Class 11 : Geography (In English) – Lesson 4. Distribution of Oceans and Continents
EXPLANATION & SUMMARY
📘 1. Detailed Explanation
🌏 Introduction
🌊 The Earth’s surface is an extraordinary mosaic of land and water, shaped and reshaped over billions of years by dynamic geological forces. About 71% of the Earth’s surface is covered by water, forming the oceans and seas, while the remaining 29% constitutes the continents and islands. The present-day distribution of oceans and continents is not accidental; it is the result of long and complex geological processes such as continental drift, seafloor spreading, and plate tectonics.
🌎 Understanding how continents and oceans were distributed in the past and how they have evolved is essential to comprehend Earth’s geological history, natural hazards, and even biological evolution. This lesson explores the origin, development, and present distribution of continents and oceans through various scientific theories and evidence.
🌋 Origin of Continents and Oceans: Early Theories
Since ancient times, scientists and philosophers have tried to explain how continents and oceans formed. Early ideas were based on speculation, but modern theories rely on scientific evidence.
🪐 1. Catastrophic and Contraction Theories (Obsolete)
Before the 20th century, some scientists believed Earth’s features formed suddenly due to catastrophic events or gradual contraction due to cooling. However, these theories lacked strong evidence and were replaced by more robust explanations based on plate dynamics.
🧭 Continental Drift Theory — Alfred Wegener (1912)
🌍 One of the most influential early ideas explaining the distribution of continents and oceans is the Continental Drift Theory proposed by German meteorologist Alfred Wegener.
🪐 Main Idea
Wegener suggested that all continents were once part of a single supercontinent called Pangaea (meaning “all Earth”), which was surrounded by a vast ocean called Panthalassa.
🌍 Pangaea existed about 300 million years ago.
🌎 Around 200 million years ago, it began to break apart.
🌍 Two major landmasses formed: Laurasia in the north and Gondwanaland in the south.
🌊 These landmasses drifted further to form present-day continents.
🧭 Evidence Supporting Continental Drift
Wegener supported his theory with multiple lines of evidence:
🧬 Fossil Evidence: Similar plant and animal fossils (like Glossopteris) found in continents now separated by oceans.
🪨 Geological Evidence: Matching rock formations and mountain ranges across continents (e.g., Appalachian Mountains in North America and Caledonian Mountains in Europe).
🧊 Glacial Evidence: Glacial deposits in tropical regions, indicating these areas were once near the poles.
🧭 Fit of Continents: Coastlines of South America and Africa fit together like puzzle pieces.
🌍 Limitations of Wegener’s Theory
Despite strong evidence, Wegener could not explain the mechanism behind continental drift — what force moved the continents. Because of this, his theory was initially rejected by the scientific community.
🌊 Seafloor Spreading Theory — Harry Hess (1960s)
🪐 In the 1960s, new evidence from ocean floor mapping revived interest in continental movement. American geologist Harry Hess proposed the Seafloor Spreading Theory, which explained the mechanism behind continental drift.
🌐 Main Idea
Hess suggested that new crust is formed at mid-ocean ridges where magma rises from the mantle, creating new ocean floor. As the seafloor spreads, it pushes the continents apart. At subduction zones, the ocean floor sinks back into the mantle.
🌊 Key features:
🌋 Mid-ocean ridges are sites of new crust formation.
🌊 Ocean trenches are sites of crust destruction.
🌍 Continents are carried passively along with moving plates.
🔬 Evidence Supporting Seafloor Spreading
🧭 Paleomagnetism: Magnetic stripes on either side of mid-ocean ridges show symmetrical patterns, proving new crust formation.
🪨 Age of Ocean Floor: Youngest rocks found near ridges, oldest near trenches.
🌊 Heat Flow and Earthquakes: Concentrated along ridges and subduction zones.
🌍 Plate Tectonic Theory — Modern Explanation
🌐 The most widely accepted explanation today for the distribution of oceans and continents is the Plate Tectonic Theory, developed in the late 1960s by scientists like McKenzie, Parker, and Morgan.
🌎 Main Idea
The Earth’s lithosphere (crust + upper mantle) is broken into 7 major and several minor plates that float on the asthenosphere. These plates move due to convection currents in the mantle, causing continents and ocean basins to shift over time.
🌏 Types of Plate Boundaries
🌊 Divergent Boundaries: Plates move apart → new crust forms (e.g., Mid-Atlantic Ridge).
🏔️ Convergent Boundaries: Plates collide → mountains or trenches form (e.g., Himalayas, Mariana Trench).
⚡ Transform Boundaries: Plates slide past each other → earthquakes occur (e.g., San Andreas Fault).
🪐 Historical Stages of Ocean and Continent Distribution
The Earth’s surface has gone through several major phases of continental rearrangement:
🪐 1. Formation of Pangaea (~300 million years ago)
All landmasses joined into one supercontinent.
Surrounded by the global ocean Panthalassa.
🪐 2. Breakup into Laurasia and Gondwanaland (~200 million years ago)
Pangaea split into northern Laurasia and southern Gondwanaland.
Tethys Sea separated them.
🪐 3. Modern Configuration (~65 million years ago to present)
Continents continued drifting into current positions.
Atlantic Ocean widened, Himalayas formed due to collision of India with Eurasia.
🌎 Present Distribution of Oceans
The Earth’s water bodies are dominated by five major oceans, each with unique features:
🌊 1. Pacific Ocean 🌊
🌏 Largest and deepest ocean (~46% of Earth’s water surface).
Surrounded by the Ring of Fire — a zone of frequent earthquakes and volcanoes.
Contains the Mariana Trench, the world’s deepest (~11,000 m).
🌊 2. Atlantic Ocean 🌊
🌎 Second largest, connecting the Arctic in the north to the Southern Ocean in the south.
Contains the Mid-Atlantic Ridge, a major divergent boundary.
Coastlines of Africa and South America show evidence of continental drift.
🌊 3. Indian Ocean 🌊
🌍 Third largest, bordered by Asia, Africa, and Australia.
Contains important trade routes and rich marine biodiversity.
Lacks extensive trenches compared to the Pacific.
🌊 4. Southern Ocean 🌊
Surrounds Antarctica and merges with other oceans.
Known for strong circumpolar currents influencing global climate.
🌊 5. Arctic Ocean 🌊
Smallest and shallowest ocean, mostly covered by ice.
Contains unique marine ecosystems and is rich in potential energy resources.
🌍 Present Distribution of Continents
The Earth’s landmasses are divided into seven continents:
🌍 1. Asia 🌏
Largest continent (~30% of land area).
Home to the Himalayas and vast plateaus.
🌍 2. Africa 🌍
Second largest, rich in minerals and biodiversity.
Cradles of ancient human civilizations.
🌍 3. North America 🌎
Surrounded by Atlantic, Pacific, and Arctic oceans.
Features large mountain chains like Rockies and Appalachians.
🌍 4. South America 🌎
Contains the Amazon Basin and Andes Mountains.
Active volcanic and seismic region.
🌍 5. Antarctica ❄️
Ice-covered continent around the South Pole.
Contains ~70% of Earth’s freshwater.
🌍 6. Europe 🌍
Small but densely populated.
Geologically diverse with old mountain ranges.
🌍 7. Australia 🌏
Smallest continent, largely desert interior.
Unique flora and fauna due to isolation.
🌊 Features of Ocean Floors
The ocean floors are not flat but composed of several distinct features:
🌋 Continental Shelf: Shallow submerged extension of continents.
🌊 Continental Slope: Steep slope connecting shelf to deep ocean floor.
🏞️ Abyssal Plain: Flat deep-sea floor.
🪨 Mid-Ocean Ridges: Underwater mountain ranges formed at divergent boundaries.
🌋 Ocean Trenches: Deep, narrow depressions at subduction zones.
🪶 Seamounts and Guyots: Submarine volcanoes and flat-topped seamounts.
🌐 Influence of Continental and Oceanic Distribution
The distribution of land and water affects Earth’s systems profoundly:
🌦️ Climate: Ocean currents and continental positions regulate global temperature and rainfall.
🌊 Ocean Circulation: Driven by continental placement and wind systems.
🪨 Biodiversity: Distribution of land influences evolution and migration of species.
🏔️ Geological Activity: Earthquakes, volcanoes, and mountain building occur along plate boundaries.
🚢 Human Activity: Trade routes, settlement patterns, and resource distribution depend on geography.
🌎 Future of Continents and Oceans
Plate movements continue at rates of 2–15 cm/year, meaning Earth’s surface is still changing:
🌍 The Atlantic Ocean is widening.
🪨 The Pacific is shrinking due to subduction.
🗺️ Africa may split into two continents.
🌏 A new supercontinent (Pangaea Proxima) could form in 200–300 million years.
📚 2. Summary (~300 Words)
The distribution of oceans and continents is the result of billions of years of geological evolution. Early theories like Wegener’s Continental Drift proposed that all continents were once part of a supercontinent, Pangaea, which broke apart into Laurasia and Gondwanaland. The Seafloor Spreading Theory provided a mechanism for this movement, showing how new crust forms at mid-ocean ridges and pushes continents apart. The Plate Tectonic Theory further explained that lithospheric plates move over the asthenosphere, causing continents and oceans to shift.
Earth’s surface comprises five major oceans — Pacific, Atlantic, Indian, Southern, and Arctic — and seven continents — Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Ocean floors include features such as continental shelves, mid-ocean ridges, trenches, and abyssal plains.
The arrangement of land and water affects climate, biodiversity, geological activity, and human society. Ocean currents regulate temperature, while continental distribution influences wind patterns, rainfall, and ecosystems.
Continental drift continues today, reshaping Earth’s surface. Over millions of years, continents may merge again into a future supercontinent. Understanding these processes is essential for predicting geological activity, managing natural resources, and comprehending Earth’s evolutionary history.
⚡ 3. Quick Recap (~100 Words)
Continents and oceans were once part of the supercontinent Pangaea, which split and drifted apart due to plate tectonics. Seafloor spreading and mantle convection explain this movement. Today, Earth has five oceans and seven continents, each with unique features and geological structures. Ocean floors consist of shelves, ridges, plains, and trenches. The distribution of land and water affects global climate, biodiversity, and human activity. Continents continue to move, and a new supercontinent may form in the distant future. Studying these processes reveals Earth’s dynamic nature and evolutionary history.
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QUESTIONS FROM TEXTBOOK
📘 Questions and Answers (Questions and Answers Together)
✨ 1. Multiple Choice Questions (MCQs)
🟢 Q1: Who amongst the following was the first to consider the possibility of Europe, Africa, and America having been located side by side?
🟢 (a) Alfred Wegener
🔵 (b) Antonio Pellegrini
🟡 (c) Abraham Ortelius
🟣 (d) Edmond Hess
✅ Answer: 🟡 (c) Abraham Ortelius
🔵 Q2: Polar fleeing force relates to:
🟢 (a) Revolution of the Earth
🔵 (b) Gravitation
🟡 (c) Rotation of the Earth
🟣 (d) Tides
✅ Answer: 🟡 (c) Rotation of the Earth
🟡 Q3: Which one of the following is not a minor plate?
🟢 (a) Nazca
🔵 (b) Arabia
🟡 (c) Philippines
🟣 (d) Antarctica
✅ Answer: 🟣 (d) Antarctica
🟣 Q4: Which one of the following facts was not considered by those while discussing the concept of sea floor spreading?
🟢 (a) Volcanic activity along the mid-oceanic ridges
🔵 (b) Stripes of normal and reverse magnetic field observed in rocks of ocean floor
🟡 (c) Distribution of fossils in different continents
🟣 (d) Age of rocks from the ocean floor
✅ Answer: 🟡 (c) Distribution of fossils in different continents
🟣 Q5: Which one of the following is the type of plate boundary of the Indian plate along the Himalayan mountains?
🟢 (a) Ocean-continent convergence
🔵 (b) Divergent boundary
🟡 (c) Transform boundary
🟣 (d) Continent-continent convergence
✅ Answer: 🟣 (d) Continent-continent convergence
✏️ 2. Short Answer Questions (About 30 Words Each)
🌍 Q1: What were the forces suggested by Wegener for the movement of the continents?
🌱 Answer: Wegener suggested two forces: (1) Polar fleeing force due to Earth’s rotation pushing continents towards the equator, and (2) Tidal force caused by gravitational attraction of the Moon and Sun, pulling continents horizontally.
🌍 Q2: How are the convectional currents in the mantle initiated and maintained?
🌱 Answer: Convection currents in the mantle are generated by heat from radioactive decay in Earth’s interior. Hot, less dense materials rise, while cooler, denser materials sink, creating continuous circulation that drives plate movement.
🌍 Q3: What is the major difference between the transform boundary and the convergent or divergent boundaries of plates?
🌱 Answer: Transform boundaries involve horizontal sliding of plates past each other without crust formation or destruction, whereas convergent boundaries involve collision and crust destruction, and divergent boundaries involve separation and crust formation.
🌍 Q4: What was the location of the Indian landmass during the formation of the Deccan Traps?
🌱 Answer: During the formation of the Deccan Traps (about 60-65 million years ago), the Indian landmass was located near the equator and was rapidly moving northward after breaking away from Gondwana.
📜 3. Long Answer Questions (About 150 Words Each)
🌋 Q1: What are the evidences in support of the continental drift theory?
🌱 Answer: Several lines of evidence support Wegener’s continental drift theory:
Coastline Fit: The coastlines of South America and Africa fit together like puzzle pieces.
Fossil Evidence: Identical fossil species like Mesosaurus and Glossopteris are found on widely separated continents.
Rock and Mountain Correlation: Similar rock formations and mountain ranges (e.g., Appalachian and Caledonian) match across continents.
Paleoclimatic Evidence: Evidence of glaciation in now-tropical regions suggests these continents were once near the poles.
Geological Structures: Similar structures and mineral belts are found across distant continents.
These evidences strongly indicate that continents were once united as a single landmass (Pangaea) and have since drifted apart.
🌋 Q2: Bring out the basic difference between the drift theory and plate tectonics.
🌱 Answer: Wegener’s drift theory (1912) proposed that continents drift through oceanic crust due to forces like Earth’s rotation and tidal pull, but it lacked a mechanism. Plate tectonics (1960s) explains that the lithosphere is broken into plates that move due to mantle convection currents. Unlike the drift theory, plate tectonics accounts for both continental and oceanic crust movement, sea-floor spreading, and subduction. It integrates various phenomena like earthquakes, volcanoes, and mountain building under one theory. Thus, plate tectonics is more comprehensive and widely accepted.
🌋 Q3: What were the major post-drift discoveries that rejuvenated the interest of scientists in the study of distribution of oceans and continents?
🌱 Answer: Post-drift discoveries included:
Paleomagnetism: Patterns of magnetic reversals on the ocean floor confirmed sea-floor spreading.
Mid-Oceanic Ridges: Discovery of continuous volcanic ridges supported new crust formation.
Age of Oceanic Crust: Younger rocks near ridges and older rocks away from them supported plate movement.
Subduction Zones: Existence of trenches and zones where crust is recycled validated plate interaction.
Global Seismicity Patterns: Earthquake distribution along plate boundaries confirmed their dynamic nature.
These discoveries provided a solid mechanism and evidence for continental movement, transforming Wegener’s drift idea into the modern theory of plate tectonics.
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OTHER IMPORTANT QUESTIONS FOR EXAMS
🌏 Section A — Multiple Choice Questions (1 mark each)
🔵 Question 1: Who among the following was the first to consider the possibility of Europe, Africa, and America having been located side by side?
🟢 1️⃣ Francis Bacon
🔴 2️⃣ Alfred Wegener
🟡 3️⃣ Antonio Snider
🔴 4️⃣ Harry Hess
✔️ Answer: Francis Bacon
🟡 Question 2: The theory of continental drift was proposed by:
🟢 1️⃣ Alfred Wegener
🔴 2️⃣ Harry Hess
🟡 3️⃣ Tuzo Wilson
🔴 4️⃣ J. Tuzo
✔️ Answer: Alfred Wegener
🔴 Question 3: Which supercontinent existed about 250 million years ago?
🟢 1️⃣ Laurasia
🔴 2️⃣ Pangaea
🟡 3️⃣ Gondwana
🔴 4️⃣ Panthalassa
✔️ Answer: Pangaea
🟢 Question 4: The supercontinent Pangaea was surrounded by a huge water body known as:
🟢 1️⃣ Pacific Ocean
🔴 2️⃣ Tethys Sea
🟡 3️⃣ Panthalassa
🔴 4️⃣ Paleo-Atlantic
✔️ Answer: Panthalassa
🔵 Question 5: According to Wegener, Pangaea split into two parts — Laurasia and Gondwana — during which geological period?
🟢 1️⃣ Jurassic
🔴 2️⃣ Triassic
🟡 3️⃣ Cretaceous
🔴 4️⃣ Permian
✔️ Answer: Triassic
🟡 Question 6: Which of the following is NOT a piece of evidence for continental drift?
🟢 1️⃣ Fit of the continents
🔴 2️⃣ Fossil evidence
🟡 3️⃣ Paleomagnetism
🔴 4️⃣ Ocean currents
✔️ Answer: Ocean currents
🔴 Question 7: Who proposed the concept of seafloor spreading?
🟢 1️⃣ Alfred Wegener
🔴 2️⃣ Harry Hess
🟡 3️⃣ Vine and Matthews
🔴 4️⃣ Joly
✔️ Answer: Harry Hess
🟢 Question 8: The ocean floor spreading occurs mainly along:
🟢 1️⃣ Mid-ocean ridges
🔴 2️⃣ Trenches
🟡 3️⃣ Subduction zones
🔴 4️⃣ Seamounts
✔️ Answer: Mid-ocean ridges
🔵 Question 9: Which concept explains the movement of lithospheric plates?
🟢 1️⃣ Plate tectonics theory
🔴 2️⃣ Continental drift theory
🟡 3️⃣ Isostasy theory
🔴 4️⃣ Geosynclinal theory
✔️ Answer: Plate tectonics theory
🟡 Question 10: Which type of plate boundary is associated with seafloor spreading?
🟢 1️⃣ Divergent boundary
🔴 2️⃣ Convergent boundary
🟡 3️⃣ Transform boundary
🔴 4️⃣ Passive margin
✔️ Answer: Divergent boundary
🔴 Question 11: Which type of rocks on the ocean floor provides evidence of magnetic reversals?
🟢 1️⃣ Sedimentary rocks
🔴 2️⃣ Igneous rocks
🟡 3️⃣ Metamorphic rocks
🔴 4️⃣ Fossiliferous rocks
✔️ Answer: Igneous rocks
🟢 Question 12: Which part of the Earth’s interior is responsible for convection currents driving plate movements?
🟢 1️⃣ Crust
🔴 2️⃣ Lithosphere
🟡 3️⃣ Mantle
🔴 4️⃣ Core
✔️ Answer: Mantle
🧭 Section B — Short Answer Questions (15–20 words each)
🔵 Question 13: Define continental drift theory.
🟢 Answer: Continental drift theory, proposed by Alfred Wegener, states that continents were once joined and later drifted apart.
🟡 Question 14: What is Pangaea?
🟢 Answer: Pangaea was a supercontinent that existed about 250 million years ago before splitting into Laurasia and Gondwana.
🔴 Question 15: Name two evidences supporting continental drift.
🟢 Answer: Fit of continents and fossil similarities on different continents support continental drift theory.
🟢 Question 16: What are mid-ocean ridges?
🟢 Answer: Mid-ocean ridges are underwater mountain chains formed by seafloor spreading at divergent plate boundaries.
🔵 Question 17: What is seafloor spreading?
🟢 Answer: Seafloor spreading is the process of new oceanic crust formation at mid-ocean ridges and its outward movement.
🟡 Question 18: Mention two types of plate boundaries.
🟢 Answer: The two types are convergent boundaries (plates collide) and divergent boundaries (plates move apart).
🔴 Question 19: What is the theory of plate tectonics?
🟢 Answer: Plate tectonics theory states that Earth’s lithosphere is divided into plates that move over the asthenosphere.
🟢 Question 20: What is paleomagnetism?
🟢 Answer: Paleomagnetism is the study of ancient magnetic records preserved in rocks, indicating past positions of continents.
🌍 Section C — Medium Answer Questions (≈60 words each)
🔵 Question 21: Explain the main evidences supporting the continental drift theory.
🟢 Answer: Wegener’s theory is supported by several evidences:
Fit of continents: South America and Africa match like puzzle pieces.
Fossil evidence: Similar fossils found on widely separated continents.
Geological structures: Similar rock formations across continents.
Climatic evidence: Past glacial deposits in tropical regions.
These show continents were once connected and later drifted apart.
🟡 Question 22: Describe the concept of seafloor spreading.
🟢 Answer: Seafloor spreading, proposed by Harry Hess, explains that new crust forms at mid-ocean ridges as magma rises and cools. This crust gradually moves away from the ridge, causing the ocean floor to widen. Magnetic stripes on either side of ridges and increasing age of rocks away from ridges provide strong evidence for this process.
🔴 Question 23: How does paleomagnetic evidence support plate movement?
🟢 Answer: Rocks formed from magma preserve Earth’s magnetic orientation. Alternating magnetic stripes on the seafloor show periodic magnetic reversals. Symmetrical patterns on either side of mid-ocean ridges indicate that new crust forms and spreads outward. This paleomagnetic record confirms seafloor spreading and supports the concept of plate movement over geological time.
🟢 Question 24: Explain the formation of mid-ocean ridges and trenches.
🟢 Answer: Mid-ocean ridges form at divergent boundaries where tectonic plates move apart and magma rises to create new crust. Trenches form at convergent boundaries where one plate subducts beneath another into the mantle. These features mark zones of crustal formation and destruction, playing a vital role in the renewal of the ocean floor.
🔵 Question 25: Differentiate between continental drift theory and plate tectonics theory.
🟢 Answer: Continental drift theory, proposed by Wegener, explains that continents once formed a supercontinent and later drifted apart. It lacked a mechanism for movement. Plate tectonics theory integrates seafloor spreading and explains movement of rigid lithospheric plates over the asthenosphere, causing continental drift, earthquakes, volcanism, and mountain formation.
🟡 Question 26: What is the role of convection currents in plate movement?
🟢 Answer: Convection currents in the mantle arise from heat generated by radioactive decay. Hot material rises, spreads beneath the lithosphere, and cools, sinking again. This continuous cycle drags tectonic plates, causing them to move. These currents drive processes like seafloor spreading, subduction, and continental drift, shaping Earth’s surface over millions of years.
🏞️ Section D — Detailed Answer Questions (≈150 words each)
🔴 Question 27: Describe the continental drift theory and discuss its limitations.
🟢 Answer: Alfred Wegener proposed the continental drift theory in 1912. He suggested that all continents were once part of a single supercontinent, Pangaea, surrounded by Panthalassa. Around 200 million years ago, Pangaea split into Laurasia (north) and Gondwana (south), which drifted apart to form the present continents. Evidence included the fit of continental margins, fossil similarities, geological structures, and paleoclimate records. However, the theory faced criticism due to the absence of a convincing mechanism for movement. Wegener believed continents plowed through the oceanic crust, which geologists found implausible. The theory also could not explain seafloor features, mountain building, or volcanic activity. Despite limitations, it laid the foundation for modern plate tectonics, which provided the mechanism Wegener’s theory lacked.
🟢 Question 28: Discuss the theory of plate tectonics and its significance.
🟢 Answer: Plate tectonics theory, developed in the 1960s, explains that Earth’s lithosphere is divided into several rigid plates that float over the semi-molten asthenosphere. These plates interact at boundaries, leading to various geological processes. Divergent boundaries create new crust, convergent boundaries cause subduction and mountain formation, and transform boundaries result in earthquakes. This theory integrates continental drift, seafloor spreading, and paleomagnetism into a single comprehensive framework. It explains the distribution of earthquakes, volcanoes, mountain chains, and ocean basins. Plate tectonics is fundamental to understanding Earth’s geological evolution, reconstructing past continental positions, and predicting future movements. It also aids resource exploration, seismic hazard assessment, and the study of Earth’s interior dynamics, making it one of the most important theories in Earth sciences.
🔵 Question 29: Explain the process and significance of seafloor spreading in the development of ocean basins.
🟢 Answer: Seafloor spreading is the process by which new oceanic crust is formed at mid-ocean ridges and gradually moves outward. Magma from the mantle rises through fractures, solidifies, and forms new crust. As the crust moves away, it cools, thickens, and eventually subducts into the mantle at trenches. This continuous cycle expands ocean basins and renews the ocean floor. Magnetic stripes and increasing rock age away from ridges confirm this process. Seafloor spreading provides a mechanism for continental drift and plate tectonics, explains the symmetrical structure of ocean basins, and contributes to the recycling of Earth’s crust. It also helps understand past plate movements, reconstruct supercontinents, and study the geological evolution of oceans. Overall, it plays a crucial role in Earth’s dynamic system.
🟡 Question 30: Discuss how the distribution of continents and oceans has changed through geological time.
🟢 Answer: Earth’s continents and oceans have undergone significant changes over geological time due to plate tectonics. About 250 million years ago, all landmasses were part of Pangaea, surrounded by Panthalassa. During the Triassic period, Pangaea split into Laurasia and Gondwana. These drifted apart to form present-day continents. The Atlantic Ocean opened as North America separated from Europe and Africa, while India moved northward to collide with Asia, forming the Himalayas. Australia and Antarctica separated later, and ocean basins continued to widen. Today, continents still move at a few centimeters per year, reshaping Earth’s surface. This shifting has influenced climate, ocean circulation, biodiversity, and geological features. Understanding these changes helps scientists reconstruct past environments and predict future continental configurations, revealing Earth’s dynamic and evolving nature.
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ONE PAGE REVISION SHEET
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MIND MAPS
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