Chemistry of the atmosphere Flashcards
Have theories for how the Earth’s atmosphere evolved changed over time?
Yes- the theories have changed a lot over the years.
Why have the theories on how the Earth’s atmosphere has evolved changed over time?
Hard to gather evidence from such a long time period and from so long ago (4.6 billion years).
What is the first phase of the evolution of the atmosphere?
Volcanoes gave out gases.
What was the surface of the Earth like in the planet’s first billion years?
Covered in volcanoes that erupted and released lots of gasses. We think this was how the early atmosphere was formed.
What gasses were found in the early atmosphere?
Probably mostly carbon dioxide, with virtually no oxygen.
Nitrogen was also release by volcanic activity and built up in the atmosphere over time.
Water vapour
Small amounts of methane and ammonia
What was the Earth’s early atmosphere similar to?
The atmospheres of Mars and Venus today.
What was the second phase of the evolution of the atmosphere?
Oceans, algae and green plants absorbed carbon dioxide.
What did the water vapour in the early atmosphere do?
It condensed and formed the oceans.
How was lots of carbon dioxide removed from the early atmosphere?
It dissolved in the oceans.
What happened to the carbon dioxide from the early atmosphere that was dissolved in oceans?
Went through a series of reactions to form carbon precipitates that formed sediments on the seabed.
What happened when green plants and algae evolved?
They absorbed some of the carbon dioxide in the early atmosphere so they could carry out photosynthesis.
What was contained inside the shells and skeletons of the marine animals that evolved?
They contained carbonated from the oceans.
What happened to some of the carbon that organisms took in from the early atmosphere and oceans?
The carbon became locked up in rocks and fossil fuels after the organism died.
What happened when plants, plankton and marine animals die?
They fall to the seabed and get buried by layers of sedimentary.
Over millions of years, they become compressed and form sedimentary rocks, oil and gas- trapping the carbon within them and helping to keep carbon dioxide levels in the atmosphere reduced.
Fossil fuels are made like this e.g. coal, crude oil and natural gas.
How is crude oil and natural gas formed?
From the deposits of plankton. These types of fossil fuels form reservoirs under the seabed when they get trapped in rocks.
What is coal?
A sedimentary rock made from thick plant deposits.
What is limestone?
A sedimentary rock.
Mostly made of calcium carbonate deposits from the shells and skeletons of marine organisms.
What is the third phase of the evolution of the atmosphere?
Green plants and algae produced oxygen
How did green plants and algae produce oxygen (in the early atmosphere)?
By absorbing CO2 and doing photosynthesis.
What is the equation for photosynthesis?
What evolved first- plants or algae?
Algae- about 2.7 billion years ago.
Over the next billion years or so, green plants also evolved.
What happened as oxygen levels built up in the atmosphere over time?
More complex life like animals could evolve.
What happened to the Earth’s atmosphere about 200 million years ago?
It reached a composition similar to what it is today. About:
80% nitrogen
20% oxygen
Small amounts of carbon dioxide, noble gasses and water vapour.
What are some examples of greenhouse gasses?
CO2
Methane
Water vapour
What do greenhouse gasses do?
Act like an insulating layer in the Earth’s atmosphere.
One of the factors that allow the Earth to be warn enough to support life.
All particles absorb…
certain frequencies of radiation.
What type of radiation does greenhouse gasses absorb?
Not the incoming short wavelength radiation from the sun but the long wavelength radiation that gets reflected back off the Earth.
What do the greenhouse gasses do with the long wavelength radiation they absorb?
Re-radiate it in all directions- including back towards the Earth. The longwave radiation is thermal radiation, so it results in the warming of the surface of the Earth. This is the greenhouse effect.