Australasian Science: Australia's authority on science since 1938

A New Cause for Three Global Mass Extinction Events

By John Long

Dangerously lows levels of trace elements might be implicated in three mass extinctions.

The full text of this article can be purchased from Informit.

Throughout the past 600 million years there have been five major mass extinction events and a host of smaller biotic crises, each of which saw the demise of large swaths of life on Earth and in the oceans. While some of these events are very well studied, such as the killer asteroid that wiped out the dinosaurs 66 million years ago, others are more enigmatic and entertain a variety of possible causes.

The first three extinction events took place near the end of the Ordovician Period (c. 445 Ma), end of the Devonian Period (385–359 Ma) and at the end of the Permian Period (252 Ma). The most devastating of these events was the end of Permian event, which wiped out 96% of all marine species and about 70% of life on Earth. The likely causes are from massive volcanic eruptions on a scale never before seen, with other effects that include a runaway greenhouse effect triggered by methane release from the seafloor. Because the devastation was so severe, recovery took around 10 million years.

The big extinction event at the end of the Ordovician is linked to glaciation and widespread anoxia, or loss of oxygen in the seas. About 57% of all genera were wiped out in the oceans, making it the second largest of all extinction events. The reliability of interpreting the past oxygen levels of the Earth is the key to understanding this event – the anoxia may have been...

The full text of this article can be purchased from Informit.