India's Major Geological Divisions

India can be broadly divided into three main geological regions based on their origin, structure,
and age:

a) The Peninsular Plateau (The Ancient Craton)

• Age: Formed during the Precambrian era, some rocks are over 2.5 billion years old.

• This is the oldest and most stable part of the Indian landmass, also known as the
Indian Shield.

• It is composed mainly of igneous and metamorphic rocks (granite, gneiss, schist).

• Geologically stable: No major folding or faulting in recent geological periods.

Important Geological Features:

• Deccan Trap (Western and Central India): Formed by extensive volcanic lava flows
during the Cretaceous period (~65 million years ago); made of basalt rock.

• Dharwar System: Found in Karnataka and parts of Maharashtra; rich in iron and
manganese ores.

• Chotanagpur Plateau: Eastern India; contains coal, bauxite, and mica.

Significance:

• The Peninsular Plateau is rich in minerals and fossil fuels.

• Serves as the foundation for the plateau region of India.

• It has undergone erosion for millions of years, giving rise to rolling hills and broad
valleys.

b) The Himalayan Mountain System (Young Fold Mountains)

• Age: Formed during the Tertiary period (~50 million years ago), making it one of the
youngest mountain ranges in the world.

• Originated from the collision between the Indian Plate and the Eurasian Plate due to
plate tectonics.

• Made up mostly of sedimentary and metamorphic rocks, which were uplifted and
folded into high mountains.

Key Geological Traits:

• Highly tectonically active and earthquake-prone region.

• Continues to rise each year due to ongoing plate movements.

• Rich in glacial features, snow-fed rivers, and alpine vegetation.

Significance:
 • Acts as a climatic barrier protecting the Indian subcontinent from cold Central Asian
winds.

• Source of major river systems like the Ganga, Brahmaputra, and Indus.

• Important for biodiversity, glaciers, and mountain ecosystems.

c) Indo-Gangetic and Brahmaputra Plains (Alluvial Deposits)

• Age: Formed during the Quaternary period (last 2.6 million years).

• This region is a vast alluvial plain created by deposition from Himalayan rivers.

• Composed of loose sediments such as silt, clay, sand, and gravel.

• Geologically young, flat, and extremely fertile.

Divisions:

• Indus Plain (Northwest India)

• Ganga Plain (North and Central India)

• Brahmaputra Plain (Northeast India)

Significance:

• Among the most densely populated and agriculturally productive regions of the world.

• Prone to flooding, soil erosion, and sedimentation due to active rivers.

Additional Geological Regions (Optional Advanced):

• Coastal Plains: Formed by recent marine deposits.

• Islands:

o Andaman-Nicobar Islands: Formed due to submarine volcanic activity.

o Lakshadweep Islands: Coral atolls built on submerged volcanic peaks.

The Himalayas and its formation

The Himalayas are the youngest and highest mountain ranges in the world, stretching across
northern India and neighbouring countries like Nepal, Bhutan, China, and Pakistan. The word
"Himalaya" comes from Sanskrit, meaning "abode of snow," as the peaks remain snow-covered
throughout the year. The formation of the Himalayas is a result of a major geological event called
plate tectonics. Around 50 million years ago, the Indian Plate, which was once part of the ancient
supercontinent Gondwana, began to move northward and collided with the Eurasian Plate. Since
both plates are continental and have similar densities, neither could sink beneath the other.
Instead, the land between them began to fold and rise, giving birth to the vast and towering
Himalayan Mountain system. This process is still ongoing, and the Himalayas continue to rise by
a few centimetres each year due to the continuous pressure from the moving Indian Plate. As a
result, the region is also prone to earthquakes and other tectonic activity. The Himalayas play a
crucial role in shaping the climate, rivers, and biodiversity of the Indian subcontinent. They act
as a natural barrier, protecting India from cold Central Asian winds and monsoon drift. These
mountains are also the source of major rivers like the Ganga, Yamuna, and Brahmaputra, and are
home to diverse flora, fauna, and culturally important sites. Their ongoing formation makes the
Himalayas a fascinating example of how Earth's surface is shaped by powerful natural forces
over millions of years.

Major Ranges of the Himalayas (Latitudinal Division)

From south to north, the Himalayas are divided into three parallel ranges:

a) Shiwalik (Outer Himalayas)

• Southernmost range.

• Lowest in elevation: 600 to 1,200 meters.

• Composed of unconsolidated sediments.

• Prone to erosion and landslides.

• Example: Jammu Hills, Dudhwa Range.

b) Lesser Himalayas (Himachal Himalayas or Middle Himalayas)

• Altitude: 1,200 to 4,500 meters.

• Made of metamorphic and sedimentary rocks.

• Popular hill stations: Shimla, Mussoorie, Nainital.

• Notable ranges: Pir Panjal, Dhauladhar, Nag Tibba.

c) Greater Himalayas (Inner Himalayas or Himadri)

• Northernmost and highest range.

• Average height: 6,000 meters and above.

• Contains the highest peaks: Mount Everest, Kanchenjunga, Nanga Parbat.

• Perennially snow-covered, origin of major rivers like Ganga and Yamuna.

4. Regional Divisions of the Himalayas (Longitudinal Division)

The Himalayas are also divided from west to east into five regional units:

a) Punjab Himalayas (Kashmir Himalayas)

• Between Indus and Sutlej rivers.

• Famous for valleys like Kashmir and Lidder.

• Peaks: Nanga Parbat.

b) Kumaon Himalayas

• Between Sutlej and Kali rivers.

• Peaks: Nanda Devi, Trisul.

• Known for tourism and apple orchards.

c) Nepal Himalayas

• Between Kali and Tista rivers.

• Contains most of the eight-thousanders (peaks above 8,000 m), including Mount
Everest.

• Densely glaciated region.

d) Assam Himalayas (Eastern Himalayas)

• Between Tista and Dihang rivers.

• Peaks: Namcha Barwa.

• Receives highest rainfall; rich biodiversity.

e) Arunachal Himalayas

• Extends from Dihang to Brahmaputra gorge.

• Lower altitude but rugged terrain.

• Home to many tribal communities and dense forests.

Peninsular Plateau and Its Formation (In Detail)

The Peninsular Plateau is one of the most prominent physiographic features of India. It is the
oldest and most stable landmass on the Indian subcontinent, formed through long and
complex geological processes. It lies to the south of the Indo-Gangetic Plain and covers a
significant part of central and southern India, spreading across states like Madhya Pradesh,
Chhattisgarh, Maharashtra, Karnataka, Andhra Pradesh, Telangana, Tamil Nadu, and parts of
Odisha and Jharkhand.

Geological Background and Age

The Peninsular Plateau was formed during the Precambrian era, making it more than 2.5 billion
years old. It is part of the Indian Shield—a stable block of the Earth's crust made up of igneous
and metamorphic rocks such as granite, gneiss, schist, and quartzite. Unlike the Himalayas,
which are young fold mountains, the Peninsular Plateau has not undergone any major folding in
recent geological history. This is why it is referred to as a tectonically stable and rigid landmass.
Formation Process

The formation of the Peninsular Plateau began when the molten magma beneath the Earth's
crust cooled and solidified into hard crystalline rocks. Over millions of years, this region was
uplifted, weathered, and eroded, resulting in a tableland or plateau-like surface. The plateau
has been exposed to volcanic activity, sedimentation, and denudation over geological time.
One major event was the Deccan Volcanism, which occurred around 65 million years ago.
During this period, huge volumes of basaltic lava flowed out and solidified, forming the Deccan
Trap—a vast region of flat-topped black basalt rock in western and central India.

Topographical Features

Although referred to as a plateau, the surface is not uniform. It consists of rolling hills, valleys,
escarpments, and broad river basins. The general slope of the plateau is from west to east,
which explains why most major rivers (like the Godavari, Krishna, and Mahanadi) flow eastward
into the Bay of Bengal.

Divisions of the Peninsular Plateau

Geographically, the Peninsular Plateau is divided into two main parts:

1. Central Highlands (Northern Part)

• Lies between the Vindhya Range and the Narmada River.

• Includes the Malwa Plateau, Bundelkhand, and Baghelkhand.

• The Chotanagpur Plateau, located to the east, is rich in minerals like coal, iron ore, and
mica.

• Rivers like the Chambal, Betwa, and Son flow here.

2. Deccan Plateau (Southern Part)

• Lies south of the Narmada River.

• Bounded by the Western Ghats and Eastern Ghats.

• Made of volcanic basalt rock from the Deccan Trap.

• Rivers like Godavari, Krishna, and Kaveri originate here and flow eastward.

Geological Importance

• The Peninsular Plateau is a storehouse of minerals, especially in the Chotanagpur

• It shows clear evidence of ancient erosion cycles, river rejuvenation, and tectonic uplift.

• The region has lava plateaus, dome hills, and relic mountains, offering insights into the
Earth's early history.
Climatic and Ecological Role

• The Western Ghats, a part of the plateau’s edge, influence the Indian monsoon and
house unique biodiversity.

• Plateau soils like black soil in the Deccan region are ideal for cotton cultivation.

• Many rivers originate from the plateau, making it crucial for irrigation, hydroelectricity,
and drinking water.

Indo-Gangetic and Brahmaputra Plain – A Detailed Note

The Indo-Gangetic and Brahmaputra Plain is one of the most important physical regions of
India. It is an extensive alluvial plain, formed by the deposition of sediments brought by rivers
like the Indus, Ganga, and Brahmaputra and their tributaries. This plain stretches from the
northwestern part of India (Punjab) to the easternmost part (Assam and Arunachal Pradesh).
It is known for its flat terrain, fertile soil, dense population, and agricultural productivity.

Geological Formation

• These plains were formed during the Quaternary period (last 2.6 million years) as a result
of the erosion of the Himalayas and deposition of sediments in the depression between
the Peninsular Plateau and the Himalayas.

• The region consists of thick layers of alluvium—a mixture of sand, silt, clay, and gravel—
carried by rivers.

• These sediments gradually built up a nearly flat and level surface, which is now one of
the largest alluvial plains in the world.

Extent and Location

• The Indo-Gangetic and Brahmaputra plain extends for about 2,400 kilometers from west
to east and is 300–400 kilometers wide.

• It covers parts of Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, Assam, and
other eastern states.

• To the north, it is bounded by the Shiwalik Hills (Outer Himalayas) and to the south by
the Peninsular Plateau.

Divisions of the Plain

1. Western Plain (Indus Basin)

• Located in Punjab, Haryana, and western Rajasthan.

• Drained by the Indus and its tributaries: Jhelum, Chenab, Ravi, Beas, and Sutlej.
 • The Thar Desert lies to the southwest.

• Features canal irrigation in arid areas.

2. Central Plain (Ganga Basin)

• Covers Uttar Pradesh and Bihar.

• Drained by the Ganga and its tributaries like Yamuna, Ghaghara, Gandak, and Kosi.

• It is the most densely populated and agriculturally productive part of India.

• Soils are rich in nutrients, ideal for crops like wheat, rice, and sugarcane.

3. Eastern Plain (Brahmaputra Basin)

• Located mainly in Assam and parts of Arunachal Pradesh.

• Drained by the Brahmaputra River, which carries a huge sediment load.

• Known for annual floods and fertile silt deposits.

• Supports tea plantations and wet rice cultivation.

Types of Alluvial Soils

• Bhangar: Older alluvium, slightly elevated, found away from river channels.

• Khadar: Newer alluvium, found along river banks, very fertile and renewed annually by
floods.

Significance of the Plain

Aspect Significance

Agriculture Extremely fertile; supports crops like rice, wheat, sugarcane, pulses.

Population Densely populated due to flat land, water availability, and fertile soil.

Transport Well-developed rail and road networks due to flat topography.

Culture Cradle of ancient Indian civilizations like Indus Valley and Vedic culture.

Economy Backbone of India’s food grain production and rural economy.