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News Picks : Tectonic activity may have driven Cambrian explosion

By: Physics Today
10 February 2014
Ars Technica: The Cambrian explosion is the period in Earth's history when new species developed at a very high rate. The Cambrian era is marked by an extremely high level of atmospheric carbon dioxide and high average temperatures. In contrast, the preceding Cryogenian era was much colder, and life forms were limited to unicellular and just a few multicellular species. Ryan McKenzie of the University of Texas at Austin and his colleagues believe that the sudden growth in CO2 levels is tied to a period of increased tectonic activity. They created a dataset of the ages of zircon crystals from around the world. Zircon is most frequently produced by volcanoes in subduction zones where ocean plates meet continental plates. It is resistant to erosion, and it traps uranium, which makes it easy to determine its date of formation. McKenzie's team found that the locations of zircon crystals revealed several continental arcs of volcanoes during the Cambrian period that were much less active before and after. They argue that the increased volcanic activity could be directly responsible for the release of a significant portion of the CO2 present during the Cambrian.


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