Evolution of Lithosphere, Atmosphere and Hydrosphere

Evolution of Lithosphere

• In the primordial stage, earth was in a volatile stage.
• As a result of the gradual increase in the density, earth started to heat up.
• Thus, the material inside earth started getting separated according to their different densities.
• This helped heavier materials like iron to sink towards the center of the earth, and the lighter ones to move towards the surface.
• After some time, cooling, solidification and condensation started.
• Hence, the outer crust was formed.
• While the moon formation took place, the giant impact heated the earth further.
• Due to this, the process of differentiation was started, which further separated the different materials and composed different layers on Earth.
• Starting from the surface to the core, we see layers like Crust, Mantle, Outer Core, and Inner Core.
• The density of material increases from the crust to the core.

Evolution of Atmosphere and Hydrosphere

• Earth’s atmosphere is chiefly composed of Nitrogen and Oxygen.
• Three Stages resulted in the evolution of the current Earth’s atmosphere.

Stage 1

• Loss of primordial atmosphere.

Stage 2

• Evolution of the atmosphere due to the hot earth’s interior.

Stage 3

• Due to the living world with plants, the process of photosynthesis was started.
• This resulted in the change in composition of the earth’s atmosphere.
• Early atmosphere with a composition of Hydrogen and Helium was eliminated as a result of solar winds.
  • Due to the solar winds, all the terrestrial planets lost their original atmosphere
• Further, due to the cooling of the earth, water vapour and gases were released from the earth’s interior.
• This started the present atmosphere’s evolution.
• The earliest atmosphere of earth consisted largely of water vapor, carbon dioxide, nitrogen and ammonia.
  • A little amount of free oxygen was also present in this atmosphere.
• Degassing – It is the process due to which gases were poured from the interior of the earth.
• Volcanic eruptions further added gases and water vapor into the atmosphere.
• As the earth cooled, condensation of water vapor started.
• Further, carbon dioxide present in the atmosphere dissolved rainwater and temperature decreased further.
  • This resulted in more condensation, and as a result, more rain.
• Rainwater filled the depressions present on the earth’s surface, and gave rise to oceans.
• Around 3800 million years back, the first life began evolving.
• But, it was only 2500 million years ago that photosynthesis started.
• Thus, it can be concluded that life was mostly confined to the oceans for a very long time.
• As oceans began contributing to Earth’s atmosphere through photosynthesis, flooding of oxygen in the earth’s atmosphere started.