EXERCISE

Give very short answer

1. Give an outline of the distribution of continents and oceans of the world.

Answer: The Earth’s surface is composed of continents (landmasses) and oceans (hydrosphere). The oceans cover about 71% of the surface, while the continents cover the remaining 29%. Continents contain features like plains, plateaus, hills, mountains, river valleys, deserts, and coastal plains. Similarly, oceans have submerged plateaus, plains, ridges, trenches, and coral reefs, along with many islands.

2. Explain why there has been change over the earth’s surface.

Answer: The Earth’s surface is always changing due to two types of forces:

1. Exogenic factors: These are external forces that work on the surface, such as sunshine, wind, rainfall, rivers, glaciers, and sea-waves.
2. Endogenic factors: These are internal forces that work from inside the Earth, like earthquakes and volcanic eruptions, which are caused by the movement of the Earth’s plates.

These two types of forces work together over long periods to constantly change the surface of the Earth.

3. What is meant by exoganic factor? Mention some exogenic factors.

Answer: Exogenic factors are forces that operate on the Earth’s surface from the outside. They are responsible for wearing down and building up landforms. Some examples of exogenic factors are sunshine, wind, rainfall, river and glacier etc.

4. Why are earthquakes and volcanic eruption called endogenic factors.

Answer: Earthquakes and volcanic eruptions are called endogenic factors because they originate from processes within the Earth’s interior. These invisible forces cause major changes on the surface by uplifting or subsiding parts of the land and ocean floor, or by forming new landforms like volcanic mountains.

5. What do you mean by a river basin? Draw a diagram of a river basin.

Answer: A river basin is the entire area of land where all the water, from rain and melting snow, drains downhill into a single river and its tributaries. It is defined by the high ground that surrounds it, which acts as a boundary.

Diagram of a river basin: 

6. What is a tributary? Name two major tributaries of the Brahmaputra.

Answer: A tributary is a smaller stream or river that flows into a larger main river. Two major tributaries of the Brahmaputra are the Manas and the Subansiri.

7. Give an outline of river erosion.

Answer: River erosion is the process by which a river wears away the land in its path. It is most powerful in the upper, mountainous course where the river flows fast, carving a deep channel. As the river reaches flatter plains, its speed decreases, and it begins to erode the banks from side to side (lateral erosion) to maintain its flow, making the channel wider.

8. What do you mean by latersal erosion of a river?

Answer: Lateral erosion is the process where a river cuts away its banks, making the river channel wider. This happens in the middle and lower courses of a river, where the slope is gentle and the river’s velocity decreases. Instead of cutting down into the land, the river erodes the sides of its channel to carry water down to the mouth.

9. What is ox-bow lake? Draw diagram to show how it is formed.

Answer: An ox-bow lake is a horseshoe-shaped lake that is formed when a river’s winding meander is cut off from the main river channel.

10. What is floodplain? Write how it is formed.

Answer: A floodplain is a wide, flat area of land next to a river channel. It is formed by the deposition of sediment (sand, mud, silt) during floods. When a river overflows its banks, the water spreads out and slows down, dropping its sediment load. Over many floods, these layers of sediment build up to create a fertile plain.

11. Write how and where sandbars are formed in a river channel.

Answer: Sandbars are temporary deposits of sand and silt formed on the bed and banks of a river. They are created when the river’s current slows down, causing it to drop the heavier sediment it was carrying. Sandbars can be found on the sides or in the middle of a river channel and become more visible when the water level is low.

12. How are the deltas formed?

Answer: Deltas are landforms that look like a triangle or fan, created at the mouth of a river where it flows into a sea or lake. When the river reaches this large body of water, its speed drops sharply, and it deposits all the sediment it has been carrying. This sediment builds up over time to form a delta.

13. Write why the wind action is strong in the deserts.

Answer: Wind action is strong in deserts because there is very little vegetation. Plants and trees usually act as a barrier to wind and help hold the soil in place. In the desert, with no such barriers, the wind can easily pick up and transport loose sand and dust, making its erosional and depositional activities very powerful.

14. What is meant by deflation?

Answer: Deflation is a type of wind erosion where wind blows away and removes loose sand, dust, and other tiny particles from the surface of the land. This process can lead to the formation of shallow depressions in the ground.

15. How are the sand dunes formed?

Answer: Sand dunes are hills of sand created by the depositional work of wind. When the wind carrying sand slows down, it drops the sand particles in one place. Over time, these deposits build up to form sand dunes, which can vary in shape and size depending on the wind’s strength and direction.

16. What is inselberg?

Answer: An inselberg is an isolated, single hill that rises sharply from a flat desert plain. The term means “island mountain” in German. Inselbergs are usually made of hard, erosion-resistant rock that has withstood the long-term erosional activities of wind, while the softer rock around it was worn away.

17. Define glacier and state how it differs from a river.

Answer: A glacier is a large body of ice that moves very slowly over the land. It forms in very cold regions from layers of compacted snow. A glacier differs from a river mainly in its composition: a river is made of flowing water, while a glacier is a mass of slowly moving ice. Both are agents of erosion and deposition, but a glacier’s movement is much slower and its effects are much more massive.

18. What is moraine? Draw a diagram to show different types of moraine.

Answer: Moraine is the name for all the rock debris, including boulders, pebbles, and sand, that is carried and deposited by a glacier.

Diagram showing different types of moraine:


19. Write how a glacial horn is formed.

Answer: A glacial horn is a sharp, pointed mountain peak that is formed when glaciers on two or more sides of a mountain erode the rock, carving out deep, bowl-shaped valleys called cirques. As the erosion continues, the steep walls of the cirques eventually meet, leaving a sharp, pyramid-shaped peak.

20. What is a coast?

Answer: A coast is the part of the land where it meets a large body of water, such as an ocean or sea. It is the boundary or contact zone between the land and the water.

21. What is a beach? State its importance.

Answer: A beach is a gentle, sloping area of land at the sea shore, typically covered with sand, pebbles, or shells. It is formed by the constant deposition of these materials by sea-waves. Beaches are important because:

1. They act as a natural barrier to protect the coast from erosion by waves and storms.
2. They provide a habitat for many coastal plants and animals.
3. They are popular places for recreation and tourism.

22. Write how sea-waves bring about change in the coasts.

Answer: Sea-waves change the coast through two main processes: erosion and deposition. Where the coast is made of hard rock, the powerful waves erode the rock, forming steep cliffs. In areas with loose sediment, the waves deposit sand and other materials, creating flat, sandy beaches. The strength and nature of the waves are influenced by factors like the geological structure of the coast and the depth of the water.

23. Connect by arrows the factors and the features on the basis of their cause-effect relation.

Answer:

• River -> Floodplain, Delta, Sandbar, Ox-bow lake
• Wind -> Inselberg, Sand dune
• Glacier -> Lateral moraine, Horn, U-shaped valley
• Sea-wave -> Beach, Coast

24. Think and wirte about the probable changes of the earth’s surface in future.

Answer: The Earth’s surface will continue to change in the future due to both natural processes and human activity. Natural factors like rivers, wind, and glaciers will keep shaping the land, but global climate change could alter their effects, for example, causing glaciers to melt and sea levels to rise. Human activities, such as building cities, farming, and deforestation, also have a huge impact, contributing to soil erosion and changing the natural landscape.

25. Prepare a note on the surface characteristics of your village or town. Draw a sketch of the area and try to show there the major features (river, hill, wetland, plain etc).

Answer: This question requires a personal and local response from the student. The answer will be unique for each person and needs a diagram of their own area. Therefore, a generic answer cannot be provided.