NCERT Class 7 Geography Chapter 3: Our Changing Earth Completes Notes Part 4

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Our Changing Earth

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Sea Action

  • Watch Video Lecture on YouTube: Coastal Landforms (By Waves & Currents): 18 Erosional & 18 Depositional Features

    Coastal Landforms (By Waves & Currents): 18 Erosional & 18 Depositional Features

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Image of Sea Action

Image of Sea Action

Image of Sea Action

Now we talked about how rivers, roots the structures and there are various formation that takes place so whenever we talk about any structure be it river be it sea waves there would be two kinds of features that are seen. (1)Erosional (2) Depositional.

Erosional means because of the action of the sea waves for example you have action of sea waves and you have a kind of rock mass that is seen here there is erosional activity and there is formation of caves that means within the rock there are certain section that is eroded away and it’s weird away and now you can have kind of cave where you can pass by so it’ a kind of erosional feature.

You have certain depositional features for example what we talked about in case of delta is the depositional features. Now when we talk about sea waves you have primarily the erosional features. We are talking about so firstly you have sea caves that is formed if this sea cave is extended and it forms a kind of tunnel through and through. So you have a sea cave and I can see from this end to this end it would be called as sea Arch and once you have the upper body that kind of disintegrates and breaks down from the remaining region you have formation which is known as stack so stack is a single piece of pillar that stands into the sea into the ocean that we could see. Now Glaciers.

Glaciers

  • Known as rivers of ice

  • Moraines: Depositions by glaciers

  • Watch Video Lecture on YouTube: Glacial Landforms: 25 Erosional & 3 Depositional Features

    Glacial Landforms: 25 Erosional & 3 Depositional Features

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Glaciers are also known as rivers of ice. They are slow moving ice masses that move along. Now glaciers move along they create feature which is known as U shaped valley, so when you have action of river which is thinner and sleek you have mountain areas which are bifurcated and you have formation of valleys which are the shape of V so with the river action you have formation of V shape valleys. However, due to the shape of the glacier and the bulkiness of the glacier you have formation of valleys which are U shaped so that is the first important different between glaciers valley and river valley.

Now when glacier moves along it carries certain deposits along with it and the deposits that glaciated carries along is known as Moraines. Now this moraines could be towards the end of the glacier so they are known as end moraines. They could be towards the side which are known as little moraines in the center which are known as medium moraines so on and so forth. So these are the common depositional features that we talked about and finally you have the wind action.

Wind Action

  • Loess: Sand deposited in large areas – China

  • Sand Dunes

  • Mushroom Rocks

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    Aeolian Landforms (By Wind) - 13 Erosional & 3 Depositional Landforms

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When we talk about wind action it’s primarily seen in desert areas where wind is predominant. So you have huge amount of sand that is blown from one region to another and deposited. Such depositions are known as loess. Loess are commonly seen in china. Then you have another structures which are known as sand dunes. We have covered the detail classification of sand dunes in our videos.

Then you have mushroom rocks which are structures again with differential erosion as you could see so you have kind of hard rock soft rock arrangement and there are further more scientific explanation which we have covered here, so what happens is the soft rock which is at the lower section erodes at a much higher pace as compared to the hard rock and there is a kind of mushroom that is seen in the desert region and this formation of mushroom by rocks is known as mushroom rocks.

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