FOR MORE UPDATES, JOIN US ON TELEGRAM: https://t.me/notesandknowledgehindienglish
The Indian craton was once part of the Super-continent of Pangaea. At that time, it was attached to Madagascar and southern Africa on the south west coast, and Australia along the east coast. During the Jurassic Period, rifting caused Pangaea to break apart into two super- continents namely, Gondwana (to the south) and Laurasia (to the north).
The Indian craton remained attached to Gondwana, until the Super-continent began
to rift apart about in the early Cretaceous, around 125 Ma. The Indian Plate
then drifted northward toward the Eurasian Plate. It is generally believed.
that the Indian plate sepa rated from Madagascar about 90 Ma. This orogeny,
which is continuing today, is related to closure of the Tethys Ocean.
The closure of this ocean, which created the Alps in Europe, and the Caucasus, range in western Asia, created Himalaya Mountains and the Tibetan Plateau in South Asia. The current orogenic event is causing parts of the Asian continent to deform westward and eastward on either side of the orogeny.
Concurrently with this collision, the Indian Plate sutured on to the adjacent Australian Plate, forming a new larger plate, the Indo- Australian Plate. Evolution of India. The cooling and solidification of the upper crust of the earth surface marked the earliest phase of tectonic evolution in the Archaean era (prior to 2.5 billion years) which is represented by the exposure of gneisses and granites especially on the Peninsula. These form the core of the Indian craton.
The Aravalli Range is the remnant of an early Proterozoic orogeny called the Aravalli-Delhi orogeny that joined the two older segments that make up the Indian craton.
Notes And Knowledge
It extends approximately 500 kilometers from its northern end to isolated hills and rocky ridges into Haryana, ending near Delhi. Minor igneous intrusions, deformation (folding and faulting) and subsequent metamorphism of the Aravalli Mountains represent the main phase of orogenesis.
The erosion of the mountains and further deformation of the sediments of the Dharwarian group marks the second phase.
The volcanic activities and intrusions, associated with this second phase are recorded in composition of these sediments. Early to Late Proterozoic calcareous and arenaceous deposits, which correspond to humid and semi-arid climatic regimes, were, deposited the Cuddapah and Vindhyan basins. These basins, which border or lie within the existing crystalline basement, were uplifted during the Cambrian (500 Ma).
The Vindhyans are believed to have been deposited between around 1700 and 650 Ma. Early Palaeozoic rocks are found in the Himalayas and consist of southerly-derived sediments eroded from the crystalline craton and deposited on the Indian platform. In the Late Paleozoic, Permo-Carboniferous glaciations left extensive glacio-fluvial deposits across central India, in new basins created by sag/normal faulting.
These tillites and glacially derived sediments are designated the Gondwana series. The sediments are overlain by rocks resulting from a Permian marine transgression(270 Ma) The late Paleozoic coincided with the deformation and drift of the Gondwana super-continent.
To this drift, the uplift of the Vindhyan sediments and the deposition of northern peripheral sediments in the Himalayan Sea can be attributed. During the Jurassic, as Pangaea began to rift apart, large grabens formed in central India filling with Upper Jurassic and Lower Cretaceous sandstones and conglomerates.
By the Late Cretaceous India had separated from Australia and Africa and was moving northward towards Asia. At this time, prior to the Deccan eruptions, uplift in southern India resulted in sedimentation in the adjacent nascent Indian Ocean. Exposures of these rocks occur along the south Indian coast at Pondicherry and in Tamil Nadu.
At the close of the Mesozoic era, one of the greatest volcanic eruptions in earth's history occurred, the Deccan lava flows.
Covering more than 500,000 square kilometers area, these mark the final break from Gondwana. In the early Tertiary, the first phase of the Himalayan orogeny, the Karakoram phase occurred. The Himalayan orogeny has continued to the present day.
Notes And Knowledge
PHYSIOGRAPHIC DIVISION
The four major geographical regions of India are:
1. The Great Himalayan range,
2. The Indo Gangetic Plain,
3. The Deccan Plateau and Peninsula
4. The Coastal plains
5. The Islands
HIMALAYAN MOUNTAIN SYSTEM
This is the great wall like physiographic unit, which stretches from Kashmir in the North West to the Indian border in the east. This region is formed by the Karakoram, Ladakh, Zaskar and the Himalayan range of mountains and the eastern highlands. These mountain ranges are subdivided into three divisions namely, Trans Himalayas, Himalayas and the Eastern Himalayas. The Trans Himalayas comprises the Karakoram, Ladakh and Zaskar ranges that originate from the Pamir Knot.The highest peak in India, 'Mount K2' (Mt.Godwin Austin, 8611m) is in the Karakoram Range.
Notes And Knowledge
The Himalayas can be divided into -
(i) The Himalayan ranges
(ii) The Trans-Himalayas
(iii) The Eastern Hills.
1. Duns: The longitudinal valley lying between Lesser Himalaya and Shiwaliks are known as duns.
2. The Himalayan Mountains are also known as the Himadri, Himaven or Himachal.
3. It consists of the youngest and the loftiest, rugged tertiary mountain chains of the World.
4. It is characterized by youthfulness, great deal of folding and deformation tectonic origin and great erosive power of rivers.
5. It stretches for a distance of over 2400 km (over 22° longitude) from Indus gorge in the west to the Brahmaputra gorge (Dihanggorge) in the east.
6. The width of the Himalayas varies from 500km in Kashmir to 200 km in Arunachal Pradesh, i.e., it becomes narrower from west to east.
7. It extends from west to east in arcate shape which is convex to the south.Origin of Himalayas Plate tectonics is the most recent and widely acclaimed theory for the origin of Himalayas. Plate is a broad segment of lithosphere that floats on the underlying asthenosphere and moves independently of other plates.
When two plates move towards each other, converge and in the process one plate overrides the other. The overridden plate is sub ducted and goes under the asthenosphere and is lost or consumed.
It is the converging boundary of plates where folded mountains like the Himalayas build up.
When two convergent plates composed of continental crusts collide against each other, the denser plate is sub ducted under the lighter plate. The resultant lateral compression squeezes and folds the sediments deposited on either side of the continental plate margins.
Notes And Knowledge
Himalayas are the product of such a process on the conveyance zone of the Asiatic plate in north and the Indian plate in the south. Some 70 million years ago, the Indian plate started moving to- wards the Asian plate and the Tethys Sea began to contract. The sediment got folded in three successive phases giving rise to three ranges of Himalayas explained below.Cross-Sectional view of Himalayas
1. The Great Himalaya:
This is also known as inner Himalaya, Central Himalaya or Himadri.
It is mainly formed of central crystallines (granites and gneisses) overlain by metamorphosed sedimentary races. It is the most continuous range consisting of loftiest peaks with an average height of 6000.meters. The core of these mountains is composed of Archaean rocks like granite, gneisses and the schists. The folds in this range are asymmetrical with steep south slope and gentle North Slope. It extends in arcate shape, from Nanga Parbat in north-west and Namcha Barwa in the north-east, which is convex to the south. Average elevation is 6100 in and average width is about 25km.
2. The Middle or the Lesser Himalaya:
It is also called the Himachal or Lower Himalaya. It is mainly composed of metamorphic rocks and unfossiliferous sedimentary rocks. Thesouthern slopes are bare and rugged while the northern slopes are thickly forested. The Pir Panjal, the Dhauladhar, the Musoorie range, Nag Tibba and the Mahabharata are the important ranges. The Pir Panjal in Kashmir is the longest and the most important range. Banihal pass situated in the Pir Panjal range is used by the Jammu-Srinagar national highway. The valley of Kashmir lies between the Pir Panjal and the Zaskar range. Most of the hill stations (Shimla, Musoorie, Ranikhet, Nainital, Almora and Darjeeling etc.) lie in this section. Average elevation in 3500 to 5000 m and average width is 60-80 km.
3. The Shiwaliks or the Outer Himalaya:
Consists of foothills which non almost from Potwar plateau to Brahmaputra valley. These ranges are mainly made up of fluvial depos- its like sand, clay, Rounded stones, gravels, slates etc. This section is characterized by poor drainage, which is move pronounced in Terai region. Its eastern part upto Nepal is thickly forested but the forest cover be-comes thin in the west. Average elevation is 1000 - 1500m while average width is 15-50km. The gorges of Tista and raidak have jointly formed a gap 80-90 km wide in the Shiwalik range. Shiwalik are known by different names in different areas. They are called Dafla, Miri, Abor and Mishmi hills in Arunachal Pradesh, and Jammu hills in Jammu Regional Division of Himalayas On the basis of river valleys Himalayas can be longitudinally divided into the following sections:
(I) Kashmir Himalaya
1. Average elevation is about 3000m.
2. This section has the largest share of shows and glaciers
3. Two important passes: Pir Panjal and Banihal - lie in Pir Panjal range.
4. The Valley of Kashmir lies in this section.
(II) Punjab Himalaya
1. Stretches eastward upto Satluj for about 570km.
2. High Peaks are rare.
3. Main ranges: Karakoram, Ladakh, Pir Panjal, Zaskar and Dhauladhar
4. Important Passes: Zojila, Rohtang and Bara Lacha la.
5. Important Valleys: Kangra, Lahul and Spiti.
6. This section is important for fruit cultivation (horticulture) and scenic beauty.
(III) Kumaon Himalaya
1. Stretches from Satluj to Kali River for about 320km and the general elevation is higher than Punjab Himalayas.
2. Its western part is called Garhwal Himalaya while eastern part is known as Kumaon Himalaya proper.
3. Important peaks: Nanda Devi, Kamet, Trishul, Badrinath, and Kedarnath
4. Nanda Devi is the highest peak in this section.
5. Important lakes: Nainital and Bhimtal
6. Several duns lie between Middle Himalayas and Shiwaliks.
Notes And Knowledge
(IV) Central Himalaya
1. Extends from river Kali to Tista for about 800km.
2. Most of it lies in Nepal and hence it is also called as Nepal Himalaya.
3. This section has some of the world's highest peaks, such as, Mt. Everest, Makalu, Kanchanjunga, Dhaulagiri, Annapurna, and Gosainthan.
4. This section is known as Sikkim Himalaya in Sikkim, Darjeeling Himalaya in West Bengal and Bhutan Himalaya in Bhutan.
5. Bilafond la also known as "pass of the butterflies".
6. Saltoro pass is a mountain pass situated in Saltoro ridge on the west of siachen glacier.
7. Chang la is the main gateway for the chang tang plateau, situated in the Himalayas.
8. The Debsa pass provides an easier and shorter alternative to the traditional Pin-Parbati pass route between Kullu and Spiti.
(V) Assam Himalaya
1. Stretches from river Tista to Brahmaputra for about 720km.
2. Pauhunri and Kulakangri are important peaks.
3. The Naga hills and Patkai Bum hills of this section form the watershed between India and Myanmar.
(VI) Trans Himalayas
1. It immediately lies north of the Great Himalayan range.
2. It is also called the Tibetan Himalaya because most of it lies in Tibet.
3. The Zaskar, the Ladakh, the Kailash and the Karakoram are the main ranges of this system.
4. Mt. K-2(Godwin Austin), Nanga Parbat, Rakaposhi, Haramosh, Gasherbrum-I (Hidden Peak), Gasherbrum-II etc. Are important peaks.
5. This section has some of the world's largest glaciers - Siachen, Hispar, Biafo, Batura and Baltoro.
6. Ladakh Plateau (5000m), the highest plateau of the Indian Union, lies to the north-east of the Karakoram range. It has been dissected into a number of plains and mountains. The most out-standing among them are Aksai Chin, Soda Plains, Lingzi Tang, Depsang Plains,and Chang Chenmo.
Notes And Knowledge
(VII) Eastern Hills or the Purvanchal Hills
After crossing the Dihang gorge (Brahmaputra gorge), the Himalayas suddenly turn southward and form a series of comparatively low hills running in the shape of a crescent with its convex side pointing towards the west. These hills are collectively called the Purvanchal because they are located in the eastern part of the country. It extends from Arunachal Pradesh in the north to Mizoram in the south and form boundary between India and Myanmar. The Indo-Burma hill range is a part of the Arakan Yoma Suture zone that stretches south through Andaman – Nicobar island chain to Sunda. The elevation of the Eastern Hills (Purvanchal) decreases from north to south and it is characterized by rough terrain, dense forests and swift streams. All these Ranges are generally 2,000m or less in height but are rather forbidding because of dense forests, very rough terrace and inhospitable tribe.
It comprises of the following hills -
a) Mishmi hills: Contains the loftiest range of the Purvanchal. Dapha Bum is its highest peak.
b) Patkai Bum Range: It is the northernmost range forming the easternmost limit of the Great Himalaya Mountains, has synclinal structure and is made up of Tipam sandstone.
c) Naga Hills: It lies south to the Patkai Bum and Saramati (3826m) is its highest peak. Patkai Bum and Naga hills form the watershed between India and Myanmar.
d) Manipur Hills: It is south to Naga hills and form boundary between Manipur and Myanmar. Its central part is a large basin which appears to be bed of an old lake, aremnant of which occupies the south-east corner of the basin and is known as Loktak Lake. The Barail Range separates Naga Hills from Manipur hills.
e) Mizo Hills (Lushai Hills): It lies south to the Manipur hills and its highest point is the Blue Mountain (2157m) in the south.
Notes And Knowledge
Significance of the Himalayas
The Himalayas comprise the most dominating geographical feature of India. No other mountain range anywhere in world has affected the life of people and shaped the destiny of a nation as the Himalayas have in respect of India. The Himalayas are the body and soul of India. In a very special measure, the Himalayas constitute India's national mountain system.
The following few points will bring out the significance of the Himalayan Mountains to India.
1. Climatic Influence. The Himalayas play a very significant role in influencing the climate of India By virtue of their high altitude, length and direction; they effectively intercept the summer monsoons coming from the Bay of Bengal and Arabian Sea and cause precipitation in the form of rain or snow.
Besides, they prevent the cold continental air masses of central Asia from entering into India. Had there been no Himalayas, the whole of Indian would have been a desert in the absence of precipitation and its winters would have been very severe under the influence of cold air masses coming from Central Asia. According to the latest meteorological studies, the Himalayas are responsible for splitting the jet stream into two branches and these in turn play and extremely important role in bring monsoons in India.
2. Defence. The Himalayas have been protecting Indian from outside invaders since the early times thus serving as a defence barrier. But the Chinese aggression on India in October, 1962 has reduced the defence significance of the Himalayas to a considerable extent. In spite of advancement in modern warfare technology, the defence significance of the Himalayas cannot be ignored altogether.
3. Source of Rivers. Almost all the great rivers of India have their sources in the Himalayas ranges. Abundant rainfall and vast snow-fields as well as large glaciers are the feeding grounds of the mighty rivers of India. Snowmelt in summer provides water to these rivers even during dry season and these are perennial rivers. The Himalayan Rivers, along with hundreds of their tributaries, form the very basis of life in the whole of north India.
4. Fertile Soil. The great rivers and their tributaries carry enormous quantities of alluvium while descending from the Himalayas. This is deposited in the Great Plain of North India in the form of fertile soil. Making the plain one of the most fertile lands of the world. It has been estimated that the Ganga and the Indus carry 19 and 10 lakh tones of silt, per day respectively and the silt carried by the Brahmaputra is even more. It is, therefore often said that the great plain of north India is a Gift of the Himalayas.
5. Hydroelectricity. The Himalayan region offers several sites which can be used for producing hydroelectricity. There are natural waterfalls at certain places while dams can be constructed across rivers at some other places. The vast power potential of the Himalayan Rivers still awaits proper utilization.
Notes And Knowledge
6. Forest Wealth. The Himalayan ranges are very rich in forest resources. In their altitude, the Himalayan ranges show a succession of vegetal cover from the tropical to the Alpine. The Himalayan forests provide fuel wood and a large variety of raw materials for forest based industries. Besides many medicinal plants grow in the Himalayan region. Several patches are covered with grass offering rich pastures for grazing animals.
7. Agriculture. The Himalayas do not offer extensive flat lands for agriculture but some of the slopes are terraced for cultivation. Rice is the main crop on the terraced slopes. The other crops are wheat, maize, potatoes, tobacco and ginger. Tea is a unique crop which can be grown on the hill slopes only. A wide variety of fruits such as apples, pears, grapes, mulberry, walnut, cherries, peaches, apricot, etc. are also grown in the Himalayan region.
8. Tourism. By virtue of their scenic beauty and healthy environment, the Himalayan ranges have developed a large number of tourist spots. The hilly areas in the Himalayas offer cool and comfortable climate when the neighbouring plains are reeling under the scorching heat of the summer season. Millions of tourists from different parts of the country as well as from abroad throng the Himalayas tourist centres to enjoy their natural beauty and to escape from the summer heat of the plains. The increasing popularity of winter sports and the craze to enjoy snowfall has increased the rust of tourists in winters also. Srinagar, Dalhousie, Dharmashala, Chamba, Shimla, Kulu, Manali, Mussoorie, Nainital, Ranikhet,Almora, Darjeeling, Mirik, Gangtok etc. Are important tourist centres in the Himalayas.
9. Pilgrimage. Apart from places of tourists interest, the Himalayas are proud of being studded with sanctified shrines which are considered to be abodes of the Gods. Largenumber of pilgrims trek through difficult terrain to pay their reverence to these sacred shrines. Kailas, Amarnath, Badrinath, Kedarnath, Vaishnu Devi, Jwalaji, Uttrkasi, Gangotri, Yamunotri, etc. are important places of pilgrimage.
10. Minerals. The Himalayan region contains many valuable minerals. There are vast potentialities of mineral oil in the tertiary ricks. Coal is found in Kashmir. Copper, lead, zinc, nickel, cobalt, antimony, tungsten, gold, silver, limestone, semi-precious and precious stones, gypsum and magnetite are known to occur at more than 100 localities in the Himalayas. Unfortunately manly of the mineral resources cannot be exploited at the present level of technological advancement due to adverse geographical conditions. Further advancements in modern technology may help in exploiting these resources, so the future possibilities of mineral exploitation in the Himalayas are great.
Notes And Knowledge
0 Comments