Q 6. Answer the following questions in brief.

(1) List the landforms that are a result of the erosional work of the rivers.
Ans: Gorges (canyons), V-shaped valleys, and waterfalls are the result of the erosional work of the rivers.

(i) ‘V’ Shaped Valley:
(a) A ‘V’ shaped valley is formed due to the erosional work of a river.
(b) Over a period of time, the amount of load in the flow starts increasing.
(c) More and more energy from the river gets consumed in transporting the material.
(d) As a result, there is less erosion of the bed. The erosion along the banks and the slopes of the valley increases.
(e) Hence, the slopes recede and the valley with near-vertical sides becomes wider, resembling the letter V.

(ii) Gorge:

(a) A gorge is found in the upper course of the river.
(b) It is a deep and narrow valley with steep sides.
(c) In mountainous areas, the river flows with great speed. Therefore, the bed of the river gets eroded more than its banks, giving rise to a gorge that has a steep bank and a narrow bed.

(iii) Waterfall:

(a) Waterfalls are formed as a result of the erosion of a river.
(b) Water flowing over a hilly region cascades down a cliff, forming a waterfall.
(c) In areas where the hard and soft rocks are next to each other, the soft rocks are eroded faster than the hard ones. A difference in height along the river bed leads to the formation of a waterfall.

(2) Which agent is responsible for formation of stalactites and stalagmites and where are they formed?
Ans:

(i) The work of groundwater is responsible for the formation of stalactites and stalagmites.
(ii) In areas of limestone, the alkaline water seeps through the roof of the limestone caves.
(iii) When this water evaporates, minerals get deposited at the bottom and at the top of the limestone caves.
(iv) This leads to the formation of stalactites and stalagmites.

(3) List the landforms that are produced by the depositional work of the sea waves.
Ans: Landforms like beaches, sand bars, and lagoons are formed due to the depositional work of the sea waves.

(i) Beach:
(a) Large amounts of sediment come from the landward side in areas between two adjoining headlands.
(b) Moreover, as these areas are shallow, the velocity of the waves decreases.
(c) As a result, the sediments that come from the land as well as those coming from the deep sea get deposited in this area.
(d) Predominantly fine sand gets settled along the coast.
(e) Such sandy deposits along the coasts are called beaches.

(ii) Lagoon:
(a) The brackish water separated from the sea water by sand bars and lying in the areas between the coast and bars is called a lagoon.
(b) As the waters are separated from the open sea, large waves are not generated.
(c) These lagoons run parallel to the seacoast.

(iii) Sand bars:
(a) Sand gets deposited along the sides of the headlands.
(b) The deposition extends parallel to the coast from one headland to the next.
(c) Over a period of time, these deposits extend over long distances, forming bars that protrude into the water at some distance from the beach. These are known as ‘sand bars’. Sometimes, the eroded material from the beach gives rise to sand bars.

(4) Name the types of moraines.
Ans: The glaciers carry sediment with them. These sediments are called moraines. Depending on the location of the deposits, moraines can be divided into four types: ground moraines, lateral moraines, medial moraines, and terminal moraines.
(i) The material deposited at the base of a glacier is called ground moraine.

(ii) The material deposited along the banks of a glacier is called a lateral moraine.
(iii) After the confluence of two glaciers, the moraine deposited in the central part of the glacier is known as the medial moraine. It is formed out of the side moraine of the inner banks of the two glaciers.
(iv) At the end, where a glacier turns into a stream, a huge quantity of moraine is deposited. The stream of water is unable to carry the moraine further. As the deposited moraine is at the terminal part of a glacier, it is called a terminal moraine.