Class 11 Geography chapter 2 Structure and physiographic notes

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 Structure and physiographic 

On the variation of geological structure India can be divided into three broad categories

1. The Peninsula block
2. The Himalayan and other Peninsula mountains
3. Indo Ganga Brahmaputra plains

The Peninsula block

Location

• It is an irregular line that runs from Kutch to the Aravali range near Delhi parallel to Yamuna then to rajmahal hills and the Ganga delta
• Apart from the irregular triangle shape it also includes kabri anglong and Meghalaya plateau in the north east and Rajasthan in the west
• The north east and parts are separated from the main block by Malda flaut

Features

• Peninsular block is formed of ancient granite and is very strong 
• Since the Cambrian period it stand like a rigid block with some little changes due to technic activity without affecting the original basement
• It has been subjected to various vertical movements and block faulting the river valleys of Narmada Tapi and Mahanadi are example of it

The Himalayan and other Peninsula mountains

• They are very young weak and flexible unlike the peninsular block
• They are subjected to inter play of exogenic and endogenic forces
• They are tectonic in nature and they have fast flowing rivers and various landforms which include oxbow Lake Georges valleys waterfalls etc

Indo Ganga Brahmaputra plains

• This cover parts of Northern planes originally it was a depression that is maximum development during the third phase of Himalayan formation
• It has been filled by sediments bought by Himalayan rivers
•  It is very fertile region are suitable for agriculture. The average depth of alluvial deposits bought by the rivers range from 1000 to 2000 m

Physiography

It means the outcome of structural, process and stage of development

Based on macro variations India can be divided into 6 physiographic division

1. The northern are north eastern mountains
2. The northern plain
3. The Peninsula plateau
4. The Indian desert
5. The coastal plains
6. The island
   
   
   

The northern and North eastern mountains

• The consists of Himalayas and north eastern hills
• The Himalayas consist of parallel mountain ranges the greater Himalayan range consists of the great Himalayas and the shivaliks

Location

• It is from Northwest to south east direction in the North Western part of India
• IND Darjeeling and Sikkim region it lies in East West direction
• In Arunachal Pradesh its from Southwest to the Northwest direction
• In Nagaland Manipur and Mizoram they are from the South North direction

Features

• The approximately length of greater Himalaya range is 2500 km from east to west and the width is 160 to 400 km from north to south
• This stand like a rigid wall between Indian subcontinent and Central and East Asian countries
• They also are a climate drainage and cultural divide with physical barrier that protect us from the cold winds of Central Asia

The northern plains

• They are found by alluvial deposits that are bought by rivers Ganga Indus and Brahmaputra
• The extend up to a length of 3200 km from east to west and the average width of 150 to 200 km from north to south

• From north to south this can be divided into three major zones the bhabar ,the tarai and the alluvial deposits. The alluvial deposits can be further divided into bhangar and khadar

• BHABAR
•  it's narrow bad that range from 8 to 10 km parallel to shivaliks
• It has lot of rocks so the rivers and streams disappear here
• The rocks are deposited by rivers as the brink huge materials

• TERAI 
• It's a belt South to Babar 10 to 20 km parallel to bhabar 
• It's the area where all rivers re emerge however they do not have a well created channel so the area is very swampy
• It is best suitable for agriculture

• ALLUVIAL DEPOSITS
• BHANGAR 
• It is known as old alluvial
• It is not renewed every year and thus less suitable for agriculture
• KHADAR
• It is known as new alluvial
• It is renewed every year and is suitable for agriculture

• The mouths of this mighty rivers make the largest deltas of the world the best example would be Sundarban delta
• The state of Haryana and Delhi forms of water divide for Indus and Ganga
• The Brahmaputra takes 90 degree turn at dhubri to enter Bangladesh

The Peninsula plateau

• It is up to 600 to 900 m about the river and is a irregular shaped triangle known as peninsular plateau

Location

• Delhi ridge in the Northwest the rajmahal hills in the east Gir range in the west and cardamom hills in the south constitute the outer extent of the peninsular plateau
• And extension of this is seen in the Shillong and karbi anglong plateau
• Hazaribagh Malwa plateau are all it's part
• The general elevation is from west to east

Features

• It has black soil 
• It has various important physiographic features such as block mountains rift valleys dykes etc
• Peninsular plateau can be divided into three broad groups the

1.  Deccan plateau
2. The central highlands
3. The north eastern plateau

The Deccan plateau

• It is bordered by Western ghats and eastern ghats and has many hills
• It is believe that it was made out of volcanic eruption
• Western ghats and eastern ghats 
• Western ghats in west are comparatively higher in elevation and continuous then eastern ghats
• Average elevation is 1500 m that increases from north to south in Western ghats
• Eastern ghats comprises of discontinuous and low hills
• Most of peninsular rivers have origin in Western ghats and float towards east ghats
• Anaimudi is the highest peak of peninsular plateau in Western ghats
• Eastern ghats are highly eroded by Godavari Krishna and Kaveri etc rivers
• Eastern ghats include important ranges like Javadi mahendragiri hills etc
• Eastern ghats and Western ghats meet each other at Nilgiri

 Central highlands

• central highlands are bounded by aravali, satpura ranges and deccan trap 
•  The general elevation of 6000 to 9000 M about sea level
• They are the example of discontinuous range or relic mountains
• They extent up to peninsular plateau and Jaisalmer in the west
• Sand dunes and bar change are found here in Jaisalmer region
• Tributaries like Yamuna tributaries have their origin here
• Banus is a major tributary of river Chambal which originates here
• It has a large reserve of resources in the form of chota Nagpur plateau mineral resources are present South Of the pleateau 

The North eastern plateau 

• It is an extension of main peninsular plateau
• Due to the forces that is exerted by the North East for movement of the Indian plate at the time of Himalayan formation a huge fault is created between rajmahal hills and Meghalaya plateau
• This was later filled by the numerous rivers of Himalayas
• The Meghalaya and karbi anglong stay detached from the main Peninsula block
• The Meghalaya plateau is divided into 3 the garo hills, the khansi hills and jayantia hills
• The Meghalaya plateau is rich in mineral resources like cool iron limestone and Uranium
• This year is maximum rainfall and has highly eroded surface

The Indian desert

• To the Northwest of the Aravali hills lies the great Indian desert
• It receives less than 150 mm of rainfall per year
• It has added area with low vegetation cover and that's why it's known as marusthali
• It is believe that turning the mesozoic era this region was covered with water
• It is a land of undulating topography dotted with longitudinal dunes and barchans
• Luni river flowing to the southern part of the desert is one of the most significant river
• Low precipitation and high evaporation make it a water deficit region
• On the basis of orientation it can be divided into two

1. The northern part sloping towards Sindh
2. The southern part sloping towards Rann of Kutch

The coastal plains

• It can be broadly divided into two
• Western coastal plains
• Eastern coastal plains

Western coastal plains

1. Western coastal plains of Submerged coastal plains

2. Western coastal plain is a narrow belt

3. Western coastal plains provide natural conditions for ports harbour like Kandla Kochi

and Mangalore

4. Western coastal plains extent from Gujarat in North to Kerala in South

5. Western coastal plains is for the divided into the konkon coast and Malabar coast

6. Western coastal plain is narrow in middle broader in North and south

7. Western coastal plains don't have any deltas because the river flowing through are seasonal and don't have much water

8. Special features like kayals backwaters gives us a tourist destination and is also useful for fishing famous nehru trophy vallamkali ( boat race) is held in punnamada Kayal in Kerala

Eastern coastal plains

1. Eastern coastal plains are broader and have a emergent coast

2. There are well developed deltas found here that are formed by river flowing East towards into the bay of Bengal

3. Due to its emergent nature there are less number of ports and harbour

4. Eastern coastal plains is divided into Coromandal coast and northern circar

5. In the eastern coastal plains there is more of fertile soil

6. Eastern coastal plains are broader and more fertile than the Western coastal plains more farming can be done here example paddy cultivation and jute cultivation

7. Eastern coastal plains has a very unique feature of Sundarban delta it is a World Heritage site

The Islands

There are two major Island groups in India the Andaman and Nicobar Island and the Lakshadweep Island

Andaman and Nicobar Island

1. Andaman and Nicobar islands are located in bay of Bengal

2. Andaman and Nicobar is a bigger group of island with 572

Islands

3. Andaman is located in North and Nicobar is located in South they are separated by

a water body called as 10 degree channel

4. These islands are believe to be an elevated portion of submarine mountains

5. Some of them are volcanic in origin too

6. Barren island is the only active volcano in India located in Nicobar Islands 

7. These are situation between 6°N to 14°N and 92°E to 94° E

Lakshadweep Island

1. Lakshadweep island is located in Arabian sea 

2. the entire group of island is built of coral deposits

3. There are approx 36 islands out of which 11 are inhabited

4. Minicoy is the largest island

5. The entire group of island is separated by 10 degree channel

6. North of which amini island and south of which is canannore island 

7. These are situation between 8 N to 12 N and 71° E to 74° E

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