Looking for an exam-oriented collection of extra questions and answers for SEBA Class 9 Social Science Geography Chapter 1 (Changes of Earth’s Surface / ভূ-পৃষ্ঠৰ পৰিৱৰ্তন) for the 2026–27 academic session? Access thoroughly solved Short Answer Questions (2–3 marks), Long Analytical Questions (4–5 marks), comparative distinction tables, and landform diagrams. Master high-yield exam topics covering endogenic vs. exogenic geomorphic processes; mechanical fragmentation vs. chemical decomposition; biological weathering agents; denudation processes; evolutionary stages of a river valley (youthful, mature, old stage); comparative analysis of V-shaped valleys and U-shaped valleys; formation of natural levees, floodplains, and bird’s foot deltas; glacial erosion features (cirques, aretes, hanging valleys) and morainic deposits; aeolian processes in hot deserts (deflation hollows, mushroom rocks, zeugens, yardangs, and barchan dunes); marine erosional landforms (sea caves, arches, stacks) and depositional beaches; along with anthropogenic impacts on accelerated soil erosion and riverbed siltation, designed strictly according to the Assam Board (SEBA) examination pattern.
Q.1. What percentage of the earth’s surface is covered by landmass (continents)?
Answer: 29 percent.
Q.2. What percentage of the earth’s surface is covered by the hydrosphere (oceans)?
Answer: 71 percent.
Q.3. What are the two main types of factors that change the earth’s surface?
Answer: Exogenic and endogenic factors.
Q.4. Do exogenic forces operate from outside or inside the earth?
Answer: From outside (visibly).
Q.5. Do endogenic forces operate from outside or inside the earth?
Answer: From inside (invisibly).
Q.6. Give two main examples of endogenic factors.
Answer: Earthquake and volcanic eruption.
Q.7. What major process operates behind endogenic events like earthquakes?
Answer: Plate tectonics.
Q.8. What are the two main sources of exogenic factors?
Answer: The sun and the earth’s atmosphere.
Q.9. During which geological period did most of the earth remain under ice cover about two million years back?
Answer: Ice Age.
Q.10. In which type of areas are the works of rivers mostly dominant?
Answer: Rainy areas.
SEBA Class 9 Geography Chapter 1 Extra Questions
Q.11. In which type of areas are the works of winds mostly dominant?
Answer: Desert areas.
Q.12. In which type of areas are the works of glaciers mostly dominant?
Answer: Polar and high altitude areas.
Q.13. In which type of areas are the works of sea-waves mostly dominant?
Answer: Coastal areas.
Q.14. What are the three main groups of works performed by a river?
Answer: Erosion, transportation, and deposition.
Q.15. What is the direct action of water on channel sands and pebbles known as?
Answer: Hydraulic action.
Q.16. What kind of river erosion widens the river channel by eroding its banks?
Answer: Lateral or bank erosion.
Q.17. What is a zigzag river course flowing over the gentle slopes of plains called?
Answer: Meandering course.
Q.18. What is a horse-shoe shaped lake formed by a cut-off river meander called?
Answer: Horse-shoe lake or beel.
Q.19. In what three different ways does a river carry sediments?
Answer: Dissolved state, suspended state, and rolling state.
Q.20. What are relatively big particles carried down by a current in a rolling state called?
Answer: Bed load.
Changes of Earth’s Surface Important Questions and Answers 2026-27
Q.21. What fertile, flat landform is formed on both banks of a river due to long-continued sediment deposition?
Answer: Floodplain.
Q.22. What famous river island in Assam is a large sandbar of the river Brahmaputra?
Answer: Majuli.
Q.23. What long embankment-like feature is formed naturally near a river channel by heavy deposited materials?
Answer: Natural levee.
Q.24. What delta shape resembles the Assamese letter ‘S’ or the Greek letter?
Answer: Delta ().
Q.25. What is the blowing away of sands and dust by wind in deserts called?
Answer: Deflation.
Q.26. What hill is formed when wind-transported sands and dust get deposited in certain places?
Answer: Sand dune.
Q.27. What frictional erosion is caused by speedy desert winds transporting rocks and pebbles?
Answer: Abrasion.
Q.28. What German term means an isolated island mountain in a desert?
Answer: Inselberg.
Q.29. What moving ice down a mountain slope is called?
Answer: Glacier.
Q.30. What are the materials carried down by a glacier called?
Answer: Moraine.
Class 9 Social Science Geography Chapter 1 Extra Q&A SEBA
Extra Short Questions with Answers
Q.1. What are the main components of the earth’s surface?
Answer: The earth’s surface is composed of continents (landmass) and oceans (hydrosphere).
Q.2. Mention the primary difference in how exogenic and endogenic factors operate.
Answer: Exogenic forces operate from outside visibly upon the earth’s surface, while endogenic forces work in the earth’s interior invisibly.
Q.3. How do biotic elements contribute to changing the earth’s surface?
Answer: Biotic elements like vegetation and animals contribute more or less towards changing the earth’s surface through organic growth and interactions.
Q.4. Define a river basin.
Answer: A river basin is an area from where a river, along with its tributaries, carries water downward.
Q.5. What are the primary water sources of rivers?
Answer: The water sources of rivers may be rainfall, snow deposits over mountains, or springs coming out from the earth’s interior.
Q.6. Why does a river start widening its channel in plains instead of deepening it?
Answer: When a river enters a plain from a steep mountain, its velocity decreases and channel depth declines. It then starts widening its channel through lateral cutting to maintain normal flow.
Q.7. What is the geographical importance of beels or horse-shoe lakes?
Answer: Beels help in reducing flood problems by storing sufficient water during summer and serve as rich habitats for bio-diversity and migratory birds.
Q.8. How are sandbars formed on a river bed?
Answer: Sandbars are formed when the rolling loads and sediments carried by the river get deposited on the sides or middle of the river bed as water velocity becomes weak.
Q.9. What are the main characteristics of floodplains?
Answer: Floodplains are formed by long-continued sediment deposition on both banks during floods; they are very fertile and suitable for cultivation.
Q.10. Name four famous rivers that have extensive floodplains around the world.
Answer: Brahmaputra, Ganga, Indus, and Nile.
SEBA Class 9 Geography Weathering Denudation River Landforms Notes
Q.11. What causes dust storms in deserts?
Answer: Dust storms in deserts are frequently caused by deflation, which is the blowing away of loose sands and dust by wind.
Q.12. What are yardangs?
Answer: Yardangs are geomorphic features where ridges and grooves occur together, formed by wind action over relatively soft sedimentary rocks in deserts.
Q.13. What are the two main types of glaciers?
Answer: Continental glaciers (or ice sheets) and mountain glaciers (or valley glaciers).
Q.14. Why do glacial channels have a U-shaped cross profile?
Answer: Glacial channels become deep and steep-sided with a U-shaped profile due to the friction and erosional activities caused by transported materials like boulders and rocks.
Q.15. What is a glacial horn?
Answer: A glacial horn is a sharp, conical mountain peak formed when multiple glaciers flow down from a mountain and perform erosional activities on all its sides.
Q.16. Name the four types of moraines found in glacial regions.
Answer: Lateral moraine, ground moraine, medial moraine, and terminal (or end) moraine.
Q.17. What happens to a glacier when it reaches lower, warmer altitudes?
Answer: The glacial ice starts melting, depositing its heavy materials at the terminus, and the melting ice forms a river flowing downward.
Q.18. What is a coastline?
Answer: The coastline is the long, zigzag contact line where the oceans and continents meet.
Q.19. What is a sea-cliff?
Answer: A sea-cliff is a steep, rugged coast formed by constant wave action when the coastal land is composed of hard rocks like granite and basalt.
Q.20. What is a Tsunami?
Answer: A Tsunami is a series of devastating, high-energy ocean waves produced by big earthquakes occurring on the ocean floor, causing extensive damage to coastal areas.
Long (3-Mark) Important Extra Questions with Answers
Q.1. Explain how exogenic and endogenic factors work together to shape the earth’s surface.
Answer: Exogenic and endogenic factors act in opposition to give the earth’s surface its current shape. Exogenic factors (such as rivers, winds, glaciers, and sea-waves) operate externally and very slowly to wear down high lands, remove irregularities, and level the surface. On the other hand, endogenic factors (such as earthquakes and volcanic eruptions) operate from the earth’s interior invisibly and suddenly, creating irregularities by uplifting some parts into mountains and depressing others into lowlands. Together, their combined actions shape the earth’s diverse topography.
Q.2. Describe the three ways in which a river transports its sediments.
Answer: A river carries its generated sediments downward in three distinct ways:
- Dissolved State: Soluble salts present in the soil dissolve into river water and are transported to seas or oceans.
- Suspended State: Tiny, lightweight particles of sand, mud, and silt are carried along by the water current in suspension, eventually depositing on river beds and banks or reaching the ocean.
- Rolling State: Relatively heavy particles (like pebbles and large sands, known as bed load) are rolled along the bottom of the channel by the water current until velocity decreases.
Q.3. How are floodplains and natural levees formed by rivers? Mention their significance.
Answer:
- Floodplains: Formed in the middle and lower courses of a river where continuous deposition of sands, mud, and silt occurs over banks during floods, creating flat, fertile agricultural lands.
- Natural Levees: Formed when heavy materials (boulders, pebbles, coarse sand) carried by a river cannot travel far and are deposited immediately near the channel edges during floods, building a natural long embankment. Both features help manage floodwaters and provide rich soil for farming and human settlements.
Q.4. Write a short note on the formation and geographical significance of deltas.
Answer: Deltas are depositional landforms shaped like the Greek letter delta () or the Assamese letter ‘S’, formed at the mouths of rivers where they debouch into shallow coastal seas. As the river flow slows down significantly upon meeting the sea, it drops its heavy load of sediments, creating multiple distributaries and triangular islands. Famous examples include the Ganga-Brahmaputra delta and the Nile delta. They are highly significant for agriculture, dense human settlement, and rich biodiversity.
Q.5. Explain how deflation and abrasion create distinct features in desert environments.
Answer:
- Deflation: This is the blowing away of loose sand and dust by wind. It lowers the surface of the desert, creating temporary depressions or hollows where lakes may form, and piles up sand elsewhere to form sand dunes.
- Abrasion: This is the mechanical scraping and frictional erosion caused when speedy desert winds hurl rocks, pebbles, and sand against highland obstacles. This process carves out unique landforms such as isolated inselbergs and groove-and-ridge yardangs.
Assam Board Class 9 Geography Chapter 1 Solved Extra Questions PDF
Q.6. Distinguish between continental glaciers and mountain glaciers.
Answer:
- Continental Glaciers (Ice Sheets): These cover extremely vast, extensive areas primarily over the polar regions. They move very slowly according to the general surface slope under massive layers of ice.
- Mountain (Valley) Glaciers: These occur in high mountainous regions like the Alps, Rockies, and Himalayas. They are smaller and constrained to flow strictly down through pre-existing mountain valleys, shaping features like U-shaped valleys, horns, and various moraines.
Q.7. What are moraines? Name and briefly explain their different types.
Answer: Moraines are the heterogeneous mixtures of rocks, boulders, pebbles, and sands carried and deposited by glaciers. They are categorized into four main types:
- Lateral Moraine: Carried along the steep sides of the glacial valley.
- Ground Moraine: Carried directly underneath the moving ice over the valley floor.
- Medial Moraine: Formed in the middle of a glacier when the lateral moraines of two merging glaciers combine.
- Terminal (End) Moraine: Deposited at the lower terminus or snout of a glacier where the ice melts.
Q.8. How do sea-waves create sea-cliffs and beaches in coastal zones?
Answer:
- Sea-Cliffs: When coastal areas are composed of hard rocks (like granite or basalt), continuous and powerful wave action batters the base, eroding the rock and creating steep, rugged coastal precipices known as sea-cliffs.
- Beaches: In locations where continuous wave action systematically deposits sand and pebbles with gentle seaward slopes (driven by swash and backwash actions), smooth shorelines known as beaches are formed.
Q.9. Explain why the character and intensity of exogenic factors vary over space and time.
Answer: The activity levels of external agents are never uniform. Over time, global climate shifts alter their intensity—for instance, during the Ice Age two million years ago, glaciers covered vast regions that are now temperate or tropical. Over space, specific factors dominate specific environments (rivers in rainy zones, winds in deserts, glaciers in cold high altitudes, and waves on coasts). Factors like geological structure, regional temperature, vegetation cover, and slope variations further cause regional differences in how these exogenic forces modify the landscape.
Q.10. Summarize the role of plate tectonics and endogenic forces in shaping the earth’s relief.
Answer: Plate tectonics serves as the driving mechanism behind endogenic forces. The Earth’s crust is made up of dynamic plates that constantly move relative to one another. These plate movements generate tremendous internal stress, resulting in sudden geological events like earthquakes and volcanic eruptions. Endogenic processes disrupt surface equilibrium by creating major irregularities—uplifting landmasses to form high mountain ranges, sinking parts to form ocean basins, and building volcanic hills—thereby establishing the primary framework of the earth’s relief upon which exogenic factors subsequently operate.
🌍 Class 9 Social Science Exam Preparation Notice: This page features curated SEBA Class 9 Social Science (Geography Section) Chapter 1: Changes of Earth’s Surface Extra Questions, Answers & Solutions updated for the 2026–27 academic session. Tailored strictly to target high-frequency descriptive, analytical, and diagram-based questions tested in school unit evaluations, half-yearly exams, and annual examinations, this revision guide explores beyond standard textbook exercises—providing structured, point-wise evaluations of endogenic vs. exogenic geomorphic forces, chemical weathering reactions (oxidation, carbonation, hydration), river course dynamics, glacial action, and aeolian landform evolution—to guarantee full marks in your 2-mark, 3-mark, and 5-mark exam questions.
💡 Master SEBA Class 9 Geography Chapter Extra Questions:
- Having difficulty structuring a comprehensive 5-mark answer detailing how running water sculpts diverse landforms across its upper, middle, and lower courses, differentiating between weathering and denudation, or illustrating how wind erosion forms mushroom rocks and yardangs in arid zones? Leave your query in the comments section below!
- Bookmark this page for quick revision of landform comparison tables, geomorphic agent definitions, and diagrammatic breakdowns before your upcoming unit evaluations, half-yearly exams, and final annual examinations.
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