Tuesday, April 1, 2014

Microbes May Have Caused Earth's Biggest Extinction

lava flows, part of the Siberian traps 
Lava flows exposed near Norilsk, Russia, are part of the Siberian Traps, the largest set of volcanic eruptions in recorded geologic history.   

A microbial feeding frenzy may have fueled the biggest mass extinction in Earth's history, new research suggests.

The findings suggest that bacteria, with a little help from massive volcanism, produced large quantities of methane, thereby killing 90 percent of life on the planet. 

Mass extinction
About 252 million years ago, more than 96 percent of ocean life and 70 percent of land-based life forms died in an event known as the end-Permian extinction. The mass die-off happened in a geologic flash of just 60,000 years. Scientists have proposed everything from massive meteor impacts to coal explosions to rifting supercontinents to explain this cataclysmic extinction. [Wipe Out: History's Most Mysterious Extinctions]

Rocks from that time period in locations such as Meishan, China, show that atmospheric carbon-dioxidelevels skyrocketed right around the time of the extinction. Sediments also show that during this time, the largest set of volcanic eruptions in recorded geologic history — called the Siberian Traps — spewed enough lava to cover the entire landmass of the United States, said study co-author Gregory Fournier, a biologist at the Massachusetts Institute of Technology. Therefore, many researchers have theorized that the Siberian Traps could have belched out the extra carbon dioxide, choking life on the planet.

Deadly microbes?

But if volcanic eruptions caused the great dying, shifts in carbon should occur as big bursts followed by gradual decays. Instead, the carbon-dioxide (CO2) levels rose at faster-than-exponential rates, which points to a biological cause of the shift, the researchers said.

For the rest of the story: http://www.livescience.com/44491-microbes-caused-mass-extinction.html

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