Explore topic-wise InterviewSolutions in .

Sand dunes, barchans, seif, ripple marks, and loess plains are created as a result of transportation and depositional work of the wind.

Beaches, sand bars and lagoons are created due to the transportation and depositional work of sea waves.

Correct answer is (b) Lagoon

The landforms like beaches, sand bar, lagoons are formed due to depositional work of the sea waves. 

(i) Beach:

• Large amount of sediments come from the landward side in areas between two adjoining headlands. 
• Moreover, as these areas are shallow, the velocity of the waves decreases.
• As a result, the sediments that come from the land, as well as those coming from the deep sea, get deposited in this area.
• Predominantly fine sand gets settled along the coast. 
• Such sandy deposits along the coasts are called beaches.

(ii) Lagoon:

• The brackish water separated from the seawater by sand bars and lying in the areas between the coast and bars is called a lagoon. 
• As the waters are separated from the open sea, large waves are not generated. 
• These lagoons run parallel to the sea coast.

(iii) Sand bars:

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

• The work of wind is predominantly found in the hot desert and semi-arid regions.
• Hot deserts are found close to the Tropic of Cancer and Tropic of Capricorn. 
• The average annual rainfall in the hot deserts is 250 mm or even less. Therefore, the vegetal cover is negligible. 
• As there are no obstacles due to lack of vegetal cover, the work of wind is effective in the desert.

• In coastal areas, the sea waves carry out erosional, depositional and transportational work.
• Winds and tides cause the movements of sea water. As a result, waves come to the coast. 
• Because of their hitting the rocks at the coasts, erosion of the rocks occurs. 
• The landforms like wave cut platforms, sea caves, sea arches, sea cliffs, etc. are formed because of the erosional work of the waves. 
• The landforms like beaches, sand bar, lagoons are formed due to depositional work of the sea waves.

• The upper level of the stored ground water is called ground water level. 
• It varies according to the slope of the land, porosity and compactness of the rocks and the rainfall in the region. 
• Ground water level also changes according to season. 
• In the rainy season, it is closer to the ground surface whereas during summer, it drops down deeper.

The agents – running water (river), glaciers, wind, sea waves and groundwater, – do the work of erosion, transportation and deposition. Because of these agents, the earth’s surface keeps undergoing changes and new landforms are formed. 

(i) Running water (river):

• The river beds, as well as the banks of a river, are eroded due to the speedy flowing stream of water. The load that a river carries also erodes the banks and the bed of the river. 
• The rocks, stones, sand, etc. collide with one another and break into fragments 
• Different landforms like gorge, V-shaped valley, pothole and waterfall are formed due to the erosional work of a river.

(ii) Glaciers:

• As a glacier is nothing but a solid mass of ice, its velocity is very low. Nevertheless, the mass of water in the solid form is quite high. Therefore, glaciers cause a considerable amount of erosion.
• The glaciers erode the ice-clad base of the mountain slopes and the snow-clad sides of the mountains to a large extent. 
• The Cirque, Arete and horn, U-Shaped valley and hanging valley are the landforms formed by the erosional work of a glacier.

(iii) Wind:

• The wind carries sand and pebbles. 
• When they strike and scratch the rocks, the elevated and basal parts of the rocks get eroded. 
• Due to the erosional processes of the wind, deflation hollows, mushroom rocks and yardangs3 are formed.

(iv) Sea waves:

• The basal portions of the headlands get severely eroded due to the continuous attack of sea waves. This leads to the erosion of the rocks on a large scale. 
• Rocky coasts are formed where the headlands get severely eroded. 
• Landforms such as sea cliffs, sea caves, wavecut platforms, sea arches and sea stacks are formed due to the erosional work of sea waves.

(v) Groundwater:

• Soluble minerals in the rocks dissolve in water and they move along with the ground water. This process is called erosion by ground water. 
• The work of ground water is predominant in the region where rock like limestone is found on a large scale. 
• Limestone dissolves in carbonic acid. Carbonic acid is formed due to the presence of carbon? dioxide in ground water. This acid dissolves carbonates like limestone. Thus, chemical weathering takes place. 
• The landforms like sinkholes and caves are the result of the erosional work of groundwater.

Stalactite and Stalagmite cave.

(a) Mushroom Rock 

(b) Sand Dune (Barchan) 

(c) Yardangs

(d) Seif (Sand Mounds)

(i) Erosional work of winds:

• Wind carries small sand particles, small pebbles, etc. along with it. 
• These particles cause erosion along rocks coming in the way due to friction. 
• This leads to formation of mushroom rocks, deflation hollows, yardangs, etc.

(ii) Depositional work of winds:

• Sand particles that blow with the winds are of different shapes and sizes. 
• Those particles which are very fine are carried to larger distances while the larger ones get transported to shorter distances only. 
• These sand particles get deposited in deserts and semi-arid climates. As a result, specific landforms are formed. 
• Sand dunes, barchans, seifs, ripple marks, loessplains, etc. are formed by deposition by wind.

• Wave-cut platform 
• Lagoon 
• Beach 
• Sea cave 
• Sea arch 
• Sea stack 
• Sea cliff

• In the high altitude areas and the areas of high elevation, the ice slides down the slope. Such a sliding mass of ice is called a glacier. 
• As the ice moving in a glacier is in the solid state, its velocity is very low. 
• The thickness of the accumulated ice, the temperature and the slope of the land are the factors that determine the velocity of the glacier.

(i) Erosional work of sea waves:

• When the waves break at the coast, they bring with them water, transported stones, pebbles,sand particles, etc. This leads to the erosion of the coast. 
• Because of the chemical and hydraulic action of the sea wave too, the erosion occurs. The landforms like wavecut platforms, sea caves, sea arches, sea cliffs, etc. are formed because of the erosional work of the waves.

(ii) Depositional work of sea waves:

• The eroded materials accumulate at the sea bed. Because of tides, they keep on moving towards the coast and away from the coast. 
• They become fine because of attrition and hitting towards each other. 
• Deposition of such materials occurs at the places where the effect of waves is less. The landforms like beaches, sand bar, lagoons are formed due to the depositional work of the sea waves.

• When the waves break at the coast, they bring with them water, transported stones, pebbles, sand particles, etc. 
• This leads to the erosion of the coast. Because of the chemical and hydraulic action of the sea wave too, the erosion occurs. 
• The landforms like wave cut platforms, sea caves, sea arches, sea cliffs, etc. are formed because of the erosional work of the waves.

Landforms like flood levees, flood plains, deltas are formed because of deposition of sediments,

1. Flood levees: When in flood, the river deposits ; the coarser material on the banks which in duecourse rises parallel to the banks of the river. These are called ‘flood levees’. 

2. Flood plains: The finer silt deposited away from the banks during the flood form plains on ! either side of the river. They are called ‘flood plains’. 

3. Delta: The continuous deposition leads to the formation of a plain in the shape of a triangle called delta. Extensive deltas have been formed ! at the mouth of rivers Ganga, Godavari, Kaveri.

• The eroded materials accumulate at the sea bed. 
• Because of tides, they keep on moving towards the coast and away from the coast.
• They become fine because of attrition and hitting towards each other. Deposition of such materials occurs at the places where the effect of waves is less. 
• The landforms like beaches, sand bar, lagoons are formed due to depositional work.

Correct option is (b) solifluction