Event that occurred Billions or millions of years ago is the build up of oxygen in the earth Atmosphere.
Event that occurred thousands of years ago is the ending of the last Ice age.
Event that occurred decades ago is the increase in the rate of carbon dioxide to its highest level of record.
Event that occurred Billions or Millions of years ago:
- The build up of oxygen in the earth Atmosphere is the event that occurred Billions or Millions of years ago.
- It is clearly stated that oxygen was first produced around 2.7 billion to 2.8 billion years ago.
- Prior that earth atmosphere was fully composed of Hydrogen.
- Then due to natural disasters such as volcanic eruption, atmosphere was made with gaseous substance such as sulphur di oxide, carbon di oxide and ammonia etc.
- Due to some tiny organism such as Blue green algae which involves in a process called photosynthesis releases oxygen in the atmosphere,Due to this the level of oxygen in the atmosphere increased and currently the earth is composed of 21% of oxygen.
Event that occurred thousands of years ago:
- Ending of the last Ice age is the event that occurred thousands of years ago.
- Ice age is the period where the temperature is decreases resulting in the expansion of polar sheets.
- This ice age came to an end when the temperature of the earth surface increases while leads to melting of glaciers and polar sheets.
- It is known that the last Ice age ended thousands of years ago back in mid 19's.
- The temperature usually rises when the sunlight reaches that northern latitude and this can thus lead to the ending of Ice age.
- This ending of the ice age has lead to certain rare species like Woolly mammoths become extinct.
Event that occurred decades ago:
- Increase in the level of carbon dioxide is the event that occurred a decades ago.
- Increase of carbon dioxide can be due to the burning of fossil fuels and other climatic changes caused by the humans.
- Increase of carbon dioxide has seen its record level of 415.70 ppm as it is thus developed as a threat to modern earth.
- This raise can cause various problems for humans such as headache,breathing problems, high heart beat rate etc.
