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Flashcards in C1g Deck (15):

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?



What processes in the carbon cycle remove carbon dioxide and release oxygen?



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