Formation of the Original Atmosphere by Gases

Formation of the Original Atmosphere by Gases

• The Earth’s original atmosphere probably formed from gases given out by volcanoes.
• It was predominantly consists of carbon dioxide, along with water vapour, nitrogen and various noble gases.

Limited Oxygen and Absence of Ozone Layer

• The early atmosphere had little or no oxygen, meaning life forms as we know them could not have survived in it.
• Absence of an ozone layer also meant that the Earth was exposed to harmful solar radiation.

Basic Formation Process

• The earth cooled down after its formation and its outer layer, the crust, solidified.
• Volcanic activities released gases trapped within the earth into the atmosphere, contributing to the formation of the original atmosphere.

Role of Water Vapour

• Water vapour in the atmosphere condensed as the Earth cooled down, forming oceans.
• This process is essential for the development of life on Earth, which started in the oceans.

Algae and Early Plants

• As the first life forms began to appear - algae and early plants - they started to absorb carbon dioxide and release oxygen through a process called photosynthesis.
• This added oxygen to the atmosphere and started to change the balance of gases, beginning the lengthy process that led to the atmosphere we know today.

Gradual Change of Earth’s Atmosphere

• Over time, the level of carbon dioxide in the atmosphere decreased due to photosynthesis and the formation of sedimentary rocks and fossil fuels.
• The level of oxygen increased due to photosynthesis, eventually supporting the evolution of more complex life forms.

Formation of the Ozone Layer

• With higher levels of oxygen in the atmosphere, the ozone layer could form, providing protection from harmful solar radiation.
• This allowed more complex life forms to evolve and live on land.