C13-The Earth’s atmosphere-History of our atmoshphere lesson created in accordance to the NEW AQA Specification (9-1). Designed for a mixed ability year 11 separates class, although content can be adjusted to suit any ability. Includes: slide animations, embedded videos, and homework with answers as well as a interactive review task. If for any reason the video link does not work, a URL has also been included in the notes.
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AQA spec link: 22.214.171.124, 3
Theories about what was in the Earth’s early atmosphere and how the atmosphere was formed have changed and developed over time.
Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years.
One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans. At the start
of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia.
When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere.
No knowledge of other theories is required.
Students should be able to, given appropriate information, interpret evidence and evaluate different theories about the Earth’s early atmosphere.
9.1.3 Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis, which can be represented by the equation:
6CO2 + 6H2O C6H12O6 + 6O2
carbon dioxide + water glucose + oxygen
Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.