AQA C1.7 The Earth

What are the 4 layers of the Earth's structure?
Inner core, outer core, mantle, crust
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What is the atmosphere
Layer of gases above the crust
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Where is the Earth's crust thinnest?
Under oceans
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What metals are found in the core?
Nickel + iron
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What's the difference between the outer and inner cores?
The outer core is liquid due to heat but the inner core is solid due to pressure
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What are tectonic plates?
Areas of the Earth's crust + upper part of the mantle that move due to convection currents in the mantle
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Why are there convection currents in the mantle layer?
Radioactive decay of atoms heats molten minerals and causes them to rise
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What happens when tectonic plates suddenly slide past each other?
Earthquakes
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How did the seas form?
Water vapour from the Earth's atmosphere condensed in hollows in the crust
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What did the first organisms use for energy?
Breakdown of other chemicals
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Where did the oxygen in the Earth's atmosphere come from?
Organisms who evolved to photosynthesise
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What made it possible for animals to develop?
Increase of oxygen in the atmosphere
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What are amino acids made from (mostly)?
Carbon, hydrogen, nitrogen and oxygen
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What was the aim of the Miller-Urey experiment?
To see if amino acids could be created in the early atmosphere
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Why did Miller and Urey use a high-voltage spark and what real-life event does it mimic?
For the energy needed to start a reaction - mimics lightning in storms
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What did Miller and Urey find once their experiment had been running for a week?
A 'brown soup' mixture containing 11 amino acids
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Why do some scientists think the Miller-Urey experiment is invalid?
It only works with the absence of oxygen, which would have been present in the early atmosphere
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What are 2 other theories for why life began on Earth?
Extra-terrestrial seeding (molecules capable of starting life came from outer space e.g. in the Murchison meteorite) or that life developed deep under the oceans
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What is a primordial soup?
A mixture of organic molecules
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What's the biggest difference (in terms of gas composition) between the early atmosphere and ours today?
Today there is a much lower concentration of carbon dioxide (0.04%)
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Where does carbon dioxide taken up during photosynthesis ultimately end up?
Plant material --> animal tissues --> carbonate rocks --> Earth's crust
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Why is there no ammonia or methane in the atmosphere today?
It reacted with the oxygen
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Why did the levels of nitrogen gradually increase?
It's very unreactive
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What process do we use to separate air in industry?
Fractional distillation
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Why have levels of carbon dioxide in the atmosphere not changed much over the last 200 million years until recently
The carbon cycle is self-regulating but now we are burning fossil fuels
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How do the oceans act as a buffer?
They absorb CO2 when there's too much in the atmsophere and then release it when there's not enough
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Why are coral reefs at increased risk from increased carbon dioxide levels?
Excess CO2 makes their environment too acidic
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Other cards in this set

Card 2

Front

What is the atmosphere

Back

Layer of gases above the crust

Card 3

Front

Where is the Earth's crust thinnest?

Back

Preview of the front of card 3

Card 4

Front

What metals are found in the core?

Back

Preview of the front of card 4

Card 5

Front

What's the difference between the outer and inner cores?

Back

Preview of the front of card 5
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