Unit A

Module 2 ~ Lesson 2

 Atmospheric Composition

NASA. Used under the Fair Dealings provision of the Canadian Copyright Act. https://climate.nasa.gov/vital-signs/carbon-dioxide/

Atmospheric carbon dioxide levels have increased rapidly since 1950

Historical carbon dioxide levels can be determined by ice core sampling 

Atmospheric carbon dioxide levels are measured and recorded daily. However, determining what the atmospheric carbon dioxide level was hundreds of thousands of years ago requires a different method. Scientists use ice core samples to determine the historical levels of atmospheric carbon dioxide.

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Atmospheric oxygen levels have fluctuated historically

Stromatolites are sedimentary rocks that scientists use to estimate the historic atmospheric levels of oxygen 

Modern oxygen, oxygen gas, was not always present in the Earth's atmosphere. The appearance of the Earth's first photosynthetic organisms, 2.5 billion years ago, saw the rise in atmospheric oxygen levels. Before this, most oxygen was already bound with iron ions as iron oxides. These iron oxides are evident in sedimentary fossils call stromatolites. Stromatolites, give scientists an indication of the fluctuating oxygen levels in the atmosphere millions of years ago.    


View this video. Think about how life on Earth depends on oxygen. Why is the balance of oxygen and carbon dioxide so important? How would life on Earth change if the atmospheric composition changed?