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- THE EARLIEST ATMOSPHERE Time period - 4.6 billion years ago
- The Earth was formed 4.6 billion years ago from a hot mixture of solids and gases and it had no atmosphere at that time. When the Earth started to cool down , the atmosphere was formed ( mainly from the gases that were expelled from the volcanoes ).
- THE ARCHEAN EONTime period - 4 to 2.5 billion years ago
- During this period , the droplets of methane present in the air shrouded the Earth in a global haze. Oxygen was only present in some compounds like water.
- The life on Earth and its atmosphere evolved together. The photosynthetic organisms were able to produce enough oxygen that reacted with methane in the atmosphere , transforming it forever. The methane haze cleared and the sky turned blue ( about 2 billion years ago )
- OXYGEN AT LASTTime period - 2.6 billion to 400 million years ago
- The oxygen levels increased between 700 - 550 million years ago ( late Proterozoic ) . It reached about 1/5 of today’s level ( 21 percent ). This oxygen boom really favored the evolution of the lifeforms that used oxygen to create energy. However , it was poisonous for the other organisms and it led to their extinction.
- OXYGEN BOOM !Time period - 700 - 550 million years ago
- THE AGE OF OXYGENTime period - 400 million - 290 million years ago
- The plants were firmly established on the land and life had a majorly affected the Earth’s atmosphere during the Carboniferous period. Oxygen made up 20 percent of the atmosphere ( almost reached today’s level ) about 350 million years ago and it rose to 35 percent over the next 50 million years.
- The Earth was much warmer during the past 290 million years than it is now. Scientists believe that the changes in the atmosphere affect the Earth’s climate. The polar caps were very small or were not present and winters were much warmer around the globe ( between 200 - 45 million years ago ) and because of these warm climates , many of the animals and plants lived in polar regions
- THE MODERN ATMOSPHERESTime period - 290 million years ago to now
- It's nice to be in here
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