Ans: Geologist and seismologist agree that humans can induce earthquake in five major ways of fluid injection into the earth, fluid extraction from the earthmining, nuclear testing and through the construction of dams and reservoirs. In fact, there are officially recorded instances of earth quake caused by human activity.
Q2: Give an account of the work of wind. [V. Imp.]
Ans: 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.
Q3: What is earthquake? What are some common earthquake prediction methods?[V. Imp.]
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. Some common earthquake prediction methods include studying animal behaviour, fish in the ponds get agitated, snakes come to the surface.
Q4: What are glaciers? Describe their erosional and depositional activities.
Ans: Glaciers are rivers of ice which erode the landscape by clearing 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 salt gets deposited. These deposits form glacial moraines.
Q5: What are volcanoes? Where are the volcanoes found?
Ans: A volcano is an opening in the earth’s crust which allows hot molten rock, ash and gases to escape from below the surface. 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.
Q6: What do you mean by lithospheric plates?
Ans: 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.
Q7: What are meanders?
Ans: 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.
Q8: Define Loess.
Ans: 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.
Q9: Give an account of the features made by a river.
Ans: A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river.The running water in the river erodes the landscape. When the river tumbles at steep valley side, it forms a waterfall.
- As the river enters the plain, it twists and turns forming large bends 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 cutoff lake, also known as oxbow lake.
- 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 floodplain.
- The raised banks are called levees. As the river approaches the sea, the speed of the flowing water decreases and the river breaks up into many distributaries. 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 mouths form a delta.
Q10: Explain the work of a river. [V. Imp.]
Ans: 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 neighboring 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.
Q11: Mention the work of ice.
Ans: 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.
Q12: Give an account of earthquake preparedness. [V. Imp.]
Ans: 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.
Q13: Define weathering.
Ans: 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.
Q14: What do you mean by mushroom rocks?
Ans: 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.
Q15: What do you know about earthquake preparedness? Explain in a brief.
Ans:
