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There are two major island groups in India

• The island groups of Bay of Bengal: Andaman & Nicobar Islands
• The island groups of Arabian Sea: Lakshadweep and Minicoy Islands

Let’s take these up one by one:

Andaman & Nicobar Islands:

• Also called the emerald islands.
• Location and Extent:
  • These are situated roughly between 6°N-14°N and 92°E -94°E.
  • The most visible feature of the alignment of these islands is their narrow longitudinal extent.
  • These islands extend from the Landfall Island in the north (in the Andamans) to the Indira Point (formerly known as Pygmalion Point and Parsons Point) in the south (In the Great Nicobar).
• Origin: The Andaman and Nicobar islands have a geological affinity with the tertiary formation of the Himalayas, and form a part of its southern loop continuing southward from the Arakan Yoma.
• The entire group of islands is divided into two broad categories:
  • The Andaman in the north, and
  • The Nicobar in the south.

They are separated by a water body which is called the Ten degree channel.

• The Andaman islands are further divided into:
  • Great Andamans
    • North Andaman
    • Middle Andaman
    • South Andaman
  • Little Andaman

Little Andaman is separated from the Great Andamans by the Duncan Passage.

• Chief Characteristics:
  • These are actually a continuation of Arakan Yoma mountain range of Myanmar and are therefore characterized by hill ranges and valleys along with the development of some coral islands.
  • Some smaller islands are volcanic in origin e.g. the Barren island and the Narcondam Island. Narcondam is supposed to be a dormant volcano but Barren perhaps is still active.
  • These islands make an arcuate curve, convex to the west.
  • These islands are formed of granitic rocks.
  • The coastal line has some coral deposits, and beautiful beaches.
  • These islands receive convectional rainfall and have an equatorial type of vegetation.
  • These islands have a warm tropical climate all year round with two monsoons.
  • The Saddle peak (North Andaman – 738 m) is the highest peak of these islands.
  • The Great Nicobar is the largest island in the Nicobar group and is the southernmost island. It is just 147 km away from the Sumatra island of Indonesia.

Lakshadweep Islands:

• These islands were earlier (before 1^st November 1973) known as Laccadive, Minicoy and Amindivi Islands.
• Location:
  • These are scattered in the Arabian Sea between 8°N-12°N and 71°E -74°E longitude.
  • These islands are located at a distance of 280 km-480 km off the Kerala coast.
• Origin: The entire island group is built of coral deposits.
• Important islands:
  • Amindivi and Cannanore islands in the north.
  • Minicoy (lies to the south of the nine degree channel) is the largest island with an area of 453 sq. km.

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• Chief Characteristics:
  • These consist of approximately 36 islands of which 11 are inhabited.
  • These islands, in general, have a north-south orientation (only Androth has an East-West orientation.
  • These islands are never more that 5 metres above sea level.
  • These islands have calcium rich soils- organic limestones and a scattered vegetation of palm species.
  • One typical feature of these islands is the formation of crescentic reef in the east and a lagoon in the west.
  • Their eastern seaboard is steeper.
  • The Islands of this archipelago have storm beaches consisting of unconsolidated pebbles, shingles, cobbles and boulders on the eastern seaboard.
  • The islands form the smallest Union Territory of India.

Other than the above mentioned two major groups, the important islands are:

• Majauli: in Assam. It is:
  • The world’s largest freshwater (Brahmaputra river) island.
  • India’s first island district
• Salsette: India’s most populous island. Mumbai city is located on this island.
• Sriharikota: A barrier island. On this island is located the satellite launching station of ISRO.
• Aliabet: India’s first off-shore oil well site (Gujarat); about 45 km from Bhavnagar, it is in the Gulf of Khambat.
• New Moore Island: in the Ganga delta. It is also known as Purbasha island. It is an island in the Sunderban deltaic region and it was a bone of contention between India and Bangladesh. In 2010, it was reported to have been completely submerged by the rising sea water due to Global warming.
• Pamban Island: lies between India and Sri Lanka.
• Abdul Kalam Island: The Wheeler Island near the Odisha coast was renamed as Abdul Kalam island in 2015. It is a missile launching station in the Bay of Bengal. The first successful land-to-land test of the Prithvi Missile was conducted from the mainland and it landed on the then uninhabited ‘Wheeler Island’ on November 30, 1993.

Now that we are done with this part, let’s try to attempt some questions from the past UPSC examinations:

Prelims:

1996

Question: ‘Saddle Peak’ the highest peak of Andaman and Nicobar islands is located in

A. Great Nicobar

B. Middle Andaman

C. Little Andaman

D. North Andaman

Ans. D

Mains:

Question: Write a short note on New Moore Island. (2006/2M)

Question: Write a short note on Indira Point. (2007/2M)

Question: Name the main physiographic divisions of India and give the salient features of each division. (2000/15M).

Question: How do the Andaman and Nicobar Islands and the Lakshadweep differ in the geological evolution and topographical conditions? (1998/15M)

The Indian desert is also known as the Thar Desert or the Great Indian Desert.

Location and Extent:

• Location – To the north-west of the Aravali hills.
• It covers Western Rajasthan and extends to the adjacent parts of Pakistan.

Geological History and Features

• Most of the arid plain was under the sea from Permo-Carboniferous period and later it was uplifted during the Pleistocene age. This can be corroborated by the evidence available at wood fossils park at Aakal and marine deposits around Brahmsar, near Jaisalmer (The approximate age of the wood fossils is estimated to be 180 million years).
• The presence of dry beds of rivers (eg Saraswati) indicates that the region was once fertile.
• Geologically, the desert area is a part of peninsular plateau region but on the surface it looks like an aggradational plain.

Chief Characteristics:

• The desert proper is called the Marusthali (dead land) as this region has an arid climate with low vegetation cover. In general, the Eastern part of the Marushthali is rocky, while its western part is covered by shifting sand dunes.
• Bagar: Bagar refers to the semi-desert area which is west of Aravallis. Bagar has a thin layer of sand. It is drained by Luni in the south whereas the northern section has a number of salt lakes.
• The Rajasthan Bagar region has a number of short seasonal streams which originate from the Aravallis. These streams support agriculture in some fertile patches called Rohi.
• Even the most important river ‘Luni’ is a seasonal stream. The Luni originates in the Pushkar valley of the Aravalli Range, near Ajmer and flows towards the southwest into the Rann of Kutch.
• The region north of Luni is known as the Thali or sandy plain.
• There are some streams which disappear after flowing for some distance and present a typical case of inland drainage by joining a lake or playa e.g. the Sambhar Lake. The lakes and the playas have brackish water which is the main source of obtaining salt.

• Well pronounced desert land features:
  • Sand dunes: It is a land of undulating topography dotted with longitudinal dunes, transverse dunes and barchans. [Barchan – A crescent-shaped sand dune, the horns of which point away from the direction of the dominant wind; Longitudinal dune – A sand dune with its crest running parallel to the direction of prevailing wind]

Image Source

• Mushroom rocks
• Shifting dunes (locally called Dhrians)
• Oasis (mostly in its southern part)

Of the total coastline of India (7517 km), that of the peninsula is 6100 km between the peninsular plateau and the sea. The peninsular plateau of India is flanked by narrow coastal plains of varied width from north to south.

On the basis of the location and active geomorphologic processes, these can be broadly divided into two parts:

• The western coastal plains
• The eastern coastal plains.

We now take them up one by one:

The Western Coastal Plain

1. Extent: The Western Coastal Plains are a thin strip of coastal plains with a width of 50 kms between the Arabian Sea and the Western Ghats.

2. Subdivisions: Extending from the Gujarat coast in the north to the Kerala coast in the south, the western coast may be divided into following divisions:

• Kachchh and Kathiawar coast in Gujarat,
• Konkan coast in Maharashtra,
• Goan Coast in Karnataka, and
• Malabar coast in Kerala

Note: Kutch and Kathiawar, though an extension of Peninsular plateau (because Kathiawar is made of the Deccan Lava and there are tertiary rocks in the Kutch area), they are still treated as an integral part of the Western Coastal Plains as they are now levelled down.

3. A coastline of submergence: 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.

4. Characteristic Features:

• The western coastal plains are narrow in the middle and get broader towards north and south. Except for the Kachchh and Kathiawar coastal region, these are narrower than their eastern counterpart.
• The coast is straight and affected by the South-West Monsoon winds over a period of six months. The western coastal plains are thus wetter than their eastern counterpart.
• The western coast being more indented than the eastern coast 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.
• The western coastal plains are dotted with a large number of coves (a very small bay), creeks (a narrow, sheltered waterway such as an inlet in a shoreline or channel in a marsh) and a few estuaries. The estuaries, of the Narmada and the Tapi are the major ones.
• The rivers flowing through this coastal plain do not form any delta. Many small rivers descend from the Western Ghats making a chain of waterfalls.
• The Kayals – The Malabar coast has a distinguishing feature in the form of ‘Kayals’ (backwaters). These backwaters are the shallow lagoons or the inlets of the sea and lie parallel to the coastline. These are used for fishing, inland navigation and are important tourist spots. The largest of these lagoons is the Vembanad lake. Kochi is situated on its opening into the sea.

The Eastern Coastal Plain

1. Extent: The Eastern Coastal Plains is a strip of coastal plain with a width of 100 – 130 kms between the Bay of Bengal and the Eastern Ghats

2. Subdivisions: It can be divided into two parts:

• Northern Circar: The northern part between Mahanadi and Krishna rivers. Additionally, the coastal tract of Odisha is called the Utkal plains.
• Coromandel Coast (or Payan Ghat): The southern part between Krishna and Kaveri rivers.

3. A coastline of emergence: The eastern coastal plain is broader and is an example of an emergent coast.

4. Characteristic features:

• The eastern coastal plains are wider and drier resulting in shifting sand dunes on its plains.
• There are well-developed deltas here, formed by the rivers flowing eastward in to the Bay of Bengal. These include the deltas of the Mahanadi, the Godavari, the Krishna and the Kaveri.
• Because of its emergent nature, it has less number of ports and harbours. The continental shelf extends up to 500 km into the sea, which makes it difficult for the development of good ports and harbours.
• Chilika lake is an important feature along the eastern coast. It is the largest salt water lake in India.

Significance of the Coastal Plains region:

• These plains are agriculturally very productive. The western coast grows specialized tropical crops while eastern coasts witnessed a green revolution in rice.
• The delta regions of eastern coastal plains have a good network of canals across the river tributaries.
• Coastal plains are a source of salt, monazite (used for nuclear power) and mineral oil and gas as well as centres of fisheries.
• Although lacking in adequate natural harbours, with a number of major and minor ports, coastal plains are centres of commerce and have attracted dense human settlements.
• The coastal regions of India are noted for tourist centres, fishing and salt making.

Now that we are done with this part, let’s try to attempt some questions from the past UPSC examinations:

Prelims:

Question: Assertion (A): The eastern coast of India produces more rice than the western coast.

Reason (R): The eastern coast receives more rainfall than the western coast.

Ans. C (Assertion is right but reason is wrong)

Mains:

Question: Assess the significance of coastal regions in the economic development of India. (2009/ 15 marks)

In the previous posts, we studied the Himalayan and Peninsular river systems in detail. Before we move further, let’s list the key differences between them:

The Shifting Courses of Rivers:

An interesting phenomenon observed in the case of most of the peninsular and extra-peninsular rivers is that they have shifting courses, especially in their lower reaches. In the upper reaches, the Himalayan rivers have the tendencies of river capturing.

Wondering why a river shifts its course? There can be numerous reasons as to why a river shifts its course. It could be a response to physiographic changes or it could be a part of its natural evolution e.g. fast-flowing rivers are prone to silting up as they surge down the hills and spread out on the plains, allowing sand and suspended matter to deposit in their slower, wider depths. Over time, the deposits create resistance, forcing the river to move to an area of lower resistance. This leads to a shift in its course.

The ancient Saraswati river, which provided an abode for the early Aryan settlers presents a typical example of shifting courses and river capturing. Descending from the Himalayan ranges, its initial course during the prehistoric period was passing near Churu (about 2000 to 3000 BC) and the Luni river was one of its tributaries.

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It gradually shifted towards west till it joined the Satluj near Ahmadpur. Later on, the water of its upper course was captured by a tributary of the Ganga river, as a result of which, its lower course became dry. This gave birth to the Yamuna river, an important tributary of the Ganga river system. Even today, the dry valley of the Saraswati river is found in the Rajasthan area in the form of Ghaggar valley.

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Similar shifting has also been observed in the rivers of Punjab during historical past. The records of 3rd century BC show that the Indus flowed more than 130 km east of its present course, through the now practically dry beds of the deserted channel, to the Rann of Kachchh which was then a gulf of the Arabian Sea. Later on it gradually shifted west and occupied its present position.

Even the entry of Brahmaputra into the plains of Assam is an outcome of the process of river capturing. According to geologists, during early days, the Tsangpo river of Tibet taking an easterly course used to join the Irrawaddy river (Myanmar) through the Chindwin, which was then a large river, transporting huge quantity of water. Later on, a small river flowing along the southern slopes of the Himalayas through its headward erosion captured the water of the Tsangpo river, and thus helped in the evolution of the stream of Brahmaputra.

Kosi and Gandak are notorious for changing their courses during floods.

With this, we conclude our discussion on the Indian Drainage system. Let’s now try to attempt some related questions from the past UPSC examinations:

Prelims

(1997)

Question: The Alamatti is on the river:

A. Godavari

B. Cauveri

C. Krishna

D. Mahanadi

Ans. C

Question: In the map shown in the given figure, river labelled as 1,2,3 and 4 respectively:

A. Kosi, Gomati, Ghaghara and Gandak

B. Kosi, Ganga, Gomati and Ghaghara

C. Gandak, Ganga, Gomati and Ghaghara

D. Teesta, Gomati, Ghaghara and Kosi

Ans. A

(1998)

Question: Which of the following east-flowing rivers of India has rift valley due to down warping?

A. Damodar

B. Mahanadi

C. Son

D. Yamuna

Ans. A

(2000)

Question: Which one of the following statements is not true?

A. Ghaggar’s water is utilised in the Indira Gandhi canal

B. Narmada rises from the Amarkantak region

C. Nizam Sagar is situated on the Manjira river

D. Penganga is a tributary of the Godavari.

Ans. A

(2002)

Question: The correct sequence of the eastward flowing rivers of the Peninsular India from north to south is

A. Subarnarekha, Mahanadi, Godavari, Krishna, Pennar, Cauvery and Vaigai

B. Subarnarekha, Mahanadi, Krishna, Godavari, Cauvery, Vaigai, and Pennar

C. Mahanadi, Subarnarekha, Godavari, Krishna, Cauvery, Pennar and Vaigai

D. Mahanadi, Subarnarekha, Krishna, Godavari, Cauveri, Vaigai and Pennar

Ans. A

(2003)

Question: What is the correct sequence of the rivers – Godavari, Mahanadi, Narmada and Tapi in the descending order of their lengths?

A. Godavari – Mahanadi – Narmada – Tapi

B. Godavari – Narmada – Mahanadi – Tapi

C. Narmada – Godavari – Tapi – Mahanadi

D. Narmada – Tapi – Godavari – Mahanadi

Ans. B

(2006)

Question: Which one of the following statements is not correct?

A. Mahanadi river rises in Chattisgarh.

B. Godavari river rises in Maharashtra.

C. Cauvery river rises in Andhra Pradesh.

D. Tapti River rises in Madhya Pradesh.

Ans. C

Question: Between which of the following was the ancient town of Takshasila located?

A. Indus and Jhelum.

B. Jhelum and Chenab.

C. Chenab and Ravi.

D. Ravi and Beas.

Ans. A

Question: From north towards south, which one of the following is the correct sequence of the given rivers in India?

A. Shyok – Spiti – Zaskar – Satluj

B. Shyok – Zaskar – Spiti – Satluj

C. Zaskar – Shyok – Satluj – Spiti

D. Zaskar – Satluj – Shyok – Spiti

Ans. B

(2007)

Question: Match List-I with List-II and select the correct answer using the code given below the lists:

List-I List-II

A. Betul 1. Indravati

B. Jagdalpur 2. Narmada

C. Jabalpur 3. Shipra

D. Ujjain 4. Tapti

A) A1 B4 C2 D3

B) A4 B1 C2 D3

C) A4 B1 C3 D2

D) A1 B4 C3 D2

Ans. B

Question: Which of the following rivers originates at Amarkantak?

A. Damodar

B. Mahanadi

C. Narmada

D. Tapti

Ans. C

Question: Assertion (A): River Kalinadi is an east-flowing river in the southern part of India.

Reason (R): The Deccan plateau is higher along its western edge and gently slopes towards the Bay of Bengal in the east.

Ans. D (A is false but R is true)

Mains:

Question: There is no formation of deltas by rivers of the Western Ghat. Why? (2013/10 marks)

Question: What are the causes for dominant dendritic pattern of drainage in the Gangetic plains? (2010/5M)

Question: Why do the rivers of west coast not form a delta? (2006/2M)

Question: Describe the major characteristics of rivers of peninsular India. (2003/10M)

Question: Write a short note on two prominent left bank tributaries of river Ganges. (2001/2M)

Question: Why do the rivers of the peninsular India have well defined rigid channels in sharp contrast to the Himalayan rivers? (1995/2M)

Question: Name the major international rivers flowing through India. What countries/States are covered by the Ganga and Godavari rivers on their course from their source to the sea? (1980/2M)

The Peninsular Drainage:

The Peninsular drainage system is older than the Himalayan one. This is evident from the broad, largely-graded shallow valleys, and the maturity of the rivers.

Evolution:

Three major geological events in the distant past have shaped the present drainage systems of Peninsular India:

• Subsidence of the western flank of the Peninsula leading to its submergence below the sea during the early tertiary period. Generally, it has disturbed the symmetrical plan of the river on either side of the original watershed and left just the upper parts of west flowing rivers above the sea level.
• Upheaval of the Himalayas when the northern flank of the Peninsular block was subjected to subsidence and the consequent trough faulting. The Narmada and The Tapi flow in trough faults and fill the original cracks with their detritus materials. Hence, there is a lack of alluvial and deltaic deposits in these rivers.
• Slight tilting of the Peninsular block from north-west to the southeastern direction gave orientation to the entire drainage system towards the Bay of Bengal during the same period.

River-Systems:

The peninsular river system can be categorised into the following sections:

• The East flowing rivers – the Mahanadi, the Godavari, the Krishna and the Cauvery flow eastwards and drain into the Bay of Bengal. These rivers make deltas at their mouths.
• The West flowing rivers:
  • Narmada and Tapi along with other small rivers originating from the Western Ghats and falling in the Arabian Sea form estuaries in place of deltas. This is due to the fact that these rivers, especially Narmada and Tapi, flow through hard rocks and are not able to form distributaries before they enter the sea.
  • Although these west flowing rivers of Sahyadri form only about 3% of the areal extent of basins of India, they contain about 18% of the country’s water resources.

Wondering what is the difference between a delta and an estuary? Let’s see:

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• The Western Ghats running close to the western coast act as a water divide between the major Peninsular Rivers discharging their water in the Bay of Bengal and the small rivulets joining the Arabian Sea.
• The Chambal, the Sind, the Betwa, the Ken, the Son, originating in the northern part of the Peninsula belong to the Ganga river system.
• The Peninsular rivers are characterized by fixed courses, absence of meanders and non-perennial flow of water. The Narmada and the Tapi which flow through the rift valley are, however, exceptions.

A brief account of the major Peninsular river systems is given below:

Smaller rivers flowing Towards the West:

The rivers flowing towards the Arabian Sea have short courses ( Because their origins lie closer to the sea, and the Western Ghats act as a water divide). Several of these small rivers are important for the production of hydroelectricity because of steep slopes and waterfalls.

Gujarat:

• The Shetruniji – It rises near Dalkahwa in Amreli district.
• The Bhadra – It originates near Aniali village in Rajkot district.
• The Dhadhar rises near Ghantar village in Panchmahal district.
• Sabarmati
• Mahi

Maharashtra:

• The Vaitarna rises from the Trimbak hills in Nasik district
• The Kalinadi rises from Belgaum district and falls in the Karwar Bay.
• The source of Bedti river lies in Hubli Dharwar and traverses a course of 161 km.
• The Sharavati is another important river in Karnataka flowing towards the west. The Sharavati originates in Shimoga district of Karnataka and drains a catchment area of 2,209 sq. km. The famous Jog or Gersoppa Falls (289m) made by Sharavati river are the highest untiered waterfalls in India.

Goa:

• Mandovi
• Juari

Kerala:

• Bharathapuzha – It is the largest river of Kerala. It is also known as Ponnani. It originates from Annamalai hills and flows into the Arabian Sea at a place called Ponnani.
• The Periyar – It is the longest and the second largest river of Kerala. [Largeness of a river is related to its basin size and the volume of water flowing in the river. At the same time when we say that a river is the longest, it means that we are referring to its geographical length]
• The Pamba river – It falls in the Vembanad lake.

Small Rivers Flowing towards the East:

There are small rivers which join the Bay of Bengal, though small, these are important in their own right.

• The Subarnrekha
• the Baitarni
• the Brahmani
• the Vamsadhara
• the Penner
• the Palar
• the Vaigai