earth and atmospheric science

Question 1

Recall that the gases produced by volcanic activity formed the
Earth’s early atmosphere

Answer 1

• volcanic activity formed the Earth’s early atmosphere
• volcanoes kept erupting after a thin crust formed on the earth’s cooled surface : volcanoes erupted releasing gases from inside the earth: this “degassing” released mainly carbon dioxide and water vapour

Question 2

describe what the Earth’s early atmosphere was thought to contain

Answer 2

• little or no oxygen
• a large amount of carbon dioxide
• water vapour
• small amounts of other gases

Question 3

Explain how condensation of water vapour formed oceans

Answer 3

the Earth cooled down. This caused water vapour in the atmosphere to condense to liquid water and fell as rain to form the oceans.

Question 4

Explain how the amount of carbon dioxide in the atmosphere
was decreased when carbon dioxide dissolved as the oceans
formed

Answer 4

• a lot of the early CO2 dissolved into oceans
  -carbon dioxide dissolved to form soluble carbonate compounds so its amount in the
  atmosphere decreased
• carbon dioxide was also absorbed from the oceans into photosynthetic plants and algae

Question 5

Explain how the growth of primitive plants used carbon dioxide
and released oxygen by photosynthesis and consequently the
amount of oxygen in the atmosphere gradually increased

Answer 5

• green plants evolved and as they photosynthesised they removed co2 and produced o2
• so the amount of o2 in the air built up and the co2 mostly got locked up in fossil fuels and sedimentary rocks

Question 6

describe the chemical test for oxygen

Answer 6

by checking if the gas will relight a glowing splint

Question 7

Describe how various gases in the atmosphere, including carbon
dioxide, methane and water vapour, absorb heat radiated from
the Earth, subsequently releasing energy which keeps the Earth
warm: this is known as the greenhouse effect

Answer 7

1. earth radiates some heat radiation it absorbs as a longer wavelength - infrared radiation
2. some of this IR radiation is absorbed by greenhouse gases
3. some IR is re-emitted back to earth by greenhouse gases
4. some IR radiation is re-emitted back into space
5. the absorption and re-emission of IR radiation by greenhouse gases is what keeps the earth warm (releases energy) - greenhouse effect

Question 8

Evaluate the evidence for human activity causing climate
change, considering:
the uncertainties caused by the location where these
measurements are taken and historical accuracy

Answer 8

• historical data is much less accurate than current records : less data taken over fewer locations and methods used to collect data are less accurate
  : estimations (ex looking at fossils, gas bubbles trapped in ice sheets) are much less precise than current measurements made using instrumental sampling - represent less of global levels

Question 9

Evaluate the evidence for human activity causing climate
change, considering:
the correlation between the change in atmospheric
carbon dioxide concentration, the consumption of fossil
fuels and temperature change

Answer 9

• human population increases more people respire and give out CO2
• more people = more energy for lifestyles (heating, lighting)
• more industrialised (energy demand per person increases (ex travel on planes)) and an increase in energy consumption comes mainly from burning of fossil fuels - more co2
• more land to grow houses = cut down trees
• fewer plants means more co2 in atmosphere as they take it out when they photosynthesise
• extra greenhouse gases from human activity have caused average temperature to increase - due to greenhouse effect

Question 10

describe the composition of today’s atmosphere

Answer 10

• mainly nitrogen and oxygen, small amounts of other gases including water vapour, nobles gases and oxygen
• build up of oxygen in the atmosphere killed of early organisms who couldn’t handle it
• this allowed evolution of more complex organisms that made use of o2
• o2 created ozone layer - enabled more complex organisms to evolve
• virtually no co2 left now

Question 11

describe the potential effects on the climate of increased levels of
carbon dioxide and methane generated by human
activity, including burning fossil fuels and livestock
farming

Answer 11

• methane has risen due to human activity = methane is produced in the digestive processes of certain livestock so more farming = more methane (bad greenhouse gas)

Question 12

Describe that these effects may be mitigated

Answer 12

• to slow down climate change we need to cut down on amount of greenhouse gases we are releasing
• to reduce carbon dioxide emissions we can try to limit our own use of fossil fuels like walking and cycling instead of driving and turning central heating down
• on a larger scale the uk gov has formed plans to encourage public and industry to become more energy efficient