Topic 9- The evolution of the atmosphere Flashcards
how much nitrogen is there in our atmosphere
about four-fifths (approximately 80%)
how much oxygen is there in our atmosphere
about one-fifth (approximately 20%)
what are the other gases in our atmosphere
carbon dioxide,
water vapour and noble gases.
why is evidence for the early atmosphere limited
because of the time scale of 4.6 billion years.
What did volcanoes do to the atmosphere?
-intense volcanic activity that released gases that formed the early atmosphere.
-water vapour that condensed to form the oceans.
- it consisted of mainly carbon dioxide with little or no oxygen gas
-volcanoes also produced nitrogen which gradually built up in the atmosphere
-may have been small proportions of methane
and ammonia.
what did oceans do to the atmosphere?
-water vapour condensed to form the oceans
-carbon dioxide dissolved in the water and
carbonates were precipitated producing sediments, which reduced the amount of carbon dioxide in the atmosphere.
how did oxygen increase?
- Algae and plants produced the oxygen by photosynthesis, that is now in the atmosphere today
- Algae first produced oxygen about 2.7 billion years ago
- Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
how did carbon dioxide decrease?
-Algae and plants decreased it by photosynthesis
- by the formation of sedimentary
rocks and fossil fuels that contain carbon
-locked up in rocks and fossil fuels after the organisms died
explain the formation of deposits of limestone
- sedimentary rock
- made of calcium carbonate deposits from the shells and skeletons of marine organisms.
explain the formation of coal crude oil and natural gas
- when plants plankton and marine animals die they fall to the seabed
- these get buried by layers of sediment
- over millions of years, they become compressed and formed sedimentary rocks, oil and gas, trapping co2 in them
what do greenhouse gases in the atmosphere do
maintain temperatures on Earth high enough to support life
give some greenhouse gases
Water vapour, carbon dioxide and
methane
what’s the greenhouse effect in terms of long and short length radiation
- all particles absorb certain frequencies of radiation
- greenhouse gases dont absorb the incoming short wavelength radiation from the sun
- they do absorb the long wavelength radiation that gets reflected back off the earth
- they then re-radiate it in all directions, including back to Earth
- longwave radiation is thermal radiation, so results in warming of the earth.
give forms of human activity which affect the amount of greenhouse gases in the atmosphere
deforestation- fewer trees makes less CO2 is removed from the atmosphere via photosynthesis
burning fossil fuels- carbon that was locked up in these fuels is released
agriculture- more farm animals produce methane through digestion
creating waste- more landfill sites and more waste from agriculture means more co2 and methane released by decomposition of waste.
give four consequences or climate change?
- polar ice caps melting, causing a rise in sea levels, increased flooding and coastal erosion.
- changes in rainfall patterns - food production
- frequency and severity of storms
- changes in temperature and amount of water available in a habitat- differences in distribution of a species
what is carbon footprint
the total amount of carbon dioxide and other
greenhouse gases emitted over the full life cycle of a product, service
or event.
describe some actions to reduce emissions of carbon dioxide and
methane
- renewable energy sources
- more efficient processes could conserve energy or cut waste, as when waste decomposes, it releases methane.
- tax cars that release more co2
- put cap on emissions of companies
- technology can capture the c0s before its released into the atmosphere, it can then be stored deep underground
why might actions to reduce the carbon footprint be limited?
- still a lot of work needed on alternative technologies
- affect economic growth of communities, which could be bad for people’s well-being for countries that are still developing.
- hard to make international agreements.
- hard to get everyone on board- education is needed
what’s a major source of atmospheric pollutants
The combustion of fuels
what do most fuels, including coal, contain?
carbon and/or hydrogen (hydrocarbons) and may also contain some sulfur
what happens during combustion of fossil fuels?
carbon and hydrogen are oxidised so that co2 and water vapour are released into the atmosphere
whats happens to the fuels when there’s lots of oxygen?
all the fuel burns- complete combustion
what happens to fuel when there isn’t enough oxygen?
some of the fuel doesn’t burn- incomplete combustion
under these conditions, solid particles (particulates) of soot (carbon) and unburnt fuel are released and carbon monoxide can be produced as well ads co2.
what problems can particulates in the air cause
if particulates are inhaled, they can get stuck in the lungs- respiratory problems
they’re bad for the environment- reflect sunlight back into space- global dimming
