Class 9 Social Science Part 2 Chapter 1: Oceans and Life | Question Answers, Easy Notes, MCQ (English Medium)
Part 2 · Chapter 1: Oceans and Life
The complete chapter in simple English – for school and board exams
🎯 The Big Questions
- What is the importance of ocean relief?
- How does ocean water movement impact life and environment?
- Why are maritime zones important for a country?
- How can we use ocean resources in a sustainable way?
- How do early warning systems help protect people from tsunamis and cyclones?
(A) In-text questions
Q 1. Observe Fig. 1.2. (a) How were these ocean floor features formed? (b) Which parts of the ocean are deep and which are shallow? (c) How might these features affect marine life and ocean movements?
(a) They were formed by forces inside the Earth. Where plates move apart, magma rises and builds the mid-ocean ridge. Where one plate sinks under another, a deep trench forms. Volcanoes build seamounts and volcanic islands. Deposition of sediments and erosion also shape the floor.
(b) The continental shelf near the coast is the shallowest. Depth increases sharply on the continental slope. Abyssal plains are very deep, and ocean trenches are the deepest parts.
(c) Sunlight reaches the shallow shelf, so it is rich in fish and other marine life. Ridges, seamounts and trenches change the path of ocean currents and spread nutrients. Different depths give homes to different kinds of marine organisms.
Q 2. Find out the names of some famous sea beaches in our country and locate them on the map of India.
Marina Beach – Chennai (Tamil Nadu), Juhu Beach – Mumbai (Maharashtra), Calangute Beach – Goa, Kovalam Beach – Thiruvananthapuram (Keralam), Puri Beach – Odisha, Radhanagar Beach – Swaraj Dweep (Andaman), Digha Beach – West Bengal, Rushikonda Beach – Visakhapatnam (Andhra Pradesh), Gokarna Beach – Karnataka.
On the map: west coast – Juhu, Calangute, Gokarna, Kovalam; east coast – Digha, Puri, Rushikonda, Marina; Bay of Bengal islands – Radhanagar.
Q 3. Observe Fig. 1.5. Do you notice the oval layer around the Earth indicating water level? Can you see how the water level rises during high tide and falls during low tide?
Yes. The oval (bulging) layer is ocean water. On the side facing the Moon (and Sun), and on the exactly opposite side, water bulges out – these places have high tide. Water is pulled away from the places in between – they have low tide.
When the Sun, Earth and Moon are in a straight line, the bulge is larger (spring tide). When they are at right angles, the bulge is smaller (neap tide).
Q 4. Observe the map (Fig. 1.9) carefully and note the movement patterns of cold and warm currents. Do you think these currents affect the temperature of nearby coastal regions?
Yes. Warm currents generally flow from the equator towards the poles, and cold currents from the poles towards the equator.
A warm current keeps its coast warm – for example, the Gulf Stream keeps Norway's waters warm, so sea ice does not form easily even at 60°–70° N.
A cold current cools its coast – for example, the Labrador Current brings freezing water along the east coast of Canada, so sea ice and icebergs form even at lower latitudes.
Q 5. Observe Fig. 1.9 and take a note on ocean currents along the coastline of India. What is the nature of ocean currents?
The currents around India (northern Indian Ocean) are mostly warm, as the region lies in the tropics. Near the equator flow the South Equatorial Current and the Equatorial Counter Current.
Their special feature is that they change direction with the seasons. As the monsoon winds reverse, the currents also reverse – they flow clockwise in summer (south-west monsoon) and anticlockwise in winter (north-east monsoon).
Further away lie the Agulhas (warm) current near Africa and the West Australian (cold) current near Australia.
Q 6. During the 2004 tsunami, Simeulue Island in Indonesia was largely spared because of local folklore. Talk to your elders – do similar folk traditions or stories related to natural disasters exist in your culture? Share and discuss how traditional knowledge can help communities stay safe.
On Simeulue, people had heard for generations: "If the earth shakes and the sea goes back, run to the hills." Because of this, very few people died there.
India has similar examples – tribes of the Andaman Islands (such as the Onge and Jarawa) moved to higher ground in 2004 after watching the sea. In villages, people say that ants carrying eggs uphill, restless birds and animals, or loud croaking of frogs signal rain or a storm.
Lesson: traditional knowledge teaches people to read danger signs early. Combined with modern warning systems, it saves even more lives.
Q 7. If you receive a tsunami or cyclone alert on your phone right now, do you know the five steps your family should take to stay safe?
1. Stay calm, read or listen to the official warning carefully and ignore rumours.
2. Keep an emergency kit ready – water, dry food, medicines, torch, charged phone, important documents.
3. For a tsunami, move away from the coast to high ground immediately; for a cyclone, stay in a strong building or a cyclone shelter.
4. Follow the evacuation route given by the authorities; help children, the elderly and persons with disabilities.
5. Do not return until officials say it is safe; keep following updates on radio/mobile. Never go to the beach to watch the waves.
Q 8. Maritime disputes are conflicts between countries over territory, resources or rights in oceans, seas or coastal regions. Can you find out some countries that have conflicts over their territorial sea waters?
South China Sea – China, Vietnam, the Philippines, Malaysia, Brunei and Taiwan.
East China Sea (Senkaku/Diaoyu Islands) – China and Japan.
Sir Creek (Arabian Sea, Kachchh) – India and Pakistan.
Aegean Sea – Greece and Turkey.
The India–Bangladesh maritime boundary dispute in the Bay of Bengal was settled peacefully by an international tribunal in 2014 – showing how rules like UNCLOS help resolve disputes.
(B) Questions and activities
Q 1. How do different features of the ocean floor affect fishing, transport and exploration?
Fishing: The continental shelf is shallow; sunlight reaches it and plankton grows well. So most of the world's fish are caught on the shelf. Fish also gather near seamounts.
Transport: Ships need enough depth. Shallow areas, rocks and seamounts can be dangerous, so sea routes are planned by checking the depth of the ocean floor. Ridges and trenches also make laying undersea cables and pipelines difficult.
Exploration: Oil and natural gas are found on the shelf, so drilling there is easier. Exploring deep trenches and ridges is hard and costly, but deep-sea minerals may be found there.
Q 2. How do waves, tides and ocean currents influence climate, marine life and human activities? Give examples.
Waves: They erode coasts to form caves, arches and stacks, and deposit sand to form beaches. Storm waves and tsunamis cause heavy damage, e.g., the 2004 tsunami.
Tides: High tide helps large ships enter harbours; VLCCs wait for high tide in the Singapore Strait. Fish come closer to the shore at high tide, helping fishers. Tides can generate electricity – Gulf of Kutch, Gulf of Khambhat, Sundarbans.
Currents: The warm Gulf Stream keeps Norway's coast warm; the cold Labrador Current cools Canada's east coast. Where warm and cold currents meet, rich fishing grounds form. Currents also affect ship journeys.
Q 3. Why are marine resources important?
Food and livelihood: Fish and seafood give protein to millions; fishing and aquaculture provide jobs.
Minerals and materials: Sand, gravel and deep-sea minerals.
Energy: Offshore oil and natural gas; clean 'blue energy' from tides, waves and offshore wind.
Trade and tourism: About 90% of global trade by volume moves by sea; coastal tourism is a multi-billion industry.
Culture and environment: The śaṅkha (conch), kapardikā (cowrie, once used as money) and the story of Samudra Manthana link the sea to our culture. Coral reefs protect biodiversity.
So they must be used responsibly so that future generations can also benefit.
Q 4. Create a poster on conservation of marine resources with a slogan like 'Save Our Seas' or 'Fish for the Future', and explain in 2–3 sentences why it is important.
Slogan: "Our Sea, Our Future – Save Our Seas!" (Option: "Fish Today, Food Tomorrow – Fish for the Future")
Poster idea: One side shows a clean blue sea with fish and corals; the other side shows a sea polluted with plastic and oil. The slogan goes in the middle.
Message: The sea gives us food, jobs and oxygen. Plastic waste, oil spills and overfishing are destroying marine life. Only if we save the seas today will future generations have food and livelihoods.
Q 5. Mark five coastal states of India that need tsunami warnings on the map of India.
Tamil Nadu, Andhra Pradesh, Keralam, Odisha and West Bengal (along with the Union Territories of Puducherry and the Andaman & Nicobar Islands).
Tamil Nadu, Puducherry, Andhra Pradesh, Keralam and the Andaman & Nicobar Islands were the worst affected in 2004. Gujarat, Maharashtra, Goa and Karnataka are coastal states on the west coast.
Map tip: shade the east-coast states in one colour and the affected Union Territories in another.
Q 6. In groups, role-play a cyclone warning – some students act as scientists, some as officials and some as villagers. Show how warnings are given and how people prepare.
Scene 1 – Scientists (IMD/INCOIS): "Satellites show a cyclone forming in the Bay of Bengal. It will hit the coast in 48 hours with winds up to 150 km/h."
Scene 2 – Officials (District Collector/Disaster Management): Send warnings by SMS, radio and loudspeakers; tell fishers not to go to sea; open cyclone shelters; arrange buses.
Scene 3 – Villagers/Fishers: Tie boats safely, pack an emergency kit, move to the shelter with children and elders, shift animals to safety.
Scene 4 – After: Return only after the all-clear; report damage. Lesson – timely warning + people's preparation = lives saved.
Q 7. Which principle allows a foreign ship to pass through India's territorial sea? What are its conditions?
The principle of Innocent Passage.
Conditions: the ship must not threaten India's peace, good order or security; it must move continuously without stopping (except in emergencies or breakdowns); it cannot fish, carry out military operations or any non-peaceful activity.
Q 8. What rights does a country have in its Exclusive Economic Zone (EEZ) up to 200 nautical miles?
In the EEZ a country has special rights to use ocean resources – fishing, extracting oil and natural gas, exploring minerals and producing ocean energy.
These rights are given under the United Nations Convention on the Law of the Sea (UNCLOS).
But the country does not fully own or control these waters – ships of other countries may still pass through peacefully.
Q 9. Make a model of the ocean showing ship routes, protected zones and safety measures, and explain how it follows maritime laws.
Materials: thermocol/cardboard, blue paint, clay, paper ships, small flags, thread.
Show: coast → baseline → territorial sea (12 NM) → contiguous zone (24 NM) → EEZ (200 NM) → high seas; fixed shipping lanes, marine protected areas (coral reef, mangroves), tsunami buoy, lighthouse, coast-guard boat.
How it follows laws: ships follow fixed lanes and collision rules (COLREGs); no fishing in protected areas; ships do not dump oil or waste (MARPOL); foreign ships cross the territorial sea under innocent passage.
1. Introduction – The Dynamic Ocean System
Oceans are not just huge stores of water. They are linked to our climate, living world, trade, transport, energy and resources. In Indian culture the ocean is called Samudra and is seen as vast, powerful and sacred.
- Ocean water is always in motion – waves, tides and currents shape our climate, support marine life and carry heat and nutrients.
- Gravity creates tides – the pull of the Moon and the Sun makes ocean water rise and fall regularly; this affects navigation, coastal environments and energy production.
- The ocean floor is a hidden landscape – there are mountains, plains and deep trenches under water, called ocean (submarine) relief.
- Blue Economy – sustainable use of oceans that give fish, energy, minerals and trade routes.
- Early warning systems save lives – seismic sensors and satellites detect tsunamis and cyclones early.
- Maritime zones set the rules – the United Nations Convention on the Law of the Sea (UNCLOS) decides how far a country can use the sea's resources.
2. Ocean Relief
Just like land has mountains, plateaus, plains and valleys, so does the ocean floor. These ups and downs of the ocean floor are called ocean relief or submarine relief.
- Mariana Trench (Pacific Ocean) – the deepest place on Earth.
- Mid-Ocean Ridge – the longest mountain range on Earth, completely under water.
- Mauna Kea (Hawai'i) – measured from its base on the ocean floor, it is taller than Mount Everest.
| Feature | Simple meaning | Key point |
|---|---|---|
| Continental shelf | Submerged shallow edge of a continent | Sunlight reaches; rich in marine life, fish, oil and gas |
| Continental slope | Steep slope after the shelf | The true edge of the continent; depth increases sharply |
| Continental rise | Gentle slope between the slope and the deep plain | Sediment sliding down the slope collects here |
| Abyssal plain | Very deep, wide, almost flat floor | Covers a large part of the ocean floor; small abyssal hills on it |
| Mid-ocean ridge | Underwater volcanic mountain range | Plates move apart, magma rises; rift valley in the middle |
| Ocean trench | Long, narrow, very deep depression | Deepest parts of the ocean, e.g., Mariana Trench |
| Seamount | Underwater volcanic mountain | Its peak does not reach the surface |
| Guyot | Flat-topped submerged mountain | Once near the surface; waves eroded its top flat, then it sank |
3. Movements of Ocean Water – (a) Waves
Ocean water moves in three ways – waves, tides and currents.
The alternate rise and fall of water on the sea surface is a wave. Waves are caused mainly by winds. Wind passes its energy to the water, and waves carry this energy over long distances before breaking on the shore.
| Term | Meaning |
|---|---|
| Crest | Highest point of a wave |
| Trough | Lowest point of a wave |
| Wavelength | Horizontal distance between two consecutive crests (or troughs) |
| Wave height | Vertical distance from trough to crest |
| Wave frequency | Number of crests passing a point each second |
| Wave period | Time taken by a crest to travel from one point to the next |
Waves as coastal architects: waves cut the coast (erosion) and also build new landforms by depositing sand (deposition).
- Hydraulic action: erosion of rock and soil by the force of moving water.
- Abrasion: sand and pebbles carried by waves rub and wear down rocks.
- Headland: high land jutting into the sea, where waves hit hardest.
- Blow hole: a hole in the roof of a sea cave through which water sprays up like a fountain.
- Beach: formed when waves deposit sand and pebbles – a depositional landform.
Waves widen a crack into a cave → the cave is eroded through to form an arch → the arch top collapses, leaving a tall stack → the stack is worn down to a stump.
Storm waves and tsunamis: storm winds make huge waves. But tsunamis are giant waves caused mainly by underwater earthquakes. On reaching the shore a tsunami can rise 30 metres or more – this maximum height is called the run-up height.
4. (b) Tides
The regular rise and fall of ocean water twice a day is called a tide. Water rising to its highest and covering the shore = high tide (flood tide); water falling to its lowest and moving away = low tide (ebb tide). Cause – the gravitational pull of the Moon and the Sun.
| Spring tide | Neap tide | |
|---|---|---|
| Position | Sun, Earth and Moon in a straight line | Sun and Moon at right angles (90°) to the Earth |
| When | Full moon and new moon | First and third quarter of the Moon |
| Effect | Very high high-tides and very low low-tides | Smaller difference between high and low tide |
Importance of tides:
- Navigation: high tide raises water near the shore, so ships enter harbours easily. Tidal ranges in some ports reach 4–5 m; the Gulf of Khambhat has one of the highest, about 12 m. So ships check depth and tidal range before berthing.
- In shallow channels like the Singapore Strait, Very Large Crude Carriers (VLCCs) wait for hours for high tide so they do not run aground.
- Tidal currents: large volumes of water flowing in and out create currents of 5–6 knots (about 9–11 km/h).
- Fishing: at high tide many fish come closer to the shore for food and shelter, giving fishers a better catch.
- Tidal energy: the rise and fall of water can generate electricity. India's coastline is 11,098.81 km. Major tidal energy sites – Gulf of Kutch, Gulf of Khambhat and the Sundarbans.
5. (c) Ocean Currents
Continuous streams of water flowing across the ocean surface in definite directions – like rivers inside the sea.
Causes: winds, the Earth's rotation (Coriolis force), differences in temperature and salinity, and the shape of continents and ocean basins.
| Warm current | Cold current |
|---|---|
| Flows from warmer regions (towards the poles) | Flows from colder regions (towards the equator) |
| Shown in red on maps | Shown in blue on maps |
| Example: Gulf Stream – from the Gulf of Mexico towards Norway; sea ice does not form easily near Norway (60°–70° N) | Example: Labrador Current – along the east coast of Canada; sea ice and icebergs form even at lower latitudes |
Major currents in Fig. 1.9: Warm – Gulf Stream, North Atlantic Drift, North & South Equatorial, Equatorial Counter, Brazilian, Agulhas, Kuroshio, Alaska, North Pacific Drift. Cold – Labrador, Canaries, Benguela, Falkland, Humboldt (Peru), California, Oyashio, West Australian, West Wind Drift.
6. Cyclones and Tsunamis – Early Warning Systems
Cyclones = large rotating storms; tsunamis = giant waves caused by earthquakes. An Early Warning System works like a giant alarm for coastal areas – it detects the hazard, predicts it and gives timely warnings so people can evacuate.
- India's Cyclone Warning Services and Marine Weather Services monitor storms on both the eastern and western coasts. Advanced technology has greatly reduced loss of human and animal lives.
- National Cyclone Risk Mitigation Project (NCRMP): builds cyclone shelters, strengthens warning systems, improves emergency response; focuses on cyclone-prone States/UTs; includes a Decision Support System (DSS) for disaster authorities.
- INCOIS (Indian National Centre for Ocean Information Services) with IMD (India Meteorological Department) set up the Storm Surge Early Warning System (SSEWS) to forecast cyclone-induced storm surges and coastal flooding.
GEMINI (GAGAN-Enabled Mariner's Instrument for Navigation and Information): a handheld device for fishers.
- Receives data from the GAGAN satellite and sends it to the fisher's mobile phone through Bluetooth.
- The INCOIS mobile app shows it in nine regional languages – high waves, strong winds, cyclone and tsunami warnings, potential fishing zones, current speeds, bathymetry (study and mapping of underwater topography) and more.
- At present it works up to 50 nautical miles into the sea; an upgraded pilot version will give two-way communication up to 300 nautical miles.
- Under the Pradhan Mantri Matsya Sampada Yojana (PMMSY) the government gives financial support for GEMINI devices.
Focus on cyclones: cyclones are caused by atmospheric disturbances over warm ocean waters. In the North Indian Ocean, cyclones are named in order from a list of 169 names given by 13 member countries, including India. Examples – Biparjoy (2023), Remal (2024). Cyclone tracks can be seen on the School Bhuvan geoportal.
ITEWC sends alerts to the Government of India → which informs state governments and emergency teams, through satellite networks, SMS, e-mails and coastal display boards. Along with technology, public awareness and training are equally important so people understand warnings and respond correctly.
7. Marine Resources and Their Significance
Materials and features in the oceans that have intrinsic or economic value are marine resources – fish and seafood, biodiversity, oil and gas, minerals, sand and gravel, tidal and wave energy, tourism, coral reefs.
| Living resources | Non-living resources |
|---|---|
| Fish: Coastal (neritic) – on the shelf, 0–200 m; Oceanic – beyond 200 m, past the shelf. Types – epipelagic, pelagic, demersal, benthopelagic, benthic | Minerals – sand, gravel, deep-sea minerals |
| Bioactive natural products (useful in medicines) | Conventional energy – oil, natural gas |
| Marine bio-organisms | Non-conventional energy – biofuels, gas hydrates, offshore wind |
| Submerged Aquatic Vegetation (SAV) – useful for biofuels | Ocean energy – tidal, wave, current energy and OTEC (electricity from temperature difference between surface and deep water) |
Significance: countries with long coastlines, like India, benefit greatly.
- Food and livelihood – protein, fishing, aquaculture.
- Minerals and materials – sand, gravel, deep-sea minerals.
- Energy – offshore oil and gas, blue (clean) energy.
- Trade and tourism – about 90% of global trade by volume moves by sea; coastal tourism is a multi-billion industry.
- Cultural – śaṅkha (conch), kapardikā (cowrie, once used as currency), Samudra Manthana.
Blue Economy: as defined by the World Bank – sustainable use of ocean resources for economic growth, better livelihoods and jobs, while keeping marine ecosystems healthy.
SDG 14 – Life Below Water: reduce marine pollution, protect ecosystems, tackle ocean acidification, regulate fishing, conserve marine areas, end harmful subsidies and increase economic benefits from marine resources.
8. Maritime Zones
Nautical mile: unit of distance at sea. 1 nautical mile = 1,852 metres (about 6,076 feet) = one minute of latitude.
| Zone | Distance (from baseline) | Rights of the country |
|---|---|---|
| Internal waters | Inside the baseline | Full control, like its land |
| Territorial sea | Up to 12 NM | Near-complete control – customs, immigration, pollution laws; foreign ships have innocent passage |
| Contiguous zone | Up to 24 NM | Limited control – customs, fiscal matters, illegal immigration |
| Exclusive Economic Zone (EEZ) | Up to 200 NM (under UNCLOS) | Special rights over fish, oil, gas; but does not fully own the waters – others may pass |
| High seas | Beyond all EEZs | Belong to no country – global commons; about 64% of world's oceans |
Freedoms on the high seas for all countries: navigation, fishing, flying over, laying undersea cables, building lawful structures such as artificial lands, and exploring for minerals.
Challenges of the high seas: overfishing, illegal fishing, conflicts over resources, difficulty in enforcing rules. Here the laws of the flag state – the country where the ship is registered – apply.
9. International Maritime Rules and Regulations
To keep sea activities safe, fair and peaceful, countries follow maritime law. It regulates how ships operate and move, protects the marine environment, deals with piracy, terrorism, disasters and accidents, safeguards trade routes and helps settle disputes.
- COLREGs (Convention on the International Regulations for Preventing Collisions at Sea) – 'rules of the road at sea': proper lookout, which side to pass, give-way and stand-on vessels, safe speed, lights, sound signals and shapes. Ships also use international signals and radio.
- MARPOL (International Convention for the Prevention of Pollution from Ships) – reduces pollution from ships such as oil, garbage and harmful substances.
Why are these rules important? They keep oceans safe, ensure fair and sustainable use of resources, help countries cooperate without conflict and protect marine life, ships, sailors and coastal communities. Without them there would be more pollution, accidents, collisions and disputes. Common standards for all ships keep oceans safe, clean and open for trade and travel.
10. Before We Move On
- Oceans are vital for global trade, travel, communication and climate regulation.
- Submarine relief (shelf, ridges, trenches, seamounts) influences marine life, resource availability and undersea exploration.
- Movements of ocean water – waves, tides and currents – affect marine ecosystems, global climate and activities like fishing and navigation.
- Maritime zones include territorial waters, EEZs and the high seas.
- Sustainable use of marine resources through cooperation, regulation and conservation protects aquatic life and future generations.
- Maritime rules exist to resolve disputes over marine boundaries.
- International laws like UNCLOS define maritime zones and settle disputes among countries.
The deepest point on Earth lies in which trench?
- (A) Mariana Trench
- (B) Java Trench
- (C) Puerto Rico Trench
- (D) Tonga Trench
Show Answer
💡 The Mariana Trench in the Pacific Ocean is the deepest part of the Earth.
Which is the longest mountain range on Earth?
- (A) Himalayas
- (B) Andes
- (C) Mid-Ocean Ridge
- (D) Rockies
Show Answer
💡 The Mid-Ocean Ridge lies completely under water and is the longest range on Earth.
Which statement about Mauna Kea is correct?
- (A) It is in the Indian Ocean
- (B) It is the deepest trench
- (C) It is a guyot
- (D) Measured from its base it is taller than Everest
Show Answer
💡 Mauna Kea in Hawai'i is taller than Everest when measured from its base on the ocean floor.
The submerged shallow edge of a continent, rich in oil, gas and fish, is the –
- (A) Continental slope
- (B) Continental shelf
- (C) Abyssal plain
- (D) Trench
Show Answer
💡 The shelf is shallow and sunlit, so marine life, oil and gas are plentiful.
Which feature marks the 'true edge' of a continent?
- (A) Continental shelf
- (B) Continental slope
- (C) Continental rise
- (D) Mid-ocean ridge
Show Answer
💡 The steep continental slope after the shelf is the true edge of the continent.
A flat-topped submerged mountain is called a –
- (A) Seamount
- (B) Volcanic island
- (C) Ridge
- (D) Guyot
Show Answer
💡 Waves erode the top of a guyot flat, and then it sinks.
Ocean waves are caused mainly by –
- (A) Winds
- (B) The Moon
- (C) Earthquakes
- (D) Salinity
Show Answer
💡 Ordinary waves are formed by wind passing its energy to water.
The horizontal distance between two consecutive crests is called –
- (A) Wave height
- (B) Wave period
- (C) Wavelength
- (D) Wave frequency
Show Answer
💡 Wavelength = distance between two consecutive crests or troughs.
The correct sequence of erosional landforms made by waves is –
- (A) Crack → Cave → Arch → Stack → Stump
- (B) Cave → Crack → Stack → Arch → Stump
- (C) Crack → Arch → Cave → Stump → Stack
- (D) Arch → Cave → Crack → Stack → Stump
Show Answer
💡 Crack widens into a cave, the cave becomes an arch, the arch collapses into a stack, the stack wears down to a stump.
Erosion of rock and soil by the force of moving water is called –
- (A) Abrasion
- (B) Deposition
- (C) Hydraulic action
- (D) Weathering
Show Answer
💡 Force of water = hydraulic action; rubbing by sand and pebbles = abrasion.
Tsunamis are mainly caused by –
- (A) Strong winds
- (B) Warm currents
- (C) Pull of the Moon
- (D) Underwater earthquakes
Show Answer
💡 Giant tsunami waves are mainly caused by undersea earthquakes.
The maximum vertical height a tsunami reaches above sea level on shore is the –
- (A) Wavelength
- (B) Run-up height
- (C) Tidal range
- (D) Crest
Show Answer
💡 It may be 30 metres or even more.
Spring tides occur on –
- (A) First and third quarter
- (B) Full moon and new moon
- (C) Full moon only
- (D) Eclipse days only
Show Answer
💡 On full and new moon days the Sun, Earth and Moon are in a straight line.
During neap tides the Sun and Moon are –
- (A) In a straight line
- (B) At 180°
- (C) On the same side
- (D) At right angles (90°)
Show Answer
💡 At right angles their pulls act in different directions, so the tidal range is smaller.
One of the highest tidal ranges in India (about 12 m) is found in the –
- (A) Gulf of Khambhat
- (B) Gulf of Mannar
- (C) Palk Strait
- (D) Chilika Lake
Show Answer
💡 The Gulf of Khambhat has a tidal range of about 12 metres.
In which shallow channel do VLCCs wait for high tide?
- (A) Strait of Gibraltar
- (B) Suez Canal
- (C) Singapore Strait
- (D) Bering Strait
Show Answer
💡 The Singapore Strait has shallow areas, so VLCCs pass only at high tide.
The Bhadkeshwar Mahadev Temple, reachable only at low tide, is in –
- (A) Dwarka
- (B) Rameswaram
- (C) Puri
- (D) Kanyakumari
Show Answer
💡 It stands on a small hillock in the Arabian Sea at Dwarka, Gujarat.
Which of these is NOT a major tidal energy site of India?
- (A) Gulf of Kutch
- (B) Gulf of Khambhat
- (C) Thar Desert
- (D) Sundarbans
Show Answer
💡 Tidal energy sites are coastal – Kutch, Khambhat and the Sundarbans.
In the Northern Hemisphere the Coriolis force deflects moving objects to the –
- (A) Left
- (B) It does not deflect
- (C) Upward
- (D) Right
Show Answer
💡 Right in the Northern Hemisphere, left in the Southern Hemisphere.
Sea ice does not form easily near Norway (60°–70° N) because of the –
- (A) Labrador Current
- (B) Gulf Stream
- (C) Benguela Current
- (D) Canaries Current
Show Answer
💡 The warm Gulf Stream carries warm water from the Gulf of Mexico towards Norway.
Which of these is a cold current?
- (A) Kuroshio
- (B) Labrador Current
- (C) Brazilian Current
- (D) Gulf Stream
Show Answer
💡 The Labrador Current is a cold current along the east coast of Canada.
Regions where warm and cold currents meet are famous as –
- (A) Deserts
- (B) Coral islands
- (C) Volcanic zones
- (D) Fishing grounds
Show Answer
💡 These waters are rich in nutrients and support many fish.
GEMINI sends information to fishers' mobile phones through –
- (A) Bluetooth
- (B) Wi-Fi
- (C) Cable
- (D) Radio tower
Show Answer
💡 GEMINI receives data from the GAGAN satellite and transfers it via Bluetooth.
The INCOIS app shows GEMINI information in how many regional languages?
- (A) Five
- (B) Seven
- (C) Nine
- (D) Twelve
Show Answer
💡 It displays the information in nine regional languages.
The study and mapping of underwater topography is called –
- (A) Bathymetry
- (B) Topography
- (C) Seismology
- (D) Climatology
Show Answer
💡 Bathymetry studies the underwater shape of oceans, rivers, lakes and streams.
North Indian Ocean cyclones are named from a list submitted by how many member countries?
- (A) 8
- (B) 10
- (C) 13
- (D) 169
Show Answer
💡 13 member countries, including India, gave a list of 169 names.
In the tsunami warning system, 'confirmation' is done by –
- (A) Coastal tide gauges
- (B) Coastal display boards
- (C) Seismic stations
- (D) Ocean Bottom Pressure Recorders (OBPRs)
Show Answer
💡 Detection – seismic stations; confirmation – OBPRs; tracking – tide gauges and radars; dissemination – satellite, SMS.
One nautical mile is equal to –
- (A) 1,000 m
- (B) 1,852 m
- (C) 1,609 m
- (D) 2,000 m
Show Answer
💡 1 nautical mile = 1,852 m = one minute of latitude.
The territorial sea extends up to how far from the baseline?
- (A) 24 NM
- (B) 12 NM
- (C) 100 NM
- (D) 200 NM
Show Answer
💡 Territorial sea 12 NM, contiguous zone 24 NM, EEZ 200 NM.
The high seas cover about what share of the world's oceans?
- (A) 24%
- (B) 46%
- (C) 90%
- (D) 64%
Show Answer
💡 About 64% – they are part of the global commons.
The international agreement to reduce pollution from ships is –
- (A) MARPOL
- (B) COLREGs
- (C) UNCLOS
- (D) SDG 14
Show Answer
💡 MARPOL prevents pollution from ships; COLREGs prevent collisions.
SDG 14 is about –
- (A) Zero hunger
- (B) Clean energy
- (C) Life below water
- (D) Life on land
Show Answer
💡 SDG 14 = Life Below Water.
Q 1. What is ocean relief? Give two examples.
Q 2. Distinguish between a seamount and a guyot.
Q 3. Why are waves called 'coastal architects'?
Q 4. Differentiate between hydraulic action and abrasion.
Q 5. Differentiate between spring tides and neap tides.
Q 6. How do tides help navigation?
Q 7. What causes ocean currents?
Q 8. What is the Coriolis force?
Q 9. How does the GEMINI device help fishers?
Q 10. What is the Blue Economy?
Q 11. What is innocent passage?
Q 12. Why are the high seas called 'global commons'?
Q 13. What are COLREGs?
Q 1. Describe the major features of the ocean floor.
- Continental shelf: submerged shallow edge of a continent; sunlit; rich in fish, oil and gas.
- Continental slope: steep slope after the shelf; the true edge of the continent.
- Continental rise: gentle slope between the slope and the deep plain.
- Abyssal plain: very deep, wide, almost flat floor with small abyssal hills.
- Mid-ocean ridge: underwater volcanic mountain range, the longest on Earth; rift valley in the middle.
- Ocean trench: the deepest parts – e.g., the Mariana Trench in the Pacific.
- Seamounts and guyots: volcanic mountains that do not reach the surface; a guyot has a flat top.
- Conclusion: these features affect fish, minerals, navigation and currents.
Q 2. Describe the erosional and depositional landforms made by waves along the coast.
- Waves are formed by wind and strike the coast with energy. They erode in two ways – hydraulic action (force of water) and abrasion (rubbing by sand and pebbles).
- Crack → cave: waves widen a crack in the rock into a sea cave.
- Cave → arch: when the back of the cave is eroded through, an arch forms.
- Arch → stack: the arch top collapses due to gravity, leaving a tall stack.
- Stack → stump: over time the stack wears down into a stump.
- Headland and blow hole: high land jutting into the sea is a headland; a hole in a cave roof is a blow hole.
- Deposition: waves deposit sand and pebbles to form beaches – e.g., Marina, Juhu, Puri.
Q 3. What are tides? Explain their types and importance.
- Meaning: regular rise (high tide) and fall (low tide) of ocean water twice a day, caused by the gravitational pull of the Moon and the Sun.
- Spring tide: Sun–Earth–Moon in a line (full/new moon); highest high tides and lowest low tides.
- Neap tide: Sun and Moon at right angles (first/third quarter); smaller tidal range.
- Navigation: high tide lets ships enter harbours; Gulf of Khambhat tidal range about 12 m; VLCCs wait for high tide in the Singapore Strait.
- Tidal currents: up to 5–6 knots (9–11 km/h).
- Fishing: fish come closer to the shore at high tide.
- Tidal energy: Kutch, Khambhat, Sundarbans; India's coastline is 11,098.81 km.
- Example: Bhadkeshwar Mahadev Temple, Dwarka – reachable only at low tide.
Q 4. What are ocean currents? How do they affect the climate of coastal areas and the fishing industry?
- Meaning: continuous streams of water flowing across the ocean surface in definite directions.
- Causes: winds, Earth's rotation (Coriolis force – right in NH, left in SH), temperature and salinity differences, shape of continents.
- Types: warm currents (from warm regions, red on maps) and cold currents (from cold regions, blue on maps).
- Effect on climate: the warm Gulf Stream keeps Norway's coast warm – sea ice does not form easily even at 60°–70°. The cold Labrador Current cools Canada's east coast – sea ice and icebergs at lower latitudes.
- Fishing: meeting zones of warm and cold currents are rich in nutrients, so the world's major fishing grounds are found there.
- Navigation: the direction of currents also affects ship speed and fuel use.
Q 5. Describe India's early warning system for tsunamis and cyclones.
- Need: the tsunami of 26 December 2004 killed about 2,30,000 people; Tamil Nadu, Puducherry, Andhra Pradesh, Keralam and the Andaman & Nicobar Islands were badly hit.
- ITEWC: real-time network of tsunami detection buoys. Four stages – detection (seismic stations) → confirmation (OBPRs) → tracking (tide gauges, radars) → warning dissemination (satellite, SMS).
- Flow of alerts: ITEWC → Government of India → state governments and emergency teams; through satellite networks, SMS, e-mails and coastal display boards.
- Cyclones: Cyclone Warning and Marine Weather Services on both coasts; NCRMP – shelters, warning systems, emergency response, DSS; SSEWS by INCOIS + IMD forecasts storm surges and flooding.
- For fishers: GEMINI device – alerts in nine languages; financial support under PMMSY.
- Naming: list of 169 names from 13 countries – e.g., Biparjoy (2023), Remal (2024).
- Public awareness: training officials and coastal communities is essential. The Simeulue example shows traditional knowledge also saves lives.
Q 6. Classify marine resources and explain their significance.
- Living resources: fish (coastal 0–200 m, oceanic beyond 200 m), bioactive natural products, marine bio-organisms, submerged aquatic vegetation (SAV).
- Non-living resources: minerals (sand, gravel, deep-sea minerals) and energy – conventional (oil, gas) and non-conventional (biofuels, gas hydrates, offshore wind, tidal/wave/current energy, OTEC).
- Significance: food and livelihood; minerals; energy; about 90% of world trade by sea; coastal tourism; cultural value – conch, cowrie, Samudra Manthana.
- Sustainable use: Blue Economy and SDG 14 – reduce pollution, stop overfishing, protect marine areas, end harmful subsidies.
Q 7. Describe the maritime zones.
- All distances are measured in nautical miles (1 NM = 1,852 m) from the baseline; waters inside it are internal waters.
- Territorial sea (12 NM): near-complete control – customs, immigration, pollution laws; foreign ships have innocent passage.
- Contiguous zone (24 NM): limited control over customs, fiscal matters and illegal immigration.
- EEZ (200 NM, UNCLOS): special rights over fish, oil and gas; but not full ownership.
- High seas (~64%): global commons; freedom of navigation, fishing, overflight, cables, structures, mineral exploration; challenges – overfishing, illegal fishing, resource conflicts; flag-state laws apply.
- Where is the deepest point on Earth? – Mariana Trench (Pacific Ocean)
- What is the highest point of a wave called? – Crest
- By what other name is high tide known? – Flood tide
- What is the length of India's coastline? – 11,098.81 km
- Name a warm ocean current. – Gulf Stream
- What is the full form of ITEWC? – Indian Tsunami Early Warning Centre
- When did the Indian Ocean tsunami occur? – 26 December 2004
- Up to how many nautical miles does the EEZ extend? – 200 nautical miles
- How far does the contiguous zone extend from the baseline? – 24 nautical miles
- Name a cyclone of 2024. – Remal
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