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Atmospheric changes over Earth's long history

Chemistry of the atmosphere • Evolution of the Earth's atmosphere

Key concepts

What you'll likely be quizzed about

  • The planet forms within a protoplanetary disc and initially acquires light gases such as hydrogen and helium from the solar nebula.
  • These light gases escape to space because Earth's gravity and the young Sun's high-energy radiation cannot retain them.
  • The efficiency of this gas loss is influenced by planetary mass and solar radiation intensity, meaning smaller bodies lose their primordial atmospheres more rapidly.

Flashcards

Test your knowledge with interactive flashcards

What evidence supports early oxygenation of the atmosphere?

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Banded iron formations and changes in sediment chemistry provide evidence of past oxygenation events.

Key notes

Important points to keep in mind

Primordial atmosphere contains light gases that escape; secondary atmosphere forms mainly from volcanic outgassing.

Cooling causes condensation of water vapor, leading to ocean formation and CO2 dissolution.

Chemical weathering of silicate rocks removes CO2 by forming carbonate minerals in oceans.

Photosynthesis produces oxygen and consumes carbon dioxide; oxygen accumulation depends on filling oxidation sinks.

The Great Oxidation Event results when oxygen sources exceed geological sinks.

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