Class 7 Geography Chapter 3
NCERT Solutions For Class 7 Geography Chapter 3 Our Changing Earth, Earth’s motions are divided on the basis of the forces that produce them. The forces acting in the interior of the earth are called endogenous forces and the forces acting on the surface of the earth are called exogenous forces.
Class 7 Geography chapter 3, Earthquakes and volcanoes cause massive destruction on the Earth’s surface. Class 7 Geography chapter 3, The landscape is continuously deteriorating by two processes – weathering and erosion. NCERT Solutions For Class 7 Geography Chapter 3.
Our Changing Earth
Question 1. Answer the following questions briefly:
1. Why do the plated move?
Answer- The plates move because of movement in the molten magma found in the Earth’s interior.
2. What are Exogenic and Endogenic forces?
- Exogenous forces are those forces that act on the surface of the earth and cause changes on the Earth’s surface.
- Example: weathering, grading, erosion, deposition.
- Endogenous forces are those forces that originate in the interior of the earth and cause changes on the surface of the earth.
- Example: Volcanoes and earthquakes.
3. What is erosion?
Erosion spoils the landscape by various agents such as running water, glaciers, wind, groundwater, and sea waves.
4. How are flood plains formed?
Answer- Flood plains are formed in the following ways:
- During the rainy season, the rivers overflow their banks.
- This fills the surrounding areas with water.
- After the flood subsides, a layer of finer material and other material is deposited on top of the plain in the form of sediment.
- This creates a flood plain.
5. What are sand dunes?
Answer- Sand dunes
Sand dunes are heaps of sand deposited at one place by the action of wind’s desert areas.
6. How are the beaches formed?
Answer- Formation of Beaches
- The waves of the sea hit the coasts.
- They erode coasts and carry erosive material in the form of silt and other materials.
- When they withdraw they deposit silt and other material (sediment) along the shore, forming wide beaches.
7. What are the ox-bow lakes?
Answer- Ox-Bow Lakes
- When the meander loop is cut off from the main river, it becomes an eroded lake.
- Its shape is like an ox-bow.
- That’s why the cut-off lake is called the ox-bow lake.
Question 2. Tick the correct answer Class 7 Geography chapter 3:
(i) Which is not an Erosional feature of sea waves?
(c) Sea cave.
Answer- (a) Cliff
(ii) The depositional feature of a glacier is
(a) Flood plain
Answer- (c) Moraine
(iii) Which is caused by the sudden movements of the Earth?
(c) Flood plain.
Answer- (a) Volcano
(iv) Mushroom rocks are found In
(b) River valleys
Answer- (a) Deserts
(v) Ox-bow lakes are found In
(b) River valleys
Answer- (b) River valleys
Q 3. Match the following Class 7 Geography chapter 3.
(i) Glacier (a) Seashore
(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) Seacliff
(g) Hard bedrock
(i) Glacier (c) River of ice
(ii) Meanders (d) Rivers
(iii) Beach (a) Seashore
(iv) Sand dunes (h) Deserts
(v) Waterfall (g) Hard bedrock
(vi) Earthquake (e) Vibrations of earth
NCERT Solutions For Class 7 Geography ch 3
Question 4. Give reasons Class 7 Geography chapter 3:
1 Some rocks have the shape of a mushroom.
Answer- Some rocks have the shape of a mushroom, because for many reasons:
- When rocks fall in the course of running dust storms, the suspended particles of sand strike the lower portion of the rocks and erode them.
- The upper portions of the rocks remain unaffected/un-eroded.
- In course of time, the rocks take up the shape of a mushroom.
2. Flood plains are very fertile.
Answer- The floodplains are very fertile due to the following reasons:
- They are made of silt and other materials brought in by the flood.
- The floodplains are fertile areas due to the spread of new silt.
3. Sea caves are turned into stacks.
Answer- Sea caves turn into piles due to the following reasons:
- Sea waves hit the shores and destroy the soft rocks. Hard rocks remain un-eroded. This action results in the formation of sea caves.
- Over time, due to erosion, the roofs of the caves also come down and the sides/walls of the caves remain standing like pillars.
- These pillar-like structures are called piles.
4. Buildings collapse due to earthquakes.
Answer- Buildings collapse due to earthquakes due to the following reasons:
- Most of the buildings are not designed/built to be earthquake resistant.
- When earthquakes strike, buildings are not able to resist earthquake tremors.
- They tend to crack due to shallow foundations, substandard interior materials, and lack of sufficient steel.
- They collapse and fall like a piece of paper/cards.
In this chapter NCERT Geography book gives detailed information about:
- Changing Environment and its Effects on Earth
- Case Study on Earthquakes
- Major Land Forms
- river work
- sea wave function
- ice work
- wind work
Class 7 Geography Chapter 3 pdf
NCERT Solutions For Class 7 Geography Chapter 3. When the wind blows, it lifts the sand and carries it from one place to another. When the wind stops blowing, the sand falls and gets deposited in low hill-like formations. These are called sand dunes. They are mostly found in desert areas. NCERT Solutions For Class 7 Geography Chapter 3 PDF.
Class 7 Geography Chapter 3 pdf Click Here to Download
Class 7 Geography Chapter 3 Extra Questions
Most Important Question
Question 1. Explain the function of the river.
Answer: Water flowing in the river destroys the landscape. When a river falls at a high angle on very hard rocks or at the bottom of a deep valley, it forms a waterfall. While entering the plain the river turns and forms large bends known as meanders. Class 7 Geography chapter 3, Due to continuous erosion and deposition along the edges of the meander, the ends of the meander loop get closer and closer.
Over time, the meander loop is cut off by the river and forms a cut-off lake, also known as the ox-bow lake. Sometimes, the river overflows on its banks, causing flooding in the surrounding areas. As it floods, it deposits layers of fine soil and other material called sediments on its banks. As a result – a fertile floodplain is formed. The raised banks are called levies.
Class 7 Geography Chapter 3, As the River, approaches the sea, the speed of the flowing water decreases, and the river begins to split into several streams called distributaries. Then there comes a time when the river becomes very slow and starts gathering its weight. Each distributor makes its own mouth. The collection of sediments from all mouths forms a delta, which is a triangular landmass.