Class 7 Chapter 3 Geography

Class 7

Chapter 3 Geography

Our Changing Earth

Worksheet

Q1. Fill in the blanks:-

a.     A place in the crust where the movement starts is called the _____. (focus)

b.     S waves are also known as ______ waves. (Transverse waves)

c.      The river of ice is known as ____. (Glacier)

Q2. Multiple Choice Questions:-

a.      The molten rocks inside the earth are known as _____. ( c)

(a)   Lava    (b)  plates  (c)  Magma  (d) Dunes

b.      The forces which work on the surface of the earth are called____.(c )

(a)   Sudden forces  (b)  Endogenic forces (c)  Exogenic forces  (d) Circular forces

c.       The highest waterfall in the world is in ___. (a)

(a)   Venezuela  (b) Africa  (c) New Zealand  (d)  Australia

d.      Which is not an erosional feature of sea waves?(b)

(a)   Cliff  (b)  Beach  (c)  Sea cave  (d) sea stack

e.      The deposition feature of a glacier is _____. (b)

(a)   Flood plain   (b) Moraine (c) beach (d) meanders.

Q3. Match the Column ‘A’ with the Column ‘B’:-

                        A                                 B

               a. Stacks                               rivers               [b]

                b. Delta                                    desert                     [d]

              c. Moraines                           sea waves        [a]

              d. Sand dunes                        Ice (glaciers)   [c]

Q4. Answer the following questions in brief (in 1 or 2 lines):-

1.      What is erosion?

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

2.      What are ox Bow Lake?

Ans: Due to the 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 loops cuts off from the river and forms a cut-off lake. This lake is called ox bow lake.

3.      How are flood plains formed?

And: 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 floodplains.

4.      What are sand dunes?

Ans: When the winds blows in the deserts, it lifts and transports sand from one place to another. When it stops blowing the sand falls and gets deposited in low hill-like structures. These are called sand dunes.

5.      How are beaches formed?

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

6.      Name the three types of earthquake waves.

Ans: The three types of earthquakes are:

a.      P waves or longitudinal waves.

b.      S waves or transverse waves.

c.       L waves or surface waves.

7.      Why do the plates move?

Ans: The lithosphere is broken into a number of plates known as the lithospheric plates. These plates move around very slowly because of the movement of the molten magma inside the earth. The molten magma inside the earth moves in a circular manner.

Q5. Answer the following questions in detail:-

1.      What are sea caves? How are caves formed along the coast?

Ans: Sea waves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Hollow like caves are formed on the rocks. They are called sea caves.

2.      What are mushroom rocks? Where are they found?

Ans: In deserts, we can see the rocks in the shape of a mushroom. These are called mushroom rocks.Winds erode the lower section of the rock more than the upper part. These rocks have narrower base and wider top like a mushrooms.

3.      Give the difference between a sea cliff and a sea beach.

Ans: Sea cliff are the steep rocky coast rising almost vertically above sea water whereas 

	Sea Cliff	Sea Beach
1.	This is formed by an erosional activity in the sea.	This is formed by a depositional activity of the sea.
2.	Sea cliff are the steep rocky coast rising almost vertically above sea water.	The sea wave deposit sediments along the shore forming sea beaches.

4.      Why flood plains are very fertile?

Ans: Flood plains are very fertile because floods deposit layers of fine soil and other material called sediments which is ideal for cultivation.

5.      Why sea caves are turned into stacks?

Ans:Sea waves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Hollow like caves are formed on the rocks. They are called sea caves. These cavities become bigger and bigger and a time comes when only the roofs of the caves remain to form the sea arches. Further the erosion breaks the roof and only walls are left. These walls like structures are called stacks. In this way, sea caves are turned into stacks.

6.      Why buildings collapse due to earthquake?

Ans: During earthquake, vibrations travel outward from the epicenter as waves and propagate through the surface of the earth which produce sudden movements that leads to the collapse of the buildings. Most of the buildings are not safe enough to resist the vibration of the earthquakes. They collapse tearing apart due to shallow foundation and lack of adequate steel in the interior design