Earth's Early Atmosphere (AQA GCSE Chemistry)

Evolution of the atmosphere

• Theories on the development of Earth’s atmosphere have altered and developed over time as instrumental analysis has improved

  • It is difficult to gather evidence about the early atmosphere because it happened 4.6 billion years ago

• The surface of the early Earth was molten for millions of years with no atmosphere 

• As cooling slowly occurred, the molten surface began to slowly solidify into land masses

• Volcanoes formed on the land masses

• One theory of how the early atmosphere formed suggests that the volcanoes released gases from the Earth’s interior through violent eruptions

• These eruptions released large amounts of carbon dioxide and water vapour, as well as nitrogen, hydrogen, and other gases which may have included small proportions of ammonia and methane

How volcanoes affected the atmosphere

 Volcanoes spewed out water, carbon dioxide and other gases from the Earth's interior

• While the surface of the Earth was still very hot the large quantities of water vapour remained in the gaseous state

• When conditions cooled sufficiently, the water vapour later condensed and fell to the surface of the Earth, forming the oceans

• Carbon dioxide is a water soluble gas (it is the gas used in fizzy drinks) and dissolves readily

• When the water vapour condensed large amounts of CO₂ dissolved in the oceans

• Carbonate substances were precipitated during this process which later formed sediments

• These processes reduced the amount of carbon dioxide in the atmosphere