The early atmosphere C1.1
The young Earth
· Scientists can find out about the Earth’s atmosphere by studying other planets.
· They think that evolution caused the change in the atmosphere.
· They study planets that they think no life exists on because the atmosphere of these places has probably not changed.
· That is why it might resemble the Earth’s early atmosphere.
· Volcanoes are studied a lot because these produce a lot of gas.
· They mainly release carbon dioxide and water vapour, with a small amount of ammonia, methane and nitrogen.
· These gases are believed to have had been present in the early atmosphere too.
· But we do not know how much of those gases were produced.
· Titan is a planet which has an atmosphere of 98% nitrogen, which scientists believe was released by volcanoes.
· The early atmosphere could have had been like this too.
· Mars and Venus also have volcanoes but their atmosphere is mainly made up of carbon dioxide.
· Space probes have shown that the interior of Titan is very icy.
· But the interior of Earth, Mars and Venus is rocky.
· This means that the Earth’s atmosphere is closer to Mars and Venus.
· However, scientists have not figured out why there is so much nitrogen in the current atmosphere of the Earth.
· So they do not know which theory is correct.
· We know that in the early atmosphere of the Earth, there was either very little or no oxygen present at all.
· This is because volcanoes do not produce oxygen.
· It is also because, iron compounds are present in the Earth’s oldest rocks which could have had only been present without oxygen.
· The older the Earth became the cooler the atmosphere became.
· This caused water vapour to be formed by the steam that was let off by the volcanoes.
· Once the water vapour had condensed into liquid it started to form oceans.
· We do not have a lot of evidence about the Earth’s atmosphere, so we are not 100% sure about how the early atmosphere of the Earth was.
A changing atmosphere C1.2
· As the Earth’s atmosphere started to cool down, water vapour was formed by steam of the volcanoes which then condensed and formed oceans.
· The carbon dioxide which was then present in the atmosphere dissolved into the oceans.
· Around half of the carbon dioxide that was present in the atmosphere was lost by this process.
· Some marine organisms such as molluscs, coral and star fishes used the carbon dioxide to create shells of calcium carbonate.
· Once these animals died, their shells fell to the sea bed which then formed sediments.
· After millions of years these sediments became, sedimentary…