Geomorphology of the Indian sub-continent | Geology Optional Notes for UPSC PDF Download

Geomorphology of India

• Geomorphic Diversity of India

  • India, a vast land, showcases unique geomorphic diversity and stunning landscapes.

• Geographic Features

  • India is an independent geographic entity, known as the Indian subcontinent.
  • The country boasts various geomorphic features like snow-clad folded mountains in the north, plateaus, uplands, and plains.
  • Narrow coastal plains line the coastal areas of India.

• Formation of Geomorphic Features

  • Distinct landforms and landscapes in India are shaped by internal (e.g., volcanic) and external (e.g., glacial, fluvial, aeolian, coastal, lacustrine, karst) geomorphic activities.

• Geomorphic Processes in India

  • Glacial processes are active in the higher Himalayan regions.
  • Aeolian processes dominate the Thar Desert in western India.
  • Fluvial processes occur across the country.
  • Marine processes shape the eastern and western coastal regions of India.

Block 1

• Geomorphology
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  • Geomorphology is the study of the Earth's landforms, their processes, and the factors that shape them.
• Impact Craters on the Moon
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  • Impact craters on the Moon are formed by the collision of celestial bodies such as asteroids or comets with the Moon's surface.
  • These craters can vary in size and shape, with some showing distinct features like central peaks and terraced walls.
• Dunes on Mars
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  • Dunes observed in the North polar region of Mars at specific coordinates are formed by wind-driven processes.
  • These dunes can provide insights into the atmospheric conditions and geological history of the planet.
• Layered Rocks on Mars
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  • Layered rocks within Schiaparelli Crater on Mars reveal the geological history and environmental changes on the planet.
  • Studying these rocks can help scientists understand past climates and the presence of water on Mars.

Unit 2: Landforms of India

• The landforms of India have been shaped over millions of years by significant tectonic events and geological processes.
• Two main tectonic events, the break-up of India from Gondwana during the Jurassic period about 170 million years ago and the collision of India with Asia during the Eocene around 55 million years ago, have greatly influenced the country's geomorphic diversity.
• Volcanic eruptions from the Reunion mantle plumes during the Upper Cretaceous era led to the formation of the Deccan plateau in peninsular India.
• The collision between India and Asia produced the Himalayas, the world's youngest and highest fold mountain belt, which has had a global impact on climate and the establishment of the monsoon system in the Indian subcontinent.

Major Geomorphic Divisions of India

• India exhibits a wide array of landforms resulting from various geomorphological processes, tectonic activities, volcanic eruptions, climatic conditions, and rock types.
• These diverse landforms make India a fascinating country for studying geography and are major tourist attractions.

Notable Landforms of India

• Deccan Traps: One of the largest igneous provinces in the world.
• Barren Island: The only active volcano in the Andaman and Nicobar Islands.
• Great Rann of Kachchh: A vast saline playa in Gujarat.
• Thar Desert: Home to various types of sand dunes.
• Estuaries and Deltas: Found along the eastern coast of India.
• Western Ghats: One of the great escarpments of the world.
• Kaimur Scarp: Located in the Vindhyan range.
• Megafans: Formed by the rivers Kosi and Gandak.
• Glacial Valleys and Lakes: Abundant in the Himalayas.
• Gulf of Kachchh and Khambhat: Home to large tidal mudflats.
• Granite Landforms: Such as those in Hampi, Karnataka.
• Volcanic Plug: Found in Mount Girnar, Gujarat.
• Lagoons: Examples include Chilika in Odisha and Pulicat in Andhra Pradesh.
• Coral Reefs: Found in Lakshadweep with central lagoons.
• Backwaters: Characteristic of the Malabar Coast.
• Mangrove Swamps: Present in various locations across India.
• Brahmaputra River: Known for its highly braided nature in Assam plains and the riverine island of Majuli.
• Ganga and Brahmaputra Plains: Vast alluvial plains in the Indo-Gangetic plain.
• Lonar Crater: A meteoritic impact crater in Maharashtra.

Basic Concepts of Geomorphology

• India showcases a variety of landforms such as rift valleys of Narmada and Tapi.
• Notable features include picturesque gorges in the Himalayas, canyons along the Narmada River near Jabalpur, and the Kaveri Canyon.
• Various waterfalls are spread across India, along with gullies, ravines, and badland topography in regions like Siwalik Foothills, Yamuna-Chambal, and Chotanagpur zone.
• Distinct karst landforms like Borra and Belum caves in eastern India, Kutumsar caves in Chhattisgarh, Mawmluh caves in Meghalaya, and others contribute to India's diverse geography.
• Additional attractions include Pachmarhi in Madhya Pradesh, Tapkeshwar in Dehradun, and Baratang and Middle Andaman in the Andaman and Nicobar Islands.

Self-Assessment Questions

• a) Explain the disparity between landscape and landform.
• b) Define the concept of relief in geomorphology.
• c) List some prominent landforms in India that serve as major tourist destinations.
• d) Describe the field of applied geomorphology and its significance.

Geomorphic Divisions of India

Himalayan Mountains System

• Stretching over 2500 km, the Himalayan range is one of the longest mountain chains globally, with peaks like Mount Everest, Kanchenjunga, Dhaulagiri, and Naga Parbat.
• It runs from Pamir in the west to Mishmi Hills in the east, featuring an arc shape with a width varying from 150 to 400 km.
• The northern boundary is demarcated by the Indus-Tsangpo Suture Zone.

Indian Peninsula

• The Indian Peninsula exhibits a diverse range of geomorphic features and is characterized by distinct geologic attributes.

Indo-Gangetic Plains

• Comprising fertile plains, the Indo-Gangetic region is vital for agricultural activities and supports a significant population density.

Other Subdivisions

• India also includes the Thar Desert, coastal regions, and various islands, each contributing uniquely to the country's geomorphological diversity.

Geomorphology of India

Introduction

• The Himalayas extend from India into Pakistan, Nepal, Bhutan, and Tibet. This mountain range began forming approximately 55 million years ago due to the collision of the Indian plate with the Eurasian plate.

Divisions of the Himalayas

• The Himalayas are divided into five sub-divisions from north to south, separated by prominent thrusts, which are faults showing maximum compression in a horizontal direction.

Trans Himalaya

• The Trans Himalaya includes the southern region of the Eurasian plate and the northernmost part of the Indian plate. It is situated north of the Tethys Himalaya and is primarily found in northern Ladakh and the northernmost part of Pakistan.
• Height ranges from 3000 to 6000 meters and encompasses regions like Kohistan, Shyok, and Karakoram.
• Also referred to as the Tibetan Himalaya due to its significant presence in Tibet.
• For example, the Trans Himalaya region includes mountain ranges like Karakoram, Shyok, and Kohistan.

Other Subdivisions

• Further divisions of the Himalayas showcase diverse geological features and landscapes.

Conclusion

• The geomorphology of India, particularly the Himalayan mountain system, plays a crucial role in shaping the region's topography and geological diversity.

Basic Concepts of Geomorphology

• Himalayan Range Overview

  • Consists of various subdivisions
  • Includes Greater Himalaya, Lesser Himalaya, and Outer Himalaya

• Tethys Himalaya

  • Located in the northernmost region, partly extending into the Tibetan plateau
  • Referred to as the "Tethys domain" or "Tethys Himalayan Zone"
  • Characterized by heights over 3000 m and sloping gently northwards
  • Comprised of sedimentary and metasedimentary rocks of various ages
  • Contact with Greater Himalaya known as Tethyan Thrust

• Greater Himalaya

  • Situated south of Tethys Himalaya and contains the highest peaks
  • Home to peaks ranging from 6000 to 8000 m
  • Main watershed for most Himalayan rivers
  • Primarily composed of deformed metamorphic rocks
  • Main Central Thrust marks the boundary with Lesser Himalaya

• Lesser Himalaya

  • Located south of Greater Himalaya with heights ranging from 1000 to 2500 m
  • Features ranges like Pir Panjal, Dhauladhar, Nag Tibba, and Mahabharat
  • Comprised of thrust sheets and Precambrian metamorphic rocks
  • Boundary with Outer Himalaya marked by Main Boundary Thrust

• Outer Himalaya

  • Southernmost part merging with the Indo-Gangetic plain
  • Consists of low hills under 1000 m in height
  • Siwalik range is prominent in this region
  • Transition zone from the hills to the plain

Fig. 2.3: Map showing major subdivisions of Himalaya. (Source: simplified after Kumar, 1988)

Unit 2: Geomorphology of India

Himalayan Region

• Geomorphic processes in the Himalayas include glacial, fluvial, fluvio-glacial, orographic, and monsoonal rainfall activities.
• Aeolian processes, such as sand dune formation, are observed in specific areas like Ladakh.
• The rugged relief of the Himalayas is a result of tectonic upliftment, valley incision, glacial erosion, and landslide movements.
• The Indus, Ganga, and Brahmaputra rivers form the primary river systems in the Himalayan region, characterized by extensive erosion and deeply incised valleys.
• Continental and maritime glaciers are found in the western Himalayas at high altitudes, contributing to various geomorphic features like cirques, U-shaped valleys, moraines, and glacial melt water streams.

Indian Peninsula

• The Indian Peninsula, enclosed by low mountain ranges like the Vindhyan hills and the Satpura chain, is known as the 'Indian shield.'
• Comprising ancient and stable blocks of the Earth's crust, the Indian Peninsula is the oldest and broadest geomorphic division in India.
• It consists of Precambrian stable blocks including cratons made up of granite and mobile belts with metamorphosed Proterozoic rocks.
• Fluvial geomorphic processes are predominant in the region, shaping various terrains like granitic, gneissic, basaltic, sandstone, and limestone landscapes.
• The Deccan Plateau, a significant geomorphic unit, features the Sahyadri escarpment along its western margin and basaltic rocks experiencing fluvial erosion and weathering.
• Weathering of Deccan trap basalts has led to the formation of black soil, ideal for cultivating crops like cotton.

Basic Concepts of Geomorphology

• The Deccan traps are surrounded by lowlands on the western and eastern sides.
• The Western coastal lowlands are narrow and consist of hills and plateaus, while the Eastern coastal lowlands are mainly aggradational and consist of deltas and deltaic plains.
• The Eastern side of the Indian Peninsula is bounded by the Eastern Ghat, which consists of discontinuous and isolated hills.

Geographical Features

• Aravalli Craton lies in the western region.
• Western Ghats extend from South Gujarat to Kerala and represent a continuous chain of hills.
• Eastern Ghats extend from Odisha to Tamil Nadu and comprise detached hills.

Western Ghats

• Western Ghats are a chain of low hills with an average height of less than 1000m.
• The highest peak, Anaimudi, reaches 2693m.
• They form the watershed for rivers like the Godavari, Krishna, and Cauvery.

Eastern Ghats

• Eastern Ghats are low hills with a maximum elevation of about 1500m at Mahendragiri in Odisha.
• The Western and Eastern Ghats join at Nilgiri hills.

River Systems

• All rivers in the Indian Peninsula are ephemeral and monsoon-fed.
• Rivers like Krishna, Cauvery, Godavari, and Mahanadi flow from west to east, draining into the Bay of Bengal.
• Rivers like Narmada and Tapti flow from east to west, draining into the Arabian Sea.

River Behavior

• Most peninsular rivers are in the stage of incision, forming broad and shallow valleys during the monsoon season.
• Badlands develop along the banks of rivers like Chambal, Mahi, Narmada, and Tapti due to incision and gully erosion.

Geomorphology of India - Indo-Gangetic Plain

Overview

• The Indo-Gangetic Plain is a significant geographical region in northern and eastern India, situated to the south of the Himalayan arc.
• This vast plain is primarily formed by sediments carried and deposited by the Ganga and Brahmaputra rivers, along with their tributaries, during the recent Holocene period.
• Geographically, it spans across states including Punjab, Haryana, Uttar Pradesh, Uttaranchal, Jharkhand, Bihar, West Bengal, Assam, and part of Rajasthan.

Physical Features

• The Indo-Gangetic plain is characterized by fertile alluvial sediments that are relatively shallow, not exceeding a depth of 2000 meters.
• It is bordered to the south by Vindhyan sedimentary rocks, contributing to its rich fertility.

Geomorphological Elements

• Various geomorphic features can be observed in the region, including:
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  • Alluvial fans
  • Floodplains
  • Channels
  • Deltas
  • Palaeochannels
  • Meandering rivers
  • Natural levees
  • Ox-bow lakes

River Characteristics

• The rivers in the Indo-Gangetic plain exhibit various patterns and behaviors:
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  • Channel shifting, especially notable in the Kosi River
  • Meandering channel in the Yamuna River
  • Braided river patterns along the Ganga, Satluj, Kosi, and Brahmaputra rivers

Alluvial Deposits

• Two main types of alluvial deposits exist in the region:
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  • Bhangar: Older deposits consisting of clay and calcareous alluvium
  • Khadar: Younger deposits composed of fine silt and clay