Q. 1. Name four features formed in upper course of a river.
Ans. Gorges, Canyons, Rapids and Waterfalls.
Q. 2. Name the three stages of a river.
Ans. Young, mature and old.
Q. 3. Name four features formed in the middle course of a river.
Ans. Meanders, flood plains, levees and ox-bow lake.
Q. 4. Name a famous canyon.
Ans. Grand Canyon on the Colorado river.
Q. 5. Name two river gorges in India.
Ans. Sutlej gorge and Dihang gorge (Assam).
Q. 6. Name the highest waterfall in India.
Ans. Jog Falls.
Q. 7. Name an important waterfall in North America.
Ans. Niagra Falls.
Q. 8. What is the relation between velocity of river and its transporting power ?
Ans. Transporting power = (velocity of river)6.
Q. 9. What are meanders ?
Ans. The river loops are called Meanders.
Q. 10. Which is an ox-bow lake ?
Ans. The horse shoe shaped strip of water is called ox-bow lake.
Q. 11. What are the levees ?
Ans. The raised banks (by deposition) of the river.
Q. 12. Name a river where levees have been formed on its banks.
Ans. River Hwang Ho (China).
Q. 13. What is a delta ?
Ans. A triangular piece of alluvial land formed at the mouth of a river.
Q. 14. Name the largest delta in the world.
Ans. Ganges delta.
Q. 15. Which rivers do not form deltas in India ?
Ans. Narmada and Tapti.
Q. 16. What are snow fields ?
Ans. The areas permanently covered with snow.
Q. 17. Which continent does not have snow fields ?
Q. 18. What is snowline ?
Ans. The height above which snow always exists.
Q. 19. What is a glacier ?
Ans. A tongue shaped large mass of moving ice.
Q. 20. What are icebergs ?
Ans. Huge masses of floating ice.
Q. 21. How much part of an iceberg remains above water ?
Ans. One tenth part.
Q. 22. Name two main types of glaciers.
Ans. (i) Mountain or Valley glaciers (ii) Continental glaciers.
Q. 23. Name a famous glacier in India.
Ans. Siachen glacier.
Q. 24. What are cirques ?
Ans. Semi-circular hollows on the side of a mountain.
Q. 25. Divide a River, from its source to its mouth, into different sections.
Ans. The river takes its rise from high mountains.
It travels over a long distance to reach the sea. From its source to its mouth, the river can be divided into three parts :
(i) The Upper or Mountain Course.
(ii) The Middle or Valley Course.
(iii) The Lower or Plain Course.
Q. 26. Describe the different types of erosion done by a river.
Ans. The river erodes the land in several ways :
(i) Solution : It dissolves the soluble rocks like limestone.
(ii) Side cutting : The river erodes its banks side ways.
(iii) Down cutting : River cuts deep into the valley floor.
(iv) Attrition : The river loads like pebbles, collide into one another and are broken.
Q. 27. How is a ‘V’-Shaped Valley formed ?
Ans. A V-shaped valley is formed by the vertical erosion of the river. Side-cutting and down-cutting of the river-bed go on simultaneously. The valley is deepened as well as widened. In this way, a broad V-shaped valley is developed.
Q. 28. On what factors does the erosional work of the river depend ?
Ans. The erosional work of the river depends upon the following factors :
(i) Volume of water.
(ii) Velocity of water.
(iii) Load of the river.
(iv) Slope of the river.
(v) The nature of the rocks.
Q. 29. Define the term ‘‘Snowline.’’ Why does the height of snowline differ in different parts of the world ?
Ans. Snowline is the height above which the snow never melts. It is as high as 2,000 metres in Alps. 5,000 metres in Himalayas, and 5,500 metres in the equatorial regions. It varies due to latitude and the nature of slope. It is higher in steep Southern slopes of the Himalayas than in the Northern slopes. Snowline is higher in areas of heavy snowfall.
Q. 30. What are the different types of Moraines ?
Ans. According to the place of deposition, the moraines are of following four types : (i) Lateral Moraines (ii) Medial Moraines (iii) Terminal Moraines (iv) Ground Moraines.
Q. 31. Why is a tributary valley called a hanging valley ?
Ans. Many tributary glaciers from the mountains, join the main glacier. A tributary valley is formed at higher level than the main valley. The main glacier valley is deeper than the tributary valley. After the melting of ice, the tributary valley is left at a height much above the main valley. The stream in this valley ‘hangs’ above the main valley and forms a waterfall. Therefore, such tributary valleys are called hanging valleys.
Q. 32. Why does the middle of a glacier move faster than the sides ?
Ans. The velocity of the glacier varies in its different parts. The velocity of a glacier decreases sidewards and with depth. The velocity decreases due to friction with valley walls and the bottom floor. The load of the glacier also checks its velocity. There is absence of any friction and load in the middle of the glacier. Therefore, the middle of the glacier moves much faster than its sides.
Q. 33. How are ox-bow lakes formed ?
Ans. Ox-bow lakes. Sometimes the meanders take the shape of letter ‘S’. The river becomes alomost a complete circle. A former bend or loop of the river is separated from the flowing river. This horse shoe shaped strip of water is known as ox-bow lake. These lakes resemble the shape of an ox-bow. These are common on flood plains.
Q. 34. What is a Delta ?
Ans. Deltas. When a river enters the sea, it becomes very slow. It deposits all the load at its mouth. Such deposits of silt are known as Deltas. A delta is a triangular piece of alluvial land formed at the mouth of the river. It resembles in shape of the Greek letter delta, after which it is named. This name was used by the Greeks for the Nile delta.
Q. 35. Describe two types of deltas with examples.
Ans. Types of Deltas :
(a) Regular Deltas. These are triangular, fanshaped deltas like Ganges delta.
(b) Bird’s Foot Deltas. These are irregular deltas which have several branches (distributaries) like the foot of a bird. The Mississippi delta is of this type and is also called a Crow’s nest delta.