Physiography Unit II 2024-25 PDF

UNIT II PHYSIOGRAPHY This unit deals with Structure and Relief; physiographic divisions Drainage systems: concept of water sheds — the Himalayan and the Peninsular 2024-25 CHAPTER...

UNIT II PHYSIOGRAPHY This unit deals with Structure and Relief; physiographic divisions Drainage systems: concept of water sheds — the Himalayan and the Peninsular 2024-25 CHAPTER STRUCTURE AND PHYSIOGRAPHY D o you know that our earth also has a geological regions broadly follow the physical history. The earth and its landforms features: that we see today have evolved over a (i) The Penisular Block very long time. Current estimation shows that (ii) The Himalayas and other Peninuslar the earth is approximately 4600 million years Mountains old. Over these long years, it has undergone (iii) Indo-Ganga-Brahmaputra Plain. many changes brought about primarily by the endogenic and exogenic forces. These forces have THE PENINSULAR BLOCK played a significant role in giving shape to various The northern boundary of the Peninsular surface and subsurface features of the earth. You Block may be taken as an irregular line have already studied about the Plate Tectonics running from Kachchh along the western and the movement of the Earth’s plates in the flank of the Aravali Range near Delhi and book Fundamentals of Physical Geography then roughly parallel to the Yamuna and (NCERT, 2006). Do you know that the Indian the Ganga as far as the Rajmahal Hills plate was to the south of the equator millions of and the Ganga delta. Apart from these, years ago? Do you also know that it was much the Karbi Anglong and the Meghalaya larger in size and the Australian plate was a part Plateau in the northeast and Rajasthan of it? Over millions of years, this plate broke into in the west are also extensions of this many parts and the Australian plate moved block. The northeastern parts are towards the southeastern direction and the separated by the Malda fault in West Indian plate to the north. Can you map Bengal from the Chotanagpur plateau. In different phases in the movement of the Rajasthan, the desert and other desert– Indian plate? This northward movement like features overlay this block. of the Indian plate is still continuing and it The Peninsula is formed essentially by has significant consequences on the a great complex of very ancient gneisses physical environment of the Indian and granites, which constitutes a major subcontinent. Can you name some important part of it. Since the Cambrian period, the consequences of the northward movement Peninsula has been standing like a rigid of the Indian plate? block with the exception of some of its It is primarily through the interplay of western coast which is submerged these endogenic and exogenic forces and beneath the sea and some other parts lateral movements of the plates that the changed due to tectonic activity without present geological structure and geomorphologic affecting the original basement. As a part of processes active in the Indian subcontinent came the Indo-Australian Plate, it has been subjected into existence. Based on the variations in its to various vertical movements and block geological structure and formations, India can be faulting. The rift valleys of the Narmada, the divided into three geological divisions. These Tapi and the Mahanadi and the Satpura block 2024-25 STRUCTURE AND PHYSIOGRAPHY 9 mountains are some examples of it. The INDO-GANGA-BRAHMAPUTRA PLAIN Peninsula mostly consists of relict and residual mountains like the Aravali hills, the Nallamala The third geological division of India hills, the Javadi hills, the Veliconda hills, the comprises the plains formed by the river Palkonda range and the Mahendragiri hills, etc. Indus, the Ganga and the Brahmaputra. The river valleys here are shallow with low Originally, it was a geo-synclinal depression which attained its maximum gradients. development during the third phase of You are aware of the method of the Himalayan mountain formation calculating the gradient as a part of your study of the book Practical Work in approximately about 64 million years ago. Geography– Part I (NCERT, 2006). Can Since then, it has been gradually filled you calculate the gradient of the by the sediments brought by the Himalayan and the Peninsular rivers and Himalayan and Peninsular rivers. draw the comparisons? Average depth of alluvial deposits in Most of the east flowing rivers form these plains ranges from 1,000-2,000 m. deltas before entering into the Bay of It is evident from the above discussion Bengal. The deltas formed by the that there are significant variations Mahanadi, the Krishna, the Kaveri and the among the different regions of India in Godavari are important examples. terms of their geological structure, which has far-reaching impact upon other THE HIMALAYAS AND OTHER related aspects. Variations in the physiography and relief are important PENINSULAR MOUNTAINS among these. The relief and physiography The Himalayas along with other Peninsular of India has been greatly influenced by mountains are young, weak and flexible in their the geological and geomorphological geological structure unlike the rigid and stable processes active in the Indian Peninsular Block. Consequently, they are still subcontinent. subjected to the interplay of exogenic and endogenic forces, resulting in the development PHYSIOGRAPHY of faults, folds and thrust plains. These ‘Physiography’ of an area is the outcome of structure, process and the stage of development. The land of India is characterised by great diversity in its physical features. The north has a vast expanse of rugged topography consisting of a series of mountain ranges with varied peaks, beautiful valleys and deep gorges. The south consists of stable table land with highly dissected plateaus, denuded rocks and developed series of scarps. In between these two lies the vast north Indian plain. Figure 2.1 : A Gorge Based on these macro variations, India can be divided into the following mountains are tectonic in origin, dissected by physiographic divisions: fast-flowing rivers which are in their youthful stage. Various landforms like gorges, V-shaped (1) The Northern and North- eastern valleys, rapids, waterfalls, etc. are indicative of Mountains this stage. (2) The Northern Plain 2024-25 10 INDIA : PHYSICAL ENVIRONMENT Figure 2.2 : India : Physical 2024-25 STRUCTURE AND PHYSIOGRAPHY 11 (3) The Peninsular Plateau the Indus, the Ganga and the Brahmaputra. (4) The Indian Desert These plains extend approximately 3,200 km (5) The Coastal Plains from the east to the west. The average width (6) The Islands. of these plains varies between 150-300 km. The maximum depth of alluvium deposits The North and Northeastern Mountains varies between 1,000-2,000 m. From the north to the south, these can be divided into The North and Northeastern Mountains consist three major zones: the Bhabar, the Tarai and of the Himalayas and the Northeastern hills. the alluvial plains. The alluvial plains can be The Himalayas consist of a series of parallel further divided into the Khadar and the mountain ranges. Some of the important Bhangar. ranges are the Greater Himalayan range, Bhabar is a narrow belt ranging between which includes the Great Himalayas and 8-10 km parallel to the Shiwalik foothills at the Shiwalik. The general orientation of these ranges is from northwest to the southeast the break-up of the slope. As a result of this, direction in the northwestern part of India. the streams and rivers coming from the Himalayas in the Darjiling and Sikkim regions mountains deposit heavy materials of rocks lie in an eastwest direction, while in Arunachal and boulders, and at times, disappear in this Pradesh they are from southwest to the zone. South of the Bhabar is the Tarai belt, with northwest direction. In Nagaland, Manipur and an approximate width of 10-20 km where most Mizoram, they are in the northsouth direction. of the streams and rivers re-emerge without The approximate length of the Great Himalayan having any properly demarcated channel, range, also known as the central axial range, is thereby, creating marshy and swampy 2,500 km from east to west, and their width varies conditions known as the Tarai. This has a between 160-400 km from north to south. It is luxurious growth of natural vegetation and also evident from the map that the Himalayas houses a varied wildlife. stand almost like a strong and long wall between The south of Tarai is a belt consisting of the Indian subcontinent and the Central and East old and new alluvial deposits known as the Asian countries. Bhangar and Khadar respectively. These plains have characteristic features of mature Himalayas are not only the physical barrier, stage of fluvial erosional and depositional they are also a climatic, drainage and cultural landforms such as sand bars, meanders, ox- divide. Can you identify the impact of Himalayas bow lakes and braided channels. The on the geoenvironment of the countries of South Brahmaputra plains are known for their Asia? Can you find some other examples of riverine islands and sand bars. Most of similar geoenvironmental divide in the world? these areas are subjected to periodic floods Figure 2.3 : The Himalayas The Northern Plains The northern plains are formed by the alluvial deposits brought by the rivers – Figure 2.4 : Northern Plain 2024-25 12 INDIA : PHYSICAL ENVIRONMENT and shifting river courses forming braided plateau, the Palamu plateau, the Ranchi streams. plateau, the Malwa plateau, the Coimbatore The mouths of these mighty rivers also form plateau and the Karnataka plateau, etc. This some of the largest deltas of the world, for is one of the oldest and the most stable example, the famous Sunderbans delta. landmass of India. The general elevation of the Otherwise, this is a featureless plain with a plateau is from the west to the east, which is general elevation of 50-150 m above the mean also proved by the pattern of the flow of rivers. sea level. The states of Haryana and Delhi form Name some rivers of the Peninsular plateau a water divide between the Indus and the which have their confluence in the Bay of Ganga river systems. As opposed to this, the Bengal and the Arabian sea and mention some Brahmaputra river flows from the northeast to landforms which are typical to the east flowing the southwest direction before it takes an rivers but are absent in the west flowing rivers. almost 90° southward turn at Dhubri before Some of the important physiographic features it enters into Bangladesh. These river valley of this region are tors, block mountains, rift plains have a fertile alluvial soil cover which valleys, spurs, bare rocky structures, series of supports a variety of crops like wheat, rice, hummocky hills and wall-like quartzite dykes sugarcane and jute, and hence, supports a offering natural sites for water storage. The large population. western and northwestern part of the plateau has an emphatic presence of black soil. The Peninsular Plateau This Peninsular plateau has undergone recurrent phases of upliftment and Rising from the height of 150 m above the river submergence accompanied by crustal faulting plains up to an elevation of 600-900 m is the and fractures. (The Bhima fault needs special irregular triangle known as the Peninsular mention, because of its recurrent seismic plateau. Delhi ridge in the northwest, (extension activities). These spatial variations have of Aravalis), the Rajmahal hills in the east, Gir brought in elements of diversity in the relief range in the west and the Cardamom hills in of the Peninsular plateau. The northwestern the south constitute the outer extent of the part of the plateau has a complex relief of Peninsular plateau. However, an extension of ravines and gorges. The ravines of Chambal, this is also seen in the northeast, in the form of Bhind and Morena are some of the well-known Shillong and Karbi-Anglong plateau. The examples. Peninsular India is made up of a series of On the basis of the prominent relief patland plateaus such as the Hazaribagh features, the Peninsular plateau can be divided into three broad groups: (i) The Deccan Plateau (ii) The Central Highlands (iii) The Northeastern Plateau. The Deccan Plateau This is bordered by the Western Ghats in the west, Eastern Ghats in the east and the Satpura, Maikal range and Mahadeo hills in the north. Western Ghats are locally known by different names such as Sahyadri in Maharashtra, Nilgiri hills in Karnataka and Figure 2.5 : A Part of Peninsular Plateau Tamil Nadu and Anaimalai hills and Cardamom hills in Kerala. Western Ghats are 2024-25 STRUCTURE AND PHYSIOGRAPHY 13 comparatively higher in elevation and more which lies a large reserve of mineral resources continuous than the Eastern Ghats. Their in the Chotanagpur plateau. average elevation is about 1,500 m with the height increasing from north to south. The Northeastern Plateau ‘Anaimudi’ (2,695 m), the highest peak of In fact it is an extension of the main Peninsular Peninsular plateau is located on the plateau. It is believed that due to the force Anaimalai hills of the Western Ghats followed exerted by the northeastward movement of the by Dodabetta (2,637 m) on the Nilgiri hills. Indian plate at the time of the Himalayan Most of the Peninsular rivers have their origin origin, a huge fault was created between the in the Wester n Ghats. Easter n Ghats Rajmahal hills and the Meghalaya plateau. comprising the discontinuous and low hills Later, this depression got filled up by the are highly eroded by the rivers such as the deposition activity of the numerous rivers. Mahanadi, the Godavari, the Krishna, the Today, the Meghalaya and Karbi Anglong Kaveri, etc. Some of the important ranges plateau stand detached from the main include the Javadi hills, the Palconda range, Peninsular Block. The Meghalaya plateau is the Nallamala hills, the Mahendragiri hills, etc. further sub-divided into three: (i) The Garo The Eastern and the Western Ghats meet each Hills; (ii) The Khasi Hills; (iii) The Jaintia Hills, other at the Nilgiri hills. named after the tribal groups inhabiting this region. An extension of this is also seen in the The Central Highlands Karbi Anglong hills of Assam. Similar to the They are bounded to the west by the Aravali Chotanagpur plateau, the Meghalaya plateau range. The Satpura range is formed by a is also rich in mineral resources like coal, iron series of scarped plateaus on the south, ore, sillimanite, limestone and uranium. This generally at an elevation varying between area receives maximum rainfall from the south 600-900 m above the mean sea level. This west monsoon. As a result, the Meghalaya forms the northernmost boundary of the plateau has a highly eroded surface. Deccan plateau. It is a classic example of the Cherrapunji displays a bare rocky surface relict mountains which are highly denuded devoid of any permanent vegetation cover. and form discontinuous ranges. The extension of the Peninsular plateau can be The Indian Desert seen as far as Jaisalmer in the West, where it has been covered by the longitudinal sand To the northwest of the Aravali hills lies the ridges and crescent-shaped sand dunes Great Indian desert. It is a land of undulating called barchans. This region has undergone topography dotted with longitudinal dunes metamorphic processes in its geological and barchans. This region receives low rainfall history, which can be corroborated by the below 150 mm per year; hence, it has arid presence of metamorphic rocks such as climate with low vegetation cover. It is because marble, slate, gneiss, etc. of these characteristic features that this is also The general elevation of the Central known as Marusthali. It is believed that Highlands ranges between 700-1,000 m during the Mesozoic era, this region was above the mean sea level and it slopes under the sea. This can be corroborated towards the north and northeastern by the evidence available at wood fossils directions. Most of the tributaries of the river park at Aakal and marine deposits around Yamuna have their origin in the Vindhyan Brahmsar, near Jaisalmer (The and Kaimur ranges. Banas is the only approximate age of the wood-fossils is significant tributary of the river Chambal that estimated to be 180 million years). Though originates from the Aravalli in the west. An the underlying rock structure of the desert eastern extension of the Central Highland is is an extension of the Peninsular plateau, formed by the Rajmahal hills, to the south of yet, due to extreme arid conditions, its surface 2024-25 14 INDIA : PHYSICAL ENVIRONMENT provides natural conditions for the development of ports and harbours. Kandla, Mazagaon, JLN port Navha Sheva, Marmagao, Mangalore, Cochin, etc. are some of the important natural ports located along the west coast. Extending from the Gujarat coast in the north to the Kerala coast in the south, the western coast may be divided into following divisions – the Kachchh and Kathiawar coast in Gujarat, Konkan coast in Maharashtra, Goan coast and Malabar coast in Karnataka and Kerala respectively. The Figure 2.6 : The Indian Desert western coastal plains are narrow in the middle and get broader towards north and Can you identify the type of sand south. The rivers flowing through this coastal dunes shown in this picture? plain do not form any delta. The Malabar coast has got certain distinguishing features in the form of ‘Kayals’ (backwaters), which are features have been carved by physical used for fishing, inland navigation and also weathering and wind actions. Some of the well due to its special attraction for tourists. Every pronounced desert land features present here year the famous Nehru Trophy Vallamkali are mushroom rocks, shifting dunes and oasis (boat race) is held in Punnamada Kayal in (mostly in its southern part). On the basis of Kerala. the orientation, the desert can be divided into As compared to the western coastal plain, two parts: the northern part is sloping towards the eastern coastal plain is broader and is an Sindh and the southern towards the Rann of example of an emergent coast. There are well- Kachchh. Most of the rivers in this region are developed deltas here, formed by the rivers ephemeral. The Luni river flowing in the flowing eastward in to the Bay of Bengal. These southern part of the desert is of some include the deltas of the Mahanadi, the significance. Low precipitation and high Godavari, the Krishna and the Kaveri. Because evaporation makes it a water deficit region. of its emergent nature, it has less number of There are some streams which disappear after ports and harbours. The continental shelf flowing for some distance and present a typical extends up to 500 km into the sea, which case of inland drainage by joining a lake or makes it difficult for the development of playa. The lakes and the playas have brackish good ports and harbours. Name some ports water which is the main source of obtaining salt. on the eastern coast. The Coastal Plains You have already read that India has a long coastline. On the basis of the location and active geomorphological processes, it can be broadly divided into two: (i) the western coastal plains; (ii) the eastern coastal plains. The western coastal plains are an example of submerged coastal plain. It is believed that the city of Dwaraka which was once a part of the Indian mainland situated along the west coast is submerged under water. Because of this submergence it is a narrow belt and Figure 2.7 : Coastal Plains 2024-25 STRUCTURE AND PHYSIOGRAPHY 15 On 26 December 2004, the Andaman and Nicobar Islands experienced one of the most devasting natural calamity. Can you name the calamity and identify some other areas which were adversely affected by the same calamity? What was its major consequence? The Islands The islands of the Arabian sea include Lakshadweep and Minicoy. These are There are two major island groups in India – scattered between 8°°N-12°°N and 71°°E -74°°E one in the Bay of Bengal and the other in the longitude. These islands are located at a Arabian Sea. The Bay of Bengal island groups distance of 220 km-440 km of f the Kerala consist of about 572 islands/islets. These are coast. The entire island group is built of situated roughly between 6°°N-14°°N and coral deposits. There are approximately 36 92°°E -94°°E. The two principal groups of islets islands of which 11 are inhabited. Minicoy is include the Ritchie’s archipelago and the the largest island with an area of 453 sq. km. Labrynth island. The entire group of island is The entire group of islands is broadly divided divided into two broad categories – the by the Nine degree channel, north of which Andaman in the north and the Nicobar in is the Amini Island and to the south of the the south. They are separated by a Canannore Island. The Islands of this waterbody which is called the Ten degree archipelago have storm beaches consisting of channel. It is believed that these islands are unconsolidated pebbles, shingles, cobbles and an elevated portion of submarine mountains. boulders on the eastern seaboard. However, some smaller islands are volcanic in origin. Barren island, the only active volcano in India is also situated in the Nicobar islands. Some important mountain peaks in Andaman and Nicobar Islands are Saddle peak (North Andaman – 738 m), Mount Diavolo (Middle Andaman – 515 m), Mount Koyob (South Andaman – 460 m) and Mount Thuiller (Great Nicobar – 642 m). The coastal line has some coral deposits, and beautiful beaches. These islands receive convectional rainfall and have an equatorial type of vegetation. Figure 2.8 : An Island 2024-25 16 INDIA : PHYSICAL ENVIRONMENT EXERCISES 1. Choose the right answer from the four alternatives given below. (i) Which one of the water bodies separates the Andaman from the Nicobar? (a) 11°° Channel (c) 10°° Channel (b) Gulf of Mannar (d) Andaman Sea (ii) On which of the following hill range is the ‘Dodabeta’ peak situated? (a) Nilgiri hills (c) Cardamom hills (b) Anaimalai hills (d) Nallamala hills 2. Answer the following questions in about 30 words. (i) If a person is to travel to Lakshadweep, from which coastal plain does he prefer and why? (ii) Where in India will you find a cold desert? Name some important ranges of this region. (iii) Why is the western coastal plain is devoid of any delta? 3. Answer the following questions in not more than 125 words. (i) Make a comparison of the island groups of the Arabian Sea and the Bay of Bengal. (ii) What are the important geomorphological features found in the river valley plains? (iii) If you move from Badrinath to Sunderbans delta along the course of the river Ganga, what major geomorphological features will you come across? Project/Activity (i) Make a list of major Himalayan peaks from the west to the east with the help of an atlas. (ii) Identify the major landforms of your state and analyse the major economic activity practised by the people in each landform. 2024-25