Class 7 Geography Chapter 3 Question Answers - Our Changing Earth

Short Q & A :

Q1: 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.

Q2: Name the two types of tectonic movement.

Ans : Vertical earth movement and horizontal earth movement are the two kinds of tectonic movement.

Q3: What are volcanoes?

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.

Q4: Where are the volcanoes found?

Ans : 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.

Q5: What is an earth quake?

Ans : 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.

Q6: 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.

Q7: How a water fall formed?

Ans : 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.

Q8: 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.

Q9: 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.

Q10: 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.

Q11: What is a delta?

Ans : 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.

Q12: How are beaches formed?

Ans : The erosion and deposition of the sea waves gives rise to coastal landforms. The sea wave deposit sediments along the shores forming beaches.

Long Q&A:

Q1: How man is also responsible for earth quake?

Ans : 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 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.