Topic 9

Question 1

Phase 1 of the Evolution of the Atmosphere

Answer 1

• Volcanoes erupted and released hot gases
• Mostly made up of carbon dioxide, with virtually no oxygen. Similar to Mars and Venus today
• Volcanic activity also released nitrogen which built up of time, water vapour, and small amounts of methane and ammonia

Question 2

Phase 2 of the Evolution of the Atmosphere

Answer 2

• The water vapour condensed to form the oceans
• Lots of carbon dioxide dissolved in the oceans, going through a series of reactions to form carbonate precipitates that formed sediments on the seabed
• Marine animals evolved. Their shells and skeletons contained some carbonates
• Green plants and algae evolved and absorbed carbon dioxide for photosynthesis

Question 3

What happens to some of the carbon during the evolution of the atmosphere?

Answer 3

• When plants, plankton, and marine animals die, they fall to the seabed and get buried by layers of sediment
• Over millions of years they become compressed into sedimentary rocks, oil, and gas - trapping the carbon - fossil fuels.
• Crude oil and natural gas are formed from deposits of plankton

Question 4

What is coal

Answer 4

• A sedimentary rock made from thick plant deposits

Question 5

What is limestone

Answer 5

• A sedimentary rock made mostly of calcium carbonate deposits from the shells and skeletons of marine organisms

Question 6

Phase 3 of the Evolution of the Atmosphere

Answer 6

• Algae evolved about 2.7 billion years ago
• Over the next billion years green plants evolved
• As oxygen levels built up in the atmosphere over time, more complex life (animals) could evolve
• Around 200 million years ago the atmosphere reached a similar composition to the present day

Question 7

Phase 3 of the Evolution of the Atmosphere

Answer 7

• Algae evolved about 2.7 billion years ago
• Over the next billion years green plants evolved
• As oxygen levels built up in the atmosphere over time, more complex life (animals) could evolve
• Around 200 million years ago the atmosphere reached a similar composition to the present day

Question 8

Approximate composition of the atmosphere 200 million years ago

Answer 8

• 80% nitrogen
• 20% oxygen
• small amounts of other gases making up 1%: mainly CO2, noble gases, and water vapour

Question 9

The composition of the modern atmosphere

Answer 9

Question 10

Greenhouse gases

Answer 10

• Carbon dioxide, methane and water vapour
• They act like an insulating layer, trapping heat, allowing the Earth to be warm enough to sustain life
• Greenhouse gases absorb the long wave radiation that gets reflected back off the Earth, and re-radiate it in all directions
• Because long-wave radiation is thermal radiation, the Earth’s surface warms up

Question 11

Human activites that affect the amount of greenhouse gases

Answer 11

• Deforestation: fewer trees means less CO2 being removed via photosynthesis
• Burning fossil fuels: Carbon that was ‘locked up’ is released as CO2
• Agriculture: More farm animals produce more methane through their digestive processes
• Creating waste: More landfill sites and waste from agriculture mean more CO2 and methane released from the decomposition of waste

Question 12

Carbon dioxide link to climate change

Answer 12

• Despite the fact that the Earth’s temperature does vary naturally, the average temperature has been increasing by amounts greater than we would expect to see naturally
• Most scientists agree that extra carbon dioxide from human activity is causing the global temperature to increase, leading to climate change
• However it is hard to fully understand the Earth’s climate - it is very complex, and there are many variables. It is very hard to make a model that is not oversimplified
• This had led to speculation about the CO2-climate change link, particularly in the media

Question 13

Consequences of climate change

Answer 13

• Polar ice caps melting: a rise in sea levels; increased flooding in coastal areas, and coastal erosion
• Changes in rainfall patterns: causing some regions to get too much or too little water. Along with temperature, could affect ability to produce food
• Frequency and severity of storms could increase
• Changes in temperature and the amount of water: may affect wild species, and their distribution could be different

Question 14

Carbon footprint

Answer 14

• A measure of the amount of carbon dioxide and other greenhouse gases released over the full life cycle of something
• Measuring the total