The Earth and its Atmosphere

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Who came up with the theory of continental drift?
Alfred Wegener
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What evidence was there that land bridges existed?
Fossils of very similar plants and animals had been found on opposite sides of the ocean, so animals would have been able to cross before the bridges 'sunk'
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What evidence did Wegener find that supported his theory?
There were matching layers in the rocks in different continent. Also, for example, fossils of tropical plants had been found on Arctic islands - more generally, fossils had been found in 'wrong' places
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When did Wegener publish his theory of continental drift?
1915
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What was the theory of continental drift?
About 300 million years ago, there was a supercontinent called Pangaea, which broke into smaller pieces and drifted apart. These pieces are the modern-day continents, and he claimed that they were still slowly drifting apart
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What did Wegener think that the movement of the continents was caused by?
He thought that the continents were 'ploughing through' the sea bed, and this was caused by the earth's rotation as well as tidal movements
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Why did other geologists say that this was impossible?
A scientist had calculated that the forces needed in order to move the continents like this would have also caused the Earth to stop rotating
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Why was Wegener generally not accepted in the scientific community?
He had studied astronomy, and there were many people that didn't trust his wild predictions
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When was new evidence found that supported Wegener's theory?
In the 1950s, as scientists were able to investigate the ocean floor
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When were geologists convinced that Wegener's theory was correct?
In the 1960s
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What are the three layers that make up the Earth?
The core, mantle and crust
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How thick is the crust and what is it surrounded by?
The thickness varies from 5km-50km, and is surrounded by the atmosphere
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What happens in the mantle and what does it produce?
Within the mantle, radioactive decay takes place. This produces lots of heat, which causes the mantle to flow in convection currents
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What do scientists think the core is made of?
Iron and nickel
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What four main gases make up the atmosphere?
Nitrogen, oxygen, carbon dioxide and water vapour
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What did the Earth's surface use to be like millions of years ago?
It used to be molten, which would have caused any atmosphere to just 'boil away' into space
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What happened when the Earth began to cool down?
A thin crust formed, but volcanoes continued to erupt
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What was the early atmosphere mostly made up of?
Most CO2, with virtually no oxygen
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Which two planets and moon was the early atmosphere like?
Mars, Venus and Titan (the largest moon of Saturn)
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When were oceans formed?
They were formed when the Earth cooled enough for the water vapour to condense
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What evolved over most of the Earth and why?
Green plants and algae evolved, as the atmosphere was rich in CO2
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How did the CO2 levels in the atmosphere decrease and oxygen levels increase?
A lot of early CO2 in the atmosphere dissolved into oceans. Green plants and algae absorbed some of the CO2, and released oxygen during photosynthesis
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How did carbon and hydrocarbons become 'locked up'?
Plants and algae died and were buried under layers of sediment, along with the skeletons and shells of marine organisms. The carbon and hydrocarbons inside became 'locked up'
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What did the carbon and hydrocarbons become in sedimentary rock?
They became insoluble carbonates (e.g. limestone) and fossil fuels
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What happens when you burn fossil fuels?
The locked up carbon is released and the concentration of CO2 in the atmosphere rises
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What does the ozone layer do?
It blocks harmful rays from the Sun and (in earlier times) enables more complex organisms to evolve
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According to the primordial soup theory, what was the early atmosphere made up of?
Nitrogen, hydrogen, ammonia and methane
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What happened to result in the formation of amino acids?
Lightning stuck, which caused a chemical reaction between the gases - this resulted in the formation of amino acids
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What is a 'primordial soup'?
A body of water with amino acids out of which life gradually formed
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What happened when these amino acids gradually combined?
They produced organic matter, which evolved into simple living organisms
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Who carried out an experiment in the 1950s to test the primordial soup theory?
Miller and Urey
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What was the conclusion about this theory?
That it was along the right lines, but not entirely correct
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Over the next six cards, describe the process of fractionally distilling air
1. Air is filtered to remove dust
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Step two
2. It's then cooled to around -200 degrees C, when it becomes a liquid
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Step three
During the cooling process, water vapour condenses and is removed
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Step four
Carbon dioxide freezes and is removed
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Step five
The liquified air then enters the fractionating column and is heated slowly
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Step six
The remaining gases are separated by fractional distillation. Oxygen and argon come out together, so another column is used to separate them
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Other cards in this set

Card 2

Front

What evidence was there that land bridges existed?

Back

Fossils of very similar plants and animals had been found on opposite sides of the ocean, so animals would have been able to cross before the bridges 'sunk'

Card 3

Front

What evidence did Wegener find that supported his theory?

Back

Preview of the front of card 3

Card 4

Front

When did Wegener publish his theory of continental drift?

Back

Preview of the front of card 4

Card 5

Front

What was the theory of continental drift?

Back

Preview of the front of card 5
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