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TOPIC: Extinction
Blobrana


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Shiva crater
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Ironically, it was while he was investigating the Deccan Traps that Chatterjee came across the evidence for Shiva. First, he found dinosaur nests that had been built between lava flows 33 to 49 feet thick -- evidence that the animals were coping well with the volcanic activity rather than being weakened by it. Then, quite suddenly, 65 million years ago, a layer of lava nearly 1.2 miles thick appears. This led him to wonder what could possibly have caused such a sudden volcanic surge.
He knew that the west coast of India had been the site of an ancient impact of unknown age and size. It was not until he was reading through a paper published by an oil company that had collected geological information in the area that he realised the volcanic surge he had seen might be related to a cosmic collision.
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Blobrana


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RE: Extinction
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A huge Siberian volcano destroyed the world's forests 250 million years ago in what scientists say was the worst extinction event the planet has ever witnessed, new research has disclosed.

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Blobrana


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The chunks of ice and dust that make their home in the Oort cloud, far beyond the orbit of Pluto, sometimes become dislodged and head into the solar system as streaky comets. Some disruptions, caused by passing stars and other interactions with the Milky Way galaxy, are severe enough to send Oort comets into orbits that buzz or even collide with Earth. New simulations have revealed a novel mechanism for their entry into our part of the solar system, a method that also suggests that comet showers may not have been strongly involved in major extinctions on Earth.

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Blobrana


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Dodo skeleton on show at World Museum Liverpool
The phrase "dead as a dodo" is proverbial for anything lifeless or extinct.
But now visitors to World Museum Liverpool can get an idea of what this near-mythical creature looked like after a rare dodo skeleton was put on display.

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Blobrana


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A dinosaur-killing asteroid may have wiped out much of life on Earth 65 million years ago, but now scientists have discovered how smaller organisms might have survived in the darkness following such a catastrophic impact.
Survival may have depended upon jack-of-all-trades organisms called mixotrophs that can consume organic matter in the absence of sunlight. That would have proved crucial during the long months of dust and debris blotting out the sun, when plenty of dead or dying organic matter filled the Earth's oceans and lakes.

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Blobrana


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Cosmic rays pour down on Earth like a constant rain. We don't much notice these high-energy particles, but they may have played a role in the evolution of life on our planet.
Some of the mass extinctions identified in the fossil record can be linked to an asteroid impact or increased volcanism, but many of the causes of those ancient die-offs are still open for debate.

"There may have been nearby astronomical goings-on that drastically increased the radiation on Earth" - Brian Fields from the University of Illinois.

A supernova going off 30 light years away could cause such a jump in radiation on our planet that could directly, or indirectly, wipe out huge numbers of species. Currently researchers are looking for possible evidence for this sort of cosmic foul play.

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Blobrana


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10 signs of a rough and tough universe
The space rock that recently ploughed into Jupiter and gave it a black eye the size of the Pacific Ocean served up a not-so-gentle reminder of the rough and tough side of our universe.

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Blobrana


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Extinction events
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Whole "chunks of life" are lost in extinction events, as related species vanish together, say scientists.
A study in the journal Science shows that extinctions tend to "cluster" on evolutionary lineages - wiping out species with a common ancestor.
The finding is based on an examination of past extinctions, but could help current conservation efforts.
Researchers say that this phenomenon can result in the loss of an entire branch of the "tree of life".

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Blobrana


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Extinction
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Should we be told if a monster rock is heading our way?

Researchers wrestled with this question at the annual meeting of the American Association for the Advancement of Science (AAAS) in Denver .
Some suggested there was no point worrying the global population about its imminent demise.
"If there is absolutely nothing you can do about it - you can't intercept it, you can't move people out of the way - then it makes no sense to incur social costs from whatever panic or overreaction there will be," argued Geoffrey Sommer, of the Rand Corporation, who has been studying how policymakers should react and prepare for Armageddon.
"If an extinction-type impact is inevitable, then ignorance for the populace is bliss."

But hang on, don't we have right to know?

I'd certainly want to know and it's not up to some bureaucrat to keep that from me.
People tend to react well in a crisis. "The single most important reason there were not more casualties at the World Trade Centre collapse was because there was no panic. It does happen - there are soccer stampedes and the like - but it is very rare."
The possibility of a major impact from space is a certainty. The geological record shows the Earth has been hit many times by large objects - some of which have come close to wiping life, clean from the face of the planet.
It is a fact that 95% of all the species that have ever existed are now extinct...
We will be hit again by objects much greater than one kilometre across - although it may not happen for tens, hundreds or even thousands of years.
Just remember, the probability of being hit is 100%


Engage!


According to current models, the amount of atmospheric dust loading after very large impacts is still very uncertain. The main killing agent may be the global ejecta fallout and the ensuing thermal pulse, popularly described as the "broiling effect". Other effects may be ozone depletion resulting from NO, H2O, and sea salt injected high into the atmosphere as a result of the impact, where global health concerns might arise for impacts smaller than the "global threshold" hitherto estimated are, however, very preliminary.
For smaller impacts that cause only regional damage, the main killing agent may be the destructive effects of impact-induced tsunami waves. Different models have yielded very differing results; one of the main issues is whether these waves break at the edge of the continental shelf.

.Engage!

The Space guard Survey, conducted by the US space agency (Nasa), is looking for these big rocks with wide-field telescopes.
In the space out to about 200 million km, it has so far found about 650 "monsters" - none of which have orbits that pose a threat to the Earth. There is possibly a similar figure of undiscovered one-km-plus-sized rocks in the same region of space that have yet to be tracked down.
If a threatening object is found, many researchers are confident Earth will have the time and the technology to do something about it.

"We've landed a spacecraft on an asteroid; we have thrusting devices. We don't need a bomb. We could push on it and push it out of the way. It would take a while but we could deal with it. The real problem arises with comets that come from the deep, dark reaches of the outer Solar System." - Clark Chapman , asteroid scientist from the Southwest Research Institute.

We don't see them until they get to Jupiter and they're in the vicinity of the Earth within a few months or a year after that. Perhaps there won't be enough time to deal with that."
All are agreed that proper disaster plans need to be put in place now and that the public needs to be educated about the real threat and how we might cope.
Every year, a small asteroid explodes in the Earth's atmosphere with an energy equivalent to 5,000 tonnes of TNT.

"Stuff comes in and it blows up. This sort of thing needs to be common knowledge." - Lee Clarke

Engage!
spacer.gif Earth periods

Mass extinctions

With surprising and mysterious regularity, life on Earth has flourished and vanished in cycles of mass extinction every 62 ± 3 million years.
The pattern emerges from a computer study of fossil records going back for more than 542 million years, to the time of the great Cambrian Explosion, when almost all the ancestral forms of multicellular life emerged.
The fossil records in Sepkoski's compendium cover the first and last known appearances of 36,380 separate marine genera, including millions of species that once thrived in the world's seas.
The cycles are so clear that the evidence "simply jumps out of the data."
It had been suggested that a faraway dwarf star, named "Nemesis", was orbiting the sun, or an unknown "Planet X" somewhere far out beyond the solar system that's disturbing the comets in the distant region called the Oort Cloud and might be possible causes for the 62-million-year cycles.
Or perhaps there's some kind of "natural timetable" deep inside the Earth that triggers cycles of massive volcanism. There's even a bit of evidence: A huge slab of volcanic basalt known as the Deccan Traps in India has been dated to 65 million years ago just when the dinosaurs died, he noted. And the similar basaltic Siberian Traps were formed by volcanism about 250 million years ago, at the end of the Permian period, when the greatest of all mass extinctions drove more than 70 percent of the entire world's marine life to death.
Anther far-out ideas is that the solar system passes through an exceptionally massive arm of our own spiral Milky Way galaxy every 62 million years, and that that increase in galactic gravity might set off a hugely destructive comet shower that would drive cycles of mass extinction on Earth.

Here are details of the five worst mass extinctions in Earths history and their possible causes:
Cretaceous-Tertiary extinction, about 65 million years ago, probably caused or aggravated by impact of a several-mile-wide asteroid that created the Chicxulub crater now hidden on the Yucatan Peninsula and beneath the Gulf of Mexico. Some argue for other causes, including gradual climate change or flood-like volcanic eruptions of basalt lava from Indias Deccan Traps. The extinction killed 16 percent of marine families, 47 percent of marine genera (the classification above species) and 18 percent of land vertebrate families, including the dinosaurs.

The Jurassic-Cretaceous boundaries, 144.6 +/- 0.8 million years before present may, or may not, involve a major impact event. An article on the "Discovery of distal ejecta from the 1850 Ma Sudbury impact event," which is "the second largest and third or fourth oldest extraterrestrial Earth impact site," says that "The debris (ejecta), landed 650 km west northwest of Sudbury near Thunder Bay, Ontario, Canada, and 875 km west of Sudbury near Hibbing, Minnesota, United States."

End Triassic extinction, roughly 199 million to 214 million years ago, most likely caused by massive floods of lava erupting from the central Atlantic magmatic province -- an event that triggered the opening of the Atlantic Ocean. The volcanism may have led to deadly global warming. Rocks from the eruptions now are found in the eastern United States, eastern Brazil, North Africa and Spain. The death toll: 22 percent of marine families, 52 percent of marine genera. Vertebrate deaths are unclear.

Permian-Triassic extinction, about 251 million years ago. Many scientists suspect a comet or asteroid impact. Others believe the cause was flood volcanism from the Siberian Traps and related loss of oxygen in the seas. Still others believe the impact triggered the volcanism and also may have done so during the Cretaceous-Tertiary extinction. The Permian-Triassic catastrophe was Earths worst mass extinction, killing 95 percent of all species, 53 percent of marine families, 84 percent of marine genera and an estimated 70 percent of land species such as plants, insects and vertebrate animals. researchers discovered tiny capsules of cosmic gas trapped inside rocks from the Permian-Triassic, deposited by a space rock colliding with the planet. Isotopes of helium and argon gases commonly found in space were found within buckyballs or fullerenes (sphere of carbon atoms).
Researchers funded by NASA and the National Science Foundation have located the site of an impact crater.

spacer.gif impact

Asteroid impact

The Bedout crater (pronounced Bedoo) is believed to be associated with the largest extinction event in Earth's history about 251 million years ago; caused by an asteroid roughly 6 to 12 kilometres wide...
Permian-Triassic impact on the giant landmass, called Pangaea, was the most severe mass extinction in the history of life on Earth. They used a new extraterrestrial tracer, fullerene; a third form of carbon besides diamond and graphite. .

Late Devonian extinction, about 364 million years ago, cause unknown. It killed 22 percent of marine families and 57 percent of marine genera. Little is known about land organisms at the time.

Ordovician-Silurian extinction, about 439 million years ago, caused by a drop in sea levels as glaciers formed, then by rising sea levels as glaciers melted. 25 percent of marine families and 60 percent of marine genera became extinct.

-- Edited by Blobrana on Saturday 8th of August 2009 09:17:44 AM

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Blobrana


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Extinction Runs in the Family
Global calamities like the one that doomed most dinosaurs forever alter the varieties of life found on Earth. But new research shows that it doesn't take a catastrophe to end entire lineages.
An analysis of 200 million years of history for marine clams found that vulnerability to extinction runs in evolutionary families, even when the losses result from ongoing, background rates of extinction.

"Biologists have long suspected that the evolutionary history of species and lineages play a big role in determining their vulnerability to extinction, with some branches of the tree of life being more extinction-prone than others. Now we know that such differential loss is not restricted to extinctions driven by us but is a general feature of the extinction process itself" - Kaustuv Roy, a biology professor at the University of California, San Diego.

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