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PORTSIDE  July 2011, Week 4

PORTSIDE July 2011, Week 4

Subject:

Mass Extinction Easier to Trigger Than Thought

From:

Portside Moderator <[log in to unmask]>

Reply-To:

[log in to unmask]

Date:

Mon, 25 Jul 2011 01:54:02 -0400

Content-Type:

text/plain

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Parts/Attachments

text/plain (139 lines)

Mass Extinction Easier to Trigger Than Thought
By Brandon Keim, wired.com 
Ars Technica
July 21, 2011
http://arstechnica.com/science/news/2011/07/mass-extinction-easier-to-trigger-than-thought.ars

The cataclysmic extinctions that scoured Earth 200
million years ago might have been easier to trigger than
expected, with potentially troubling contemporary
implications.

Rather than 600,000 years of volcanic activity choking
Earth's atmosphere with carbon dioxide, just a few
thousand years apparently sufficed to raise ocean
temperatures so that potent greenhouse gases trapped in
seafloor mud came bubbling up.

Most of everything alive on Earth was soon wiped out.
Another half-million years of vulcanism were just icing
on the cake. The immediate question: What lessons, if
any, can be drawn?

"Scientists have been worried about the current release
of methane from seafloors. What this study shows is that
it already happened in the past," said paleoecologist
Micha Ruhl of Utrecht University, whose findings are
published July 21 in Science. "It could happen again.
It's only the boundary conditions that we don't know."

In what scientists call the end-Triassic mass
extinction, at least half of all living species simply
disappear from the fossil record. The die-off didn't
merely cause ecological disruption. It was so sudden and
profound that planetary chemical cycles went haywire for
the next several million years.

The leading explanation for the extinction invokes
extended, climate-altering volcanic activity caused by
splitting continental plates, but earlier research by
Ruhl suggested a more nuanced and jarring narrative.

By calculating how changes in ancient sediment
composition corresponded to natural cycles in Earth's
distance to the Sun, he could study the end-Triassic's
onset in fine-grained chronological detail. Ruhl found
that limestone-the geological remains of corals and
shellfish-vanish within the first 20,000 years. Similar
terrestrial disruption can be inferred from changes in
fossilized plant spores. The end-Triassic extinction
must have occurred far more suddenly than believed.

In the latest study, Ruhl's team examined chemical
traces left by dying plants on the shores of the Tethys
Sea, a body of water that separated the ancient
continents of Laurasia and Gondwana. Today those shores
are sedimentary layers in the Austrian Alps.

The researchers concentrated on changes to carbon
isotopes, or subtly different elemental formations that
betray whether carbon in plants came from carbon dioxide
or methane. At 201.4 million years ago, in that narrow
20,000 year window of their updated end-Triassic
cataclysm, they found a rise in CO2 followed by a
tremendous spike of methane.

"A small release of CO2 from volcanoes triggered a small
change in the global climate, raising land and ocean
temperatures. That led to the release of methane from
the seafloor," said Ruhl.

Methane, familiar to most people as the main component
of natural gas fuels, is a greenhouse gas less common
than carbon dioxide in the atmosphere but far more
potent. Most of Earth's supply is contained in soils and
seabeds.

Scientists have raised the possibility that rising
global temperatures could release trapped methane into
the atmosphere, further raising temperatures and
releasing more methane in a feedback loop of warming and
planetary disruption. That's apparently what happened
during the end-Triassic extinction.

According to paleobiologist Jessica Whiteside of Brown
University, a leading researcher on end-Triassic
vulcanism, more evidence is needed before Ruhl's
interpretations are conclusively supported. It's
possible that the new study reflects localized rather
than planetary patterns.

But though Whiteside is uncertain about methane's end-
Triassic role, she said the possibility of a CO2-methane
warming loop is real and likely fueled climate change
leading into the Eocene, an epoch lasting from 55 to 35
million years ago.

"It was a very hot time, so hot there were crocodiles in
the Arctic Circle and palm trees extending to the North
Pole," said Whiteside. "It's the most recent time in
Earth's history that greenhouse gases were at the level
where we're predicted to be in the next century."

Exactly how much warming would be needed to start the
loop anew, and how much methane would flow forth, are
open questions.

"We could potentially trigger a small increase in ocean
temperatures, which triggers methane release," said
Ruhl. "But it's difficult to quantify how much methane
is in the ocean these days. Maybe we have less methane
in seafloors now. Maybe we have more."


[moderator: the following is a special bonus science 
post for this week - please click on the link]
Cambrian Explosion
Brighter Lights, Thicker Glasses
John Palmer on guitar/vocals, Michael Dunn on dobro 
and Brian Samuels on cello.
http://www.youtube.com/watch?v=EMwxwRA9Xr8&feature=player_embedded

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