Geomorphology

IAS Notes October 13, 2022
Unit - 2 (Geomorphology)

Next Unit - Climatology

geomorphology


Geomorphology - It is the study of physical features on the surface of the Earth (land) and also the processes from which those features are formed.


Origin of the Earth - The planet Earth before 4,800 Million years ago was barren, rocky and hot with a very thin atmosphere of Hydrogen and helium. It was in a volatile state during this Primordial state.

Due to gradual increase in density, the interior temperature increased and gradually the heavy materials like Iron and Nickel started to sink towards the centre of the Earth and the lighter one moves towards the centre through the process of density separation.


With time the Earth cooled further and gradually condensed into smaller size.


Further process of differentiation led to the formation of different layers in the interior of the Earth.


Aspect before 4,800 Million years ago was discussed in Nebula Hypothesis

evolution of the earth


Evolution of the Earth - It includes the following stages -
🠚 Stages in the formation of Earth's interior
  • Molten state - Volatile
  • Density separation
  • Gradual condensation
  • Differentiation of layers
🠚Stages in the formation of Earth's atmosphere
  • Primordial atmosphere - Primitive atmosphere mainly made up of lighter elements like hydrogen and helium. This atmosphere was stripped away by Sun's solar wind.
  • Degassing - During density separation heavier elements started to sink and lighter elements started to accumulate near to the surface and the lightest elements (mainly gases) were released, forming an atmosphere which mainly consists of Carbon di-oxide, Water vapour, Nitrogen, Methane and a very few amount of Oxygen.
  • Condensation - Amount of water vapour increases which later started to condense. It causes precipitation which leads to drop in temperature which further stimulate condensation. This cycle went on for years which eventually led to the formation of Oceans by 4000 Million years ago.
  • Increasing the concentration of Oxygen in the atmosphere - Between 3000 to 2000 Million years ago, Blue-Green algae evolved which released Oxygen in the atmosphere during Photosynthesis. This led to the increase in the amount of Oxygen in the atmosphere.

Formation of Earth's atmosphere - 
The early thin primordial atmosphere with Hydrogen and Helium was stripped off due to solar wind. 


During the cooling of the Earth, various gases and water vapour were released from the Earth's interior. This process through which gases outpour from the Earth's atmosphere is known as Degassing. The important gases at this stage included Carbon di-oxide, Nitrogen, Methane, Ammonia, Water vapour and Oxygen (very little). 


The continuous volcanic eruptions released more and more water vapour. As the Earth cooled down, water vapour started to condense and caused precipitation. Carbon di-oxide in the atmosphere got dissolved in the rain water and is brought down. Through condensation and precipitation, the temperature of the atmosphere further decreased this led to more condensation and more precipitation.


The rainwater gradually collected in the depressions forming seas and oceans which was completed 4,000 Million years ago.


Between 3,000 to 2,500 Millions years ago, Blue-Green Algae emerged in the ocean which released Oxygen through Photosynthesis. By 2,000 Million years ago, the oceans were saturated with Oxygen and the Oxygen started to flood the atmosphere resulting in gradual increase of Oxygen in atmosphere.



How the amount of Carbon di-oxide in the atmosphere reduced?
🠚 Because of precipitation, the Carbon di-oxide got dissolved in the rain water and hence got trapped in the Ocean water.


Geological time scale - The geological history of the Earth has been divided into several Super eons, Eons and Eras. Each era is further divided into Periods which are sub-divided into Epochs. 

Eon 🠚 Era 🠚 Period 🠚 Epoch 🠚 Age

Number of Eons - 4 
1.  Phanerozoic Eon (divided into 3 eras)
  • Cainozoic Era
  • Mesozoic Era
  • Paleozoic Era 
2.  Proterozoic Eon
3.  Archean Eon
4.  Hadean Eon

geological time scale

The Period Carboniferous got its name because at that time there were many cracks on the surface. Many huge forests go inside the Earth which led to the formation of coal (a carbon form).

Holocene
  • Greenlandian (11,700 - 8,400)
  • Northgrippean (8,400 - 4,200)
  • Meghalayan (4,200 - till now) - evidence of this age was first found in a place called Mawluh, Meghalaya.


Previous Article - Eclipse
Next Article - Interior of the Earth

Notes on other subjects


Optional Notes
Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own. 

Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍
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