the ocean’s geographical configuration.
4. Why does the Arabian Sea record higher salinity than the Bay of Bengal?
Answer: The Arabian Sea has higher salinity due to high temperatures, low rainfall, and limited river inflow near the Somali Peninsula and Saudi Arabia, leading to greater evaporation. In contrast, the Bay of Bengal receives substantial freshwater from the Ganga and peninsular rivers, especially during the southwest monsoon, which dilutes its salinity. This contrast is most pronounced during the monsoon season.
5. How do ocean currents in the northern Indian Ocean differ between seasons?
Answer: In the northern Indian Ocean, ocean currents reverse seasonally due to monsoon winds, flowing clockwise during the southwest monsoon and anticlockwise during the northeast monsoon. These currents follow coastlines and are influenced by the monsoon wind system’s direction. The reversal facilitates water mixing and impacts regional climate patterns.
6. What is the significance of the Strait of Hormuz in global trade?
Answer: The Strait of Hormuz, linking the Persian Gulf to the Arabian Sea, is a critical chokepoint for global oil trade, handling about 30% of the world’s oil exports. Its strategic location between Iran and Oman makes it vital for energy supplies from Gulf countries. Any disruption here could significantly impact global energy markets.
7. How does the Indian Ocean contribute to India’s energy security?
Answer: India relies on the Indian Ocean for 70% of its oil imports, primarily from Gulf countries, transported via routes like the Strait of Hormuz. The ocean’s offshore areas, such as those near India and Saudi Arabia, also provide significant hydrocarbon reserves. Securing these maritime routes is crucial for India’s energy needs and economic stability.
8. Describe the role of mid-oceanic ridges in the Indian Ocean’s relief.
Answer: Mid-oceanic ridges, like the Mid-Indian Oceanic Ridge, are submerged mountain ranges that separate deep ocean floor portions, formed by tectonic and volcanic processes. The Mid-Indian Ridge originates in the Gulf of Aden, splits near Madagascar, and is discontinuous due to fracture zones like Owen and Amsterdam. These ridges shape the ocean’s topography and influence current patterns.
9. Why are temperatures higher in the pre-monsoon season in the northern Indian Ocean?
Answer: Temperatures in the northern Indian Ocean are higher during the pre-monsoon season due to increased solar insolation as the summer solstice approaches, especially near the equator. The equatorial region receives intense solar radiation, elevating sea surface temperatures. This pattern changes with the onset of monsoon winds, which cool areas like the Arabian Sea.
10. Evaluate the economic importance of the Indian Ocean for island nations like the Maldives.
Answer: The Indian Ocean is the economic lifeline for island nations like the Maldives, whose economies heavily depend on marine tourism and the marine ecosystem. Activities such as fishing, coral reef tourism, and marine-based recreation drive their GDP. The ocean’s strategic location also supports trade and connectivity, enhancing their economic prospects.
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