Posted on 08/09/2007 7:47:19 PM PDT by blam
Source: Stanford University
Date: August 10, 2007
What We Can Learn From The Biggest Extinction In The History Of Earth
Science Daily — Approximately 250 million years ago, vast numbers of species disappeared from Earth. This mass-extinction event may hold clues to current global carbon cycle changes, according to Jonathan Payne, assistant professor of geological and environmental sciences. Payne, a paleobiologist who joined the Stanford faculty in 2005, studies the Permian-Triassic extinction and the following 4 million years of instability in the global carbon cycle.
Jiayong Wei, Payne's colleague, examined a block of early Triassic microbial limestone. (Credit: Jonathan Payne)
In the July issue of the Geological Society of America Bulletin, Payne presented evidence that a massive, rapid release of carbon may have triggered this extinction.
"People point to the fossil record as a place where we can learn about how our actions today may affect the future course of evolution," Payne said. "That's certainly true: The deep geologic record provides context for modern events. We may miss very important processes or underestimate the magnitude of changes in the future by using only the past couple thousand years as a baseline."
Great bank of Guizhou
Payne has spent the past five years unearthing the deep geologic record in south China. The kilometer-thick, limestone fossil beds at the Great Bank of Guizhou formed in shallow ocean waters during the late Permian and early Triassic periods. As the ocean floor sank, new, younger layers of limestone formed on top of deeper, older ones. Since then, plate tectonics have turned these rocks on their side. Now, Payne and his colleagues can walk back in time across the formerly horizontal layers.
Marine fossil beds such as these offer two advantages for someone studying broad patterns in the history of life, according to Payne. Because ocean waters cover large areas for long periods of time and somewhat protect the underlying rocks from erosion, marine fossil beds tend to be physically larger and cover a longer period of time with finer temporal resolution.
More than 90 percent of all marine species disappeared from the Great Bank of Guizhou and other end-Permian fossil formations 250 million years ago. Land plants and animals suffered similar losses. Douglas Erwin, curator of the Paleozoic invertebrates collection at the Smithsonian National Museum of Natural History, has dubbed this event "the greatest biodiversity crisis in the history of life." An unusually long period of time passed before biological diversity began to reappear. Scientists disagree on the causes of this extinction. However, nearly all explanations cite the high levels of greenhouse gases, including carbon dioxide, low levels of oxygen in the oceans and high levels of toxic gases.
Siberian traps
In 1991, scientists reported that the largest known volcanic event in the past 600 million years occurred at the same time as the end-Permian extinction. Magma extruded through coal-rich regions of the Earth's crust and blanketed a region the size of the continental United States with basalt to a depth of up to 6 kilometers. The eruptions that formed the Siberian Traps not only threw ash, debris and toxic gases into the atmosphere but also may have heated the coal and released vast quantities of carbon dioxide and methane into the atmosphere.
Rapid release of these greenhouse gases would have caused the oceans first to become acidic and then to become supersaturated with calcium carbonate. In the July Bulletin, Payne presents evidence that underwater limestone beds around the world eroded at the time of the end-Permian extinction. This finding, coupled with geochemical evidence for changes in the relative abundances of carbon isotopes, strongly suggests an acidic marine environment at the time of the extinction. The rock layers immediately covering this eroded surface include carbonate crystal fans, which indicate oceans supersaturated with calcium carbonate.
"This end-Permian extinction is beginning to look a whole lot like the world we live in right now," Payne said. "The good news, if there is good news, is that we have not yet released as much carbon into the atmosphere as would be hypothesized for the end-Permian extinction. Whether or not we get there depends largely on future policy decisions and what happens over the next couple of centuries."
Coral reefs
Payne plans to learn more about the causes and consequences of this massive extinction event this summer. Three students left August 1 to join him in southern China for four weeks of field studies.
If volcanic activity released sufficient quantities of carbon into the air within less than 100,000 years, the Earth would have transiently cooled and then experienced a prolonged period of global warming, Payne said. This summer, Ellen Schaal, a graduate student in the Department of Geological and Earth Sciences, will use one geochemical index to try to understand how climate did change during the end-Permian period.
Two other students will examine coral reef structures. The Great Bank of Guizhou contains the fossilized reefs from just before and just after this extinction event. Undergraduate Mindi Summers hopes to describe the ecological structure of coral reefs just before the extinction, and graduate student Brian Kelley will study the development and diversification of reefs after the global carbon cycle began to stabilize.
Reef communities are a sort of canary in the mineshaft, Payne explained. Today, coral reef health is considered a measure of environmental stability. When stressed by environmental conditions, the algae that inhabit the reef leave, and the reef loses color-and one reason why algae might leave is temperature. For example, when ocean temperatures rise during El Niño years, corals bleach. This type of immediate response to environmental change is hard to track in the geologic record.
"We hope to reconcile the short-term processes we observe operating in the modern world with the very long time scales seen in the geologic record," said Seth Finnegan, a postdoctoral scholar in Payne's lab.
Co-authors of the paper are Daniel Lehrmann, David Follett and Margaret Seibel of the University of Wisconsin-Oshkosh; Lee Kump and Anthony Riccardi of Pennsylvania State University; Demir Altiner of Middle East Technical University; Hiroyoshi Sano of Kyushu University; and Jiayong Wei of Guizhou Geological Survey. The study was sponsored by the National Science Foundation, NASA's Astrobiology Institute and Sigma Xi.
Fieldwork this summer is sponsored by the National Geographic Society and the Petroleum Research Fund (administered by the American Chemical Society).
Note: This story has been adapted from a news release issued by Stanford University.
You are onto something.
Actually, the shock waves from the huge meteor impact went clean around the globe, and when they all got to the other side together they once again amplified and cracked the crust there bad enough to let that huge volcanic event begin. If I’m not mistaken, that big one is down by Mexico or in the gulf there. If my memory serves me, it left a 10 mile wide crater.
No kidding.
I did a google.
The event was where a meteor the size of Mt. Everest struck. It created a crater 250 miles across.
The Sudbury event. 1.8 billion YA.
From the title, I thought this thread was about conservative GOP political candidates.
I just googled ‘extinction event’ and came back from the Wikipedia with some excellent entries and examples.
Something I ponder — You know that all the big craters on the moon are on the same side? Was that the side facing something when it exploded? Wouldn’t the debris hitting the earth be at least as dense?
YEC INTREP
B.S. Prove it.
Besides, they never disappeared, They gathered into groups of 50 billion each, and turned into oil wells in various locations around the earth....
As though hot magma, and the gasses and ash it released, covering the expanse of land the size of the US wasn’t, in itself, enough to affect world climate, not to mention all the life in that area and nearby. The Deccan Traps did the same thing at another time. No need to attach it to global warming unless the grant reviewers get tickled by it.
You have been watching WAAAAAAY TOOOOOO MUCH Stargate, Startrek, etc. My prognosis... No soup for you.
DUDE, R U into Mara-T-Wanna?
If it really was 250 years ago maybe it was Bush 41 fault.
I recall reading about a partial crater (other part would be in australia) in antarctica beneath ice which was dated to more or less the time frame of the P-T extinction. IIRC it was the first impact crater dated to the P-T event, and it is huge, far larger than the alvarez crater in yucatan.
This may sound far out but Raup and Stepkowski(sp?) some years ago theorized that the extinctions on earth(250M and 65M years ago)were caused by comets kicking asteroids out of orbit, which then impacted the earth. The question then was : what kicked the oort cloud comets out of stable orbits in the first place?
3 possibilities were mentioned: nemesis, a dark companion star to the sun on a very elliptical orbit; the solar system passing thru the galactic plane; or some other still unknown factor. My shot : two globular clouds of comets on nearly parallel orbits passing through each other every 65 million years and throwing comets out by wave forces rather than direct collisions : Outer X and Inner X or Ox/Ix.
Brian Marsden thought it an unorthodOX/unorthodIX idea but hey....You could possibly find them by sending out pulsed laser shots and waiting DAYS for an ever so faint pulse to return, lasar wavelengths matched to known(strongly guessed anyway)surface chemicals.
But now we’ve discovered the Kuiper Belt Objects and the outer solar sysytem picture has changed once again, no longer just random comets in the oort cloud. What other strange beasts are lurking out there in the darkness?
Note: this topic is from 08/09/2007. Thanks blam.
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Note: this topic is from 08/09/2007. Thanks blam.
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