Posted on 06/01/2006 2:26:58 PM PDT by PatrickHenry
Ancient mega-catastrophe paved way for the dinosaurs, spawned Australian continent.
Planetary scientists have found evidence of a meteor impact much larger and earlier than the one that killed the dinosaurs -- an impact that they believe caused the biggest mass extinction in Earth's history.
The 300-mile-wide crater lies hidden more than a mile beneath the East Antarctic Ice Sheet. And the gravity measurements that reveal its existence suggest that it could date back about 250 million years -- the time of the Permian-Triassic extinction, when almost all animal life on Earth died out.
Its size and location -- in the Wilkes Land region of East Antarctica, south of Australia -- also suggest that it could have begun the breakup of the Gondwana supercontinent by creating the tectonic rift that pushed Australia northward.
Scientists believe that the Permian-Triassic extinction paved the way for the dinosaurs to rise to prominence. The Wilkes Land crater is more than twice the size of the Chicxulub crater in the Yucatan peninsula, which marks the impact that may have ultimately killed the dinosaurs 65 million years ago. The Chicxulub meteor is thought to have been 6 miles wide, while the Wilkes Land meteor could have been up to 30 miles wide -- four or five times wider.
"This Wilkes Land impact is much bigger than the impact that killed the dinosaurs, and probably would have caused catastrophic damage at the time," said Ralph von Frese, a professor of geological sciences at Ohio State University.
He and Laramie Potts, a postdoctoral researcher in geological sciences, led the team that discovered the crater. They collaborated with other Ohio State and NASA scientists, as well as international partners from Russia and Korea. They reported their preliminary results in a recent poster session at the American Geophysical Union Joint Assembly meeting in Baltimore.
The scientists used gravity fluctuations measured by NASA's GRACE satellites to peer beneath Antarctica's icy surface, and found a 200-mile-wide plug of mantle material -- a mass concentration, or "mascon" in geological parlance -- that had risen up into the Earth's crust.
Mascons are the planetary equivalent of a bump on the head. They form where large objects slam into a planet's surface. Upon impact, the denser mantle layer bounces up into the overlying crust, which holds it in place beneath the crater.
When the scientists overlaid their gravity image with airborne radar images of the ground beneath the ice, they found the mascon perfectly centered inside a circular ridge some 300 miles wide -- a crater easily large enough to hold the state of Ohio.
Taken alone, the ridge structure wouldn't prove anything. But to von Frese, the addition of the mascon means "impact." Years of studying similar impacts on the moon have honed his ability to find them.
"If I saw this same mascon signal on the moon, I'd expect to see a crater around it," he said. "And when we looked at the ice-probing airborne radar, there it was."
"There are at least 20 impact craters this size or larger on the moon, so it is not surprising to find one here," he continued. "The active geology of the Earth likely scrubbed its surface clean of many more."
He and Potts admitted that such signals are open to interpretation. Even with radar and gravity measurements, scientists are only just beginning to understand what's happening inside the planet. Still, von Frese said that the circumstances of the radar and mascon signals support their interpretation.
"We compared two completely different data sets taken under different conditions, and they matched up," he said.
To estimate when the impact took place, the scientists took a clue from the fact that the mascon is still visible.
"On the moon, you can look at craters, and the mascons are still there," von Frese said. "But on Earth, it's unusual to find mascons, because the planet is geologically active. The interior eventually recovers and the mascon goes away." He cited the very large and much older Vredefort crater in South Africa that must have once had a mascon, but no evidence of it can be seen now.
"Based on what we know about the geologic history of the region, this Wilkes Land mascon formed recently by geologic standards -- probably about 250 million years ago," he said. "In another half a billion years, the Wilkes Land mascon will probably disappear, too."
Approximately 100 million years ago, Australia split from the ancient Gondwana supercontinent and began drifting north, pushed away by the expansion of a rift valley into the eastern Indian Ocean. The rift cuts directly through the crater, so the impact may have helped the rift to form, von Frese said.
But the more immediate effects of the impact would have devastated life on Earth.
"All the environmental changes that would have resulted from the impact would have created a highly caustic environment that was really hard to endure. So it makes sense that a lot of life went extinct at that time," he said.
He and Potts would like to go to Antarctica to confirm the finding. The best evidence would come from the rocks within the crater. Since the cost of drilling through more than a mile of ice to reach these rocks directly is prohibitive, they want to hunt for them at the base of the ice along the coast where the ice streams are pushing scoured rock into the sea. Airborne gravity and magnetic surveys would also be very useful for testing their interpretation of the satellite data, they said.
NSF and NASA funded this work. Collaborators included Stuart Wells and Orlando Hernandez, graduate students in geological sciences at Ohio State; Luis Gaya-Piqué and Hyung Rae Kim, both of NASA's Goddard Space Flight Center; Alexander Golynsky of the All-Russia Research Institute for Geology and Mineral Resources of the World Ocean; and Jeong Woo Kim and Jong Sun Hwang, both of Sejong University in Korea.
I couldn't find the spot I referred to earlier, but his site has a simple graphic of the continents dancing around on the globe:
http://www.enchantedlearning.com/subjects/dinosaurs/dinofossils/locations/Antarctica.shtml
Al Gore has been on this from the get go....wait'll tomorrow and he'll fess up? Ya'll didn't believe me on the "Internet" thing either....
In all seriousness, we know less about our oceans than we do about space....
So, what defines truth? Or is the scientific model the best we are going to get?
http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=060601_crater_gravity_02.jpg∩=Gravity+fluctuations+beneath+East+Antarctica+measured+by+GRACE+satellite.+Denser+regions+appear+more+red;+the+location+of+the+Wilkes+Land+crater+is+circled+(above+center).+Credit%3A+Ohio+State+University+
Bedout High: c.250 MYA, ~200km diameter The Bedout structure 300km west of Broome, in the Canning Basin off the coast of Western Australia, has been sited as one of the possible impacts that contributed to one of the greatest extinction events known. At the end of the Permian Period, around 250 MYA, it has been estimated that more than 90% of marine species, and 70% of terrestrial species, may have become extinct. The extinction event seems to have been a sudden, global occurrance, lasting less than a million years (which in geological terms is very rapid).
http://home.alphalink.com.au/~dannj/craters.htm
So many craters, so many extinctions...
I 'discovered' another one recently, named in 2003 IIRC. Not yet on the map of Australian Impact Craters.
Google pic follows...
So, you care to illuminate us about why a man who nails catastrophism as a prime vehicle of environmental change decades before his (ahem) peers is, in your opinion, a kook and a fool?
It's a baby...only 8.5 klm.
http://www.unb.ca/passc/ImpactDatabase/austr.html
So much fun stuff, where to begin.
Regarding this graph, I see that the CO2 levels and temperatures were similar to those today. The proto-mammalian therapsids were evolving just fine until the big disaster, then Lystrosaurus held out for a time, and the dinosaurs/lizards ruled for 150 million years. Perhaps there is an important difference in mammalian style vs lizard style metabolism that caused the failure of the therapsid line, leaving only a few tiny proto-mammalians to hide in the bushes for all those years. Should this worry us today with increasing CO2?
As to why the dinosaurs did not survive the meteor event(s) of 65mya, a theory I have not heard is that it/they probably destroyed the ozone layer for quite some time. I can see the poor dinosaurs dying of skin cancer. Note the creatures that did survive. Birds covered with feathers, frogs and salamanders living in water or under plants and rocks, alligators living and resting in mud bank caves, mammals covered with fur and living in bushes.
A great book is "When Life Nearly Died: The Greatest Mass Extinction of All Time," by Michael J. Benton, 2003. There is an interesting graph on pg. 172 showing "radiometric ages, the carbon isotope curve, and the ranges of 333 species of fossils identified from 90 metres of rock in the Meishan quarries. A, B and C mark the three apparent pulses of extinction." These three pulses occurred over a million year spread, and could coincide with several boloid events.
For those who like the vulcanism explanation, see pg. 275 with "A summary diagram showing how the eruption of the Siberian Traps led to major atmospheric changes and to the collapse of most of life on Earth 251mya." [I would post these, but don't have the computer capability or knowledge.]
Regarding the idea of contrecoup damage, is this the same concept as when a bullet hits a skull it causes a small hole going in but a big hole or bulge on the opposite side of the head? If so, then this was my initial thought for the Yucatan/Deccan Traps situation, until I heard about the "Shiva Crater". There is a lot on google there. At the end Permian, all the land masses were pretty much stuck together as Pangea. I think that the Bedout and Antarctic Craters would have been toward the south end, and the Siberian Traps toward the north end, but I am not sure there would have been enough oppositeness for a ballistic type effect. That is why I think there may be a crater hidden under the Traps.
Ia Shub and all that. You know old Howard Phillips was remote viewing, if unconsciously, all that Antarctic activity. You also know that Lake Vostok is the Lake of Living Past. Read Poe's "Diary of Arthur Gordon Pym," if you haven't already. It's all there, people, and it's not pretty but it sure is cool!!
The evidence of catastrophism is all around you - not up your butt.
Silly git, you mean the NARRATIVE of Arthur Gordon Pym.
Bump.
It seems to me that the fact that he got out there with a contrarian explanation at a time when uniformitarianism reigned was just too radical for establishment thinkers. No doubt he had a few wild and wooleys, but at least give the man credit for calling the fundamental mechanics what they were/are. When you reflect on it, even hallowed science, in every epoch, essentially pulls their theories out of their butts, too - though highly educated butts they may be.
The history of science is nothing if it is not supposition after supposition being overturned. That means the scientists in the status quo crowd have their heads up their butts and like the atmosphere. Sorry to say, but 'Science' is nothing more than another human agency and prone to hubris the same as any other. Velikovsky promoted the idea of catastrophism in an era that rejected the premise. Even a guy in his backyard can see it today.
...we WERE....
...we were left with Neanderthals....
And I was impressed with Meteor crater in AZ!
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