The earths early atmosphere 4.9.1.2

Question 1

How has the earths atmosphere changed over time?

Answer 1

• Earth formed from debris orbiting the sun. earth was a ball of molten rock. The surface cooled, forming a crust, covered with volcanoes. Volcanoes produced ammonia, stem and carbon dioxide.
• Earth continued to cool. the stem condensed into water vapour then liquid and it fell as rain. Sea/oceans are formed.
• Carbon dioxide from the atmosphere is dissolved in the oceans. limestone formed which trapped carbon in rocks.
• First life form developed in oceans. This is because water protects from UV radiation. These organisms do photosynthesis. This removes carbon dioxide from the atmosphere, and produces oxygen. More carbon is trapped in rocks when organisms die.
• Ammonia reacted with the oxygen to produce nitrogen. Some bacteria break down ammonia to produce nitrogen.
• Oxygen found its way into the atmosphere and it formed the ozone layer. Life evolves and colonises land.
• reasonable steady atmosphere composition.