<http://www.sciencedaily.com/releases/2009/04/090408145336.htm>Link
--Posted By johannes to <http://www.monochrom.at/english/2009/04/earths-great-oxidation-event.htm>monochrom at 4/09/2009 05:41:00 PM
The Earth's original atmosphere held very little oxygen. This began
to change around 2.4 billion years ago when oxygen levels increased
dramatically during what scientists call the "Great Oxidation Event."
The cause of this event has puzzled scientists, but researchers
writing in Nature have found indications in ancient sedimentary rocks
that it may have been linked to a drop in the level of dissolved
nickel in seawater.
