Atmosphere Flashcards
How was the early atmosphere formed?
Volcanoes erupted realising lots of gases, mostly carbon dioxide, with virtually no oxygen (similar to Mars and Venus today).
Also released nitrogen which built up in atmosphere overtime as well as water vapour and small amounts of methane and ammonia.
What happened to the CO2
Water vapour condensed forming oceans.
Lots of carbon dioxide was removed from early atmosphere as it dissolved in the oceans then went through a series of reactions to from carbonate precipitates that formed sediments.
Marine animals evolved and their shells/skeletons contained some carbonates from oceans
Green plants and algae evolved and absorbed some of the carbon dioxide so that they could carry out photosynthesis.
Some got locked up in rocks and fossil fuels when organisms died.
How are fossil fuels formed?
- When plants, plankton and marine animals die, they fall to the seabed and get buried by layers of sediment.
- Over millions of years they become compressed and form sedimentary rocks, oil and gas - trapping the carbon within them (helping to keep it out of the atmosphere).
- Things like coal, crude oil and natural gas that are made by this process are called “fossil fuels”
- Crude oil and natural gas are formed from deposits of plankton. These fossil fuels form reservoirs under the seabed when they get trapped in rocks..
- Coal is a sedimentary rock made from thick plant deposits.
- Limestone is also a sedimentary rock. It’s mostly made of calcium carbonate deposits from the shells and skeletons of marine organisms.
How did oxygen come to be in the atmosphere?
- As well as absorbing the carbon dioxide in the atmosphere, green plants and algae produced oxygen by photosynthesis - this is when plants use light to convert carbon dioxide and water into sugars
carbondioxide+water->glucose+oxygen
6CO2. + 6H20-> C6H12O6 +6O2
- Algae evolved first - about 2.7 billion years ago
- Then over the next billion years or so, green plants also evolved
- As oxygen levels build up in the atmosphere over time, more complex life (like animals) could evolve.
- Eventually, about 200 million years ago, the atmosphere reached a composition similiar to how it is today:
Approx 80% Nitrogen
Approx 20% Oxygen
Small amounts of other gases
Mainly carbon dioxide, noble gases and water vapour
How does the greenhouse effect work?
- Greenhouse gases like carbon dioxide, methane and water vapour act like an insulating layer in the Earth’s atmosphere - this, amongst other factors, allows the Earth to be warm enough to support life.
- All particles absorb certain frequencies of radiation. Greenhouse gases don’t absorb the incoming short wavelength radiation from the sun - but they do absorb the long wavelength radiation that gets reflected back off the Earth.
- Then they re-radiate it in all directions - including back towards the Earth.
- The long-wave radiation is thermal radiation, so it results in warming of the surface of the Earth. This is the greenhouse effect.
What affects greenhouse gases in the atmosphere?
.Deforestation - fewer trees means less CO2 is removed from the atmosphere via photosynthesis.
.Burning fossil fuels - carbon that was “locked up” in these fuels is released a CO2.
Agriculture - more farm animals produce more methane through their digestive processes.
Creating waste - more landfill sites and more waste from agriculture means more CO2 and methane released by decomposition of waste.
Could we live without greenhouse gases? Why?
Without greenhouse gases our planet would be incredibly cold - the greenhouse effect warms the Earth enough for it to support living things. Without it we wouldn’t be here. But the overall balance of gases in the atmosphere matters.
What are carbon footprints?
Carbon footprints are basically a measure of the amount carbon dioxide and other greenhouse gases released over the full life cycle of something.
What can have a carbon footprint?
Almost Anything
For example
A service (E.g. School bus)
An event (E.g. Olympics)
A product (E.g. A toastie maker)
Ways to reduce Carbon Footprints?
- Renewable energy sources or nuclear energy could be used instead of fossil fuels.
- Using more efficient processes could conserve energy and cut waste. Lots of waste decomposes to release methane, so this will reduce methane emissions.
- Governments could tax companies or individuals based on the amount of greenhouse gases they emit - e.g. taxing cars based on the amount of carbon dioxide they emit over a set distance could mean that people choose to buy cars that are more fuel-efficient and so less polluting.
- Governments can also put a cap on emissions of all greenhouse gases that companies make - then sell licences for emissions up to that cap.
- There’s also tech that captures the CO2 produced by burning fossil fuels before its released into the atmosphere - it can then be stored deep underground in cracks in the rock, such as old oil wells.
Why are some reluctant to make reductions?
- There is still a lot of work to be done on alternative technologies that result in lower CO2
- Governments are worried making changes to reduce carbon dioxide emissions could have an impact on economic growth. Important for developing countries.
- Hard to made international agreements to reduce emissions. Most countries don’t want to sacrifice their economic development if they thank that others won’t do the same.
- Individuals don’t want to change lifestyle.
How Gases and particles are released into the atmosphere
- Fossil fuels, such as crude oil and coal, contains hydrocarbons. During combustion, the carbon and hydrogen in these compounds are oxidised, so that carbon dioxide and water vapour are released back into the atmosphere.
2.
