NCERT Solutions for Class 7 Geography Social Science Chapter 3 | Extra questions . yash singhal edu tech world.

VERY SHORT QUESTION ANSWER.

"Welcome To My World"

Q1. What are the major agents of erosion?

Ans. Water, wind and ice are the major agents of erosion.

Q2. Define loess?

Ans. When sand is deposited in large areas, it is called loess.

Q3. What is vent?

Ans. The narrow opening of a volcano is called vent.

Q4. What is a seismograph?

Ans. An earthquake is measured with a machine called a seismograph.

Q5. What is the name of the scale used to measure earthquakes?

Ans. The magnitude of the earthquake is measured on the Richter scale.

Q6. Write names of a few rivers of the world that form a delta.

Ans. Ganga-brahmaputra, Zaire, Murray-Darling, Amazon, Nile, Murray-Darling

Q7. What are distributaries?

Ans. The river begins to break up into a number of streams called distributaries.

Q8. What are meanders?

Ans. As the river enters the plain it twists and turns forming large bends known as meanders.

Q9. What are Lithospheric plates?

Ans. The lithosphere is broken into a number of plates known as the Lithospheric plates.

Q10. What is a volcano?

Ans. A volcano is a vent (opening) in the earth’s crust through which molten material erupts suddenly.

SHORT QUESTION ANSWER .

Q1. What is erosion?

Ans. Erosion is the wearing away of the landscape by different agents like water, wind and ice.

Q2. Why do the plates move?

Ans. Plates move because of the movement of the molten magma inside the earth.

Q3. What are ox bow lakes?

Ans. Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loop come closer and closer. In due course of time the meander loop cuts off from the river and forms a cut-off lake, also called an ox-bow lake.

Q4. What are exogenic and endogenic forces?

Ans. Exogenic forces - The forces that work on the surface of the earth are called as Exogenic forces.

Endogenic forces - The forces which act in the interior of the earth are called as Endogenic forces.

Q5. How are beaches formed?

Ans. Beaches are formed when the sea waves deposit sediments along the shores.

Q6. How are flood plains formed?

Ans. At times the river overflows its banks. This leads to the flooding of the neighbouring areas. As it floods, it deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of a flat fertile flood plain.

Q7. What are sand dunes?

Ans. When the wind blows, it lifts and transports sand from one place to another. When the wind stops blowing, the sand falls and gets deposited in the low hill-like structures. These are called sand dunes. They are mostly found in desert areas .

GIVE REASONS :-

Q1. Why do buildings collapse due to earthquakes?

Ans. Buildings collapse due to earthquakes because

Earthquakes move the ground side to side and up and down—simultaneously. The force behind this movement is powerful enough to turn soft soil instantly into quicksand, eliminating its ability to bear weight.

Q2. Why some rocks have a shape of a mushroom?

Ans. Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top which resembles a mushroom. These rocks in the shape of a mushroom, commonly called mushroom rocks.

Q3. Why are the flood plains very fertile?

Ans. The flood plains are very fertile because these plains are formed by the fine soil and sediments brought by the flood water.

Q4. Sea caves are turned into stacks.

Ans.

1. Sea waves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Thus, hollow like caves are formed on the rocks. They are called sea caves.

2. As these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches. Further, erosion breaks the roof and only walls are left. These walls like features are called stacks.

LONG QUESTION ANSWER.

Q1. What are earthquakes? What are the three types of earthquake waves? earthquake preparedness.

ANS:

When the Lithospheric plates move, the surface of the earth vibrates. The vibrations can travel all-round the earth. These vibrations are called earthquakes.

There are three types of earthquake waves:

1. P waves or longitudinal waves

2. S waves or transverse waves

3. L waves or surface waves

Although earthquakes cannot be predicted, the impact can certainly be minimised if we keep the following points in mind.

Safe Spot – Take shelter during an earthquake under a kitchen counter, table or desk, against an inside corner or wall.

Stay Away from – Fire places, areas around chimneys, windows that shatter including mirrors and picture frames.

Be Prepared – Spread awareness amongst our friends and family members and face any disaster confidently.

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