C1.7- Our Changing Planet

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What is the inner layer of the Earth called?
The core
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What layer surrounds the core?
The mantle
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What is the outer layer of the Earth called?
The crust
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What is the atmosphere?
A thin layer of gases
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Where is the Earth’s crust thinnest?
Under the deep oceans
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How thick is the mantle layer?
Almost 3,000 km
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What metals are found in the core?
Nickel and iron
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What is different between the inner and outer cores?
The outer core is liquid, the inner core is solid
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From which layers of the Earth do we get all our resources?
The crust and the atmosphere
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What evidence is there that Africa and South America used to be joined?
The rocks from these two continents contain the fossils of the same reptiles and plants and appear to have been built up in the same sequence.
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How fast do the continents move?
A few centimetres a year
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Why do the continents move?
Because the crust and upper part of the mantle are cracked into massive pieces
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What are the areas that move around called?
Tectonic plates
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Why are there convection currents in the Earth’s mantle layer?
Huge amounts of energy are released by decaying radioactive atoms, this energy heats up the mantle making it less dense and as a result is rises towards the surface. The cooler material from above moves to replace it forming currents.
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What happens when the tectonic plates suddenly slide past each other?
An earthquake
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What layers of the Earth make up the tectonic plates?
The crust and the upper part of the mantle
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How long ago do scientists believe the Earth was formed?
4.5 billion year ago
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Which gas was thought to be most prevalent in the Earth’s early atmosphere?
Carbon dioxide
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Where did the seas come from?
Water vapour condensed as the Earth cooled, falling as rain and collected in lower areas
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Was life present on Earth in these very early stages?
No
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When do scientists believe that life first formed on Earth?
About 3.4 billion years ago
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What was the first life on Earth?
Simple organisms similar to bacteria
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What did these organisms use for energy?
Chemicals, they broke them down into other usable chemicals
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Where did the oxygen in the earth’s atmosphere come from?
Bacteria and algae photosynthesising producing oxygen as a waste product
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What made it possible for animals to develop?
The atmosphere became richer in oxygen as more and more plants colonised the earth.
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What was the other impact of the increasing oxygen concentration?
Early organisms which learnt to survive without oxygen could not tolerate the higher levels of oxygen and died out.
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What do amino acids join together to form?
Proteins
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What elements are in most amino acids?
Carbon, hydrogen, nitrogen and oxygen
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What was the aim of the Miler–Urey experiment?
To mimic the conditions of the early atmosphere on Earth and see if it would produce amino acids
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Why did Miller and Urey use a high voltage spark? What real-life event is it mimicking?
To get the gases in the primitive atmosphere to react. It is mimicking lightning.
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What did Miller and Urey find after their experiment had been running for a week?
11 amino acids
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What do some scientists say that might make the results of Miller and Urey invalid?
The reaction only works in the absence of oxygen which would have been around at the time these amino acid molecules would have formed.
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What theory did the Murchison meteorite mean could have been a possibility?
The molecules that started life on Earth could have arrived from outer space.
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What other theory has been proposed for the origins of biological molecules?
They were formed near volcanic vents near the bottom of the sea where the conditions and chemicals would have been present.
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What is meant by a primordial soup?
A collection of molecules that are needed to form biological building blocks that are all together in a medium which allows them to react together
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What is meant by extra-terrestrial seeding?
The theory that the first organisms came from outer space and came to the Earth on meteors
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What is the greatest difference, in terms of gas composition, between the early atmosphere and today’s?
The amount of carbon dioxide, the early atmosphere was mainly carbon dioxide whereas today it only accounts for 0.04%
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Where does the carbon dioxide taken up during photosynthesis ultimately end up?
In sedimentary carbonate rocks (e.g. limestone) and in fossil fuels (e.g. crude oil)
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Where else did the carbon dioxide from the early atmosphere end up?
It was dissolved in the oceans.
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Why is there no ammonia and methane in the atmosphere today?
It all reacted with oxygen to form carbon dioxide, nitrogen and water.
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Why did the levels of nitrogen gradually increase?
It is a very unreactive gas so does not react again to form other products.
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How long ago did the Earth’s atmosphere stabilise at proportions similar to those today?
200 million years ago
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What process is used to separate air in industry?
Fractional distillation of liquid air
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How do we get air to form a liquid?
Cool it to a temperature of below -200C
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Why can carbon dioxide and water be removed from liquid air easily?
Because they are solid at such relatively high temperatures compared to the other gases present
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Which gas reaches its boiling point first?
Nitrogen
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What properties of nitrogen make it quite useful in industry?
It is very cold in its liquid form so can cool things down and is very unreactive.
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In what state is oxygen when it is separated out of the liquid air?
Liquid
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Why have the levels of carbon dioxide not changed much in the last 200 million years?
The natural cycle of carbon in which carbon moved between oceans, rocks and the atmosphere
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Why are plants and the oceans known as carbon dioxide ‘sinks’?
They act as a reservoir of carbon which can remove or provide carbon dioxide when needed.
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Why is the balance of carbon changing?
We are producing a huge amount of carbon dioxide as waste from burning fossil fuels.
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Why does the level of carbon dioxide in the atmosphere fluctuate yearly?
Due to the seasonal changes in plants
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What is the overall trend in carbon dioxide levels in the atmosphere?
Increasing/positive
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Why are coral reefs at risk from the increased levels of carbon dioxide?
As more carbon dioxide absorbs in the sea it becomes more acidic which causes some of the coral to die.
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Other cards in this set

Card 2

Front

What layer surrounds the core?

Back

The mantle

Card 3

Front

What is the outer layer of the Earth called?

Back

Preview of the front of card 3

Card 4

Front

What is the atmosphere?

Back

Preview of the front of card 4

Card 5

Front

Where is the Earth’s crust thinnest?

Back

Preview of the front of card 5
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