C11 - The Earth’s Atmosphere Flashcards
How was the Earth’s early atmosphere formed?
• Volcanic activity
What did the earth’s early atmosphere probably consist of?
• Mainly carbon dioxide
• May have also been nitrogen and water vapour
• Traces of ammonia
Why did the earth’s early atmosphere change?
• plants developed and therefore levels of oxygen increased
• over time, more and more plants developed and the concentration of CO2 compared to oxygen decreased greatly
• more oxygen made it possible for first animals to form
• most early organisms died as they couldn’t tolerate the high concentration of oxygen
How can scientists observe what Earth’s early atmosphere could have consisted of?
• evidence from gas bubbles trapped in ancient rock almost as old as the Earth
• fossilised remains of living organisms that were alive at different times since the composition of the atmosphere
How did water come about on Earth?
• water vapour condensed as the Earth gradually cooled down, and fell as rain
• water collected in hollows in the crust as the rock solidified and first oceans formed
• comet could have brought to earth
• icy comets came to the surface of the Earth and melted
Where did the carbon dioxide go?
• Photosynthesis by algae and plants decreased the percentage of carbon dioxide in the early atmosphere
• Formation of sedimentary rocks and fossil fuels that contain carbon dioxide from the atmosphere
• Dissolved in the ocean and was trapped in carbonate rocks
• Absorbed by photosynthesis
Where did the traces of ammonia and methane go?
• removed by reactions with oxygen once formed
Main greenhouse gases
Carbon dioxide
Methane
Water vapour
Why is there more nitrogen?
Released by volcanoes
6 marker: Explain the changes that have occurred to the composition of the atmosphere since it was formed.
• indirect evidence may include the composition of rocks that are almost as old as the Earth, and also the fossilised remains of living organisms that were alive at different times since then
• carbon dioxide decreased due to dissolving in the oceans, being trapped in carbonate rocks and being absorbed by photosynthesis
• oxygen increased due to photosynthesis
• nitrogen was released by volcanoes
• steam condensed to form the oceans
How can increasing levels of greenhouse gases cause an increase in temperature of the Earth’s atmosphere?
• 30% of light from the sun to earth is reflected back into space. However, greenhouse gases trap this heat because they absorb infrared radiation in the atmosphere. This is necessary for survival, but now more heat is trapped due to blanket of carbon dioxide
• Less ice caps due to melting, so less light is reflected out of the atmosphere and instead absorbed
Why are there more greenhouses in the atmosphere now?
• fossil fuels to make electricity
• increasing amount of transport run by fossil fuels
• energy used to heat homes
• deforestation - less CO2 removed
• agriculture- more farm animals providing methane from digestive processes
• creating waste - land fill and decomposition of waste
Consequences of rising levels of greenhouse gases
• rising sea levels due to melting ice caps - causes dangerous and more frequent flooding
• increasingly common extreme weather events, e.g. severe storms
• changes in temperature and amount/timing of rainfall - affects yield and profit for agricultural workers and ability to produce food, e.g. heavier monsoons in Asia
What is a carbon footprint?
• The carbon footprint of a product, service or event is the total amount of carbon dioxide and other greenhouse gases emitted over its full life cycle.
How can we reduce carbon footprint?
• pump carbon dioxide produced in fossil fuel power stations deep underground to be absorbed by porous rocks - can be done in old, redundant fields
• called carbon capture and storage
• increase cost of producing electricity by 10%
• renewable energy sources instead of fossil fuels
• efficient process to conserve energy and cut water
• gov. could tax companies/individuals based on the amount of GHGs they emit
Problems with reducing carbon footprint
• governments are worried about the lack of economical growth - important for developing countries in particular
• hard to make international agreements to reduce emissions if not everyone does
• not enough education about how individuals can make lifestyle changes
• a lot of work to be done on alternative technologies which can lower CO2 emissions
Problem with particulates produced by diesel?
Global dimming
Why is carbon monoxide difficult to detect?
Colourless/odourless
Why is water vapour (not liquid vapour) produced when diesel burns?
Diesel burns at a temp greater than 100 degrees which is above the BP of water
Pollution from fuels
• fuels contain other substances as well as hydrocarbons
• impurities containing sulfur found in fuels can cause major problems
How is sulfur dioxide formed from car engines?
• fossil fuels contain some sulfur
• this reacts with oxygen when a fossil fuel is burned and forms a gas called sulfure dioxide
• causes acid rain which damages trees and wildlife, pollutes waterways
• attacks buildings (especially those built with limestone or metal structures)
How can we prevent sulfur dioxide from causing pollution?
• sulfur impurities can be removed from a fuel before it is burnt - happens in petrol and diesel for cars, and in gas-fired power stations
• in coal fired power stations, sulfur dioxide can be removed from the waste gases by reacting it with calcium hydroxide or basic calcium oxide
How is CO formed in car engines?
• when there is not enough oxygen inside an engine, incomplete combustion occurs
How are nitrogen oxides formed in car engines?
• high temp inside an engine causes nitrogen in the air to react with oxygen
• nitrogen oxides are toxic - trigger asthma
• nitrogen oxides also cause acid rain
What is global dimming?
• when the amount of sunlight reaching the Earth’s surface decreases
Describe the formation of crude oil
• dead plants and animals (algae and diatoms) accumulate on the bottom of ancient oceans and lakes
• layers of sand, silt and rock cover the organic matter
• over millions of years, organic matter is broken down and transformed into liquid and gaseous hydrocarbons through bacterial decomposition and chemical reactions
• oil and gas collect in underground formations to form oil and gas fields
