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English · हिन्दी · తెలుగు · தமிழ் · മലയാളം · मराठी · ಕನ್ನಡ

El Niño, the Indian Ocean Dipole, coral reefs and ocean resources

मराठीत स्पष्टीकरण

Oceanography: the ocean floor, ocean water and its movements · Part 3 / 3 · Fact-checked on · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

The normal Walker circulation and the Southern Oscillation; how El Niño and La Niña develop and affect rainfall worldwide and the Indian monsoon; the Indian Ocean Dipole and its interplay with El Niño; how coral polyps and their algae build reefs, the three types of reef, India's reef areas and coral bleaching; and the maritime zones of UNCLOS, Article 297, polymetallic nodules, the International Seabed Authority and India's Deep Ocean Mission.

Each idea is explained first in Marathi (मराठी), ending with the English and Hindi exam terms, followed by the same point in exam English. UPSC Prelims is in English or Hindi, so understand it in Marathi and revise it in English.

आतापर्यंत समुद्र नेहमी कसा वागतो ते पाहिले; आता तो नेहमीचा नमुना बदलला तर काय होते ते. घरातल्या सगळ्यांचा मूड एका व्यक्तीवर अवलंबून असतो तसा, पॅसिफिकमधल्या पाण्याचे तापमान थोडे बदलले की आपला मान्सून चांगला येईल की कमकुवत ते ठरते — हीच एल निनो, ला निना आणि हिंदी महासागर द्विध्रुवाची गोष्ट; पिके, भाव, पिण्याचे पाणी त्यावरच. मग लहान जीवांनी बांधलेली जिवंत रचना म्हणजे प्रवाळ भिंत, आणि ती पांढरी पडण्याचा धोका. शेवटी सागरी कायदा: एखाद्या देशाचा हक्क समुद्रात किती दूर, आणि खोल तळातील खनिजे कोणाची. (→ English: El Niño, coral reef · हिन्दी: एल नीनो, प्रवाल भित्ति)

In exam EnglishParts 1 and 2 described the ocean as it normally behaves. This last part looks at what happens when that normal pattern shifts, and at what the sea gives us. It begins with El Niño, La Niña and the Indian Ocean Dipole, the swings in ocean temperature that decide whether India's monsoon is generous or weak, and so touch farm output, food prices and water supply. It then turns to the coral reef, a living structure built by tiny animals in warm, clear seas, and to the threat of bleaching. It ends with the law of the sea: how far a country's control reaches into the ocean, and how the minerals of the deep seabed are shared.

सामान्य वर्षी पॅसिफिकवर व्यापारी वारे पूर्वेकडून पश्चिमेकडे वाहतात आणि उबदार पाणी इंडोनेशिया-ऑस्ट्रेलियाकडे ढकलतात — न्हाणीघरातले पाणी एका कोपऱ्यात लोटावे तसे. तिथे उबदार पाणी साचते. पेरूजवळ रिकाम्या झालेल्या जागी तळातून थंड पाणी वर येते — तोच ऊर्ध्व प्रवाह. उबदार पश्चिमेला हवा वर चढून पाऊस; थंड पूर्वेला हवा खाली उतरून कोरडेपणा. वर हवा पुन्हा पूर्वेकडे जाऊन चक्र पूर्ण — तेच वॉकर अभिसरण. भारतात हवामान वेधशाळांचे प्रमुख राहिलेल्या गिल्बर्ट वॉकर यांचे नाव त्याला. एका टोकाला हवेचा दाब वाढला की दुसऱ्या टोकाला कमी होतो, हा झोपाळ्यासारखा खेळ म्हणजे 'दक्षिणी दोलन'. (→ English: Walker circulation, Southern Oscillation · हिन्दी: वॉकर परिसंचरण, दक्षिणी दोलन)

In exam EnglishTo understand El Niño, start with a normal year in the tropical Pacific. The trade winds blow steadily from east to west, pushing warm surface water towards Indonesia and Australia, where it piles up into a deep pool of the warmest water on Earth. Off the coast of Peru, the water pushed away is replaced by upwelling cold water, which keeps the eastern Pacific cool. Over the warm west, air rises, forms clouds and brings heavy rain; over the cool east, air sinks and skies stay dry. High in the atmosphere the air returns eastward, completing a loop called the Walker circulation, after Gilbert Walker, a British scientist who headed weather observatories in India in the early twentieth century. He found a see-saw of air pressure between the eastern and western Pacific, known as the Southern Oscillation: when pressure rises at one end, it tends to fall at the other.

हे यंत्र अडखळले की येतो तो एल निनो. काही वर्षांनी व्यापारी वारे कमकुवत होतात, साचलेले उबदार पाणी पुन्हा पूर्वेकडे पसरते — झाडू थांबवल्यावर लोटलेले पाणी मागे वाहते तसे. पेरूजवळ तळातून थंड पाणी येणे कमी होते, समुद्र तापतो, आणि थंड पाण्यावर जगणारे अँकोव्ही मासे दुर्मीळ होतात. स्पॅनिशमध्ये अर्थ 'लहान मुलगा'; नाताळच्या सुमारास उबदार पाणी येताना पाहणाऱ्या पेरूच्या मच्छीमारांनी दिलेले नाव. समुद्रातला बदल आणि हवेच्या दाबाचा झोका ही एकाच नाण्याच्या दोन बाजू, म्हणून मिळून ENSO. दोन ते सात वर्षांनी, अनियमितपणे येतो; साधारण वर्षभर टिकतो. (→ English: El Niño, ENSO · हिन्दी: एल नीनो, एल नीनो–दक्षिणी दोलन)

In exam EnglishEl Niño is what happens when this machine falters. Every few years the trade winds weaken, or even reverse in the western Pacific, and the pool of warm water spreads eastward across the central and eastern Pacific. Upwelling off Peru weakens, the coastal sea warms, and the fish that depend on cold, nutrient-rich water, such as anchovies, become scarce. The name, Spanish for 'the little boy' and a reference to the Christ child, comes from Peruvian fishermen who noticed warm water arriving around Christmas. Because the ocean change and the swing in air pressure are two sides of one event, scientists join them as ENSO, El Niño–Southern Oscillation. El Niño recurs irregularly, roughly every two to seven years, and an episode usually lasts nine to twelve months. NOAA declares El Niño conditions when the surface of the central equatorial Pacific stays at least 0.5°C warmer than its long-term average, along with matching changes in the atmosphere.

उबदार पाणी आणि त्याचे पावसाळी ढग पूर्वेकडे सरकले की पावसाची वाटणी बदलते: नेहमी कोरड्या पेरूत पूर, इंडोनेशिया-ऑस्ट्रेलियात दुष्काळ आणि वणवे. आपल्यासाठी महत्त्वाचा मान्सून. वर चढणारी हवा पॅसिफिककडे गेली की आपल्यावर हवा खाली उतरते, ढग कमी — म्हणून एल निनो वर्षी पाऊस कमी, दुष्काळाची शक्यता जास्त. पण ही फक्त 'शक्यता', पक्का नियम नाही — आभाळ भरून आले म्हणजे पाऊस नक्की असे नाही ना; हिंदी महासागरासारखे इतर घटकही काम करतात. म्हणूनच IMD दरवर्षी अंदाज देण्याआधी पॅसिफिकवर लक्ष ठेवते. (→ English: El Niño, monsoon · हिन्दी: एल नीनो, मानसून)

In exam EnglishWhen the warm pool and its rain clouds shift east, rainfall patterns change across much of the tropics. Peru and Ecuador, normally dry, can receive heavy rain and floods, while Indonesia and eastern Australia often suffer drought and forest fires. For India the key effect is on the south-west monsoon. With rising air and cloud displaced towards the central Pacific, air tends to sink over the Indian region, so El Niño years are more likely to bring a weak monsoon and drought. The link is a tendency, not a rule: some El Niño years have still brought near-normal rain, while some weak monsoons came without El Niño, because other factors, including the Indian Ocean itself, also play a part. That is why the India Meteorological Department watches the Pacific closely before it issues its monsoon forecasts each year.

ला निना म्हणजे 'लहान मुलगी' — एल निनोच्या अगदी उलट. व्यापारी वारे नेहमीपेक्षा जोरात वाहतात, आणखी उबदार पाणी पश्चिमेकडे जाते, पेरूजवळ थंड पाणी जास्त वर येते, पूर्व पॅसिफिक अधिक थंड होतो. पश्चिम पॅसिफिकवर वर चढणारी हवा बळकट होते; आपल्याला साधारणपणे चांगला किंवा जास्त मान्सून, कधी पूरही. दोघांच्या मध्ये 'तटस्थ' वर्षे. घड्याळाच्या लंबकासारखे समजा: एका टोकाला एल निनो, दुसऱ्या टोकाला ला निना, बरीच वर्षे मध्येच. (→ English: La Niña · हिन्दी: ला नीना)

In exam EnglishLa Niña, 'the little girl', is the opposite phase. The trade winds blow harder than usual, more warm water is driven west, upwelling off Peru strengthens and the central and eastern Pacific turn cooler than normal. The rising branch of the Walker circulation over the western Pacific becomes stronger, and for India this usually means a normal or above-normal monsoon, though it can also bring floods. La Niña tends to bring wetter conditions to Indonesia and Australia and drier ones to parts of the Americas. Between the two phases lie neutral years, when neither pattern is established. A useful way to see the whole system is as a pendulum: El Niño and La Niña are its two extremes, and in many years the ocean sits near the middle.

आपल्या हिंदी महासागरातही एक झोका आहे — तोच हिंदी महासागर द्विध्रुव. अरबी समुद्र-आफ्रिकेकडच्या (पश्चिम) पाण्याच्या तापमानाची तुलना सुमात्रा-जावाकडच्या (पूर्व) पाण्याशी करतात. 'धन' अवस्थेत पश्चिम उबदार, पूर्व थंड — पावसाचे ढग पश्चिमेकडे, आपल्या मान्सूनला बळ, आफ्रिकेत मुसळधार, इंडोनेशिया कोरडा. 'ऋण' अवस्थेत उलटे होऊन मान्सून कमकुवत. संघात एक गोलंदाज अपयशी ठरला तरी दुसरा सावरतो तसे — 1997 मध्ये जोरदार एल निनो असूनही धन द्विध्रुवाने आपल्याला दुष्काळापासून वाचवले. (→ English: Indian Ocean Dipole · हिन्दी: हिंद महासागर द्विध्रुव)

In exam EnglishIndia's own ocean has a see-saw too. The Indian Ocean Dipole (IOD) compares the sea-surface temperature of the western tropical Indian Ocean, near the Arabian Sea and East Africa, with that of the eastern part, near Sumatra and Java. In a positive phase the west is warmer than usual and the east cooler; rising air and rain shift towards the west, which tends to strengthen the Indian monsoon and bring heavy rain to East Africa, while Indonesia and Australia turn dry. A negative phase reverses this and tends to weaken the monsoon. The dipole was described by scientists in 1999 and usually develops around the middle of the year, peaking in September or October. Its importance for exams lies in its interplay with El Niño: in 1997 a strong positive IOD helped India escape the drought that a powerful El Niño might otherwise have brought.

प्रवाळ भिंत बांधतात ते दगड नव्हे, जीव. प्रत्येक प्रवाळ कीटक हा छोटा जीव; समुद्राच्या पाण्यातून चुना घेऊन स्वतःभोवती कठीण घर बांधतो — हजारो वर्षांत लाखो घरे साचून भिंत तयार होते, मुंग्या वारूळ बांधतात तशी. त्याच्या शरीरात सूक्ष्म शेवाळ (झूझँथेली) राहते: सूर्यप्रकाशाने अन्न तयार करून प्रवाळाला देते, रंगही देते; प्रवाळ त्याला घर देतो — घरमालक आणि भाडेकरू एकमेकांना मदत करतात तसे. म्हणून उबदार, स्वच्छ, उथळ, खारे पाणी लागते; गढूळ नदीमुखे आणि थंड खोल पाणी चालत नाही. (→ English: coral reef, coral polyp · हिन्दी: प्रवाल भित्ति, प्रवाल पॉलिप)

In exam EnglishA coral reef is built by animals. Each coral polyp is a tiny creature, related to sea anemones and jellyfish, that draws calcium carbonate from sea water to build a hard limestone cup around itself; over thousands of years millions of these skeletons pile up into reefs. Inside the polyp's tissue live microscopic algae called zooxanthellae. The algae use sunlight to make food, share it with the coral and give it colour, while the coral gives them shelter. Because of this partnership, reef-building corals need warm, clear, shallow and salty water, mostly within the tropics, where sunlight reaches the algae. Muddy river mouths and very deep or cold water do not suit them.

भिंती तीन प्रकारच्या. किनाऱ्याला चिकटून वाढते ती किनारी भिंत — घराच्या भिंतीला लागून वाढणाऱ्या वेलीसारखी. किनाऱ्याला समांतर, मध्ये रुंद खोल खाजणाने दूर असते ती अडथळा भिंत — गावापासून थोड्या अंतरावर बांधलेल्या तटबंदीसारखी; ऑस्ट्रेलियातली ग्रेट बॅरियर रीफ जगातली सर्वात मोठी. मध्ये जमीन नसताना खाजणाभोवती अंगठीसारखी असते ती कंकणद्वीप (अ‍ॅटॉल) — बहुधा समुद्रात हळूहळू बुडालेल्या ज्वालामुखी बेटाभोवती. आपल्या देशात मन्नार आणि कच्छच्या आखातात किनारी भिंती, लक्षद्वीप कंकणद्वीपे, अंदमान-निकोबारमध्ये विस्तृत किनारी भिंती. (→ English: coral reef, atoll · हिन्दी: प्रवाल भित्ति, एटॉल)

In exam EnglishReefs come in three main forms. A fringing reef grows close to the shore with little or no water between it and the land. A barrier reef runs parallel to the coast but is separated from it by a wide, deep lagoon; the Great Barrier Reef off Queensland in Australia is the largest reef system in the world. An atoll is a ring or horseshoe of reef enclosing a lagoon, with no central land; it often forms around a volcanic island that has slowly sunk beneath the sea. India has reefs in four main areas: the Gulf of Mannar and the Gulf of Kachchh, which have fringing reefs, the Lakshadweep islands, which are atolls, and the Andaman and Nicobar Islands, which have extensive fringing reefs.
Three types of coral reef
TypeFormExample
Fringing reefGrows close to the shore, little or no lagoonGulf of Mannar, Gulf of Kachchh, Andaman and Nicobar
Barrier reefParallel to the coast, separated by a wide, deep lagoonGreat Barrier Reef, Australia
AtollRing of reef around a lagoon, no central landLakshadweep

पाणी आठवडेभर नेहमीपेक्षा गरम राहिले की प्रवाळ ताणाखाली येऊन आतले शेवाळ बाहेर टाकतो; रंग देणारे शेवाळ गेले की आतले पांढरे चुन्याचे घर दिसते — तेच प्रवाळ विरंजन. ताप आलेला माणूस मेला असे नाही ना: उष्णता लवकर कमी झाली तर शेवाळ परत येते आणि प्रवाळ सावरतो; उष्णता जास्त काळ टिकली तर अन्नाशिवाय मरू शकतो. प्रदूषण, जमिनीवरून येणारा गाळ हीही कारणे. समुद्र तापत असल्याने हे वारंवार घडते; एल निनो वर्षांनी जगभरच्या घटनांना चालना दिली. एप्रिल 2024 मध्ये NOAA ने चौथ्या जागतिक घटनेची पुष्टी केली. (→ English: coral bleaching · हिन्दी: प्रवाल विरंजन)

In exam Englishcoral bleaching happens when corals are stressed, above all by water that stays unusually warm for weeks. The stressed polyps expel their algae, and without them the white limestone skeleton shows through the clear tissue. A bleached coral is not yet dead: if temperatures fall soon, the algae can return and the coral recovers, but prolonged heat leaves it starving and it may die. Pollution, sediment from the land and very low tides can also cause bleaching. Warming seas have made mass bleaching more frequent, and El Niño years, which heat large areas of tropical ocean, have triggered several worldwide episodes. In April 2024 NOAA confirmed the fourth global bleaching event on record.

समुद्र कोणाचा? 1982 चा संयुक्त राष्ट्र सागरी कायदा करार (UNCLOS) किनाऱ्यापासून सागरी मैलांत पट्टे पाडतो — घराचे अंगण, कुंपण, रस्ता, गावची वेस तसे. 12 मैलांपर्यंत प्रादेशिक जलक्षेत्र: देश पूर्ण मालक, पण परदेशी जहाजे निरुपद्रवीपणे जाऊ शकतात. 24 मैलांपर्यंत संलग्न क्षेत्र: सीमाशुल्क, कर, स्थलांतर, आरोग्य कायदे लागू करता येतात. 200 मैलांपर्यंत अनन्य आर्थिक क्षेत्र: मासे, तेल, खनिजांवर देशाचा हक्क, इतर देश जहाजे चालवू, विमाने उडवू शकतात. आपल्या संविधानात अनुच्छेद 297 ही संपत्ती संघाकडे सोपवतो. (→ English: territorial waters, exclusive economic zone · हिन्दी: राज्यक्षेत्रीय सागर-खंड, अनन्य आर्थिक क्षेत्र)

In exam EnglishWho owns the sea? The United Nations Convention on the Law of the Sea (UNCLOS), adopted in 1982 and in force since 1994, divides it into zones measured from a baseline along the coast, in nautical miles (one nautical mile is about 1.85 km). The territorial waters extend up to 12 nautical miles; here the coastal state is sovereign, though foreign ships keep a right of innocent passage. The contiguous zone extends to 24 nautical miles, where the state may enforce its customs, tax, immigration and health laws. The exclusive economic zone reaches 200 nautical miles: the state has sovereign rights over fish, oil, gas and minerals, while other countries may still sail and fly through. In India, Article 297 of the Constitution vests all land, minerals and things of value in the territorial waters, the continental shelf and the exclusive economic zone in the Union.
Maritime zones under UNCLOS (measured from the baseline)
ZoneExtentRights of the coastal state
Territorial watersUp to 12 nautical milesFull sovereignty; innocent passage for foreign ships
Contiguous zoneUp to 24 nautical milesEnforce customs, tax, immigration and health laws
Exclusive economic zoneUp to 200 nautical milesSovereign rights over living and mineral resources; others may navigate and overfly
High seas and the AreaBeyond national zonesOpen to all; seabed minerals are common heritage, managed by the International Seabed Authority

देशांचे पट्टे ओलांडले की खोल समुद्रतळ — तो 'मानवजातीचा सामायिक वारसा', गावच्या सार्वजनिक तळ्यासारखा कोणाच्या एकट्याचा नाही. त्याची देखरेख जमैकातील आंतरराष्ट्रीय समुद्रतळ प्राधिकरण करते, शोधासाठी परवाने देते. तिथे बटाट्याएवढे बहुधातू गोळे पसरलेले असतात — मँगनीज, निकेल, कोबाल्ट, तांबे, बॅटरीसाठी लागणारे धातू. 1987 मध्ये या गोळ्यांसाठी 'पायोनियर इन्व्हेस्टर' म्हणून नोंदलेला पहिला देश भारत; मध्य हिंदी महासागरात शोध करार आहे. 2021 मध्ये मंजूर झालेल्या डीप ओशन मिशनचा भाग समुद्रयान: तिघांना 6,000 मीटर खोल नेणारी 'मत्स्य-6000'. (→ English: polymetallic nodules, Deep Ocean Mission · हिन्दी: बहुधात्विक पिंड, गहन महासागर मिशन)

In exam EnglishBeyond national zones lies the deep seabed, which UNCLOS calls the common heritage of mankind. Its minerals are managed by the International Seabed Authority, based in Kingston, Jamaica, which grants contracts for exploration. The best-known resource is polymetallic nodules: potato-sized lumps scattered over the abyssal plains and rich in manganese, nickel, cobalt and copper, metals needed for batteries and electronics. India was the first country to be registered as a pioneer investor for nodules, in 1987, and holds an exploration contract with the Authority in the Central Indian Ocean Basin. To go further, the Union Cabinet approved the Deep Ocean Mission of the Ministry of Earth Sciences in 2021. Its parts include deep-sea mining technology and Samudrayaan, a crewed submersible, MATSYA-6000, being built by the National Institute of Ocean Technology in Chennai to carry three people to a depth of 6,000 metres.

या भागात समुद्र हा हवेचा भागीदार आणि एक संपत्तीही. एल निनो आणि ला निना एकाच पॅसिफिक झोक्याची दोन टोके; हिंदी महासागर द्विध्रुव आपल्या जवळचा दुसरा झोका — घरातल्या आजोबांचा राग आई शांत करते तसा, तो एल निनोचा तडाखा कमी किंवा जास्त करू शकतो. प्रवाळ भिंतींना उबदार स्वच्छ पाणी लागते, पण अति उष्णता त्यांना पांढरे पाडते. सागरी कायदा कोणाला काय ते सांगतो: 12 मैलांपर्यंत सार्वभौमत्व, 200 पर्यंत संपत्तीवर हक्क, खोल तळ सगळ्यांचा. तिन्ही भाग मिळून समुद्राचे पूर्ण चित्र. (→ English: El Niño, Indian Ocean Dipole · हिन्दी: एल नीनो, हिंद महासागर द्विध्रुव)

In exam EnglishThis part shows the ocean as a partner of the atmosphere and as a resource. El Niño and La Niña are two swings of one Pacific system, read through sea temperatures and the Southern Oscillation, and the Indian Ocean Dipole adds a second, closer influence that can soften or sharpen El Niño's effect on India's monsoon. Coral reefs depend on warm, clear water, and the same warming that drives strong El Niño years pushes them towards bleaching. The law of the sea then decides who may use what: sovereignty to 12 nautical miles, control of resources to 200, and a shared deep seabed managed for all. Together with Parts 1 and 2, this completes the picture of the oceans: their floor, their water, its movements and their place in India's weather and economy.

Exam traps

Recap

Practice questions

Q1. During an El Niño event, which one of the following usually happens?

  1. The trade winds over the tropical Pacific become stronger than normal
  2. Upwelling of cold water off the coast of Peru weakens
  3. The central and eastern Pacific become cooler than normal
  4. Indonesia receives unusually heavy rainfall
Show answer

Answer: B. Upwelling of cold water off the coast of Peru weakens

In El Niño the trade winds weaken, warm water spreads east and the upwelling of cold water off Peru weakens. Stronger trade winds and a cooler eastern Pacific describe La Niña, not El Niño. Indonesia usually turns dry during El Niño because the rain clouds shift east, so heavy rain there is the opposite of the typical effect.

Q2. Consider the following statements:
1. A positive Indian Ocean Dipole is marked by a warmer western and a cooler eastern tropical Indian Ocean.
2. A positive Indian Ocean Dipole tends to weaken the Indian south-west monsoon.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: A. 1 only

Statement 1 is correct: in the positive phase the western Indian Ocean, near the Arabian Sea and East Africa, is warmer than usual and the east, near Sumatra and Java, is cooler. Statement 2 is wrong: a positive dipole tends to strengthen the Indian monsoon, and it helped offset El Niño in 1997; it is the negative phase that tends to weaken it. So '2 only' and 'both' are wrong, and 'neither' rejects a true statement.

Q3. The term 'Southern Oscillation' refers to

  1. a see-saw of air pressure between the eastern and western tropical Pacific
  2. the seasonal reversal of currents in the north Indian Ocean
  3. the eastward flow of water around Antarctica
  4. the alternation of spring and neap tides
Show answer

Answer: A. a see-saw of air pressure between the eastern and western tropical Pacific

The Southern Oscillation, described by Gilbert Walker, is the see-saw of surface air pressure across the tropical Pacific; joined with El Niño it forms ENSO. The monsoon reversal of north Indian Ocean currents, the West Wind Drift around Antarctica and the cycle of spring and neap tides are different phenomena with no link to this term.

Q4. Consider the following statements about corals:
1. Corals are plants that make their own food by photosynthesis.
2. A bleached coral is not necessarily dead and can recover if the stress ends soon.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: B. 2 only

Statement 1 is wrong: corals are animals related to jellyfish and sea anemones; it is the algae (zooxanthellae) living in their tissue that photosynthesise. Statement 2 is correct: bleaching means the algae have been expelled, and if temperatures fall soon the algae can return and the coral recovers. So '1 only' and 'both' include a false statement, and 'neither' rejects a true one.

Q5. Match the following:
A. Atoll — 1. Great Barrier Reef
B. Barrier reef — 2. Lakshadweep
C. Fringing reef — 3. Gulf of Kachchh
Select the correct answer using the code given below:

  1. A-2, B-1, C-3
  2. A-1, B-2, C-3
  3. A-3, B-1, C-2
  4. A-2, B-3, C-1
Show answer

Answer: A. A-2, B-1, C-3

Lakshadweep is made of atolls, the Great Barrier Reef off Australia is a barrier reef, and the Gulf of Kachchh has fringing reefs. The second code wrongly calls the Great Barrier Reef an atoll and Lakshadweep a barrier reef; the third makes the Gulf of Kachchh an atoll; the fourth swaps the barrier and fringing examples.

Q6. Under the United Nations Convention on the Law of the Sea, a coastal state may enforce its customs and immigration laws in the contiguous zone, which extends up to how many nautical miles from the baseline?

  1. 12
  2. 24
  3. 200
  4. 350
Show answer

Answer: B. 24

The contiguous zone extends up to 24 nautical miles. Twelve nautical miles is the limit of the territorial waters, 200 is the limit of the exclusive economic zone, and 350 is the outer cap that can apply to a continental shelf extending beyond 200 miles, not to the contiguous zone.

Q7. Consider the following statements:
1. Under Article 297 of the Constitution of India, things of value in the exclusive economic zone vest in the Union.
2. In its exclusive economic zone a coastal state may bar foreign ships from navigating.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: A. 1 only

Statement 1 is correct: Article 297 vests all lands, minerals and other things of value in the territorial waters, the continental shelf and the exclusive economic zone in the Union. Statement 2 is wrong: in the EEZ the coastal state has sovereign rights over resources, but other countries keep freedom of navigation and overflight. So '2 only' and 'both' are wrong, and 'neither' rejects a true statement.

Q8. With reference to India's activities in the deep ocean, consider the following statements:
1. India holds an exploration contract with the International Seabed Authority for polymetallic nodules in the Central Indian Ocean Basin.
2. MATSYA-6000 is a crewed submersible being developed under the Deep Ocean Mission.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: C. Both 1 and 2

Both statements are correct. India, the first registered pioneer investor for nodules (1987), holds an exploration contract with the International Seabed Authority in the Central Indian Ocean Basin, and MATSYA-6000, the vehicle of Samudrayaan under the Deep Ocean Mission, is designed to carry three people to 6,000 metres. So '1 only', '2 only' and 'neither' each leave out a true statement.

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