What are the stages of the evolution of the atmosphere?
- volcanoes gave out steam and CO2
- green plants evolved and produced oxygen
- ozone layer allowed evolution of complex animals
What happened in phase 1 of the evolution of the atmosphere?
1-Earth surface originally molten, any atmosphere boiled away
2-it cooled and thin crust formed, volcanoes kept erupting, releasing gases from inside the earth. Degassing released mainly CO2, but also steam and ammonia
-atmosphere mostly CO2 and water vapour
-water vapour condensed to form oceans
-very little oxygen
What happened in phase 2 of the evolution of the atmosphere?
- lots of CO2 dissolved into oceans
- green plants evolved almost everywhere and photosythesised, removing CO2 and producing O2
- O2 gradually built up and CO2 locked up in fossil fuels and sedimentary rocks
- N2 put in atmosphere by ammonia reacting with oxygen and released form denitryfying bacteria
- N2 is not very reactive so the amount in the atmosphere increased
What happened in phase 3 of the evolution of the atmosphere?
- buildup of oxygen killed early organisms that couldn’t tolerate it
- allowing evolution of complex organisms that make use of oxygen
- oxygen created the ozone layer (O3), blocking harmful UV rays and enabling even more complex organisms to evolve
- virtually no CO2 left
What does today’s atmosphere contain?
- 78% nitrogen
- 21% oxygen
- 0.035% carbon dioxide
- varying amounts of water vapour
- noble gases (mainly argon)
What processes in the carbon cycle remove oxygen and release carbon dioxide?
- respiration
- combustion
- decay
What processes in the carbon cycle remove carbon dioxide and release oxygen?
-photosyntehsis
How has human activity affected the composition of air?
- more people and developing countries, more energy needed, more fuel burnt, more pollutants released
- more people=more land to grow food and build houses, deforestation to make space, less plants, less photosynthesis, less carbon dioxide taken out of the atmposphere
What do catalytic converters do?
- are one motor vehicles to reduce amount of carbon monoxide and nitrogen oxides getting in the atmosphere
- made of mixture of platinum and rhodium
What is photochemical smog, how it it caused, and what effects does it have?
- caused by sunlight reacting with nitrogen oxides
- oxides combine with oxygen to produce ozone (O3)
- breathing difficulties, headaches and tiredness
How does carbon monoxide get into the atmosphere?
-formed when petrol or diesel in car engines burns without enough oxygen, incomplete combustion
How is acid rain caused?
- burning fossil fuels also releases sulfur dioxide and nitrogen oxides
- when the gases mix with the clouds they form dilute sulphuric and nitric acid
- this falls as rain
- main cause:power stations and internal combustion engines
What does acid rain cause?
- causes lake to become acidic and may plants and animals die
- kills trees and erodes limestone buildings and stone statues
- makes metal corrode
Where does sulfur dioxide come from?
-sulfur impurities in fossil fuels
Where does nitrogen oxides come from?
- a reaction between oxygen and nitrogen in air, caused by the heat of burning
- happens in car engines
