CBSE Class 7 Geography Our Changing Earth Worksheet

Question. Alfred Wegener proposed that millions of years ago , there was a super-Continent called-
1] Africa
2] Pangaea
3] Asia
4] Gondwanaland
Answer : [ 2 ]

Question. Which of the following is an active Volcano -
1] Kilmanjaro
2] Mt.Kea
3] Mt.Vesuvius
4] Cotopaxi
Answer : [ 4 ]

Question. Which of the following is not caused by endogenic forces -
1] Glaciers
2] Landslides
3] Volcanic eruptions
4] Earthquake
Answer : [ 1 ]

Question. The place of origin of an earthquake is called-
1] Vent
2] Zone
3] Focus
4] Epicentre
Answer : [ 3 ]

Question. Which of the following is an extinct volcano –
1] Stromboli
2] Mt. Aconcagua
3] Mt.Vesuvius
4] Mt.Kea
Answer : [ 2 ]

 FILL IN THE BLANKS :

Question. Active Valcanoes are also called………………
Answer : Live volcanoes

Question. The conical……….is formed when the erupted materials collect around the vent .
Answer : mountain

Question. The intensity of the earthquake is maximum near the ……………..
Answer : epicentre

Question. The magnitude of earthquake waves is measured on the …………scale.
Answer : Richter 

Question. The forces which originate from within the earth are called…………forces .
Answer : endogenic

VERY SHORT QUESTION ANSWERS :

Question. What is the theory of Continental Drift ?
Answer : Theory of continental drift suggested, that millions of years ago ,all Landmasses were joined together into a supercontinent , called the Pangaea.

Question. What do you mean by epicentre ?
Answer : The point on the earth’s surface ,which is vertically above the focus. The intensity of an earthquake is maximum near the epicentre.

Question. Define Seismograph ?
Answer : An instrument that detects , measures and records an earthquake Is called seismograph.

Question. What are the three major earthquake zones ?
Answer : The Earth has three major earthquake zones. The first large area kn- own as the Pacific Ring of Fire. The second major earthquake zone is along the mid-Ocean ridges.The third major earthquake zone is the Eurasian-Melanesian Mountain belt .

Question. What are the two types of Earthquake waves ?
Answer : There are two types of earthquake waves , Body Waves- which travel through the interior of the earth . Surface Waves arrive and travel on the earth’s surface starting from the epicentre.

SHORT QUESTION ANSWERS :

Question. Explain the concept of Plate Tectonic ?
Answer : Plate tectonics explains the features and movements of earth sur- face , from deepest ocean trench to the tallest mountain. The earth’s crust consists of lithosphere. There are several major and minor plates, all float independently . The rate of movement of the plates is extrem- ely slow , about a few millimetres per year . Tectonic activities such as earthquakes and volcanicity , occur along the plate margins. The plates are in a constant motion.

Question. What do we understand by Richter scale ?
Answer : The magnitude of an earthquake is measured on the Richter Scale. The Richter Scale ranges from zero to nine. An increase in one point on the Richter scale indicates that the force of the earthquake is 10 time greater than the strength of the previous number. The Richter Scale is used to rate the amount of energy released during an earth- quake.

LONG QUESTION ANSWER :

Question. Describe a Volcano, explain its various parts with the help of diagram?
Answer : A Volcano is a vent or opening in the earth’s crust through which molten material erupts suddenly. Magma and other volcanic materials are chann- eled to the surface where they expelled through a crack or hole. The three main parts of a volcano are the chamber ,vent ,and the crater. Way below the surface of the earth is the crust, where volcanic activity begins . Mag- ma is contained in magma chamber. A space within the earth that holds the hot melted rock. Magma also contains gasses, that start to build up pressure over times. When the pressure becomes extreme,the magma is pushed out of the earth through main vent, somewhat like pipeline. The magma shoots through this pipeline in order to escape the earth. A crater is formed when the volcano literally blows its top ,pushing out anything on the earth’s surface, e.g. the Deccan Plateau in India.

Choose the correct answer:

1. The earth’s crust consists of several large and small plates which carry continents and the ocean floor, known as ________________.

a. Exogenic forces

b. Lithospheric plates

c. Mantle

2. The forces that act in the interior of the earth are called_________________.

a. Endogenic forces

b. Exogenic forces

3. The forces that work on the surface of the earth are called _______________.

a. Endogenic forces

b. Exogenic forces

4. The place in the crust where the movement starts is called the _____________.

a. Focus

b. Epicentre

c. Magma chamber

5. The place on the surface above the focus is called the _______________ .

a. Focus

b. Epicentre

c. Crater

6. When the river enters the plain it twists and turns forming large bends known as _____________ .

a. Ox-bow lake

b. Levees

c. Meanders

7. Crescent shaped lake formed by meandering river is known as ____________.

a. Ox-bow lake

b. Levees

c. Meanders

8. Near the sea the river begins to breakup into a number of streams called_______.

a. Tributaries

b. Distributaries

Fill in the blanks:

9. The Lithospheric plates move because of the movement of ________________ inside the earth.

10. Because of the sudden forces, movements like ____________ and _________ takes place.

11. A ____________ is a vent in the earth’s crust through which molten material erupts suddenly.

I. Give reasons :-

1. A river is more energetic in the upper course.

2. A river flows slowly as it approaches sea.

3. Mushroom rocks are found in deserts.

II Stuff to do :-

Paste picture of meanders and deltas by citing examples from India.

Question. Why we study Atmosphere in Geography?
Answer : Because Atmosphere is responsible for creating and maintaining of plants and animal life on the Earth.

Question. Which is called Tropopause limit?
Answer : Tropopause limit is the boundary between Troposphere and Stratosphere.

Question. What are the elements other than the gases present in the Atmosphere?
Answer : Water vapours and dust particles.

Question. What is temperature and what are the units of measuring the temperature?
Answer : The heat of the air and the internal heat of a good or living being, is called temperature. It is measured in Celsius and Fahrenheit.

Short Answer Type Question
 

Question. What are the main factors that cause air pollution?
Answer : Solid pollutants: - 1. Volcanoes pollute the air by dust particles.
2. Smoke from the burning of fuels release carbon particles into the air.
Gaseous pollutants:- 1. Exhaust materials of automobiles pollute the air.
2. Smog causes air pollution.

Question. Write the ratio of main gases in the air.
Answer : 1.Nitrogen- 78.03%,
2. Oxygen- 20.99%
3. Argon- 0.94%
4. Carbon dioxide- 0.03%
5. Hydrogen- 0.01%
6. Dust particles and water vapours.

Very Short Answer Type Question

Question. What do you understand by the Atmosphere?
Answer : The earth is surrounded by a cover of air. This cover is known as Atmosphere.

Question. Name the layers of Atmosphere.
Answer : 1.Troposphere 2. Stratosphere
3. Mesosphere 4. Thermosphere (Ionosphere+ Exosphere)

Question. What do you understand by Exosphere?
Answer : The outermost layer of Atmosphere is called Exosphere. It has gases like Hydrogen and Helium.

Question. What is air pollution?
Answer : Foreign substances in the Atmosphere make air unhealthy. This is called air pollution. Smoke, dust particles and pesticides are the main sources of air pollution.

Question. Why is the temperature very high on the Equator?
Answer : The rays of the sun fall directly on the Equator. Therefore the temperature is high over there.

Short Answer Type Question
 

Question. What we call the lower layer of the atmosphere?
Answer : 1. The lowest layer of the atmosphere is called Troposphere. Its average height is 12 Km.
2. The entire weather phenomenon like rainfall, storm, clouds etc. takes place only in this layer.
3. The 75% of all the air, is present in this layer.

Question. In which layer of the Atmosphere the Ozone gas exists? Why is it so important?
Answer : Ozone gas exists in Stratosphere layer.it absorbs the Ultraviolet rays of the Sun, which are very harmful to the life of living beings on the earth.

Fill in the blanks

1. As we go up to the hills the temperature decreases.
2. The main sources of the temperature are Sun and internal part of the Earth.
3. The Ozone gas absorbs Ultraviolet rays.
4. The electrically charged particles are found in Thermosphere or Ionosphere layer.
5. The wireless communication system works under Radio waves.
6. Nitrogen gas is found in maximum quantity in atmosphere.

Chapter 3: Our changing earth

Q1.What are lithospheric plates?

Q2.How are earthquakes and volcanoes caused?

Q3What is a volcano?Explain with the help of a diagram.

Q4.Describe earthquake with the help of a diagram?

Q5.How are the earthquakes predicted?

Q6.How are the earthquakes measured?

Q7.Define weathering?

Q8.Discuss the work of river in detail?

Q9. Discuss the work of sea waves and glaciers?

Q10.What are mushroom rocks,sand dunes and loess?

Q11. Which processes modify the earth?

Q12. Fill in the blanks:-

         a) The act of carrying away weathered particles is called______.

         b) Old and coarse alluvial is called________.

         c) The point where vibrations originate is clled_____.

         d) The highest waterfall is_______.

Q13.What is the depositional feature of the river called?

Q14. The depositional feature formed by sea waves is called________.

Q15. Why is the work of erosion and transportation more in the mountains than in the plains?

Q16. Why do human beings throw waste such as wrappers, plastic bottles, poly bags on roads and in water bodies. Such careless disposal is known as litter. Discuss in detail in the class on what you can do to keep the environment clean?