C13 The Earth's Atmosphere Flashcards
Where is Earth’s atmosphere?
Earth’s atmosphere extends from the Earth’s surface to an altitude of approximately 10,000 km
Earth’s atmosphere today
For 200 million years, the proportions of gases in the atmosphere have been about the same as they are today:
- About 80% nitrogen
- About 20% oxygen
- Small proportions of other gases which include carbon dioxide, argon and water vapour
Why are we not certain what the Earth’s early atmosphere was like?
The Earth is 4.6 billion years old - a very long timescale - so there is a lack of evidence
Volcanic Activity Theory for the Origin of the Atmosphere
- This theory suggests that intense volcanic activity released carbon dioxide and water vapour which formed the early atmosphere
- Volcanoes also released the water vapour that condensed to form the oceans
- When the oceans formed, carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere
- Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia
Describe how oxygen increased
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis
- Algae first produced oxygen by photosynthesis
- Soon after, this oxygen appeared in the atmosphere
- Over the next billion years, plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve
Describe how carbon dioxide decreased
- Plant and algae photosynthesis produced oxygen and used up carbon dioxide from the atmosphere
- Carbon dioxide was also removed from the atmosphere as it was used to form sedimentary rocks and fossil fuels that contain carbon
How was coal formed
- Plants and trees used carbon dioxide during photosynthesis to build their tissues
- Plants and trees died in swamps and decayed in the absence of oxygen
- They were compressed over time to produce coal
Describe how methane decreased
- Methane reacted with the oxygen that was being produced by photosynthesis
- This produced more carbon dioxide
Methane + oxygen = carbon dioxide
+ water
Describe how ammonia decreased
- Ammonia reacted with the oxygen that was being produced by photosynthesis
- This produced more nitrogen
Ammonia + oxygen = nitrogen + water
Describe how nitrogen increased
Nitrogen gas is very un-reactive so was able to build up in the atmosphere
What is ‘locked up carbon’?
Carbon from Earth’s early atmosphere now trapped in rocks and fossil fuels
Which were the first organisms to produce oxygen on Earth?
Algae/photosynthetic bacteria
How did oil and natural gas form?
- Crude oil and natural gas were formed from the remains of plankton deposited in muds on the seabed
- These remains were covered by sediments that became layers of rock when compressed over millions of years
- The crude oil and natural gas formed is found trapped beneath these layers of rock
In the EM spectrum, what is the relationship between wavelength and amount of energy transferred?
Longer wavelengths transfer less energy
The greenhouse effect on Earth
- The Earth has a layer of gases around it: carbon dioxide, methane and water vapour
- Without the greenhouse effect, Earth would be too cold to support life
- Humans are increasing the levels of greenhouse gases in the atmosphere, which is warming the Earth too much
What are the three greenhouse gases?
Carbon dioxide, methane, and water vapour
Which type of wavelength transfers the most energy?
Short
What two things can happen to the infrared waves that reach Earth?
Reflected or absorbed
How is the wavelength of the reflected waves different from the waves from the Sun?
The reflected waves have a longer wavelength, meaning they transfer less energy
What happens to the longer wavelengths of Infrared waves?
They are trapped in the Earth’s atmosphere, warming the Earth
Why is the greenhouse effect important?
The greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life
Why are greenhouse gas levels rising?
- Deforestation, less carbon dioxide being absorbed results in more in the atmosphere
- Factories, burning fossil fuels (such as oil and coal) which releases carbon dioxide
- Landfills, anaerobic respiration as waste decomposes which releases methane
- Rice paddy, underwater mud anaerobically respires releasing methane
- Cattle production, cows’ fart contains methane
Why are carbon dioxide levels rising?
Deforestation - cutting down trees reduces the amount of carbon dioxide absorbed from the atmosphere by photosynthesis
Factories - burning fossil fuels for electricity and running cars e.g. combustion of propane
propane + oxygen –> carbon dioxide + water
Why are methane levels rising?
Landfill sites - the decay of waste in landfill by microorganisms produces methane
Rice paddy fields - rice is grown in muddy waters, the water blocks oxygen from penetrating the soil, creating ideal conditions for bacteria that emit methane
Cattle producing methane - cattle reared for humans to eat as beef or for milk produce methane
Potential consequences of global warming
- Higher temperatures and more heat waves
- More droughts and wildfires
- Rising sea level
- Thawing permafrost
- Changes in plant life cycles
- Stronger storms
How is an increase in greenhouse gases thought to be causing the earth to warm?
It makes the greenhouse layer thicker and traps more long wave radiation and heat
Climate change
- Most scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will cause global climate change
- This is based on peer-reviewed evidence
Peer-reviewed evidence
- Scientists collecting and analysing data
- Other scientists checking the evidence before it is published
Why is it important to peer review evidence?
The peer-review process stops scientists publishing opinions rather than hard evidence
What were the 5 gases in the Earth’s early atmosphere?
Carbon dioxide, methane, water vapour, ammonia, and nitrogen
What is the word equation for photosynthesis?
carbon dioxide + water –> glucose + oxygen
What happens to the wavelength of the radiation emitted from the sun when it reaches the Earth?
The wavelength becomes longer because some energy is absorbed
What is a carbon footprint?
The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event
Four potential effects of global climate change
- Flooding
- Extreme weather
- Changes in rainfall
- Extinction
Effects of global climate change - Flooding
- As average global temperature increases: polar ice caps melt, sea level rises, flooding of land results
- Flooding causes coastal erosion and habitat loss
Effects of global climate change - Extreme weather
- Extreme weather events more common and severe e.g. storms
- Causes damage
Effects of global climate change - Changes in rainfall
- How much rain, when it occurs, where it occurs
- Heavy rain can damage crops, lack of rain causes drought
- Affects food production
Effects of global climate change - Extinction
- As climate changes rapidly, animals and plants cannot adapt to the environment quick enough and die out
- Rodent species on Great Barrier Reef island, first mammal to become extinct due to climate change
Complete combustion of a hydrocarbon (word equation)
hydrocarbon + oxygen = carbon dioxide + water + energy
Incomplete combustion of hydrocarbons
- Produces carbon dioxide and carbon particles (soot)
- It also releases much less energy than complete combustion
- Carbon monoxide is poisonous because it reduces the ability of blood to carry oxygen
Carbon monoxide
- Produced during the incomplete combustion of hydrocarbons
- Causes breathing problems as it reduces the ability of blood to carry oxygen by binding to the haemoglobin in red blood cells (where oxygen binds, reducing the capacity to carry oxygen)
Carbon dioxide
- Produced during the complete combustion of hydrocarbons
- It is a greenhouse gas, so it contributes to global warming
Soot/particulates
- Produced during the incomplete combustion of hydrocarbons
- Causes global dimming and breathing problems e.g. asthma attacks and lung cancer
Sulfur dioxide
- Fossil fuels contain small quantities of sulphur
- When the fuels are burned, the sulphur reacts with oxygen in the air
- Sulphur + oxygen = sulphur dioxide
- Sulphur dioxide then dissolves in the moisture/water in the air which causes acid rain
Nitrogen oxides
- Formed from the reaction of nitrogen and oxygen in the air inside hot engines
- Nitrogen + oxygen = nitrogen oxides
- Causes acid rain and breathing problems
