Class 7 Geography Chapter 3 Our Changing Earth Important Questions and Answers
CBSE Class 7 Geography Chapter 3 Our Changing Earth Important Questions and answers cover all the major concepts of the chapter. Solving answers of these important questions help students to revise the Chapter most competently. We prepared these questions as per the latest NCERT book and CBSE syllabus. Practising class 7 important questions before the exam will ensure excellent marks in the exam.
Our Changing Earth Class 7 Geography Important Questions
Very Short Answer Type Question
1: Define focus.
Answer: The place in the crust where the movement starts is called the focus.
2: _________ is used to measure magnitude of earth quake.
Answer: Richter scale
3: The highest water fall is ________ falls of Venezuela.
4: What is vent?
Answer: The narrow opening of a volcanoes is called vent.
5. What do you know about the lithospheric plates?
Answer: The earth’s crust consists of several large and some small, rigid, irregularly— shaped plates, Le., slabs which cany continents and the ocean floor.
6. How do the lithospheric plates move?
Answer: They move around very slowly, just a few millimeters each year.
7. What is a volcano?
Answer: A volcano is a vent or opening in the earth’s crust through which molten material erupts suddenly.
8. Define focus’ and ‘epicentre’. [Imp.]
Answer: The place in the crust where the movement starts is called the ‘focus’. The place on the surface above the focus is called the ‘epicentre’.
9. What is a seismograph? [V. Imp.]
Answer: A seismograph is a machine which measures an earthquake.
10. Name the scale on which the magnitude of the earthquake is measured.
Answer: Richter scale.
11. Which earthquake is classified as a major earthquake?
Answer: An earthquake of 7.0 magnitude is classified as a major earthquake.
12. Where is Victoria Falls located? [Imp.]
Answer: Victoria Falls is located on the borders of Zambia and Zimbabwe in Africa.
13. What is a delta?
Answer: The collection of sediments from all the mouths forms a delta. It is triangular shaped landmass.
14. Name some coastal landforms.
Answer: Sea caves, sea arches, stacks and sea cliff.
15. How are glacial moraines formed? [V. Imp.]
Answer: The material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines.
16. Name the two processes which wear away the landscape.
Answer: Weathering and erosion.
17. What does the process of erosion and deposition create?
Answer: The process of erosion and deposition create different landforms on the surface of the earth.
18. Name a few rivers of the world that form a delta?
Answer: Nile, Zaire, Ganga-Brahmaputra, Hwangotto, Murray-Darling, Amazon, etc.
Short Answer Type Questions
1: What do you mean by lithospheric plates?
Answer: The solid crust of the rocks forming the surface of the earth is known as Lithosphere. The lithosphere is broken into a number of plates. These plates are known as lithospheric plates.
2: Name the two types of tectonic movement.
Answer: Vertical earth movement and horizontal earth movement are the two kinds of tectonic movement.
3: What are volcanoes?
Answer: A volcano is an opening in the earth’s crust which allows hot molten rock, ash and gases to escape from below the surface.
4: Where are the volcanoes found?
Answer: Volcanoes are generally found where tectonic plates are pulled apart or come together. Volcanoes can also form where there is stretching and thinning of earth’s crust, such as in the (African) rift valley.
5: What is an earth quake?
Answer: When the lithosphere plates moves, the surface of the earth vibrates. The vibration can travel all around the earth. These vibrations are called earth quake.
6: Define weathering.
Answer: Weathering is the process by which a bed rock may creemble or decay, because of the action of atmospheric moisture, rain, frost, temperature changes, chemical action or underlying water and other associated features.
7: How a water fall formed?
Answer: The running water in the river erodes the landscape. When the river tumbles at steep angle over very hard rocks or down a steep valley side it forms a waterfall.
8: What are meanders?
Answer: As the river enter the plains it twists and turns forming large bends known as meanders. Due to continuous erosion and deposition along the side of the meander, the ends of the meander loop come closer and closer.
9: What do you mean by mushroom rocks?
Answer: An active agent of erosion and deposition in the deserts is wind. In desert we can see rocks in the shape of mushroom, commonly called mushroom rocks. The wind erodes the lower section of the rock more than the upper part.
10: Define Loess.
Answer: When the grains of sand are very fine and light, the wind can carry it over very long distance. When such sand is deposited in large areas, it is termed as loess.
11: What is a delta?
Answer: The river becomes so slow that it begins to deposit its load. Each distributary forms its own mouth. The collection of sediments from all the mouth forms a delta.
12: How are beaches formed?
Answer: The erosion and deposition of the sea waves gives rise to coastal landforms. The sea wave deposit sediments along the shores forming beaches.
Long Answer Type Questions
1: How man is also responsible for earth quake?
Answer: Officially, there is such an area of research devoted to man made earth quake. Geologist and seismologist agree that humans can induce earthquake in five major ways of fluid injection into the earth, fluid extraction from the earth mining, nuclear testing and through the construction of dams and reservoirs. In fact, there are officially recorded instances of earth quake caused by human activity.
2. Mention the work of ice.
Answer: Glaciers are rivers of ice which erode the landscape by destroying soil and stones to expose the solid rock below. Glaciers carve out deep hollows. As the ice melts they get filled up with water and become beautiful lakes in the mountains. The material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines.
3. What is earthquake? What are some common earthquake prediction methods? [V. Imp.]
Answer: When the lithospheric plates move, the surface of the earth vibrates. The vibrations can travel all round the earth. These vibrations are called earthquakes. Some common earthquake prediction methods include studying animal behaviour, fish in the ponds get agitated, snakes come to the surface.
4. Give an account of earthquake preparedness. [V. Imp.]
Answer: Earthquake is a natural calamity which we cannot stop. But we can minimise its impact if we are prepared before-hand. During an earthquake, we should shift to some safe spot. We should hide under a kitchen counter, table or desk against an inside comer or wall. We should stay away from fire places, areas around chimneys, windows that shelter including mirrors and picture frames. Moreover, we should spread awareness amongst our friends and family members.
5. Explain the work of a river. [V. Imp.]
Answer: The running water in the river erodes the landscape. When the river tumbles at steep angle over very hard rocks or down a deep valley side it forms a waterfall. While entering the plain the river twists and turns and forms large bends which are known as meanders. 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, which is also called ox-bow lake. Sometimes, the river overflows its banks causing flood in the neighbouring areas. As it floods, it deposits layers of fine soil and other material called sediments along its banks. As a result—fertile floodplain is formed. The raised banks are called levees.
As the river approaches the sea, the speed of the flowing water decreases and the river begins to break up into several streams known as distributaries. Then a time comes when the river becomes very slow and it begins to deposit its load. Each distributary forms its own mouth. The collection of sediments from all the mouths forms a delta, which is a triangular landmass.
6. Give an account of the work of wind. [V. Imp.]
Answer: Wind is an active agent of erosion and deposition in the deserts. In deserts we often notice rocks in the shape of a mushroom, known as mushroom rocks. Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top. 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 low hill-like structures. These are called sand dunes. When the grains are very fine and light, the wind can carry it over long distances. When such sand is deposited in large area, it is called loess.