The Evolution of the Atmosphere Flashcards
How long has the atmosphere been like it is today?
200 million years or so.
What gases does our atmosphere consist of today?
78% nitrogen. 21% oxygen. 0.93% argon. 0.038% carbon dioxide. WATER VAPOUR.
What happened in phase 1?
Volcanoes gave out gases.
Initially what was the Earth’s surface like?
Molten for many millions of years.
It was that hot any atmosphere just ‘boiled away’ into space.
Eventually when the Earth’s surface cooled down what happened?
A thin crust formed.
But volcanoes kept erupting.
What did the volcanoes give out?
Lost of gas.
We think this was how the oceans and atmosphere was formed.
What was the early atmosphere?
Probably mostly CO2 with virtually no oxygen.
May have been water vapour.
Small amounts of methane and ammonia.
The Earth’s early atmosphere is quite like what?
The atmosphere of Mars and Venus today.
How did the oceans form?
When the water vapour condensed.
What happened on phase 2?
Green plants and algae evolved.
Producing oxygen.
They were quite happy in the CO2 atmosphere.
What did a lot of the early CO2 do?
Dissolved into the oceans.
In phase 2 what did the green plants and algae do?
They also absorbed some of the CO2 and produced oxygen by photosynthesis.
In phase 2 what happened to the green plants and algae?
They died.
Buried under layers of sediment.
Along with skeletons and shells of marine organisms.
What happened to the hydrocarbons and carbon inside the green plants and algae?
They became ‘locked up’ in sedimentary rocks as insoluble carbonates and fossil fuels.
So what happens when we burn fossil fuels todY?
The ‘locked up’ carbon is released and the concentration of CO2 in the atmosphere rises.
