C1 NOTES EDEXCEL

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  • Created by: KAK
  • Created on: 31-01-16 16:41

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.

Oxygen

·         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

The oceans

·         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…

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