Which one among the following statements is not correct?

1. The Peninsular Plateau: Geological Evolution (basic)

To understand India's geography, we must start with its 'foundation stone' — the Peninsular Plateau. This is not just a feature; it is the oldest and most stable landmass of the Indian subcontinent. Unlike the Himalayas, which are 'young' and still rising, the Peninsular Plateau is a tectonically stable shield that has remained largely above sea level for over 3,600 million years Geography of India, Physiography, p.48. It is primarily a tableland composed of ancient crystalline, igneous, and metamorphic rocks that have weathered the elements for eons CONTEMPORARY INDIA-I, Physical Features of India, p.12. Historically, this massive block was a core part of the supercontinent known as Gondwanaland, which also included present-day South America, Africa, Antarctica, and Australia Physical Geography by PMF IAS, Convergent Boundary, p.121. Around 250 million years ago, during the Carboniferous Period, the plateau began its unique journey. While it stayed rigid and avoided the intense 'folding' that creates massive mountain chains, it did experience block faulting and displacement. This internal cracking created the deep rift valleys where the Narmada and Tapi rivers flow today, and allowed for the formation of massive coal deposits in the Damodar and Godavari basins Geography of India, Physiography, p.48. As Gondwanaland broke apart, the Indian plate drifted northward. This movement eventually led to the collision with the Eurasian plate, giving birth to the Himalayas. However, the Peninsular Plateau remained the 'anchor' — a rigid block of ancient rock that resisted subduction. Today, we see it as a series of broad, shallow valleys and rounded hills, a testament to millions of years of erosion acting on a very hard, stable base CONTEMPORARY INDIA-I, Physical Features of India, p.12.

Sources: Geography of India (Majid Husain), Physiography, p.48; CONTEMPORARY INDIA-I (NCERT Class IX), Physical Features of India, p.12; Physical Geography by PMF IAS, Convergent Boundary, p.121

2. Mountain Types: Fold, Block, and Residual (basic)

To understand the majestic landscapes of India and the world, we must first look at how mountains are born. Mountains are not static; they are the result of intense geological forces acting over millions of years. Geologists primarily classify mountains into three categories based on their mode of formation: Fold, Block, and Residual mountains.

1. Fold Mountains: These are the most common and expansive mountains. They are formed when the Earth's crust is subjected to horizontal compression—imagine pushing a rug from both ends; it wrinkles and rises. These 'wrinkles' are called folds. The upward folds are anticlines and the downward folds are synclines. We distinguish between Young Fold Mountains (like the Himalayas or Alps), which are high and rugged, and Old Fold Mountains (like the Urals or Appalachians), which have been worn down over time Physical Geography by PMF IAS, Convergent Boundary, p.123. If the pressure is extreme, the crust might even fracture and slide over itself, creating a complex structure known as a nappe Certificate Physical and Human Geography, The Earth's Crust, p.22.

2. Block Mountains: Unlike folding, these are created by faulting. When the Earth's crust cracks due to tension or compression, large blocks of earth are displaced vertically. The uplifted blocks are known as Horsts (Block Mountains), and the subsided blocks are called Graben (Rift Valleys). A classic example is the Vindhyan Range in India, which is often classified as a block mountain because it consists of horizontally bedded rocks that have been uplifted with minimal folding Physical Geography by PMF IAS, Types of Mountains, p.136.

3. Residual or Relict Mountains: These are 'mountains of denudation.' They are formed when an existing elevated area (like an old mountain range or a plateau) is worn down by agents of erosion like rivers, wind, and glaciers. What remains are the hard, resistant rocks that refused to be eroded away. The Aravalli Range in India is a prime example; once a mighty fold mountain system, it is now a residual range due to millions of years of weathering Physical Geography by PMF IAS, Types of Mountains, p.133.

Feature	Fold Mountains	Block Mountains	Residual Mountains
Primary Force	Compression (Folding)	Tension/Compression (Faulting)	Erosion (Denudation)
Structure	Wave-like (Anticlines/Synclines)	Flat tops, steep sides (Horst/Graben)	Irregular remnants of old uplands
Examples	Himalayas, Alps, Rockies	Vindhyas, Vosges, Rhine Valley	Aravallis, Highlands of Scotland

Sources: Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.), Types of Mountains, p.136; Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.), Convergent Boundary, p.123; Certificate Physical and Human Geography, GC Leong (Oxford University press 3rd ed.), The Earth's Crust, p.22; Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.), Types of Mountains, p.133; Certificate Physical and Human Geography, GC Leong (Oxford University press 3rd ed.), The Earth's Crust, p.23

3. Major Divisions: Central Highlands vs Deccan Plateau (intermediate)

The Peninsular Plateau of India is not a single uniform block but is divided into two broad regions by the Narmada River. To the north lies the Central Highlands, and to the south lies the Deccan Plateau. Understanding the distinction between these two is fundamental to grasping India’s drainage patterns and mineral distribution CONTEMPORARY INDIA-I, Geography, Class IX, Chapter 2, p.12.

The Central Highlands encompass the area north of the Narmada, covering a major part of the Malwa Plateau. This region is bounded by the Aravalli Range in the northwest and the Vindhyan Range in the south Geography of India, Majid Husain, Chapter 2, p.54. One of the most important features here is the slope: the land tilts from the southwest towards the northeast. We know this because rivers like the Chambal, Sind, Betwa, and Ken flow in that direction to join the Yamuna INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Chapter 2, p.13. Geologically, it's a mix of old fold mountains (like the highly denuded Aravallis) and block/residual mountains (like the Vindhyans).

In contrast, the Deccan Plateau is a triangular landmass situated south of the Narmada. Its base is formed by the Satpura Range in the north, while its eastern extensions include the Mahadev, the Kaimur hills, and the Maikal range. Unlike the Central Highlands, the Deccan Plateau is generally higher in the west and slopes gently eastwards, causing major rivers like the Godavari and Krishna to flow toward the Bay of Bengal. Interestingly, the plateau extends even further northeast into the Meghalaya Plateau (Shillong Plateau), which is actually a piece of the Peninsular block separated by a massive geological fault known as the Malda Gap INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Chapter 2, p.13.

Feature	Central Highlands	Deccan Plateau
Location	North of Narmada River	South of Narmada River
General Slope	Southwest to Northeast	West to East
Major Ranges	Aravalli, Vindhyan	Satpura, Western/Eastern Ghats

Sources: CONTEMPORARY INDIA-I, Geography, Class IX, Chapter 2: Physical Features of India, p.12; Geography of India, Majid Husain, Chapter 2: Physiography, p.54; INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Chapter 2: Structure and Physiography, p.13

4. The Malda Gap and Northeastern Plateau Extensions (intermediate)

While we often think of the Peninsular Plateau as ending in Central India, it actually extends much further into the northeast. Geologically, the Shillong (Meghalaya) Plateau and the Karbi Anglong Plateau in Assam are structural outliers of the main Peninsular block INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.8. These plateaus are composed of the same ancient gneisses and granites that form the bedrock of South India, proving they were once part of the same continuous landmass.

The separation occurred during the Himalayan orogeny. As the Indian Plate moved northeastward and collided with the Eurasian Plate, the immense tectonic force caused a portion of the crust to sink. This created a massive tectonic depression or fault between the Rajmahal Hills (in present-day Jharkhand) and the Garo Hills (in Meghalaya) INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.13. This feature is known as the Malda Gap (or the Garo-Rajmahal Gap). Over millions of years, this deep depression was filled by the sediment (alluvium) carried by the Ganga and Brahmaputra river systems, effectively 'masking' the geological connection under a thick layer of fertile soil.

Today, the Meghalaya Plateau stands as a distinct tableland, further subdivided by local tribal names into the Garo, Khasi, and Jaintia Hills INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.13. To the east of these hills lies the Kopili Fault, another tectonic lineament that separates the Meghalaya Plateau from the Karbi Anglong region Physical Geography by PMF IAS, Earthquakes, p.189.

Feature	Rajmahal Hills (Main Block)	Meghalaya Plateau (Extension)
Location	Eastern edge of Chotanagpur	Northeastern outlier
Formation	Volcanic (Rajmahal Traps)	Ancient Crystalline Rocks
Separated By	Malda Gap (West)	Malda Gap (East)

Sources: INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.8; INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.13; Physical Geography by PMF IAS, Earthquakes, p.189

5. Igneous Features: Deccan Traps and Rajmahal Traps (exam-level)

When we look at the geological map of India, two massive volcanic features stand out due to their unique step-like topography: the Deccan Traps and the Rajmahal Traps. The term 'Trap' is derived from the Swedish word 'trappa', meaning stairs. This describes the landscape created by successive flows of basaltic lava that cooled and solidified, layer upon layer, forming a staircase appearance through erosion.

The Deccan Traps represent one of the largest volcanic features on Earth. They were formed during the Late Cretaceous period (roughly 66 million years ago) when the Indian plate passed over the Reunion Hotspot. This was a 'fissure eruption,' where lava didn't erupt from a single volcano but poured out of long cracks in the earth's crust. This basaltic lava covered nearly 5 lakh sq. km, spanning Maharashtra, Gujarat (Kutch and Kathiawad), Madhya Pradesh (Malwa Plateau), and parts of Karnataka and Andhra Pradesh Geography of India, Geological Structure and formation of India, p.19. The thickness of this lava is staggering, reaching up to 3,000 meters near the Mumbai coast and thinning out as it moves inland to places like Amarkantak (150m) and Belgaum (60m) Geography of India, Geological Structure and formation of India, p.20.

While the Deccan Traps are more famous, the Rajmahal Traps in Jharkhand are an older sibling, having formed during the Mesozoic Era (specifically the Early Cretaceous). These highlands are composed of volcanic lava deposits that predate the bulk of the Deccan eruptions. A fascinating feature of the Rajmahal formation is the presence of inter-trappean beds—sedimentary layers sandwiched between lava flows—which contain significant plant fossils, providing a window into India's ancient flora Geography of India, Geological Structure and formation of India, p.30.

From a functional perspective, these igneous provinces are critical to India's economy and geography. The weathering of these basaltic rocks produced the fertile Black Cotton Soil (Regur), which is excellent for moisture retention. However, because basalt is very dense, the Deccan Trap region often faces underground water scarcity, as water can only seep through secondary cracks and fissures rather than the rock itself Geography of India, The Drainage System of India, p.44.

Feature	Deccan Traps	Rajmahal Traps
Primary Location	Maharashtra, MP, Gujarat, Karnataka	Jharkhand (Rajmahal Hills)
Geological Age	Late Cretaceous (approx. 66 Ma)	Early Cretaceous (approx. 110-120 Ma)
Rock Type	Basaltic Lava (Flood Basalt)	Volcanic Lava Deposits

Sources: Geography of India, Geological Structure and formation of India, p.19; Geography of India, Geological Structure and formation of India, p.20; Geography of India, Geological Structure and formation of India, p.30; Geography of India, The Drainage System of India, p.44

6. Deep Dive: Vindhyan and Aravalli Systems (exam-level)

To understand the backbone of the Indian Peninsular Plateau, we must distinguish between two of its most iconic features: the Aravalli and the Vindhyan systems. While they both define the Central Highlands, they are geologically worlds apart. The Aravalli Range is one of the oldest fold mountain systems in the world, dating back nearly 2.5 billion years to the Precambrian era Exploring Society: India and Beyond, Geographical Diversity of India, p.14. Stretching roughly 800 km from Delhi to Palanpur in Gujarat, it has been subjected to millions of years of weathering. Consequently, it is now a relict or denuded mountain range, meaning its once-mighty peaks have been worn down to rounded hills and ridges, with Guru Shikhar (1722 m) remaining as its highest point Geography of India, Physiography, p.54.

In contrast, the Vindhyan Range is not a fold mountain system. It is primarily classified as a block mountain or a massive escarpment. Unlike the folded and crumpled strata of the Aravallis, the Vindhyans consist of horizontally bedded sedimentary rocks—such as sandstones, shales, and limestones—that have remained remarkably stable since the Proterozoic age Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.172. This range acts as a primary water divide in India, separating the Ganga river system from the river systems of the Deccan. A fascinating tectonic feature to note is the Great Boundary Fault (GBF), a major geological lineament that separates the ancient Aravallis from the younger Vindhyan formations Geography of India, Physiography, p.54.

Feature	Aravalli System	Vindhyan System
Mountain Type	Old Fold Mountain (Relict/Residual)	Block Mountain / Escarpment
Geological Age	Precambrian (approx. 2.5 billion years)	Proterozoic (Sedimentary deposits)
Composition	Quartzites, Gneisses, and Schists	Sandstone, Shale, and Limestone
Highest Point	Guru Shikhar (Mt. Abu)	Sadbhawna Shikhar (Goodwill Peak)

Sources: Exploring Society: India and Beyond, Geographical Diversity of India, p.14; Geography of India, Physiography, p.54; Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.172

7. Solving the Original PYQ (exam-level)

You have just mastered the structural evolution of the Indian plate, and this question is the ultimate test of your ability to distinguish between different mountain-building processes (Orogeny) and the geological continuity of the Peninsular block. It brings together your knowledge of Tectonic Faulting (the Malda Gap), Volcanism (Rajmahal Traps), and the specific Geomorphology of central India. To solve this, you must apply the principle that the Peninsular Plateau is a stable block where mountains are often the result of denudation or vertical movement (faulting) rather than the intense horizontal compression that creates young fold mountains like the Himalayas.

Walking through the reasoning, we look for the outlier in geological classification. While the Aravallis are indeed recognized as the oldest fold mountains (now highly eroded), the Vindhyans represent a different structural narrative. As explained in CONTEMPORARY INDIA-I, Geography, Class IX NCERT, the Vindhyan Range consists of horizontally bedded sedimentary rocks that have undergone minimal folding. They are primarily classified as Block Mountains or Residual Mountains. Therefore, the statement (C) Vindhyans are examples of fold mountain is the incorrect one and our target answer.

UPSC frequently uses "spatial traps" to confuse students regarding the Shillong Plateau. Even though it is geographically separated from the main plateau by the Malda Gap, INDIA PHYSICAL ENVIRONMENT, Geography Class XI NCERT confirms it is a geological outlier of the Peninsular block. Similarly, the Rajmahal Highlands are correctly identified as lava deposits (Rajmahal Traps) from the Mesozoic era. A common mistake is to assume all ancient Indian ranges are "fold" mountains because of the Aravalli precedent; however, the stable nature of the Peninsular Plateau means most its internal ranges are the result of uplift and erosion rather than active folding.