The Earth's early atmosphere Flashcards – AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Higher

How do scientists determine what Earth's early atmosphere was like?

They infer it from the limited evidence that remains, rather than observing it directly.

Why is evidence about Earth's early atmosphere limited?

The events occurred about 4.6 billion years ago, and much of the original evidence has been lost or altered.

Why can theories about Earth's early atmosphere change?

New evidence or better interpretations can lead scientists to revise and improve them.

How should competing explanations of Earth's early atmosphere be evaluated?

Compare how strongly the available evidence supports each explanation, recognising that the evidence is incomplete.

According to the volcanic theory, how did Earth's early atmosphere form?

During Earth's first billion years, intense volcanic activity released gases from inside the planet, building the atmosphere.

What were the main carbon dioxide and oxygen characteristics of Earth's early atmosphere?

It contained mainly carbon dioxide, with little or no oxygen.

Which two present-day planetary atmospheres were more like Earth's early atmosphere than modern Earth's atmosphere?

Those of Mars and Venus.

How did volcanic water vapour contribute to the formation of Earth's oceans?

As Earth cooled, the water vapour condensed to form the oceans.

What happened to nitrogen released by volcanoes into Earth's early atmosphere?

It gradually accumulated in the atmosphere.

Which two gases may have been present in small amounts in Earth's early atmosphere?

Methane and ammonia.

How did the oceans reduce carbon dioxide in Earth's early atmosphere?

Carbon dioxide dissolved in seawater, became part of carbonate compounds, and was deposited as sediments when those carbonates precipitated.