Class-8 Lesson7 Geography (EXTERNAL FORCES-RESPONSIBLE FOR CHANGES)

                                                                Lesson7 Geography

        (EXTERNAL FORCES-RESPONSIBLE FOR CHANGES)

A.Choose the correct option of the following

Question 1.By which process the materials of broken rocks assemble at its original place
(a) Weathering
(b) Transportation
(c) Erosion
(d) Deposition
Answer:
(a) Weathering

Question 2.Where among the following winds perform its work?
(a) In deserts
(b) In Mountains
(c) In coastal areas
(d) In plains
Answer:
(a) In deserts

Question 3.Which is vital factor that makes soil fer-tile?
(a) The original rock materials
(b) Humus
(c) Climate
(d) Man
Answer:
(b) Humus

B.Fill in the blanks:

     1.When the rock breaks into pieces without chemical reaction is Biological

      weathering

2.The process of flattening of unleavened surface is called Surface Balancing

3.With the deposition Oxbow lake is formed.
4.On the  Orissa coast in India Chilka Lake  is an example of lagoon-lake.

   C. Very Short Answer Type Questions

Question 1.Which are the three works of river?
Answer:Erosion, Transportation & Deposition are three works of river.

Question 2.Which are three stages of river?
Answer:There are three stages of river, young, matured and old age.

Question 3.What is estuary?
Answer:Some of the rivers become wider at their meeting point with sea and sweep away into deep sea.

Question 4.What is geyser?
Answer:The underground hot water is thrown up in the form of fountain is called geyser.

Question 5.How is the Yardage formed?
Answer:Yardage is formed by wind erosion.

Question 6.What is Lagoon?
Answer:The sea water enclosed between the coast and sand bar is known as lagoon.

D.Short Answer Type Questions

Question 1.Write the factors that help soil formation?
Answer:The weathering and erosion process of rocks from the soil. The helping agents in soil formation are parent rocks, surface shape, climate & vegetation.

Question 2.What is weathering? Write the names of different types of weathering?
Answer:Weathering is the iocal process in which graduation and split of rocks occur at their original place. The types are physical, chemical and biological weathering.

Question 3.Differentiate between slow and rapid wasting?
Answer:The process of surface sliding by weathering is slow wasting and the process of filling up the holes is high wasting.

Question 4.How the V – shaped valley is formed?
Answer:The V – shaped valley is formed when river reaches its base level and widens its banks. V – Shaped Valley

 E. Long Answer Type Questions

Question 1.Discuss the surface Balancing?
Answer:The widening and flattening of the surface is called surface Balancing. Rivers, glaciers, wind, underground water and sea waves are the key agents of leveling. The Surface Balancing can be classified in to two categories.

1.     Slow wasting

2.     Rapid wasting.

1. Slow wasting:
The rapid erosion cycle shifts the rocks from its original place by rubbing, cut-ting & peeling to decrease the high elevated areas.

2. Rapid wasting:
The process of deposition of weathered materials in low-lying regions or holes is called aggravation and the weathered materials fill up the holes whose height kept on growing is called Rapid wasting.

Question 2.What is soil erosion? Write its cause and ways to conserve soil?
Answer:The natural forces or human activities which help in removing the layer of soil is called soil erosion. The causes of soil erosion are as follows:

• When the cover of vegetation is removed the upper layer of soil gets loose.
• Heavy rains and powerful wind remove the Soil content and layer.
• Overgrazing by domestic animals.
• Cutting trees and clearing forest cover.
• Excess use of fertilize & pesticide.

The measures to conserve soil are:

• To protect forest. Trees tighten the soil material.
• Tree plantation in river valleys, barren land and mountain slopes.
• Soil rehab of the land which becomes uneven due to water can be leveled to stop erosion.
• Controlled grazing.
• Flood control measures by building stop dams.
• Crop rotation by planting crops alter – neatly.