Decreasing Carbon Dioxide in the Atmosphere

Why did atmospheric carbon dioxide decrease over time?

It dissolved in oceans, became locked in carbonate rocks and fossil fuels, and was removed by photosynthesis.

How did ocean formation reduce atmospheric carbon dioxide?

Carbon dioxide dissolved into seawater.

How did photosynthesis reduce atmospheric carbon dioxide?

Photosynthetic organisms absorbed carbon dioxide to make organic molecules.

How did carbonate rocks reduce atmospheric carbon dioxide?

Carbon dioxide became stored as carbonate minerals in sedimentary rocks.

How did marine organisms contribute to carbon storage?

They used dissolved carbon compounds to form shells and skeletons, which accumulated in sediments.

What is a carbon sink?

A reservoir or process that absorbs and stores more carbon than it releases.

What are examples of carbon sinks?

Oceans, forests, soils and carbonate rocks.

How did fossil fuels form?

From the remains of ancient organisms buried and transformed over millions of years.

How did fossil fuel formation affect atmospheric carbon dioxide?

Carbon became stored underground rather than remaining in the atmosphere.

What is the difference between short-term and long-term carbon storage?

Short-term stores exchange carbon relatively quickly, while long-term stores can retain carbon for millions of years.

Why is carbon stored in limestone considered long-term storage?

Carbon is locked into solid carbonate minerals.

What happens when fossil fuels are burned?

Stored carbon is released into the atmosphere as carbon dioxide.

Why is burning fossil fuels significant for atmospheric composition?

It returns carbon stored underground for millions of years to the atmosphere.

Why is the modern carbon dioxide concentration much lower than that of the early atmosphere?

Large amounts of carbon became stored in oceans, rocks and biological materials.