Geological Formation

  • The geological evolution of India started 4.57 billion years ago. Geologically, the country represents a monumental assemblage of land pieces varying in age from pre-Cambrian period to the recent. The peninsular massif is the core upon which different geological processes took place and resulted in different landforms of India.
  • The different landforms like mountain summits, entrenched valleys, islands, the dykes, folds and faults, all indicate the alternating periods of disturbances and activities responsible for the present configuration of the country.
  • Geological history is the historical study of earth, which studies the patterns of development of the crust in time and space.
  • India is composed of three geological units:
    1. The Peninsular Plateaus
    2. The Himalayan Mountains, and
    3. The Indo-Gangetic Plains
  • The Peninsular Plateau lies in the southern part of India. It is surrounded by water bodies from three sides. It consists of an old plateau, which is known as Southern Plateau. There was a large depression in Pre-Cambrian Era, in which sediments were deposited by rivers. Peninsular plateau came out of this depression as a block of crystal rocks and never submerged again.
  • The Himalayas are the young fold mountains. They are formed recently about 20-30 million years ago. About seventy million years ago, the Himalayas and the northern plains remain under the geosynclines of Tethys Sea as sediments. The sediments were deposited by the rivers of the two land masses called Angaraland and the Gondwanaland. The sediments were folded and the Himalayas were formed.
  • The Great Plains lie between the Himalayas in the north and the Peninsular Plateau in the south. They are mainly drained by Indus River, Ganga River, Brahmaputra River and their tributaries.
  • Eras are the primary interval of time and periods are the secondary interval. India has its own geological eras and periods. The standard geological eras are:
    1. The Pre-Cambrian (over 570 million years old)
    2. The Paleozoic (245-570 million years old)
    3. The Mesozoic (66-245 million years old), and
    4. The Cenozoic (66 million years old to the present)

 

  • According to Geological Survey of India, major geological phases responsible for making of India can be divided into four eras. These are:
    1. The Archean
    2. The Purana
    3. The Dravidian, and
    4. The Aryan

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  • Q1

    Where do we find the rocks of Vindhyan system? Give examples of these rocks.

    Marks:2
    Answer:

    The Vindhyan rocks generally stand over the Cuddapah rocks. They are found in Rajasthan, Madhya Pradesh, Uttar Pradesh and Chhattisgarh. These rocks are rich in red-sandstone, limestone, sandstone, shales and slates.

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  • Q2

    Name the standard geological eras and mention their time periods and the kind of fossils found in those eras.

    Marks:2
    Answer:

    The standard geological eras are as follows:

    Geological Era

    Time Period

    Fossils

    Pre-Cambrian

    over 570 million years old

    Do not contain fossils of plants and animals

    The Paleozoic

    245-570 million years old

    Fossils of very early lives

    The Mesozoic

    66-245 million years old

    Fossils of middle lives

    The Cenozoic

    66 million years old to the present

    Fossils of recent lives

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  • Q3

    Name the three geological units of India.

    Marks:1
    Answer:

    The three geological units of India are:
    i. The Peninsular Plateaus

    ii. The Himalayan mountains
    iii. The Indo-Gangetic plains

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  • Q4

    Name the Indian geological eras.

    Marks:1
    Answer:

    The Indian Geological eras are:
    i. The Archean or Early Pre-Cambrian

    ii. The Purana or Late Pre Cambrian
    iii. The Dravidian (400-570 million years old)
    iv. The Aryan (400 million years old to the present)

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  • Q5

    What is stratigraphy and physiography?

    Marks:1
    Answer:

    Stratigraphy is the lithological study of rock beds, sequence of their occurrences and their thickness and age.

    Physiography is the study of the formation and development of surface features of land like mountains, plateaus and plains.

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