Geological Structure and Physiographic Division of India

India boasts a rich geological heritage, housing some of the world's oldest geological structures and features that span various epochs on the geological time scale. The country exhibits unique geological and structural conditions, showcasing a diverse array of rock masses, mineral deposits, and mineral fuels, including coal and oil.

• The geographical landscape of India is incredibly varied, encompassing the snow-capped peaks of the Himalayas in the north, contrasting with sun-drenched coastal settlements in the south. 
• The southern region is further characterised by humid tropical forests along the southwest coast. 
• The eastern part of the country is marked by the fertile Brahmaputra valley.
• While the western expanse is dominated by the arid Thar Desert.

This geological diversity not only contributes to India's scenic beauty but also plays a crucial role in shaping the nation's ecological and economic characteristics. The geological wealth of India has influenced its natural resources, climate, and overall topography, making it a fascinating and geologically significant part of the world.

GEOLOGICAL STRUCTURE OF INDIA

Geologists categorise geologic divisions based on similarities in rocks, structures, and the overall geological history of an area. Over the course of about a century, extensive geological research and exploration in India have provided a wealth of information about its diverse geology. India is geologically divided into several distinct divisions, each characterised by unique geological features. These divisions include:

NORTH WESTERN HIMALAYAS

The region you are referring to is the Himalayan region in northern India. 

This area is marked by a complex network of mountain ranges and features, including the Karakoram, Ladakh, Zaskar, and Pir Panjal ranges.

Karakoram, Ladakh, Zaskar, and Pir Panjal Ranges:

• These mountain ranges collectively contribute to the rugged and majestic terrain of the Himalayan region, shaping its landscape and influencing local climates.

Frigid Desert in the Northeastern Half:

• The northeastern half of the Kashmir Himalayas is characterised by a frigid desert environment, situated between the Greater Himalayas and the Karakoram ranges. 
• This region experiences cold temperatures and challenging climatic conditions.

Kashmir Valley and Dal Lake:

• Nestled between the Great Himalayas and the Pir Panjal range, the Kashmir valley is renowned for its breathtaking beauty. 
• The iconic Dal Lake, surrounded by snow-capped peaks, adds to the picturesque charm of this region.

South Asian Glaciers:

• Notable glaciers, including the Baltoro and Siachen, are found in this Himalayan region. 
• These glaciers play a crucial role in regional water resources and contribute to the formation of major rivers.

Karewa Formations and Zafran Cultivation:

• The Kashmir Himalayas are known for the Karewa formations, which are geological formations consisting of lacustrine and fluvioglacial deposits. 
• These formations are utilised for the cultivation of Zafran, a local variety of saffron, showcasing the region's agricultural significance.

HIMACHAL AND UTTARAKHAND HIMALAYA

• The Himalayan ranges of Himachal and Uttarakhand extend across three states: Jammu and Kashmir, Himachal Pradesh, and Uttarakhand. 
• This geographical expanse is situated approximately between the Ravi River (a tributary of the Ghaghara) in the west and the Kali River (a tributary of the Ghaghara) in the east.
• These mountainous terrains are drained by two of India's most significant river systems, namely the Indus and the Ganga. 
• The Ravi, Beas, and Satluj serve as tributaries to the Indus, while the Yamuna and Ghaghara contribute as tributaries to the Ganga, coursing through this region.
• The northernmost reaches of the Himachal Himalayas form an extension of the Ladakh cold desert, situated in the Lahaul and Spiti subdivision. 
• This region showcases a diverse landscape, featuring rugged terrains and vital river systems that play a crucial role in the overall hydrology of the Indian subcontinent.

NORTH EASTERN HIMALAYAS

Situated between the Nepal Himalayas to the west and the Bhutan Himalayas to the east, this relatively small section of the Himalayas holds significant importance. 

Despite its size, it is home to notable features, including towering peaks like Kanchenjunga (also known as Kanchengiri), deep valleys, and rapid-flowing rivers such as the Tista.

The higher elevations of this region are inhabited by the Lepcha tribes, contributing to the cultural diversity of the area. 

In contrast, the lower elevations, particularly in the Darjeeling Himalayas, are home to a mix of communities including Nepalis, Bengalis, and Central Indian tribes. 

The Arunachal Himalayas extend from the east of the Bhutan Himalayas to the Diphu Pass in the east, running in a broad southwest-to-northeast direction. 

Notable peaks in this range include Kangtu and Namcha Barwa.

Fast-flowing rivers traverse the region, cutting through the mountains from north to south and creating deep gorges. 

The Brahmaputra, after passing Namcha Barwa, continues its course through a profound gorge.

The Eastern Hills & Mountains form part of the broader Himalayan mountain chain, aligning from north to south. 

Recognized by various local names, they are referred to as Patkai Bum in the north, Naga hills in the south, and Manipur hills in the north.

• Populated by diverse tribes practising Jhum agriculture, these low hills in the Eastern Hills & Mountains region are characterised by geological instability, featuring multiple faults crisscrossing the area. 
• The north–south hill ranges are defined by small parallel valleys sloping westward, contributing to the unique topography and geological dynamics of the region.

GANGA -BRAHMAPUTRA PLAIN

• The Indo-Gangetic-Brahmaputra plain, alternatively known as the Northern lowlands of India or the Great Plain of India.
• It serves as a transitional zone between the northern Himalayas and Peninsular India. 
• This expansive plain is renowned as the world's largest alluvial tract.
• Positioned to the south of the Himalayas and to the north of the Peninsula, the Great Plain of North India is an aggradational plain formed through the deposition of sediments by three major river systems: the Indus, Ganga, and Brahmaputra. 
• This remarkable geological feature is a result of the cumulative depositional actions of these significant rivers, shaping a vast and fertile expanse that plays a crucial role in the agricultural and hydrological dynamics of the region.

PENINSULAR PLATEAU

• The Peninsular Block, once part of the Gondwanaland/plate, underwent geological processes leading to its separation. 
• Over time, it moved in various directions as distinct plates, including the Indian plate, Australian plate, Antarctica plate, and African plate.
• The Indian Peninsular Plateau, forming an uneven triangle, elevates from approximately 150 metres above river lowlands to heights ranging between 600-900 metres. 
• This prominent plateau is characterised by its diverse topography and geological features.
• Bounded by geographical landmarks, the Peninsular Plateau is delineated by the Delhi Ridge in the northwest (an extension of the Aravallis), the Rajmahal hills in the east, the Gir range in the west, and the Cardamom hills in the south. 
• Also known as the Plateau of Peninsular India, it stands as one of the nation's foremost physiographic features, showcasing a rich geological history and playing a pivotal role in shaping India's landscape.

PENINSULAR MOUNTAIN

• Peninsular India mirrors the geographical and climatic patterns of South India, forming an inverted triangle shape with the Arabian Sea to the west, the Bay of Bengal to the east, and the Vindhya and Satpura ranges to the north. 
• The region's landscape is predominantly characterised by residual mountains, representing remnants of ancient horsts and hills that have endured for millions of years.
• Plateaus in the peninsular region are interspersed with various mountain ranges and diverse river basins. 
• The historic demarcation between northern and southern India is marked by the Narmada and Mahanadi rivers. 
• The geographical boundaries are further defined on the north by the Aravallis, on the northeast by the Hazaribagh and Rajmahal Hills, on the west by the Western Ghats (Sahyadri Mountains), and on the east by the Eastern Ghats.

Anamudi stands as the highest peak in Peninsular India, soaring to an elevation of 2695 metres above sea level. 

This distinctive topography, coupled with the influence of surrounding bodies of water, contributes to the region's diverse climates, ecosystems, and cultural landscapes.

COASTAL PLAIN

India, surrounded on three sides by the sea, possesses a coastline shaped by the faulting of Gondwanaland during the Cretaceous period, a process driven by Continental Drift. 

This geological event resulted in India's straight and regular coastline, albeit with limited natural harbours along its shores.

The Bay of Bengal and the Arabian Sea, formations arising from the dissolution of Gondwanaland during the Cretaceous or early Tertiary periods, flank India on the east and west, respectively. 

India's coastal plains extend in an east-west direction, covering a total area of 7516.6 km and are categorised into two distinct types:

Eastern Coastal Plains of India:

• Stretching along the eastern seaboard, these plains are marked by their expansive coastline along the Bay of Bengal. 
• The flat terrain of the Eastern Coastal Plains supports various agricultural activities.

Western Coastal Plains of India:

• Running parallel to the Arabian Sea on the western side of the country, the Western Coastal Plains boast a diverse landscape, including fertile plains and hilly regions. 
• This coastal stretch is known for its scenic beauty and unique ecosystems.

The distinct characteristics of India's coastal plains, shaped by geological processes over time, contribute to the nation's diverse geography and play a significant role in its cultural and economic activities.

ISLANDS

India is home to two significant island groups: the Andaman and Nicobar Archipelago in the Bay of Bengal and the Lakshadweep Islands in the Arabian Sea.

• The Andaman and Nicobar Islands were formed through the collision of the Indian Plate and the Burma Minor Plate (a part of the Eurasian Plate), similar to the geological processes that gave rise to the Himalayas. 
• These islands are considered a southern extension of Myanmar's Arakan Yoma range, which itself is a continuation of the Purvanchal Hills.

In contrast

• The Lakshadweep Islands are a collection of coral islands situated off the Indian coast. 
• They are associated with the Reunion Volcanic Hotspot.

Apart from these prominent island groups, there are additional islands found in the Indo-Gangetic Delta, although they are more integral to the delta's structure than standalone islands. Additionally, there are islands located between India and Sri Lanka, often referred to as the remains of Adam's Bridge, Rama's Bridge, or Rama Setu. The formation of these islands is attributed to submergence over time. Together, these island groups contribute to the diverse geography of India and its surrounding waters.

FAQs on India's Rich Geological Heritage

1. What makes India's geological heritage unique?

Ans. India is home to some of the world's oldest geological structures and features, spanning various epochs on the geological time scale. Its diverse rock masses, mineral deposits, and mineral fuels, including coal and oil, contribute to its rich geological heritage.

2. How has the geographical landscape influenced India's climate?

Ans. India's varied landscape, from the snow-capped Himalayas to the sun-drenched coastal areas, creates diverse climates. The Thar Desert in the west and the humid tropical forests in the southwest are examples of the contrasting climates shaped by India's geography.

3. How is India geologically divided?

Ans. Geologists categorise India into several divisions based on rock types, structures, and geological history. Notable divisions include the North Western Himalayas, Himachal and Uttarakhand Himalaya, Sikkim Himalaya, Peninsular Mountain, Ganga-Brahmaputra Plain, Peninsular Plateau, Coastal Plain, and Islands.

4. What are the key features of the North Western Himalayas?

Ans. The North Western Himalayas encompass the Karakoram, Ladakh, Zaskar, and Pir Panjal ranges. This region is characterised by rugged terrain, frigid desert in the northeastern half, iconic Kashmir Valley, South Asian glaciers, and Karewa formations used for Zafran cultivation.

5. What is unique about the Peninsular Plateau?

Ans. The Peninsular Plateau, once part of Gondwana land, moved in various directions as distinct plates. It forms an uneven triangle with diverse topography, bounded by the Delhi Ridge, Rajmahal hills, Gir range, and Cardamom hills.

6. How did the Coastal Plains of India form?

Ans. India's straight and regular coastline is a result of the faulting of Gondwanaland during the Cretaceous period, driven by Continental Drift. The Bay of Bengal and the Arabian Sea, formed during the Cretaceous or early Tertiary periods, flank India's east and west. The coastal plains extend east-west and are categorised as Eastern and Western Coastal Plains.

7. Tell us about the significant island groups in India.

Ans. India hosts two major island groups - the Andaman and Nicobar Archipelago in the Bay of Bengal and the Lakshadweep Islands in the Arabian Sea. The Andaman and Nicobar Islands are a southern extension of Myanmar's Arakan Yoma range, while the Lakshadweep Islands are coral islands associated with the Reunion Volcanic Hotspot.

8. How did the Indo-Gangetic-Brahmaputra Plain form?

Ans. The Indo-Gangetic-Brahmaputra Plain, known as the Northern lowlands of India, is the world's largest alluvial tract. It formed through aggradational processes driven by the depositional action of three main river systems: the Indus, Ganga, and Brahmaputra.

9. Why is the Peninsular Plateau considered a significant physiographic feature?

Ans. The Peninsular Plateau, once part of Gondwana land, showcases diverse topography and geological features. Bounded by prominent landmarks, it is delineated by the Delhi Ridge, Rajmahal hills, Gir range, and Cardamom hills, standing as one of India's foremost physiographic features.

10. How has the dissolution of Gondwanaland influenced India's islands?

Ans. The Andaman and Nicobar Islands were formed through the collision of the Indian Plate and the Burma Minor Plate, similar to the processes that gave rise to the Himalayas. The Lakshadweep Islands are coral islands associated with the Reunion Volcanic Hotspot. Other islands are found in the Indo-Gangetic Delta and between India and Sri Lanka, forming due to submergence over time.