SC21 Earth and Atmospheric Science
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Describe how the Earth’s early atmosphere was formed
Produced through volcanic activity, which released gases from the Earth’s interior through violent explosions. Earth’s gravity prevented the gases from escaping into outer space and they formed the atmosphere
State the names and relative amounts of gas found in the Earth’s early atmosphere
• little or no oxygen • a large amount of C02 • water vapour
How were oceans formed?
When the conditions of the Earth’s surface cooled significantly,water vapour condensed and fell to the surface of the Earth, forming oceans
How did the carbon dioxide concentration in the atmosphere decrease?
• CO2 is a very water soluble gas, so when the oceans formed, large amounts of condensed CO2 dissolved into the oceans • carbonates were precipitated, which later on formed sediments on the seabed
How did photosynthetic organisms change the composition of the atmosphere?
They absorbed considerable amounts of carbon dioxide through photosynthesis, and instead produced oxygen, therefore decreasing the carbon concentration and increasing the oxygen concentration
State the chemical test for oxygen
Placing a glowing splint inside a test tube of gas. If oxygen is present, the splint will relight
What is the effect of greenhouse gases?
• they absorb heat radiated from the Earth • then release the energy in all directions, which keeps the Earth warm
State the names of the main greenhouse gases
Carbon dioxed, water vapour and methane
What is the greenhouse effect?
The retention of the sun’s infrared radiation by greenhouse gases
Define global warming
The gradual warming of the Earth’s atmosphere
What is the enhanced greenhouse effect?
The increase in the amount of greenhouse gases in the atmosphere is causing inbalance to the Earth’s natural conditions by trapping extra heat
Describe how human activity increases the concentration of greenhouse gases
• deforestation: which reduces the amount of plants available to photosynthesise and convert the C02 into 02 • industrial revolution: which increased the amount of greenhouse gases released, causing pollution • increased burning of fossil fuels in recent centuries
What are the sources of carbon dioxide?
• combustion of wood and fossil fuels • respiration of plants and animals • thermal decomposition of carbonate rocks • effects of acids on carbonates
What are the sources of methane?
• digestive processes of animals • decomposition of vegetation • bacterial action in swamps • rice paddy fields
How do scientists show a causal link?
• collect evidence • explain how and why correlation occurs
What are the current effects of climate change?
• glaciers melting • sea levels rising • rainfall changing, producing floods or droughts • habitats changing
What is the link between carbon dioxide and global warming?
• There is a strong correlation between the % of carbon dioxide in the atmosphere and increased global temperatures • the impact of this is the melting glaciers and ice caps, changing rainfall etc
How can we reduce the impact of global warming?
• By using renewable energy supplies such as solar or wind to power our industries and houses rather than fossil fuels • many nations have signed treaties aimed at reducing emissions of carbon dioxide and other gases
How can we mitigate the effects of climate change?
• building flood defences to manage floods from rivers and seas • building irrigation systems to provide water in droughts • planting different crops, better adapted to a new climate