Last Test Flashcards
3 main phases in the evolution of the earth atmosphere
The 3 main phases of the atmosphere was phase 1- gases released by volcanoes
phase 2- CO2 absorbed by oceans, green plants ans algae
phase 3- O2 released by green plants and algae by photosynthesis
What happened in phase 1
Over a billion years ago
Atmosphere was mostly CO2
Volcanoes also released water vapour, nitrogen, methane and ammonia
What happened in phase 2?
Water vapour condensed into oceans, CO2 levels fell bcs CO2 dissolved into oceans ( which eventually formed carbon precipitates and sediments at the seabed ) and green plants and algae evolved to absorbed CO2 through photosynthesis
What happened in phase 3?
O2 levels increased when:
Algae and green plants evolved to release O2
( as O2 increased more complex life could form )
How did CO2 become locked up in sedimentary rocks?
CO2 became lockwd up in sedimentary rocks because:
Shells and skeletons of animals contain carbonate compounds that then sink to the seabed where they are compresses for millions of years. This process forms sedimentary rocks and fossil fuels.
How long ago did the atmosphere reach its current composition
About 200 million years ago
What is the current composition of the atmosphere?
The current composition of the atmosphere is 78% nitrogen, 20% oxygen, 0.04% CO2 and small amounts of noble gases and water vapour
What are the greenhouse gases
The greenhouse gases are CO2, methane and water vapour
How do greenhosue gases cause global warming?
Greenhouse gases cause global warming when shortwave length radiation from the sun enters the earth atmosphere, which then emits longwave length radiation. The greenhouse gases then absorb the longwave length radiation and emit it back, some towards earth, which heats the earth and causes global warming
What human activies contribute to the greenhouse effect?
Deforestation, burning fossil fuels, agriculture
How does deforestation contribute to global warming?
Less trees -> less CO2 is removed from atmosphere by photosynthesis -> more greenhouse gases
How does burning fossil fuels contribute to global warming?
Burning fossil fuels contributes to global warming by released CO2 that was locked inside fossil fuels into the atmosphere
How does agriculture contribute to global warming
Agriculture contributes to global warming when farm animals produce methane through digestion
How does creating waste contribute to global warming?
Creating waste contributes to global warming when landfill sites release CO2 and methane as the waste decomposes
What evidence links CO2 to climate change?
Peer reviewed science links the increase in CO2 levels to the increase in the Earths surface temp.
But models of the atmosphere are complex and some media can be biased against currently agreed science
