Changes in the Earth and its Atmosphere Flashcards
What is the mantle?
Extends almost halfway to the centre
Has properties of a solid even though it flows very slowly
Way are the four main layers if the earth?
Thin crust
Mantle
Inner core
Outer core
What are the inner and outer cores made from?
Nickel
Iron
What is the outer core?
Liquid
What is the inner core?
Solid
What is the rock cycle?
Rocks continually being broken up, reformed and changed
What early theory was rejected?
The features on the earth’s surface were caused by shrinkage as the earth cooled
What did scientists notice that was similar about the east coast of South America and the west coast of Africa?
Closely matching coastlines
Similar patterns of rocks which contain fossils of the same plants and animals
What is tectonic theory?
At one point the land had been part of a few single land masses
The movement of the crust was responsible for the separation of the land (continental drift)
What causes the tectonic plates to move apart slightly every year?
Radioactive decay deep in the earth releases heat
Causes molten rock to rise to the surface at the boundary between the plates
How does convection work in the mantle?
Hot molten rock rises the the surface, creating a new crust
The older crust slowly sinks to where the convection current starts to fall
Causes land masses on these plates to slowly move across the globe
What happens when the movement of the tectonic plates is not gradual?
Earthquakes and volcanic eruptions
How long ago did the earth form?
4.6 billion years ago
What was the main gas when the earth first formed?
Carbon dioxide
What did intense volcanic activity release when the earth was first formed?
Water vapour which condenses to form the oceans
Mainly carbon dioxide with little or no oxygen
Small amounts of methane and ammonia
What happened as green plants evolved?
Oxygen produced and carbon dioxide removed as plants photosynthesise
Microorganisms that cannot tolerate oxygen die
Most carbon from carbon dioxide in the air becomes locked up in sedimentary rocks
Some carbon dioxide dissolves in ocean
Ammonia breaks down to produce nitrogen
Other gases react with oxygen to release nitrogen
What is the current atmosphere like?
Carbon dioxide has decreased significantly
Nitrogen and oxygen have increased
What percentage is nitrogen in today’s atmosphere?
78%
What percentage is oxygen in today’s atmosphere?
21%
What percentage is carbon dioxide in today’s atmosphere?
0.03%
How do we separate the gases in the air?
Fractional distillation
Gases can then be used as a source of raw materials in a variety of industrial processes
Why are the levels of carbon dioxide increasing in the atmosphere today?
Volcanic activity
Burning fossil fuels
What increases the reaction between carbon dioxide and sea water?
Increased carbon dioxide
What is produced when carbon dioxide reacts with sea water?
Insoluble carbonates which are deposited as sediments
Soluble hydrogencarbonates
What is the main effect of more carbon dioxide dissolving in the sea?
Lowers pH of seawater which impacts the marine environment
What is the Primordial Soup Theory?
Life on earth began in an ocean or pond when a form of energy caused the combination of chemicals from the atmosphere to combine and make amino acids
What was the form of energy in the Primordial Soup Theory?
Lightning
What happened in 1950?
Two people carried out an experiment to test the Primordial Soup Theory by using electricity to represent lightning
They did generate amino acids
However a problem with this was that amino acids are not a living material
