Prehistoric Giant Tsunami - Killed EVERYTHING!

(Courtesy NatGeo & Newswise)

Scientists have found traces of an asteroid-collision event that they say would have created a giant tsunami that swept around the Earth several times, inundating everything except the mountains. The coastline of the continents was changed drastically and almost all life on land was exterminated.

This cataclysm some 3.5 billion years ago is the earliest known meteor strike to hit the Earth, and one of at least four that have been identified in a geologically brief 300-million-year period. The strike is the subject of an article published in the current issue of the journal Science by Louisiana State University geologist Gary Byerly and others.

Byerly and Xiaogang Xie, also of LSU, and Donald Lowe and Joseph Wooden of Stanford, identified traces of the event in some of the oldest known rocks on Earth—in South Africa and northwest Australia.

When the asteroid hit, it was vaporized by the extreme energy of the impact. Condensation of this vapor produced droplets of melt, called spherules, which dropped into the roiling sea over the next few days and were deposited in layers on the sea floor.

Byerly said it was not known where the meteor hit, but it was probably some distance from where they found the spherules and probably in water rather than on land. He deduced this because the composition of the spherules lacked the mineral composition that would have been expected from vaporization of the continental crust, and because there was even more water covering the surface of the Earth then than there is today.

Byerly illustrated with a slab of grayish rock about the size of a large hand. In it could be seen layers of spherules interlaced with layers of finer sand or silt. "It would take about 30 hours from impact for the tsunami to travel all the way around the world. Then, of course, it wouldn't stop, but bounce all the way back till it met itself 30 hours later, then bounce the other way again, setting up a harmonic." Several thin layers of mud within the spherule layer represent periods of quiet sedimentation between the arrival of tsunami waves.

The water would likely have inundated everything but the mountains, Byerly said, and drastically eroded the continental land masses, changing their coastlines dramatically. The heat of the impact would have evaporated the upper 30 to 300 feet of water in the oceans. It would also have killed everything, or almost everything, that was alive at that time on land or near the ocean surface.

"There was almost certainly life at this time. Primitive, bacterial life, and if the impacts were made by a meteor 20 miles in diameter, they would have killed everything on the surface of the Earth," he said. First a hot steam of molten rock and water would have withered most life, then the massively destructive tsunamis would have destroyed even more. After that, years of incredibly cold winters, caused by particles in the atmosphere blocking out the sun, would have conspired to kill nearly everything else.

"Anything that survived would have been in deep rocks or below the surface of the Earth," he said.

Byerly first came upon evidence of these impacts by chance in 1984 while he was studying ancient volcanism in Australia and South Africa. He published his first paper on them in 1986. This year alone he and his team will have four papers published on the subject. It is now generally accepted that the inner solar system was battered twice by massive meteor impacts of mysterious origin.

"It is assumed that the solar system was created by a cloud of dust and rocks that condensed into the sun and planets, with larger and larger chunks falling in near the end. This process would have finished about 4.5 billion years ago.

"But about 3.8 billion years ago the inner solar system was torn up by some cataclysmic event. The evidence is found in the crater basins on the moon and Mars and Venus." The Earth was probably heavily battered at that time too, but since the oldest known surface rocks on Earth are about 3.5 billion years old, no evidence of that exists, Byerly said.

A second battering took place 3.5 billion years ago, and it is this event that left the record in the rocks Byerly is studying. This was a smaller series of impacts with a gradual dropoff rate, he said. That the 3.8 billion-year-old event occurred is accepted by most scientists, and Byerly's work is substantiating the existence of the second, which, up to now, has not been as well accepted.

Byerly and his team have been able to date the event very accurately using an instrument at Stanford that measures the decay of uranium into lead. The uranium was found in zircons at both the Australian and South African sites and was dated to within 2 million years of 3.47 billion years ago. The fact that zircons of identical ages were found in impact strata on two continents shows the worldwide effects of the impact, Byerly said.

The zircons were not created by the impact but probably by volcanic action and deposited in the impact layers when the tsunami washed over the land.

These massive, early impacts were similar to the one that killed the dinosaurs 65 million years ago. But, they were hundreds to thousands of times more powerful. Probabilities for a similar impact today are predicted to be about one such strike every 100 million years.

"What that means is, eventually there will be another such event. We know that large asteroids get disturbed by interactions with Jupiter and fall into Earth's orbit. When that happens they will strike the Earth. We can't say when it will happen but we can say for certain that it will happen," Byerly said.

The evidence is on a small, grayish slab of rock on his desk.

Copyright 2002 Newswise

ASTEROID ASSETS

Ominous Arctic Melt Worries Experts - Dooms Day is here... Sooner than expected... Is this theh POINT OF NO RETURN???

Ominous Arctic Melt Worries Experts
By SETH BORENSTEINAP Science Writer
AP Photo/JOHN MCCONNICO
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Ominous Arctic Melt Worries Experts

WASHINGTON (AP) -- An already relentless melting of the Arctic greatly accelerated this summer, a warning sign that some scientists worry could mean global warming has passed an ominous tipping point. One even speculated that summer sea ice would be gone in five years.
Greenland's ice sheet melted nearly 19 billion tons more than the previous high mark, and the volume of Arctic sea ice at summer's end was half what it was just four years earlier, according to new NASA satellite data obtained by The Associated Press.
"The Arctic is screaming," said Mark Serreze, senior scientist at the government's snow and ice data center in Boulder, Colo.
Just last year, two top scientists surprised their colleagues by projecting that the Arctic sea ice was melting so rapidly that it could disappear entirely by the summer of 2040.
This week, after reviewing his own new data, NASA climate scientist Jay Zwally said: "At this rate, the Arctic Ocean could be nearly ice-free at the end of summer by 2012, much faster than previous predictions."
So scientists in recent days have been asking themselves these questions: Was the record melt seen all over the Arctic in 2007 a blip amid relentless and steady warming? Or has everything sped up to a new climate cycle that goes beyond the worst case scenarios presented by computer models?
"The Arctic is often cited as the canary in the coal mine for climate warming," said Zwally, who as a teenager hauled coal. "Now as a sign of climate warming, the canary has died. It is time to start getting out of the coal mines."
It is the burning of coal, oil and other fossil fuels that produces carbon dioxide and other greenhouse gases, responsible for man-made global warming. For the past several days, government diplomats have been debating in Bali, Indonesia, the outlines of a new climate treaty calling for tougher limits on these gases.
What happens in the Arctic has implications for the rest of the world. Faster melting there means eventual sea level rise and more immediate changes in winter weather because of less sea ice.
In the United States, a weakened Arctic blast moving south to collide with moist air from the Gulf of Mexico can mean less rain and snow in some areas, including the drought-stricken Southeast, said Michael MacCracken, a former federal climate scientist who now heads the nonprofit Climate Institute. Some regions, like Colorado, would likely get extra rain or snow.
More than 18 scientists told the AP that they were surprised by the level of ice melt this year.
"I don't pay much attention to one year ... but this year the change is so big, particularly in the Arctic sea ice, that you've got to stop and say, 'What is going on here?' You can't look away from what's happening here," said Waleed Abdalati, NASA's chief of cyrospheric sciences. "This is going to be a watershed year."
2007 shattered records for Arctic melt in the following ways:
- 552 billion tons of ice melted this summer from the Greenland ice sheet, according to preliminary satellite data to be released by NASA Wednesday. That's 15 percent more than the annual average summer melt, beating 2005's record.
- A record amount of surface ice was lost over Greenland this year, 12 percent more than the previous worst year, 2005, according to data the University of Colorado released Monday. That's nearly quadruple the amount that melted just 15 years ago. It's an amount of water that could cover Washington, D.C., a half-mile deep, researchers calculated.
- The surface area of summer sea ice floating in the Arctic Ocean this summer was nearly 23 percent below the previous record. The dwindling sea ice already has affected wildlife, with 6,000 walruses coming ashore in northwest Alaska in October for the first time in recorded history. Another first: the Northwest Passage was open to navigation.
- Still to be released is NASA data showing the remaining Arctic sea ice to be unusually thin, another record. That makes it more likely to melt in future summers. Combining the shrinking area covered by sea ice with the new thinness of the remaining ice, scientists calculate that the overall volume of ice is half of 2004's total.
- Alaska's frozen permafrost is warming, not quite thawing yet. But temperature measurements 66 feet deep in the frozen soil rose nearly four-tenths of a degree from 2006 to 2007, according to measurements from the University of Alaska. While that may not sound like much, "it's very significant," said University of Alaska professor Vladimir Romanovsky.
- Surface temperatures in the Arctic Ocean this summer were the highest in 77 years of record-keeping, with some places 8 degrees Fahrenheit above normal, according to research to be released Wednesday by University of Washington's Michael Steele.
Greenland, in particular, is a significant bellwether. Most of its surface is covered by ice. If it completely melted - something key scientists think would likely take centuries, not decades - it could add more than 22 feet to the world's sea level.
However, for nearly the past 30 years, the data pattern of its ice sheet melt has zigzagged. A bad year, like 2005, would be followed by a couple of lesser years.
According to that pattern, 2007 shouldn't have been a major melt year, but it was, said Konrad Steffen, of the University of Colorado, which gathered the latest data.
"I'm quite concerned," he said. "Now I look at 2008. Will it be even warmer than the past year?"
Other new data, from a NASA satellite, measures ice volume. NASA geophysicist Scott Luthcke, reviewing it and other Greenland numbers, concluded: "We are quite likely entering a new regime."
Melting of sea ice and Greenland's ice sheets also alarms scientists because they become part of a troubling spiral.
White sea ice reflects about 80 percent of the sun's heat off Earth, NASA's Zwally said. When there is no sea ice, about 90 percent of the heat goes into the ocean which then warms everything else up. Warmer oceans then lead to more melting.
"That feedback is the key to why the models predict that the Arctic warming is going to be faster," Zwally said. "It's getting even worse than the models predicted."
NASA scientist James Hansen, the lone-wolf researcher often called the godfather of global warming, on Thursday was to tell scientists and others at the American Geophysical Union scientific in San Francisco that in some ways Earth has hit one of his so-called tipping points, based on Greenland melt data.
"We have passed that and some other tipping points in the way that I will define them," Hansen said in an e-mail. "We have not passed a point of no return. We can still roll things back in time - but it is going to require a quick turn in direction."
Last year, Cecilia Bitz at the University of Washington and Marika Holland at the National Center for Atmospheric Research in Colorado startled their colleagues when they predicted an Arctic free of sea ice in just a few decades. Both say they are surprised by the dramatic melt of 2007.
Bitz, unlike others at NASA, believes that "next year we'll be back to normal, but we'll be seeing big anomalies again, occurring more frequently in the future." And that normal, she said, is still a "relentless decline" in ice.
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On the Net:
National Snow and Ice Data Center on 2007 Arctic sea ice:
http://nsidc.org/news/press/2007-seaiceminimum/20070810-index.html
NASA's "Tipping Points" panel and slide show materials:
http://www.nasa.gov/topics/earth/tipping-points.html
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Source: WIRED.COM - CondéNet, Inc

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