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.

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.

Choose the correct answer:

Question 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
Answer: (b) Lithospheric plates
In simple words: The outer shell of the earth is broken into massive slabs called lithospheric plates.

Exam Tip: Remember that lithospheric plates carry both landmasses and ocean floors on their surface.

Question 2. The forces that act in the interior of the earth are called_________________.
(a) Endogenic forces
(b) Exogenic forces
Answer: (a) Endogenic forces
In simple words: Forces that start deep inside the earth are named endogenic forces.

Exam Tip: Recall the prefix "endo" means inside, which helps identify internal earth forces.

Question 3. The forces that work on the surface of the earth are called _______________.
(a) Endogenic forces
(b) Exogenic forces
Answer: (b) Exogenic forces
In simple words: Energy acting on the earth's outer surface is called an exogenic force.

Exam Tip: Remember that "exo" means outside, pointing to surface forces like wind and flowing water.

Question 4. The place in the crust where the movement starts is called the _______________
(a) Focus
(b) Epicentre
(c) Magma chamber
Answer: (a) Focus
In simple words: The exact point inside the crust where an earthquake begins is called the focus.

Exam Tip: Do not confuse the focus (underground origin) with the epicentre (surface point directly above it).

Question 5. The place on the surface above the focus is called the _______________
(a) Focus
(b) Epicentre
(c) Crater
Answer: (b) Epicentre
In simple words: The spot on ground level straight above the earthquake focus is the epicentre.

Exam Tip: Earthquake vibrations travel outward from the epicentre, making this area suffer the greatest damage.

Question 6. When the river enters the plain it twists and turns forming large bends known as __________________
(a) Ox-bow lake
(b) Levees
(c) Meanders
Answer: (c) Meanders
In simple words: Wide curves and loops formed by a river on flat plains are called meanders.

Exam Tip: Continuous erosion and deposition along the sides of a meander eventually create ox-bow lakes.

Question 7. Crescent shaped lake formed by meandering river is known as _______________
(a) Ox-bow lake
(b) Levees
(c) Meanders
Answer: (a) Ox-bow lake
In simple words: A curved lake left behind when a river loop gets cut off is an ox-bow lake.

Exam Tip: Look for terms like "crescent-shaped" or "cut-off lake" to identify an ox-bow lake quickly.

Question 8. Near the sea the river begins to breakup into a number of streams called_______________
(a) Tributaries
(b) Distributaries
Answer: (b) Distributaries
In simple words: Small channels that branch away from the main river near the coast are distributaries.

Exam Tip: Remember that tributaries join a main river, whereas distributaries branch out away from it.

Fill in the blanks:

Question 9. The Lithospheric plates move because of the movement of ____________________ inside the earth.
Answer: molten magma
In simple words: Plates shift slowly because melted rock circulates deep inside the mantle.

Exam Tip: Mention that molten magma moves in a circular manner within the earth.

Question 10. Because of the sudden forces, movements like ____________________ and ____________________ takes place.
Answer: earthquakes and volcanoes (or volcanic eruptions / landslides)
In simple words: Sudden forces cause quick, powerful events like tremors and volcanic blasts.

Exam Tip: Sudden endogenic forces produce rapid disasters, unlike slow forces that build mountains.

Question 11. A ____________________ is a vent in the earth's crust through which molten material erupts suddenly.
Answer: volcano
In simple words: A volcano is an opening in the earth where melted rock bursts out.

Exam Tip: Include the keyword "vent" or "opening" whenever defining a volcano.

Question 12. The three types of earthquake waves are :
a. ____________________
b. ____________________
c. ____________________
Answer:
a. P waves (or Primary / longitudinal waves)
b. S waves (or Secondary / transverse waves)
c. L waves (or Surface waves)
In simple words: Earthquakes produce three wave types: primary waves, secondary waves, and surface waves.

Exam Tip: Surface waves (L waves) travel along the crust and cause the most destruction.

Question 13. Greatest damage is usually closest to the ____________________ of the earthquake.
Answer: epicentre
In simple words: Places right next to the epicentre face the strongest shaking and harm.

Exam Tip: Earthquake strength steadily decreases as distance from the epicentre increases.

Question 14. The earthquake is measured with a machine called ____________________.
Answer: seismograph
In simple words: Scientists record ground tremors using an instrument called a seismograph.

Exam Tip: Clearly separate the recording tool (seismograph) from the intensity scale (Richter scale).

Question 15. The ____________________ of the earthquake is measured on Richter scale.
Answer: magnitude
In simple words: The Richter scale measures the total power or magnitude of an earthquake.

Exam Tip: An earthquake over 7.0 on the Richter scale is classified as a major tremor.

Question 16. ____________________ is the breaking up of the rocks on the earth surface.
Answer: Weathering
In simple words: The natural breaking down of surface rocks into smaller pieces is called weathering.

Exam Tip: Weathering happens in place, while erosion involves the moving away of rock fragments.

Question 17. The process of ____________________ and ____________________ create different landforms on the surface of the earth.
Answer: erosion and deposition (or weathering and erosion)
In simple words: Wearing away land and laying down sediments shapes hills, plains, and valleys.

Exam Tip: Natural agents such as water, wind, and ice drive both erosion and deposition.

Question 18. The highest waterfall is the ____________________ of Venezuela.
Answer: Angel Falls
In simple words: Angel Falls in Venezuela is the tallest waterfall anywhere on earth.

Exam Tip: Remember Angel Falls is located in South America within the country of Venezuela.

Question 19. As the river approaches the sea the speed of the flowing water____________________.
Answer: decreases (or slows down)
In simple words: A river moves much slower as it gets closer to entering the sea.

Exam Tip: Reduced water speed forces the river to drop its sediments at its mouth.

Question 20. Deposits at the mouth of the river are known as ____________________
Answer: delta
In simple words: A triangular piece of land made by river silt at the sea is a delta.

Exam Tip: The collection of sediments from all distributary mouths forms a delta.

Question 21. Natural cavity or hollow like cave formed on weak rocks by the action of waves is known as ____________________.
Answer: sea cave (or sea caves)
In simple words: Sea waves hollow out hollow openings in coastal cliffs to make sea caves.

Exam Tip: When sea caves grow larger until only the roof remains, they become sea arches.

Question 22. Flat plain formed by river deposits during the time of flood is known as________________
Answer: floodplain (or flood plain)
In simple words: Rich soil left behind after river floods creates a very flat floodplain.

Exam Tip: Floodplains are extremely fertile because rivers spread fine silt and minerals across them.

Question 23. The raised banks are called ____________________.
Answer: levees
In simple words: High natural ridges built up along river edges are called levees.

Exam Tip: Levees form naturally as repeated flooding drops coarse material directly beside the river channel.

Question 24. Steep rocky coast rising almost vertically above sea water is called ____________________
Answer: sea cliff
In simple words: A tall, steep wall of rock standing straight above ocean water is a sea cliff.

Exam Tip: Constant wave action striking the base of coastal rocks cuts out a steep sea cliff.

Question 25. ____________________ is the active agent of erosion and deposition in deserts.
Answer: Wind
In simple words: Blowing wind is the main force shaping land inside dry desert regions.

Exam Tip: In arid areas without vegetation, wind easily lifts and transports loose sand grains.

Question 26. When winds erode the lower section of the rock more than the upper part ____________________ rocks are formed.
Answer: mushroom
In simple words: Wind wears down rock bases faster than tops, leaving mushroom-shaped rocks.

Exam Tip: Desert winds carry heavier grains near the ground, eroding rock bases much quicker.

Question 27. Small hills of sand caused by the action of wind are ____________________
Answer: sand dunes
In simple words: Low mounds made of blown sand in deserts are known as sand dunes.

Exam Tip: When the wind stops blowing, sand drops down to pile into low ridge-like dunes.

Question 28. Fine sand deposited by the wind over a large area is known as ____________________.
Answer: loess
In simple words: Very light, yellowish dust carried far and laid down by wind is called loess.

Exam Tip: Vast deposits of wind-blown loess are famously found in northern China.

Question 29. Draw the diagram of a volcano and label it.
Answer: A volcano is an opening in the earth's crust through which molten magma erupts. Its main labeled parts include: 1. Magma chamber: The underground reservoir storing liquid rock. 2. Vent: The central pipe through which magma ascends. 3. Crater: The bowl-shaped opening at the mountain summit. 4. Lava: Molten rock spilling down the slopes after reaching the surface. 5. Gases and ash: Plumes of smoke, vapor, and pulverized rock shooting into the sky. In simple words: A volcano has a vent pipe, an ash cloud on top, and a magma pool below.

Exam Tip: Ensure that your diagram always shows and labels the crater, vent, and magma chamber clearly.