️ Introduction (Earth) :-
The Earth is about 460 million years old. During this entire period, many changes have taken place on the earth's surface due to the dynamics of internal and external forces. These changes have also happened in the Indian subcontinent which was part of Gondwana land.
Millions of years ago the ' Indian Plate ' was located south of the equator, which was huge in size and the Australian plate was also a part of it.
Over the course of millions of years, this plate broke into many parts and the Australian plate started moving towards the southeast and the Indian plate in the north direction .
️ The division of India into geological divisions :-
On the basis of the difference of geological structure and rock group, India is divided into three geological divisions:-
- 1. Peninsula Section.
- 2. Himalayas and other extra peninsular mountain ranges.
- 3. Indus-Ganga-Brahmaputra plain.
️ Peninsula Section :-
The northern boundary of the peninsula section is torn , starting from Kutch, passing through the west of the Aravalli hills to Delhi, and then parallel to the Yamuna and Ganges rivers, till the hills of Rajmahal and the Ganges delta .
The peninsular part is mainly composed of ancient neise and granite which has stood as a rigid block from the Cambrian era .
Features of Peninsular Plateau :-
The peninsular plateau is a triangular shaped cut-torn plot . Delhi-Cuttack in the north-west, Rajmahal hills in the east, Gir hills in the west, Cardamom hills in the south determine the boundaries of the peninsular plateau. Shillong and Karbi-Anglong plateau in the north-east is also an extension of this plot.
The Peninsular Plateau is mainly composed of ancient Neisse and granite.
This plateau is the oldest part of the earth's crust, with an average height of 600 and 900 meters . From the Cambrian eon this plot has stood as a rigid section.
In the north-western part of this plateau lies the Aravalli hills, the Vindhyachal and Satpura hills in the north, the Western Ghats and the Eastern Ghats in the east. In general, the height of the peninsula decreases from west to east. The slope of the northern part of this plateau is towards the north.
Being the front of the Indo-Australian plate, this section is affected by vertical movements and faults. Narmada river, Tapi and Mahanadi, of fault valleys and Satpura are examples of block mountains.
️ Himalayas and other extra peninsular mountain ranges :-
The geological structure of the Himalayas and the extra-peninsular ranges is young, weak and flexible, in contrast to the rigid and stable peninsular section.
These mountains are affected by the interactions of exogenous and endogenous forces even in the present time. As a result, folds, degrees and thrusts are formed in them.
The origin of these mountains is associated with tectonic movements. These mountains, eroded by fast flowing rivers, are still in their youth. Gorges, V-shaped valleys, cliffs and waterfalls etc. are proof of this.
️ Indus – Ganga – Brahmaputra plain :-
The third geological section of India is the plain of the Indus, Ganges and Brahmaputra rivers. Basically it is a geomorphic trough, which was mainly formed in the third phase of the Himalayan range formation process, about 64 million years ago.
Since then it has been filled with sediments brought by the Himalayas and the rivers originating from the peninsula. The average depth of alluvium in these plains is 1000 to 2000 m.
️ Do it :-
The 'Karewa' is a glacial deposit located at an altitude of 1000-1500 meters on the Pir Panjal range, which has been deposited by glaciers. Saffron (Jaffran) is cultivated here.
️ Another name for the Greater Himalaya Range :-
The Greater Himalayan range is also called the 'Central Axis Range' or the Great Himalayas. Its east-west length is about 2500 km. And the north-south width is 160 to 400 km. Till then .
️ Bhabar :-
- This region extends from the Indus River to the Teesta River.
- It is in the form of a thin strip from 8 to 10 km. spread across its width.
- Bhabar region is not suitable for agriculture.
- The rivers originating from the Himalayas collect pebbles, stones, sand, gravel brought with them here.
Terai: -
- Terai region is -2 extended along it to the south of Bhabar region.
- Its width is 10 to 20 km parallel to Bhabar. Is .
- Forests in the Terai region have been cleared and made cultivable.
- This is an area covered with forests made up of fine-grained alluvium.
️ Bangar :-
- The Bangar region is higher than the flood level.
- It is not useful for agriculture.
- It is a highland made up of old alluvial soil.
- Somewhere -2 lime-rich sandy soil is found.
- In Punjab it is called Chhaya.
️ Cold desert in India :-
The cold desert in India is located in the north eastern region of the Kashmir Himalayas in Leh-Ladakh.
This cold desert is situated between the Greater Himalayas and the Karakoram ranges.
The main categories of this sector are as follows:
- (a) Ladakh range
- (b) Josker Series
- (c) Karakoram range
Features of Eastern Hills of Himalaya Range :-
The direction of the hills in this part of the Himalaya Mountains is from north to south.
These hills are known by various local names. Known as Patkai Boom, Naga Hills, Manipur Hills in the North and Mizo or Lusai Hills in the South.
It is an area of low hills where many tribes are engaged in 'Jhum' or shifting cultivation/agriculture.
️ Islands of Arabian Sea :-
- The islands of the Arabian Sea are small and not habitable.
- No volcano is found in the islands of the Arabian Sea.
- There are 36 islands here. And only 11 of these islands have human settlement.
- Minicoy Island is the largest island, it includes Lakshadweep.
- It is separated by an 11 degree channel.
- This entire island group is made up of coral deposits.
️ Islands of Bay of Bengal :-
- The islands of the Bay of Bengal are large and habitable.
- Here Barren Island is a lively volcano.
- There are about 572 islands in the Bay of Bengal.
- Here the Andaman and Nicobar Islands are included, they are separated by a 10 degree channel.
- These islands have originated from volcanoes.
️ Western Coastal Plains of India :-
This coastal plain is narrow in the central part but widens in the north and south. Average width is 64 km. Is .
The rivers flowing here are relatively small and they do not form deltas as they are fast flowing.
This plain is more eroded, due to which the natural conditions are favorable for the development of ports and ports. It is called Goa coast in the north, Konkan coast and Malabar coast till Kerala in the south.
️ Eastern Coastal Plains of India :-
The eastern coastal plain is wider than the western coastal plain, it is (80 to 100 km) wide.
The rivers flowing here form long, wide deltas.
It includes the deltas of Mahanadi, Godavari, Krishna and Kaveri.
There are few ports due to the raised coast. It is difficult to develop ports and ports here.
From the mouth of the Godavari river to the north, it is called the Northern Sarkar Coast and to the south it is called the Coromandel Coast.
Why is there no delta on the western coastal plain?
The Western Coastal Plain is a narrow plain spread along the coast of the Arabian Sea. To its east are the hills of the Western Ghats, from which many small and fast-moving rivers originate. Due to the short passage and hard rock, these rivers do not bring much sediment. Due to insufficient deposit of sediments, no delta can be formed here.
️ "Indian desert was once part of the sea. Justify this statement?
The Indian desert is located in the north-west of the Aravalli hills. It is believed that this area was part of the sea during the Mesozoic period. Following are the proofs of this –
- Wood Fossil Park located in Akal and
- There are oceanic deposits around the Brahmasar near Jaisalmer.
️ Tribes living in Arunachal Pradesh :-
The Monpa, Dafla, Abar, Mishmi, Nishi and Naga tribes reside in the Arunachal Himalayas from west to east respectively.
️ Details of North and North Eastern Ranges of India :-
The North and North Eastern ranges include the Himalaya Mountains and the North Eastern Hills. These ranges have originated from tectonic movements. These mountain ranges, eroded by fast flowing rivers, are still in their youth.
The Himalaya Mountains are about 2500 km between the Indus and Brahmaputra rivers from west to east in the shape of an arc in the north of India. extends to. Its width varies from 160 to 400 km. Till then .
These hills are spread in north-south direction in Mizoram, Nagaland and Manipur. These hills are known as Patkoi Bum, Naga Hills, Manipur Hills in the north and Mizo or Lusai Hills in the south.
There are three mountain ranges spread parallel to the Himalaya Mountains :-
Greater Himalaya:- It is the highest range of Himalayas. Due to the high altitude, it is always covered with snow.
Middle Himalaya or Lesser Himalaya:- It extends from east to west direction almost parallel to the south of the Greater Himalaya. Most of the healthy places in India are located on the southern slopes of the Lesser Himalayas. Dharamsala, Shimla, Dalhousie, Mussoorie, Nainital, Darjeeling etc. are such places.
Shivalik Range:- It is spread parallel to the south of the central Himalayas. It is the last range of the Himalayan mountain range and is connected to the plains.
The Himalayan mountain range stands as a strong wall between the Indian subcontinent and the countries of Central and East Asia. The Himalayas are not only a natural barrier but also a climatic divide, runoff and cultural divide.
️ Difference between Western Ghat Mountains and Eastern Ghat Mountains :-
Western Ghat Mountains :-
The Western Ghats range from Maharashtra in the north to Kanyakumari in the south along the eastern coast of the Arabian Sea.
They are known as Sahyadri hills in Maharashtra and Goa, Nilgiris in Karnataka and Tamil Nadu and Anamalai and Cardamom hills in Kerala.
This mountain is continuously in the form of a range. Three passes from north to south, Thalghat, Bhorghat and Palghat seem to disturb its continuity.
The average height of this mountain range is about 1500 meters, which increases from north to south.
Anaimudi is the highest peak of the peninsular plateau at 2695 meters, which is situated in the Anaimalai hills of the Western Ghats Mountains. Most of the peninsular rivers have their origin from the Western Ghats.
Eastern Ghat Mountains :-
On the eastern boundary of the Deccan Plateau, the mountains of the Eastern Ghats extend from the Mahanadi valley to the Nilgiris in the south.
The main ranges of Eastern Ghats are Javadi Hills, Palkonda Range, Nallamala Hills and Mahendragiri Hills.
The range of Eastern Ghats is not continuous. Many big rivers have made their way by cutting them.
The average height of this mountain range is about 600 meters, due to erosion by rivers, only the residual range remains.
The mountains of the Eastern and Western Ghats meet in the Nilgiri Hills. No major river originates from this range.
