Passage Based Questions: Structure and Physiography

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1. Passage - 1
2. Passage - 2
3. Passage - 3
4. Passage - 4
5. Passage - 5
6. Passage - 6
7. Passage - 7
8. Passage - 8
9. Passage - 9
10. Passage - 10
11. Passage - 11
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Passage - 1

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It is primarily through the interplay of these endogenic and exogenic forces and lateral movements of the plates that the present geological structure and geomorphologic processes active in the Indian subcontinent came into existence. Based on the variations in its geological structure and formations, India can be divided into three geological divisions. These geological regions broadly follow the physical features: (i) The Penisular Block (ii) The Himalayas and other Peninuslar Mountains (iii) Indo-Ganga-Brahmaputra Plain.

Q1: What are the three geological divisions of India based on its geological structure and formations?
Ans:

• The Peninsular Block - the old, stable part of the Indian landmass formed of crystalline rocks.
• The Himalayas and other extra-peninsular mountains - the younger, folded or uplifted mountain systems.
• Indo-Ganga-Brahmaputra Plain - the large alluvial plain formed by sediments brought down by rivers.

Q2: What are the primary factors responsible for shaping the geological structure and geomorphologic processes in the Indian subcontinent?
Ans:

• Endogenic forces - internal earth processes such as tectonic movements and uplift that build landforms.
• Exogenic forces - external processes like weathering, erosion and deposition that wear down and reshape the surface.
• Lateral movements of tectonic plates - horizontal motion of plates that causes folding, faulting and major rearrangement of landforms.

Q3: How do the geological regions in India relate to its physical features?
Ans:

• The geological regions correspond closely to major physical regions of the country.
• For example, the Peninsular Block forms the stable southern plateau, the Himalayan mountain systems form the high northern ranges, and the Indo-Ganga-Brahmaputra division corresponds to the vast alluvial plains between them.

Passage - 2

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The Peninsula is formed essentially by a great complex of very ancient gneisses and granites, which constitutes a major part of it. Since the Cambrian period, the Peninsula has been standing like a rigid block with the exception of some of its western coast which is submerged beneath the sea and some other parts changed due to tectonic activity without affecting the original basement. As a part of the Indo-Australian Plate, it has been subjected to various vertical movements and block faulting. The rift valleys of the Narmada, the Tapi and the Mahanadi and the Satpura block mountains are some examples of it. 

Q1: What are the primary geological compositions of the Peninsula in India?
Ans:

• The Peninsula is primarily composed of very ancient crystalline rocks, mainly gneisses and granites.
• These basement rocks form the stable core of the Peninsular block and have remained largely unchanged since the Cambrian period.

Q2: How has the Peninsula's geological structure been affected by tectonic activity?
Ans:

• Although largely stable, the Peninsular block as part of the Indo-Australian Plate has experienced vertical movements and block faulting.
• Such tectonic activity created features like the rift valleys of the Narmada, Tapi and Mahanadi, and block mountains such as the Satpura range.

Q3: Which parts of the Peninsula have remained relatively stable despite tectonic activity?
Ans:

• Most of the Peninsular region has stood as a rigid block since the Cambrian and has retained its original basement rocks.
• Exceptions include sections of the western coast that are submerged and local areas altered by tectonic movements, though the deeper basement generally remains unaffected.

Passage - 3

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Originally, it was a geo-synclinal depression which attained its maximum development during the third phase of the Himalayan mountain formation approximately about 64 million years ago. Since then, it has been gradually filled by the sediments brought by the Himalayan and Peninsular rivers. Average depth of alluvial deposits in these plains ranges from 1,000-2,000 m.

Q1: What was the original geological state of the Indo-Ganga-Brahmaputra Plain, and when did it experience significant geological development?
Ans:

• The Indo-Ganga-Brahmaputra Plain began as a geo-synclinal depression - a large downfolded trough between rising mountain ranges.
• Its greatest development occurred during the third phase of Himalayan uplift, roughly 64 million years ago, after which it began to receive large amounts of sediment.

Q2: How has the plain been filled over time, and what is the source of the sediments that have filled the plain?
Ans:

• The plain has been progressively filled by sediments carried by rivers originating in the Himalayas and by rivers draining the peninsular region.
• These rivers have deposited thick layers of alluvium, raising and levelling the plain over geological time.

Q3: What is the average depth range of the alluvial deposits in the Indo-Ganga-Brahmaputra Plain?
Ans: The alluvial deposits in the Indo-Ganga-Brahmaputra Plain typically range in depth from about 1,000 m to 2,000 m, forming a very thick cover of fertile sediments.

Passage - 4

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'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.

Q1: What factors contribute to the physiography of an area?
Ans: The physiography of an area results from its underlying geological structure, the natural processes acting on it (such as uplift, erosion and deposition), and the stage of landscape development it has reached.

Q2: How is the physical landscape of Northern India described?
Ans: Northern India displays a rugged landscape made up of several parallel mountain ranges with varied peaks, numerous valleys and deep gorges formed by uplift and river action.

Q3: What are the prominent features of the southern region of India's physical landscape?
Ans: The southern region is dominated by a stable tableland formed of dissected plateaus, exposed and weathered (denuded) rocks, and a series of escarpments (scarps) indicating long-term erosion and landscape maturity.

Passage - 5

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The North and Northeastern Mountains consist of the Himalayas and the Northeastern hills. The Himalayas consist of a series of parallel mountain ranges. Some of the important ranges are the Greater Himalayan range, which includes the Great Himalayas and the Shiwalik. The general orientation of these ranges is from northwest to the southeast direction in the northwestern part of India. Himalayas in the Darjiling and Sikkim regions lie in an eastwest direction, while in Arunachal Pradesh they are from southwest to the northwest direction. In Nagaland, Manipur and Mizoram, they are in the northsouth direction.

Q1: What are the main mountainous regions in North and Northeastern India?
Ans: The principal mountainous regions in the north and northeast are the Himalayas and the Northeastern hills.

Q2: Describe the structure of the Himalayas and its important ranges.
Ans:  The Himalayas consist of three main parallel ranges: Himadri (Greater Himalayas), Himachal (Lesser Himalayas), and Shiwalik (Outer Himalayas).

Q3: What is the general orientation of the Himalayan ranges in different regions of India?
Ans:

• In the northwestern sector, the main Himalayan ranges trend from northwest to southeast.
• In the Darjeeling and Sikkim areas they lie approximately east-west; in Arunachal Pradesh they trend from southwest to northwest; and in Nagaland, Manipur and Mizoram the ranges run roughly north-south.

Passage - 6

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Bhabar is a narrow belt ranging between 8-10 km parallel to the Shiwalik foothills at the break-up of the slope. As a result of this, the streams and rivers coming from the mountains deposit heavy materials of rocks and boulders, and at times, disappear in this zone. South of the Bhabar is the Tarai belt, with an approximate width of 10-20 km where most of the streams and rivers re-emerge without having any properly demarcated channel, thereby, creating marshy and swampy conditions known as the Tarai. This has a luxurious growth of natural vegetation and houses a varied wildlife.

Q1: What is the Bhabar, and what is its significance in the landscape?
Ans:

• The Bhabar is a narrow belt about 8-10 km wide lying at the foot of the Shiwaliks where rivers deposit coarse material such as boulders and pebbles.
• Because of the coarse deposits, many streams disappear into the porous ground here, making the Bhabar an important zone that separates the higher ranges from the lowland Tarai.

Q2: Describe the characteristics of the Tarai belt.
Ans:

• The Tarai lies just south of the Bhabar, about 10-20 km wide, where rivers re-emerge and spread into poorly defined channels.
• This leads to marshy, swampy conditions that support luxuriant natural vegetation and a rich variety of wildlife due to high soil moisture and sediment accumulation.

Passage - 7

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Rising from the height of 150 m above the river plains up to an elevation of 600-900 m is the irregular triangle known as the Peninsular plateau. Delhi ridge in the northwest, (extension of Aravalis), the Rajmahal hills in the east, Gir range in the west and the Cardamom hills in the south constitute the outer extent of the Peninsular plateau. However , an extension of this is also seen in the northeast, in the form of Shillong and Karbi-Anglong plateau. The Peninsular India is made up of a series of patland plateaus such as the Hazaribagh plateau, the Palamu plateau, the Ranchi plateau, the Malwa plateau, the Coimbatore plateau and the Karnataka plateau, etc.

Q1: What is the elevation range of the Peninsular plateau in India?
Ans: The Peninsular plateau rises from about 150 m above the surrounding river plains up to elevations generally between 600 m and 900 m.

Q2: Name some of the prominent geographical features constituting the outer extent of the Peninsular plateau.
Ans:

• Outer limits include the Delhi Ridge (an extension of the Aravalis) in the northwest, the Rajmahal hills in the east, the Gir range in the west and the Cardamom hills in the south.
• Extensions of the plateau are also seen in the northeast as the Shillong and Karbi-Anglong plateaux.

Q3: What are some examples of the patland plateaus that make up the Peninsular India?
Ans: Peninsular India consists of several patland plateaus, for example Hazaribagh, Palamu, Ranchi, Malwa, Coimbatore and the Karnataka plateau, each forming part of the step-like plateau system.

Passage - 8

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Western Ghats are comparatively higher in elevation and more continuous than the Eastern Ghats. Their average elevation is about 1,500 m with the height increasing from north to south. 'Anaimudi' (2,695 m), the highest peak of Peninsular plateau is located on the Anaimalai hills of the Western Ghats followed by Dodabetta (2,637 m) on the Nilgiri hills. Most of the Peninsular rivers have their origin in the Western Ghats. Eastern Ghats comprising the discontinuous and low hills are highly eroded by the rivers such as the Mahanadi, the Godavari, the Krishna, the Kaveri, etc.

Q1: How does the elevation of the Western Ghats compare to the Eastern Ghats?
Ans: The Western Ghats are higher and form a more continuous range, whereas the Eastern Ghats are lower, more broken and more eroded.

Q2: What is the average elevation of the Western Ghats, and how does it vary from north to south?
Ans:

• The Western Ghats have an average elevation of about 1,500 m.
• The heights generally increase from the northern end towards the southern end, reaching the highest peaks such as Anaimudi (2,695 m) in the south.

Passage - 9

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They are bounded to the west by the Aravali range. The Satpura range is formed by a series of scarped plateaus on the south, generally at an elevation varying between 600-900 m above the mean sea level. This forms the northernmost boundary of the Deccan plateau. It is a classic example of the relict mountains which are highly denuded and form discontinuous ranges. The extension of the Peninsular plateau can be seen as far as Jaisalmer in the West, where it has been covered by the longitudinal sand ridges and crescent-shaped sand dunes called barchans.

Q1: What geographical feature forms the western boundary of the Peninsular plateau?
Ans: The Aravali range forms the western boundary of the Peninsular plateau.

Q2: Describe the characteristics of the Satpura range.
Ans:

• The Satpura range consists of a series of scarped plateaus lying generally between 600 m and 900 m above mean sea level.
• It marks the northern edge of the Deccan plateau and represents relict, highly denuded landforms that now appear as discontinuous ranges.

Q3: How far does the extension of the Peninsular plateau reach in the west, and what covers this extension in that region?
Ans:

• The Peninsular plateau extends westward as far as the Jaisalmer region.
• In that area the plateau surface has been overlain by longitudinal sand ridges and crescent-shaped dunes known as barchans.

Passage - 10

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The Meghalaya plateau is further sub-divided into three: (i) The Garo Hills; (ii) The Khasi Hills; (iii) The Jaintia Hills, named after the tribal groups inhabiting this region. An extension of this is also seen in the Karbi Anglong hills of Assam. Similar to the Chotanagpur plateau, the Meghalaya plateau is also rich in mineral resources like coal, iron ore, sillimanite, limestone and uranium. This area receives maximum rainfall from the south west monsoon. As a result, the Meghalaya plateau has a highly eroded surface. Cherrapunji displays a bare rocky surface devoid of any permanent vegetation cover.

Q1: Which region in Assam is considered as an extension of the Meghalaya plateau?
Ans: The Karbi Anglong hills of Assam are regarded as an extension of the Meghalaya plateau.

Q2: What mineral resources are found in the Meghalaya plateau, similar to the Chotanagpur plateau?
Ans: The Meghalaya plateau contains minerals such as coal, iron ore, sillimanite, limestone and uranium, similar to resources found in the Chotanagpur plateau.

Q3: What is the significant feature of the surface in Cherrapunji, a part of the Meghalaya plateau?
Ans: Cherrapunji exhibits a highly eroded, largely bare rocky surface with little permanent vegetation cover, a result of very high rainfall that strips away soil and prevents stable vegetation from establishing.

Passage - 11

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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 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 western coastal plains are narrow in the middle and get broader towards north and south.

Q1: What type of coastal plain are the western coastal plains of India?
Ans: The western coastal plains are an example of a submerged coastal plain, formed where parts of the coast have been flooded or lowered relative to sea level.

Q2: Why is the western coastal plain a narrow belt?
Ans: Submergence along the western margin has kept the coastal plain narrow, as much of the former land is now below sea level or has steep relief close to the shore.

Q3: How has the submergence of the western coastal plain affected the development of ports and harbors?
Ans: Because the coast is submerged and often has a gently sloping continental shelf, natural sheltered bays and inlets have formed, creating favourable conditions for the development of many natural ports and harbours such as Kandla, Marmagao, Mangalore and Cochin.