c9 - atmosphere Flashcards
what are the two main gases in theatmosphere for the last 200 years + their abundance
- 80% nitrogen
- 20% oxygen
- <1% trace other gases
name 3 gases other than oxygen and nitrogen in the current atmosphere
- carbon dioxide
- water vapour
- noble gases
why is evidence of the early atmosphere limited
Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years.
volcanic activity theory
During the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans.
describe earths early atmosphere
At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
what was the role of volcanoes in the earths early atmosphere
Volcanoes produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia.
how did the formation of oceans reduce co2 in the earths early atmosphere
When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere.
what role did green plants and algae play in producing 02 in the earths early atmosphere
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis. Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere.
Describe how Animals were able to evolved after the Earth’s early atmosphere.
Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
Describe how Algae and Plant decreased Carbon Dioxide levels in the Earth’s early atmosphere.
Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis.
Describe how sedimentary rocks decreased Carbon Dioxide levels in the Earth’s early atmosphere.
Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
purpose of greenhouse gases
Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.
3 examples of greenhouse gases
Water vapour, carbon dioxide and methane are greenhouse gases.
Based on peer-reviewed evidence, what do scientists believe regarding climate change.
Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change.
Explain why climate change is difficult to model.
It is difficult to model such complex systems as global climate change. This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased.
