C1.7 Changes in the Earth and its Atomosphere Flashcards
What is the modern theory of how mountains were formed?
The earth’s surface is split up into big chunks called tectonic plates, and mountains are formed when these tectonic plates collide
Who created the theory of ‘continental drift’?
Alfred Wegner
What was the theory of continental drift?
That about 300 million years ago, there had been just one ‘supercontinent’ called Pangaea - which eventually drifted apart into smaller chunks which are now their own continent
What was Wegner’s evidence for continental drift? (3)
Fossils of similar plants and animals were found on the opposite sides of the Atlantic ocean, he noticed that the coastlines of south America and Africa fit together like a jigsaw and fossils were found in areas where that particular organism would not be able to survive
Reactions to Wegner’s was mostly hostile, why? (3)
Wegner couldn’t explain how the continents moved - he believed their movement was caused by tidal forces, but other geologists said that was impossible, also, land bridges explained a lot of Wegner’s evidence and Wegner wasn’t a geologist, he studied astronomy
Why did the theory of land bridges prove Wegner’s theory wrong?
Land bridges between continents meant that animals could easily move between continents, (explaining why fossils were found) and over time they sunk or were covered
When did Wegner’s theory get some appreciation?
In the 1950s, when the ocean floor could be investigated - he wasn’t completely right, but his main idea was right, and by the 1960s tectonic plates were discovered
What are the layers of the earth, from outside in? (4)
Atmosphere, crust, mantle and an iron and nickel core
What are the properties of the earth’s crust?
It’s the bit we live on, it’s very thin and is surrounded by the atmosphere
What are the properties of the earth’s mantle?
It has all the properties of a solid, except that it can flow very slowly in convention currents - due to the large amounts of heat produced by radioactive decay in the core
Where do humans get our resources from? (3)
The crust, oceans and the atmospheres
What are tectonic plates?
Large pieces of rock which ‘float’ on the mantle
How do tectonic plates move?
Due to convention currents from the mantle, the plates drift
How quickly do tectonic plates move? What happens if they move quickly?
They move a few centimetres a year, if they move suddenly they can cause earthquakes
Why is it so difficult to predict an earthquake?
Because we can’t see what’s happening deep underground
Why are predictions for earthquakes ignored by people? (4)
Because predictions don’t have an exact date, you can’t predict the strength of the earthquake - many earthquakes cause little or no damage, the exact location of an earthquake isn’t accurate and you can’t stop an earthquake, you can only evacuate, which can be expensive so people want to be sure that there is an earthquake before leaving
How are volcanic eruptions predicted?
Before an eruption molten rock rises up into chambers near the surface which causes mini-earthquakes near the volcano - but sometimes molten rock cools down instead of erupting, so it can be a false alarm
What are the main gases in the atmosphere? What else is there?
Oxygen (20%) and nitrogen (80%) - but there’s also carbon dioxide, water vapour and noble gases
Before an atmosphere was formed, what was the surface of the earth like?
Molten - any formation of an atmosphere just boiled away into space
What is theory for how oceans were formed?
It is thought that the atmosphere was once mainly CO2* and water vapour - and as the earth cooled, the water vapour condensed to form oceans
If levels of CO2* were so high, why is there such a low % of CO2* now?
Due to the absorption by ocean and the absorption by plants and algae - photosynthesis produces oxygen, which is why levels of oxygen are so much higher now
How was the carbon that was once in our atmosphere, ‘locked away’?
In fossil fuels - which is made is made of the remains of plants and animals
How does increasing levels of carbon dioxide affect the earth?
Global warming - an increase in the average temp. on earth, and acidity in oceans - the oceans absorb the carbon dioxide which increases their acidity, this can lead to the death of marine animals
Why is air fractionally distilled?
To get a variety of products that can be used as raw materials in industry
How are impurities removed from the air (in the fractional distillation of air)?
The air is first filtered to remove dust. It is then cooled to -200C and becomes liquid - here, carbon dioxide freezes so it can be removed
Why is the fractional distillation of air possible?
Because different gases in air have different boiling points so they will condense at different temperatures
How are the different gases from air extracted from a fractionating column?
Once the air vaporises, the different gases can be extracted at the different levels where they condense
What is the primordial soup theory?
Lightning struck earth which had an atmosphere rich in nitrogen, hydrogen, ammonia and methane. This caused a chemical reaction which formed amino acids - these then collected to form a body of water out which life gradually crawled
Who tested the primordial soup theory?
Miller and Urey
Why will there always be a mystery of life?
Because we are unable to know exactly what happened 3 billion years ago - we can only guess
