Access the latest NCERT Solutions for Class 7 Geography Chapter-3: Our Changing Earth, updated for 2024-2025. Solution is designed to help students tackle difficult questions with ease. The content is written in simple, easy-to-understand language.
Exercise
1. Answer the following questions:
(i) Why do the plates move?
The plates move due to the movement of molten magma inside the Earth. The magma moves in a circular manner beneath the Earth’s crust, causing the lithospheric plates to slowly shift.
(ii) What are exogenic and endogenic forces?
Exogenic forces are external forces that shape the Earth’s surface, like wind, water, and ice. Endogenic forces originate inside the Earth and cause movements like earthquakes and volcanoes.
(iii) What is erosion?
Erosion is the process by which the landscape is worn away by natural agents like wind, water, and ice.
(iv) How are flood plains formed?
Flood plains are formed when rivers overflow their banks, depositing layers of fine soil and sediments, which makes the land flat and fertile.
(v) What are sand dunes?
Sand dunes are low hills of sand formed in deserts when wind deposits sand after carrying it over long distances.
(vi) How are beaches formed?
Beaches are formed by the deposition of sediments like sand along the shores by sea waves.
(vii) What are oxbow lakes?
Oxbow lakes are crescent-shaped lakes formed when a river meander is cut off from the main river, leaving a standalone water body.
2. Tick the correct answer:
(i) Which is not an erosional feature of sea waves?
(a) Cliff
(b) Beach ☑
(c) Sea cave
(ii) The depositional feature of a glacier is:
(a) Flood plain
(b) Beach
(c) Moraine ☑
(iii) Which is caused by the sudden movements of the earth?
(a) Volcano ☑
(b) Folding
(c) Flood plain
(iv) Mushroom rocks are found in:
(a) Deserts ☑
(b) River valleys
(c) Glaciers
(v) Ox bow lakes are found in:
(a) Glaciers
(b) River valleys ☑
(c) Deserts
3. Match the following:
(i) Glacier (a) Sea shore
(ii) Meanders (b) Mushroom rock
(iii) Beach (c) River of ice
(iv) Sand dunes (d) Rivers
(v) Waterfall (e) Vibrations of earth
(vi) Earthquake (f) Sea cliff
(g) Hard bedrock
(h) Deserts
Ans.
(i) Glacier – (c) River of ice
(ii) Meanders – (d) Rivers
(iii) Beach – (a) Sea shore
(iv) Sand dunes – (h) Deserts
(v) Waterfall – (g) Hard bedrock
(vi) Earthquake – (e) Vibrations of earth
4. Give reasons:
(i) Some rocks have the shape of a mushroom.
In deserts, wind erodes the lower part of rocks more than the upper part, giving them a narrow base and wider top, resembling a mushroom.
(ii) Flood plains are very fertile.
Flood plains are fertile because rivers deposit fine sediments, including soil, which enriches the land during floods.
(iii) Sea caves are turned into stacks.
Sea caves are formed by the erosion of rocks by sea waves. Over time, the roof of the cave collapses, leaving a stack.
(iv) Buildings collapse due to earthquakes.
Buildings collapse during earthquakes because the sudden shaking of the Earth causes the ground to vibrate violently, which weakens the structures.
Other Important Short-answer Type Questions
Here are some important short-answer type questions from NCERT Class 7 Geography Chapter 3: Our Changing Earth, based on previous exams and UPSC patterns.
1. What are lithospheric plates and how do they move?
Lithospheric plates are rigid slabs that make up the Earth’s crust. These plates move due to the motion of molten magma in the Earth’s mantle, which causes them to shift a few millimeters each year. This slow movement can lead to changes on the Earth’s surface, including earthquakes and the formation of mountains.
2. What are endogenic and exogenic forces?
Endogenic forces originate within the Earth and include movements such as earthquakes and volcanic activity, which can result in both sudden and slow changes. Exogenic forces operate on the Earth’s surface, such as weathering, erosion by water, wind, and ice, which wear away landscapes and create various landforms.
3. How are ox-bow lakes formed?
Ox-bow lakes are formed when a meander of a river becomes cut off from the main flow due to continuous erosion and deposition. Over time, the meander loop gets isolated and forms a crescent-shaped lake. This typically occurs in the floodplains of rivers.
4. What are the different types of earthquake waves?
There are three main types of earthquake waves:
- P waves (Primary waves): These are longitudinal waves that travel the fastest.
- S waves (Secondary waves): These are transverse waves that travel slower than P waves.
- L waves (Surface waves): These cause the most destruction and move along the Earth’s surface.
5. What is erosion and how does it shape landforms?
Erosion is the process of wearing away the Earth’s surface by natural agents such as water, wind, and ice. It shapes landforms by removing soil and rock, transporting it elsewhere, and depositing it, leading to the formation of valleys, canyons, and coastal features like cliffs and beaches.
6. How do glaciers contribute to landform formation?
Glaciers, also known as “rivers of ice,” erode the landscape by bulldozing soil and rocks, exposing solid rock beneath. They carve out deep hollows, which can become lakes after the ice melts. The debris left behind by glaciers forms landforms called moraines, consisting of rocks and sediment.
MCQs on “Our Changing Earth”:
Here are 20 MCQs based on Chapter 3: Our Changing Earth from NCERT Class 7th Geography, which have been designed with both previous NCERT 7th class and UPSC examinations in mind. The answers are provided at the end of the list.
- What are lithospheric plates?
(a) Layers of the atmosphere
(b) Layers of the hydrosphere
(c) Large, rigid plates of Earth’s crust
(d) Layers of molten magma under the Earth - What is the movement of lithospheric plates caused by?
(a) Ocean currents
(b) Tectonic activity
(c) Gravitational force
(d) Movement of molten magma - Which forces act inside the Earth’s surface?
(a) Exogenic forces
(b) Erosional forces
(c) Endogenic forces
(d) Wind forces - Sudden movements of Earth’s crust, like earthquakes, are caused by which forces?
(a) Exogenic forces
(b) Endogenic forces
(c) Erosional forces
(d) Coastal forces - What is the place on the surface directly above the earthquake focus called?
(a) Epicenter
(b) Seismic point
(c) Crater
(d) Lava point - Which machine is used to measure the magnitude of an earthquake?
(a) Thermometer
(b) Seismograph
(c) Barometer
(d) Richter scale - Which is the highest waterfall in the world?
(a) Niagara Falls
(b) Victoria Falls
(c) Angel Falls
(d) Jog Falls - Which type of lake is formed by the cutting off of a meander in a river?
(a) Delta lake
(b) Ox-bow lake
(c) Tectonic lake
(d) Glacial lake - The raised banks along rivers, formed by deposits of sediments, are called?
(a) Delta
(b) Levees
(c) Sand dunes
(d) Moraines - What are rivers that break into many distributaries near their mouths called?
(a) Meanders
(b) Tributaries
(c) Distributaries
(d) Deltas - Which feature is NOT created by sea waves?
(a) Sea cave
(b) Cliff
(c) Waterfall
(d) Stack - Which depositional feature is formed by glaciers?
(a) Floodplain
(b) Beach
(c) Moraine
(d) Cliff - What is the term used for narrow bases and wider tops of rocks found in deserts?
(a) Mushroom rocks
(b) Moraines
(c) Sand dunes
(d) Delta - What is the process of breaking up rocks on Earth’s surface called?
(a) Deposition
(b) Erosion
(c) Weathering
(d) Lithification - What are the agents responsible for deposition in deserts?
(a) Wind
(b) Glaciers
(c) Rivers
(d) Earthquakes - Which coastal feature forms when sea waves erode only the lower section of the rock?
(a) Cliff
(b) Sea cave
(c) Sea arch
(d) Stack - What is a delta?
(a) A type of mountain range
(b) A flat plain formed by river deposits
(c) A landform made by wind
(d) A hill formed by ice deposits - What is the main cause of an earthquake?
(a) Atmospheric pressure
(b) Volcanic activity
(c) Lithospheric plate movement
(d) Melting of glaciers - Which of the following statements is true about glaciers?
(a) Glaciers only deposit sand
(b) Glaciers create ox-bow lakes
(c) Glaciers carve out deep hollows in the landscape
(d) Glaciers do not transport materials - How is a floodplain formed?
(a) By deposition of wind-blown sand
(b) By rivers depositing layers of sediments during floods
(c) By glacier movement in mountains
(d) By volcanic eruptions
Answers:
- (c)
- (d)
- (c)
- (b)
- (a)
- (b)
- (c)
- (b)
- (b)
- (c)
- (c)
- (c)
- (a)
- (c)
- (a)
- (b)
- (b)
- (c)
- (c)
- (b)
Other Chapters
| Chapter 1:- Environment | Chapter 2:- Inside Our Earth |
| Chapter 4:- Air | Chapter 5:- Water |
| Chapter 6:- Human Environment | Chapter: 7- Life in the Deserts |
