Reviewing the Class 9 SST Extra Questions and Class 9 SST Chapter 2 Shaping of the Earth’s Surface Extra Questions and Answers before exams can boost your confidence.
Shaping of the Earth’s Surface Class 9 Extra Question Answer
Class 9 SST Chapter 2 Shaping of the Earth’s Surface Extra Questions
Shaping of the Earth’s Surface Class 9 Very Short Question Answer
Question 1.
“The Earth’s interior is divided into distinct layers, each with unique properties.” Explain the statement by stating the composition of the core.
Answer:
The Earth’s interior is divided into distinct layers with unique properties. The core, being the innermost layer, is mainly composed of iron and nickel, making it the densest. Its outer part is liquid and generates the magnetic field, while the inner part remains solid due to extreme pressure.
Question 2.
Explain any two significances of the ‘asthenosphere’ in the theory of plate tectonics.
Answer:
The significance of the asthenosphere in the theory of plate tectonics is as follows.
- It provides a soft, partially molten surface that enables tectonic plates to move slowly over it.
- It facilitates plate movement driven by mantle convection currents, leading to geological processes like earthquakes and mountain formation.
Question 3.
“Agents of gradation are responsible for shaping the Earth’s surface.” Explain the statement by naming the five main agents of gradation.
Answer:
Agents of gradation shape the Earth’s surface through processes of erosion and deposition. The five main agents of gradation are
- Rivers
- Waves and Currents
- Wind
- Glaciers
- Underground Water
Question 4.
“The process of gradation involves both the wearing down and building up of the Earth’s surface.” Explain the statement with examples.
Answer:
The process of gradation involves both the wearing down and building up of the Earth’s surface in the following ways.
- Wearing down occurs through erosion, where agents like rivers, wind, and glaciers remove rock and soil from higher areas.
- Building up occurs through deposition, where these materials are deposited in lower areas, forming landforms like plains, deltas, and dunes.
Question 5.
What causes the formation of a waterfall in the upper course of a river?
Answer:
A waterfall forms in the upper course of a river when there is a sudden steep drop in the river bed, often due to differences in rock hardness. Softer rock erodes faster than harder rock, creating a vertical fall.
Question 6.
Why are beaches important for both nature and human life? Give any two reasons.
Answer:
Beaches are important for both nature and human life because
- They attract tourists for relaxation, swimming, and recreation, which supports the local tourism industry and economy.
- They provide fishing areas; many coastal communities depend on beaches for fishing and the collection of shells.
Question 7.
“Landforms have greatly influenced the development of human civilisations.” Explain the statement with examples.
Answer:
Landforms have greatly influenced the development of human civilisations in the following ways.
- Rivers and fertile plains, such as the Ganga, Nile, Brahmaputra, and Indus, supported agriculture and led to the growth of early cities.
- Mountains, such as the Himalayas, acted as natural barriers for protection and also allowed cultural exchange through passes like the Khyber Pass.
Question 8.
“Human activities in hilly areas can increase the risk of landslides.” Explain the statement with any two points.
Answer:
Human activities in hilly areas can increase the risk of landslides in the following ways.
- Deforestation removes vegetation cover that holds the soil together, weakening slope stability and making it prone to sliding.
- Construction and mining on hillsides disturb the natural structure of slopes, increasing the chances of soil and rock movement.
Shaping of the Earth’s Surface Class 9 Short Question Answer
Question 1.
“The theory of plate tectonics is a unifying theory that explains many geological phenomena.” Explain this statement by describing how plate tectonics leads to the formation of mountains and ocean trenches.
Answer:
The theory of plate tectonics explains the formation of mountains and ocean trenches in the following ways.
Formation of Mountains: At convergent boundaries, when two continental plates collide, the crust is forced to buckle and fold upward, forming fold mountains.
For example, the Himalayas were formed by the collision of the Indian and Eurasian plates.
Formation of Ocean Trenches: At convergent boundaries, when an oceanic plate subducts under a continental plate, it sinks into the mantle, forming deep ocean trenches.
For example, the Mariana Trench in the Pacific Ocean was formed by the subduction of the Pacific Plate.
Question 2.
How do the three types of plate boundaries (divergent, convergent, and transform) differ in their movement and the geological features they create?
Answer:
The three types of plate boundaries differ in the following ways.
| Plate Boundary | Movement | Geological Features |
| Divergent Boundary | Plates move away from each other as magma rises due to mantle convection currents. | Magma rises through cracks, forming new crust and volcanic landforms. |
| Convergent Boundary | Plates move towards each other and collide. | Crust folds to form mountains; subduction creates deep ocean trenches. |
| Transform Boundary | Plates slide past each other horizontally. | Friction causes stress buildup and sudden release, resulting in earthquakes. |
Question 3.
Explain how the process of chemical weathering differs from physical weathering, giving one example of each.
Answer:
Chemical weathering differs from physical weathering in the following ways.
| Aspect | Physical Weathering | Chemical Weathering |
| Process | Breaks rocks into smaller pieces without changing their chemical composition through mechanical forces like pressure and temperature changes. | Changes the chemical composition of rocks by forming new minerals and weakening them through chemical reactions. |
| Conditions | Common in areas with large temperature variations and less moisture. | Occurs mainly in warm and humid climates where reactions are faster. |
| Example | Frost action breaks rocks as water freezes and expands in cracks. | Oxidation forms rust when minerals react with oxygen, altering rock composition. |
Question 4.
“The course of a river is divided into three stages, each characterised by different landforms.” Describe the landforms found in the middle course of a river.
Answer:
The landforms found in the middle course of a river are as follows.
- Floodplain: Flat and fertile land formed when the river deposits fine soil (alluvium) during floods.
- Meanders: Broad, looping bends formed as the river flows from side to side.
- Ox-bow Lake: A crescent-shaped lake formed when a meander loop gets cut off from the main river channel.
Question 5.
Describe the role of wind as an agent of gradation. Name one erosional and one depositional landform created by it.
Answer:
Wind acts as an agent of gradation by eroding, transporting, and depositing sand and dust, especially in dry regions. Through these processes, it shapes landforms such as mushroom rocks, dunes, and loess.
Erosional and depositional landforms created by it are as follows.
- An erosional landform is a Mushroom Rock (or pedestal rock), formed when wind erodes the lower part of a rock more than the upper part.
- A depositional landform is Loess, which is fine dust particles deposited over large areas, forming fertile soil.
Question 6.
Why are glaciers called the ‘freshwater reservoirs’ of the Earth? Explain any three reasons.
Answer:
Glaciers are called the ‘freshwater reservoirs’ of the Earth because
- They store a large amount of the Earth’s freshwater in the form of ice, making them the largest natural source of freshwater.
- They feed rivers as they melt, providing a continuous supply of freshwater for drinking, irrigation, and hydroelectric power.
- They support ecosystems and human populations downstream, especially during dry seasons when river flow depends largely on melting glaciers.
Question 7.
How does a Glacial Lake Outburst Flood (GLOF) occur, and why is it a serious hazard in the Himalayan region?
Answer:
A Glacial Lake Outburst Flood (GLOF) occurs when a glacial lake suddenly releases water due to the breaking or overtopping of its natural ice or moraine dam. This can happen because of glacial melting, dam failure, ice avalanches, or earthquakes. Glacial Lake Outburst Flood is a serious hazard in the Himalayan region due to the following reasons.
- Rapid melting of glaciers due to climate change increases the size of glacial lakes and pressure on dams.
- Sudden flooding causes heavy loss of life and damage to infrastructure in downstream areas.
Shaping of the Earth’s Surface Class 9 Long Question Answer
Question 1.
A geography student visited two different regions. In Region A, people frequently experienced earthquakes and volcanic eruptions. In Region B, such events were extremely rare. Based on the observations, the student concluded that Region A was located near a tectonic plate boundary, while Region B was not. Analyse the geographical differences between the two regions that enabled the student to reach this conclusion.
Answer:
The student could conclude that Region A was located near a tectonic plate boundary due to the following geographical differences.
Occurrence of Earthquakes: Region A experiences frequent earthquakes because tectonic plates interact along plate boundaries, whereas Region B experiences very few earthquakes as it is located away from plate boundaries.
Volcanic Activity: Frequent volcanic eruptions in Region A indicate the presence of active plate movements that allow magma to reach the Earth’s surface. Region B shows little or no volcanic activity.
Plate Movement: Region A lies where tectonic plates converge, diverge, or slide past each other, resulting in intense geological activity. Region B is situated within the stable interior of a tectonic plate.
Formation of Landforms: Region A is more likely to have young fold mountains, volcanoes, and fault lines formed by plate movements, while Region B has comparatively stable and older landforms.
Geological Stability: Region A is geologically active and more prone to natural disasters such as earthquakes and volcanic eruptions. In contrast, Region B is relatively stable because it is located away from active plate boundaries.
Question 2
“The work of a river is a continuous process of erosion, transportation, and deposition, which changes its character as it flows from its source to its mouth.” Describe the features formed by a river in its upper, middle, and lower courses.
Answer:
The features formed by a river in its upper, middle, and lower courses are
- In the upper course, the river flows over a steep slope and mainly performs vertical erosion. It cuts deep valleys and forms features like waterfalls due to differences in rock hardness, showing strong erosional activity.
- In the middle course, the slope becomes gentler, and the river begins to widen. Both erosion and deposition occur, leading to the formation of floodplains, meanders, and ox-bow lakes as the river swings from side to side and deposits sediments along its banks.
- In the lower course, the river flows over a very gentle slope and deposition becomes dominant. It carries large amounts of sediment and deposits them near its mouth, forming extensive plains and delta regions, continuously reshaping the land.
Question 3.
“Underground water forms unique landforms through chemical weathering.” Explain the statement with suitable examples.
Answer:
Underground water forms unique landforms through chemical weathering because it dissolves soluble rocks such as limestone over a long period. Some common landforms formed by underground water are
- Caves are formed when underground water dissolves limestone. For example, the Ajanta and Ellora Caves in India are associated with underground weathering processes.
- Stalactites are icicle-shaped formations that hang from the roofs of caves. For example, the Borra Caves in Andhra Pradesh contain spectacular stalactites.
- Stalagmites are rock formations that grow upward from the floors of caves. For example, the Borra Caves also contain well-developed stalagmites.
- Sinkholes (dolines) are formed when the roof of an underground cavity collapses. For example, sinkholes are commonly found in limestone (karst) regions of the world.
- Underground rivers flow through cave systems created by the continuous action of underground water. For example, the Puerto Princesa Underground River in the Philippines flows through a limestone cave system.
Question 4.
Differentiate between beaches and coastal erosion landforms.
Answer:
The difference between beaches and coastal erosion landforms is as follows.
| Beaches | Coastal Erosion Landforms |
| Beaches are formed by the deposition of sand, pebbles, and rocks by waves along the shore. | Coastal erosion landforms are formed by the erosional action of waves, tides and coastal currents. |
| Beaches support tourism, fishing, and recreation and protect nearby settlements from strong waves. | Coastal erosion landforms such as cliffs, wave-cut platforms, caves, arches, and stacks mainly reshape the coastline and attract tourists. |
| Beaches are found along the shore of a sea, ocean, or lake. | These landforms develop along eroding coastlines. |
| Beaches generally have a gentle and broad surface made of sand or pebbles. | Coastal erosion landforms often have steep, rocky features such as cliffs, caves, arches, and stacks. |
| Example: Marina Beach, Chennai. | Examples: Cliffs, wave-cut platforms, sea caves, arches, and stacks. |
Question 5.
“Natural disasters linked to landforms are a recurring threat, but their impact can be significantly reduced through effective mitigation strategies.” Analyse this statement by describing the causes and mitigation strategies of the following: earthquakes, landslides or dust storms.
Answer:
The causes and mitigation strategies for earthquakes, landslides and dust storms are as follows.
Earthquakes: They can be caused by tectonic plate movement, where stress builds up along plate boundaries and is suddenly released, and by faulting along cracks in the Earth’s crust. Mitigation includes constructing earthquake-resistant buildings using strong and flexible materials on firm ground, and spreading awareness through safety practices like “Drop, Cover, Hold On” along with enforcing building codes.
Landslides: They can be caused by heavy rainfall that weakens soil and by steep slopes with loose or fractured rocks, along with human activities like deforestation. Mitigation includes building retaining walls and proper drainage systems, and adopting afforestation and hazard mapping to stabilise slopes and restrict construction.
Dust Storms: They can be caused by prolonged drought and strong winds over loose, dry soil, and by deforestation and overgrazing. Mitigation includes afforestation and shelter belts, along with sustainable land management practices like controlled grazing and soil conservation.
Shaping of the Earth’s Surface Class 9 Case Based Questions
Question 1.
Read the given source and answer the questions that follow.
Plate tectonics is an important theory, given by W.J. Morgan, in earth science, that explains the movement of the Earth’s crust. According to this theory, the outermost layer of the Earth is not one single piece but is broken into several large and small pieces called tectonic plates. These plates move slowly over the semi-molten layer beneath them and are responsible for major physical features and natural phenomena, such as mountains, earthquakes, and volcanoes. Tectonic plates are massive slabs of solid rock that move very slowly, usually a few centimetres per year. There are three main types of tectonic plates: continental plates, which carry continents; oceanic plates, which carry ocean floors; and mixed plates, which carry both continents and oceans. Some of the major tectonic plates of the world include the Pacific Plate, Eurasian Plate, African Plate, North American Plate, South American Plate, Indo-Australian Plate and Antarctic Plate. The movement of tectonic plates is caused by convection currents in the mantle. Heat from the Earth’s core causes molten material in the mantle to rise, while cooler material sinks. This continuous movement creates convection currents that push and pull the tectonic plates, causing them to move in different directions. The edges where tectonic plates meet are called plate boundaries.
(i) How are fold mountains formed?
Answer:
Fold mountains are formed when two continental plates collide, forcing the crust to buckle and fold upward, as in the Himalayas.
(ii) Why do most earthquakes occur along plate boundaries?
Answer:
Most earthquakes occur along plate boundaries because the movement of plates-colliding, sliding past, or pulling apart-releases stored energy in the form of seismic waves.
(iii) Explain in two ways how plate tectonics affects the Earth’s surface.
Answer:
Plate tectonics affects the Earth’s surface in the following ways.
- It creates landforms such as mountains, volcanoes, and ocean trenches through processes like collision, subduction, and volcanic activity.
- It explains the drift and distribution of continents, showing how they moved from the supercontinent Pangaea to their current positions.
Question 2.
Read the given source and answer the questions that follow.
Agents of gradation are natural forces that wear down, transport, and deposit materials on the Earth’s surface, helping to level or smooth it over time. The main agents of gradation are running water, glaciers, wind, waves and groundwater. Running water erodes rocks and soils to form valleys and plains. Glaciers scrape and carry huge amounts of material, carving U-shaped valleys. Wind shapes deserts by eroding and depositing sand. Sea waves erode coastlines to form cliffs, beaches and bays. Groundwater dissolves rocks, such as limestone, creating caves and sinkholes. Together, these agents are continuously modifying landforms, lowering high areas and filling up low areas. Rivers shape the land through the processes of erosion, transportation and deposition, creating a variety of landforms along their course. At the upper course, rivers often form V-shaped valleys, waterfalls, and rapids due to steep gradients and strong erosive forces. In the middle course, the river starts to meander, forming oxbow lakes and floodplains as it loses energy and begins depositing sediments. In the lower course, the river slows further and deposits large amounts of sediment, forming deltas, levees and alluvial fans. These landforms are not only important for understanding river dynamics but also play a vital role in agriculture, settlement and ecosystems.
(i) How do rivers act as agents of gradation?
Answer:
Rivers act as agents of gradation by eroding rocks in their upper course, transporting sediments in the middle course, and depositing materials in the lower course and delta regions.
(ii) Why is wind an important agent of gradation in dry regions?
Answer:
Wind is an important agent of gradation in dry regions because it can erode, transport, and deposit sand and dust where there is little vegetation.
(iii) Explain in two ways how glaciers and underground water shape the Earth’s surface.
Answer:
Glaciers and underground water shape the Earth’s surface in the following two ways.
- Glaciers erode valleys and mountains as they slowly move, and deposit rocks and debris, forming landforms like moraines and fjords.
- Underground water dissolves soluble rocks like limestone, creating features such as caves, sinkholes, and karst topography.
Shaping of the Earth’s Surface Class 9 Picture Based Questions
Question 1.
The given image shows rocks breaking down into smaller pieces due to natural forces. Identify the concept shown in the picture.
Options:
(a) Erosion
(b) Weathering
(c) Deposition
(d) Landslide
Answer:
(b) Weathering
Question 2.
The given image shows a large mass of snow rapidly sliding down a mountain slope. Identify the natural disaster shown in the picture.
Options:
(a) Landslide
(b) Avalanche
(c) Dust Storm
(d) Earthquake
Answer:
(b) Avalanche
Shaping of the Earth’s Surface Class 9 Map Based Questions
Question 1.
On the outline map of the world, locate and label the following with suitable symbols.
(i) African Plate
(ii) Eurasian Plate
(iii) Australian Plate
(iv) Pacific Plate
(v) North American Plate
(vi) South American Plate
(vii) Antarctic Plate
Answer:
Question 2.
On the outline map of the world, shade the Ring of Fire region.
Answer:
