Plate Tectonics Flashcards
What was Alfred Wegner’s evidence for his theory?
> first noticed that same species of plants and animals had been found on opposite ends of Atlantic Ocean
> investigated further and found that the same species of fossils has been found in opposite continents of the world
> noticed that South America and Africa seemed to match
> same layers of rock on the different continents
> tropical fossils had been found in the Antarctic
What was Wegner’s theory of ‘continental drift’?
> 300 million years ago the continents had been one giant land mass
> the ‘super continent’ Pangea, had split into chunks which gradually moved apart
> claimed that these chunks were our continents and they were still moving apart
Why wasn’t Wegner’s theory accepted at first?
> his explanation wasn’t very convincing
- said that the continents were ploughing through the sea bed because of tidal forces and the earth’s rotation
> he used inaccurate data and so produced wild predictions about the rate of movement of the continents
> he’d studied astronomy
> one scientist predicted that the force needed for this to have happe we would have stopped the earth’s rotation.
What is the earth comprised of?
> crust 5-50km
> mantle
> core
What is the mantle?
> area between crust and core
- has properties of solid but can flow like liquid
> radioactive decay takes place producing heat energy causing the mantle to flow in convection currents
Why do the tectonic plates drift?
> because of the convection currents in the mantle
What are earthquakes caused by?
> vibrations or sudden movements of the tectonic plates
> caused by convection current in the mantle
> more earthquakes and volcanoes occur at the plate boundaries
What was phase 1 of the earth’s atmosphere?
> was molten for many millions of years- atmosphere just evaporates I to space
> eventually cooler to form a thin crust
- still many volcanoes
How did volcanoes form the atmosphere and the ocean?
> they released gas which formed the atmosphere
- mostly CO2 with some CH4 and ammonia and a little water vapour
- water vapour condensed to form the oceans
What was phase 2 of the earth’s atmosphere?
> green plants and algae evolved happily in the CO2 atmosphere
> some CO2 was sequestered and was used up by green plants which released O2 with photosynthesis
> when green plants and marine organisms died, their carbons and hydrocarbons were stored in the sedimentary rocks and insolvable carbonates
> when we burn these fossil fuels the carbon is re released into the atmosphere as CO2
What was phase 3 of the earth’s atmosphere?
> buildup of oxygen killed off some of the organisms that could not survive, meanwhile some evolved and flourished
> oxygen created and ozone layer (03) which blocked the harmful rays of the sun, allowing more complex organisms to grow and evolve
> virtually no CO2 left
How was nitrogen produced in the atmosphere?
> produced by bacterial decay of dead organisms
> built up as is unreactive
Describe the primordial soup theory.
> billions of years ago the atmosphere was just H2 N2 NH3 and CH4
- lightening struck, causing a chemical reaction in the gases and creating amino acids
> amino acids gathered in a ‘primordial soup’ out of which life eventually crawled
> the amino acids combined to produce organic matter which eventually produced simple organisms
What was the Urey-Miller experimentation?
> they chimed the gases present in the earth’s atmosphere in apparatus and heated and supplied electrical charge for a week
- found that some amino acids were formed but not as many as on earth
- not quite right yet
List the process of the fractional distillation of air.
> filtered to remove dust
> cooled to -200 degree Celsius and becomes a liquid
- during cooling water vapour condenses and is tapped out
> CO2 freezes and is tapped out
> liquified air is put into a fractionating column and heated slowly
> remaining gases are separated this way
- oxygen and argon are separated together and so are put through another column
