A Walk Through Time

Some Like It Cool

800 Million Years Ago

One of a world-wide series of ice ages sets in. Thick ice sheets expand over vast areas of the Earth. What causes these ice ages is not completely understood. One theory attributes the ice ages to fluctuations in Earth's orbit, which affect the delivery of solar radiation to Earth.

Temperature swings can be amplified by other factors. If solar radiation decreases, for example, Earth cools and glaciers expand. Since glaciers are reflective, the expansion reduces the amount of heat absorbed by the Earth. Thus, temperature spirals down.

The life system of Earth is closely coupled to climate change. Microbes have, since the origin of life, played a major role in the carbon cycle. Ocean-floor and ice-core drilling shows precision synchrony between climate change and atmospheric carbon dioxide. This coupling affects the magnitude of climate change.

Diverse new planktic and benthic communities evolve from these ice ages, thanks to the rich nutrients found in colder waters. Some land protoctists, like these red snow algae, also like it cool. (Photography by Brian Duval)

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