What Really Did Kill The Dinosaurs?

akaWiintermoon

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Taken from AOL news (No link, sorry, members only access.)

DINOSAUR EXTINCTION THEORY BLOWN APART

NEW dinosaur discoveries have blown apart the theory that the reptiles died out as the result of a giant meteorite striking Earth.

Scientists had thought a single impact off the coast of Venezuela may have been responsible for the dinosaurs' demise.

But new evidence shows one well-known 15 mile wide meteor crater in the Ukraine had been wrongly dated.

And the discovery throws the extinction debate wide open again.

However, the leading theory is still meteor-based - but now experts believe many smaller impacts were to blame instead of one Deep Impact-style collision.

Leading US geoscientist Dr Gerta Keller said: "A tremendous amount of new data has been accumulated over the past few years that points in the direction of multiple impacts."

Other slightly less convincing extinction theories include:

-- Aliens landed on Earth and brought a killer cosmic virus with them;

-- Smaller mammals killed them off by eating their eggs;

-- Volcanic eruptions made the atmosphere unbreathable;

-- Some religions believe they never existed and in fact the fossilised bones were placed there by God.
 

Beakmoo

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As I read it in the Metro (ha! science reporting in the Metro, I must be insane), they now reckon that instead of just the one meteor strike, there were several, including the S American one they originally fancied done it. Which kind of strengthens the meteor-strike theory. Though I've always favoured the basalt lava theory myself.
 

oll_lewis

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It was the result of meterite impact and lava flows, at least thats the opinion of one of my lecturers (dr Alan Turner) who did the consultacy work for walking with mammals and channal 4's 'extinct' :)
(Part of the oll lewis name drop series #6)
 
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Anonymous

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I've always thought that the extinction was caused by a variety of factors,not just one or two things.I believe this idea is rather more accepted by some scientists,but popular writers in the last few years have become obsessed with the Chicxulub Crater.

I think humans in general are usually trying to oversimplify complex issues instead of looking for complexity.It's the way the human brain appears to be wired.
 
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Anonymous

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I favour the more complex, combination-of-factors theories myself, but the spectacular single event idea no doubt appeals more to a world which cannot grasp the immensity of history.
And now we've had this single event explanation propounded with such certainty that any denial or amendment would almost amount to a complete paradigm shift.
I think, once again, the truth has to struggle against the simple explanation.
 

MrSnowman

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Would it be acceptable to suggest that the dinosaurs could possibly have been quite highly evolved, and managed to destroy themselves in some kind of nuclear (or advanced weaponry of which we know little) war? (Ref. a Future Shock in 2000ad many years ago, and an episode of ST:Voyager)

Was it also in an issue of FT a couple of years back, that archaeologists discovered strata in various parts of the world which were covered in sheet glass, which could only have occurred during the supposed time of their creation by a fission reaction?

Apologies if I'm completely off the mark :(
 
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Snowman X said:
Would it be acceptable to suggest that the dinosaurs could possibly have been quite highly evolved, and managed to destroy themselves in some kind of nuclear (or advanced weaponry of which we know little) war? (Ref. a Future Shock in 2000ad many years ago, and an episode of ST:Voyager)

Was it also in an issue of FT a couple of years back, that archaeologists discovered strata in various parts of the world which were covered in sheet glass, which could only have occurred during the supposed time of their creation by a fission reaction?

Apologies if I'm completely off the mark :(

Actually Snowman, I've often wondered that myself, although there is of course no evidence. But why shouldn't a species of dinosaur have evolved to a similar level of intelligence as ourselves? Who knows. Maybe they did and hunted the other big dinosaurs to extinction before fnally being wiped out themselves by a meterorite strike.

But generally I think it was a combination of factors - primarily climate change which was probably linked to the Deccan Traps basaltic eruptions, with (as now seems the case) a series of meteorite strikes adding to problems until a final meteorite laid the final blow c65mya

Thats of course until new evidence presents a new theory......

btw it was once suggested that the Chicxulub impact triggered the Deccan Traps, but the timing didn't match. Maybe if there was a series of strikes over several 100,000 years then the 1st strike started the basalt eruptions and the last one finished off the dinosaurs once and for all?
 

mejane

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Prospect said:
---
btw it was once suggested that the Chicxulub impact triggered the Deccan Traps, but the timing didn't match. Maybe if there was a series of strikes over several 100,000 years then the 1st strike started the basalt eruptions and the last one finished off the dinosaurs once and for all?

A very good point. Most "popular science" programmes give the impression that the dinos where wiped out almost overnight, but the fossil record (which is the only record we have) shows that some at least survived for several hundred thousand years - it could be argued that some still survive, eg crocodiles/alligators; Komodo dragons; coelacanth (okay, the last one is a fish, but a very odd and old fish!).

Snowman's idea of intelligent (using the term loosely) dinos who blew themselves up is also interesting, but IMHO is not supported by the available evidence. The glass strata, for example, could be explained by volcanic eruptions. T-Rex and friends also didn't have opposible (sp?) thumbs which would have made tool-making hard...

But then, what do I know? Maybe aliens planted the fossils when they terraformed the planet (was that a Terry Pratchett book?)

Jane.
 

Spookyangel

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mejane said:
Snowman's idea of intelligent (using the term loosely) dinos who blew themselves up is also interesting, but IMHO is not supported by the available evidence. The glass strata, for example, could be explained by volcanic eruptions. T-Rex and friends also didn't have opposible (sp?) thumbs which would have made tool-making hard...Jane.

I remember seeing a TV prog ages back that showed a theoretical version of "early man" had the dinosaurs survived. Just say they found fossils to prove that theory correct? Probably not likely, but interesting thought!

I find it hard to believe that one meteor could destroy them all over the world apart from a few species.
It it was poisonous gases, then why would some species survive? I'm just wondering becaude I don't understand that part.
 
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mejane said:
The glass strata, for example, could be explained by volcanic eruptions.

Yes, but not the Iridium in the K-T layer which is very likely to have come from a metal-rich meteor, this metal gets more abundant as you get closer to the sun I believe, so probably came form a perisolar body of some sort. Just possibly it might have come from deep volcanism, as there is quite abit in the earth's core, evidently.
Anyway, the combo theory is probably right, as the world was undergoing a lot of basaltic eruption in India so the atmosphere would have been full of dust and sulphur but particularly carbon dioxide.This would have put the biosphere under so much stress that there would have been a mass extinction anyway.
Perhaps the meteor tipped the balance between a mass extinction that would remove many families of dinosaurs, like that between say the Jurassic and the Cretaceous, and a full blown mega extinction where you lose them all .
Some people say that the compression waves in the Galaxy spiral structure had something to do with it, so who knows.
steve b
 

James_H

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mejane said:
But then, what do I know? Maybe aliens planted the fossils when they terraformed the planet (was that a Terry Pratchett book?)

Jane.
Douglas adams, deary


I have recently liked the theory that the dinos got technologically advanced and wiped emselves out, as we are to do tomorrow

do bones petrify better than machine parts? i can't imagine a tractor or some scissors lasting 65 million years
 

Spookyangel

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I guess we couldn't know if they last though, could we? I mean if they could last, that means the dinosaurs didn't have them, and if they couldn't the dinosaurs might have had them, but we can't tell.
Does that make the slightest bit of sense to anyone? Thought not.
 

oll_lewis

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Faggus said:
Douglas adams, deary


I have recently liked the theory that the dinos got technologically advanced and wiped emselves out, as we are to do tomorrow

do bones petrify better than machine parts? i can't imagine a tractor or some scissors lasting 65 million years

Doglas adams might have but terry pratchett also used this idea in his book "Strata".

Faggus:
because of rusting of metals (some take hundreds of years to corrode and others less than a year) you would only find 'fossils' of metalic objects as lagarslatten in peat bogs etc.
When metalic instrements are found by archeologists from say, the iron age the items are nearly all corroded to preserve metal items you nead a lack of some factor involved in the corrosion process, this is why the lack of oxigen in peat is perfect for preservation.


Spooky:
I think I remember that program, wasn't the 'man' kind of grey-green in colour?
 

Spookyangel

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Oll_Lewis said:
Spooky:
I think I remember that program, wasn't the 'man' kind of grey-green in colour?

Yes, he was, with huge eyes.
 

DerekH16

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mejane said:
.... T-Rex and friends also didn't have opposible (sp?) thumbs which would have made tool-making hard.......

Since we only know T-Rex from less than a dozen examples (if memory serves...), and these are spread over millions of years, there may well have been 'dinosaurs' with opposable thumbs that we haven't discovered yet. A few hundred million years of plate tectonics/vulcanism/weather etc. would make finding traces of them (or their civilisation?) pretty difficult.
 
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Oll_Lewis said:
When metalic instruments are found by archeologists from say, the iron age the items are nearly all corroded

to preserve metal items you nead a lack of some factor involved in the corrosion process, this is why the lack of oxygen in peat is perfect for preservation.
Yes, this is true of any metal except perhaps gold. Then again a small soft golden artifact might get so distorted that it would just look like a lump of native metal.

Flints and stone tablets should survive, so the dinomen would have to have skipped the stone age seeing as these have not been found in context AFAIK

Plastic would degrade to oil.
When the alien archaeologists come to earth in sixty million years all they will find is achelian handaxes, microliths and with luck the Rosetta stone.
Steve b
 

mejane

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DerekH said:
Since we only know T-Rex from less than a dozen examples (if memory serves...), and these are spread over millions of years, there may well have been 'dinosaurs' with opposable thumbs that we haven't discovered yet. A few hundred million years of plate tectonics/vulcanism/weather etc. would make finding traces of them (or their civilisation?) pretty difficult.

True. There is also no guarantee that we are putting the fossils that we do have together correctly - I don't know much about palaentology, but I'm guessing that the remains of these huge beasts are not found complete but in pieces which have to be painstakingly put back together.

Anyway, it's very anthropocentric of me to think opposable thumbs are necessary - other modern animals are capable of making and using tools (badgers, octopusi, etc) without this adaptation.

Jane.
 

Mighty_Emperor

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Double whammy link to extinctions

By Paul Rincon
BBC News Online science staff

The chances that asteroid impacts and huge bouts of volcanism coincide randomly to cause mass extinctions may be greater than previously imagined.

UK researchers conducted statistical tests to determine the probability of such catastrophic events happening at the same time in Earth history.

They found massive releases of lava and space collisions should have overlapped three times in the last 300 million years.

Details will be published in a future issue of the geological journal Lithos.

The idea that [flood basalts and impacts] could be purely coincidental is rather a negative one - a null hypothesis - but it strikes me as quite reasonable
Prof Tony Hallam, University of Birmingham

The work has been done by Dr Rosalind White and Professor Andy Saunders of the University of Leicester.

The probabilities they calculated assumed there was no causal link between the two phenomena - that impacts from space did not set off the volcanism.

Smoking guns

Flood basalts, as the term suggests, are formed by massive outpourings of lava from beneath the Earth. Hundreds of thousands of cubic km of material can be spewed on to the surface in short geological timescales.

These eruptions have, like space impacts, been blamed for some of Earth's mass extinctions due to the environmental changes they may trigger.

Over a million cubic km of lava erupted on to surface

Event occurred over several hundred thousand years
The Leicester authors contend that because impacts and flood basalts occur more frequently than mass extinctions, it is unlikely the two phenomena bring about mass extinctions on their own.

However, mass extinctions may be triggered when the two events occur together, they argue.

There is evidence of both phenomena happening at the same time 65 million years ago, when the dinosaurs disappeared from the fossil record. The impact that created the 180km-wide impact crater at Chicxulub in Mexico is generally thought to have played a major part in this extinction.

But some experts think the flood basalts known as the Deccan Traps in India are an alternative "smoking gun". The gases released in this volcanic event would have resulted in major climate changes.

Impact trigger

Firstly, the Leicester scientists determined the probability that a flood basalt would coincide with a Chicxulub-sized crater.

They found the probability of this happening at least once over a period of 300 million years was 57%.

Once the researchers reduced the size of the impact slightly, the probabilities increased sharply.

For craters exceeding 100km, the probability of at least three co-occurrences between flood basalts and impacts was 46%. For craters exceeding 60km, the probability of three or more was 97%.

Professor Saunders and Dr White point out that impacts and flood basalt volcanism have been implicated in three major mass extinctions in the past.

Some researchers, such as Professor David Price, of University College London, argue that asteroid impacts can themselves bring on catastrophic volcanism.

Professor Price says there is geochemical evidence to suggest an impactor started the Siberian trap flood basalts, which are associated with the end-Permian mass extinction 251 million years ago.

"I wouldn't be very convinced by the robustness of any statistical analysis when you're dealing with just half a dozen events in the last billion years," Professor Price told BBC News Online.

'Kill mechanism'

He also points to evidence uncovered by Professor Mike Coffin, of the University of Texas at Austin, which shows the Ontong Java Plateau - a submarine flood basalt in the western Pacific Ocean thought to be the world's largest - was initiated by the impact of a 20km object from space.

The Leicester researchers say the idea of impacts causing massive volcanism is interesting, but no causal link has been proven.

"In the case of the Ontong Java Plateau, we would expect such a large impact to have left lots of signs in the geological record, but none have been found," Dr White said.

Professor Tony Hallam, of the University of Birmingham, commented: "The idea that [flood basalts and impacts] could be purely coincidental is rather a negative one - a null hypothesis - but it strikes me as quite reasonable."

Dr White and Professor Saunders propose in their paper that the "kill mechanisms" associated with flood basalts or impacts by themselves are not sufficiently powerful to cause the worldwide collapse of ecosystems - a point disputed by many other scientists.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/3582767.stm

Published: 2004/04/01 15:57:26 GMT

© BBC MMIV

Also some discussion of this here:

http://www.forteantimes.com/forum/showthread.php?s=&threadid=13328&highlight=dinosaur+extinction

Flood baslats also get a mention in the Supervolcano thread.

Emps
 

MeteorMaker

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Maybe their Creator was simply more efficient than our Creator in finding a way to deal with the wickedness on earth.

One thing, with a bearing on another thread: If a dinosaur species actually managed to become the masters of the planet through intelligence and technology, wouldn't it be littered with their tombs? Wouldn't there be satellites still in orbit with the reptilian equivalent of Walt Disney et deep-frozen al?
 

sunsplash1

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It was a Nephilm (sp?) piloting a spaceship that impacted on a shallow sea...
:)
 

OneWingedBird

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Wouldn't there be satellites still in orbit with the reptilian equivalent of Walt Disney et deep-frozen al?

I've no idea how long a sattellite in a 'stable' orbit can last for, or if even the stablest orbit would have decayed after 65 million years, though it would have been funny if the Mars lander had discovered a lander from a previous civilisation.

An interesting problem that IIRC was pointed out to Walter Miller after he wrote A Canticle for Leibowitz is that if there had been a technologically advanced culture before ours, then most of the mineral resources would have been mined out of the Earth's crust.

They'd still be around in some form (possibly oxides in the soil after all our cars have rusted to nothing) but without them being present as ores it's questionable as to wether you could have a second bronze or iron age.
 

Seminole10

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I have no idea what actually led to the extinction. I have always been a bit skeptical of the meteor theory however.

Perhaps the terrestrial forms might have been wiped out by such an event. It is difficult to understand exactly how the after effects of an asteroid strike could selectively and completely wipe out all marine dinosaur species ,while at the same time, leaving other species like sharks largely unaffected and able to continue to the present era.
 

Mighty_Emperor

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Lack of females?

Lack of females may have done in dinosaurs - study

21 April 2004


WASHINGTON: An asteroid may have wiped out the dinosaurs 65 million years ago not simply by changing the world's climate and causing years of dark skies, but also by causing too many of them to be born male, US and British researchers said today.


If dinosaurs were like modern-day reptiles such as crocodiles, they change sex based on temperature, David Miller of the University of Leeds in Britain and colleagues noted. And even a small skewing of populations toward males would have led to eventual extinction.

Most experts agree that one or more asteroid impacts probably triggered a series of global changes that killed off the dinosaurs and many other species of life on Earth.

The impacts would have kicked up dust that cooled the air and also triggered volcanic activity that would have created even more dust and ash.

No one really knows if dinosaurs were more like reptiles, or something closer to mammals. Reptiles have very different metabolisms than mammals and also have various ways of determining the sex of offspring.

In mammals, if a baby gets an X and a Y chromosome, it will be male and if it gets two X chromosomes it will be female, with a few very rare exceptions. Similar mechanisms work for birds, snakes and some reptiles such as lizards.

In crocodiles, turtles and some fish, the temperature at which eggs are incubated can affect the sex of the developing babies.

Miller's team ran an analysis that showed a temperature shift could theoretically have led to a preponderance of males. Other studies have shown that when there are too few females, eventually the population dies out.

"The earth did not become so toxic that life died out 65 million years ago; the temperature just changed, and these great beasts had not evolved a genetic mechanism (like our Y chromosome) to cope with that," said Dr Sherman Silber, an infertility expert in St. Louis who worked on the study.

However, crocodiles and turtles had already evolved at the time of the great extinction 65 million years ago. How did they survive?

"These animals live at the intersection of aquatic and terrestrial environments, in estuarine waters and river beds, which might have afforded some protection against the more extreme effects of environmental change, hence giving them more time to adapt," the researchers wrote.

http://www.stuff.co.nz/stuff/0,2106,2881926a4560,00.html
 

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New Theory

Fewer females wiped out dinosaurs

By Dr David Whitehouse
BBC News Online science editor

Too many males may have been the reason the dinosaurs died out 65 million years ago, say Leeds University researchers.
They believe that dinosaurs may have been like modern-day reptiles such as crocodiles whose sex depends upon the temperature before they were born.

The new idea is that the asteroid that struck changed the world's climate causing it to be cooler, which led too many dinosaurs to be born male.

The male-female imbalance would have led to their extinction, they say.

Sun block

You have to feel sorry for the dinosaurs.

There they were, the top of the ecological tree, uncontested masters of the world for almost 200 million years when things suddenly start going wrong for them.

Although there are some that say they were on their way out before the space rock hit, most experts agree that one or more asteroid impacts probably triggered a series of global changes that killed off the dinosaurs and many other species of life on Earth.

Some scientists believe the impacts would have kicked up dust that cooled the air and also triggered volcanic activity that would have created even more dust and ash which would have blocked out the Sun and chilled the Earth.

Bad news for the dinosaurs because it is well known that those at the top of the evolutionary pile are especially vulnerable to ecological changes.

And, if this new theory is correct, it would not have been much fun being a dinosaur during these troubled times even if you had survived everything nature could hurl at you.

If the conditions were not bad enough those that did manage to eke out a meagre living could not find a mate.

Preponderance of males

No one really knows whether dinosaurs were much like other reptiles, or whether they resembled other animal groups, such as mammals, in some respects. Reptiles have a different type of metabolism to mammals and have various ways of determining the sex of their offspring.

In mammals, if a baby gets an X and a Y chromosome, it will be male and if it gets two X chromosomes it will be female, with a few very rare exceptions. Similar mechanisms work for birds, snakes and some reptiles such as lizards.

But in crocodilians, turtles and some fish, the temperature at which eggs are incubated can affect the sex of the developing babies.

David Miller of the University of Leeds and colleagues ran an analysis that showed a temperature shift could theoretically have led to a preponderance of males.

Other studies have shown that when there are too few females, eventually the population dies out.

"The Earth did not become so toxic that life died out 65 million years ago; the temperature just changed, and these great beasts had not evolved a genetic mechanism (like our Y chromosome) to cope with that," says Dr Sherman Silber, an infertility expert in St Louis who worked on the study.

But crocodiles and turtles had already evolved at the time of the great extinction 65 million years ago. How did they survive?

"These animals live at the intersection of aquatic and terrestrial environments, in estuarine waters and river beds, which might have afforded some protection against the more extreme effects of environmental change, hence giving them more time to adapt," the researchers say.

But some experts are not convinced by the idea.

"More than 50% of all species that lived prior to the mass extinction were wiped out. In fact, the dinosaurs were not among the most numerous of the casualties - the worst hit organisms were those in the oceans," said Benny Pieser of Liverpool John Moores University.

"I am afraid sex-selection mechanisms are an unlikely cause for the termination of the age of dinosaurs - despite the sexed-up headlines."

http://news.bbc.co.uk/2/hi/science/nature/3647115.stm

edit: bugger. Didn't spot this had been posted - i'll leave it as an alternative source. :)
 
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Periodic extinctions, not just of dinosaurs, but of other forms of life, have been proven to some scientist's satisfaction. Luis Alvarez and his student Richard Muller (Mueller?) came up with this theory and the companion theory of the cause of the periodicy, a distant dark-star companion to our sun, with a huge orbit, which perturbs the Oort cloud and cometary orbits on a regular (every 125 million years or some such) basis.


Muller wrote a pretty darn good book about it called "Nemesis, the Death Star." Never let it be said that academics don't have a flair for the dramatic.
 

sunsplash1

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Fallen Angel said:
Muller wrote a pretty darn good book about it called "Nemesis, the Death Star." Never let it be said that academics don't have a flair for the dramatic.

Good book maybe but very dodgy science...
 

Mighty_Emperor

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Dino impact gave Earth the chill

Evidence has been found for a global winter following the asteroid impact that is thought to have killed off the dinosaurs 65 million years ago.

Rocks in Tunisia reveal microscopic cold-water creatures invaded a warm sea just after the space rock struck Earth.

The global winter was probably caused by a pollutant cloud of sulphate particles released when the asteroid vapourised rocks at Chicxulub, Mexico.

The results are reported in the latest issue of the journal Geology.

Italian, US and Dutch researchers studied rocks at El Kef in Tunisia which cover the Cretaceous-Tertiary (K-T) boundary, when dinosaurs - amongst other species - vanished from our planet.

Sun block

At the time of the dinosaurs, El-Kef was part of the warm western Tethys Sea. When the scientists studied the types of microscopic fossil creatures present in the Tunisian rocks, they found some surprising changes after the K-T boundary.

Firstly, two new species of benthic foraminifera - simple animals that live near the sea floor - appeared. These newcomers were cold-water types found in more northerly oceans.

Secondly, they found a curious difference in the shape of a microscopic snail-like creature called Cibicidoides pseudoacutus . This creature's shell is said to coil in either a left or a right direction.

In cold waters there are proportionally more left-coiling individuals, while in warmer waters this pattern is reversed. The researchers found a proportional increase in left-coiling Cibicidoides , after the K-T boundary.

"It's the first time we have found physical evidence for cooling at the K-T boundary," said Dr Simone Galeotti of the University of Urbino, Italy.

Dr Galeotti and his colleagues think the most likely cause of the cooling was a pollutant cloud of airborne sulphate particles, or aerosols, that blocked out sunlight.

Heat 'switch'

These would have been released when the asteroid collision vapourised rocks rich in sulphate salts at Chicxulub.

Matthew Huber of Purdue University in Indiana, US, calculated the global impact of the winter.

"The results we got are fairly consistent with the impact winter decreasing the amount of sunlight hitting the Earth by 90%. If you turn off that heat source, the Earth will cool in a big way," he told BBC News Online.

The oceans would have acted as a reservoir of heat to prevent the surface temperature of the planet from cooling too much. However, this reservoir is not infinite. If the sunlight was blocked out for long enough, the oceans would eventually have frozen solid.

"It must have been dark long enough to cool the oceans, but not long enough that the whole planet iced over - that's not what we see in the fossil record," said Dr Huber.

This impact-induced darkness would have lasted between one and ten years on land, but there is evidence for a cooling of up to 2,000 years at El Kef.

Positive feedback mechanisms may have prolonged the cooling effect of the impact winter in waters of intermediate depth - such as those at El Kef - and deeper.

The Cretaceous-Tertiary extinction was a selective one; entire groups such as dinosaurs and ammonites were killed off, while others were left unaffected.

The latest research does not probe this mystery, but it does help fill in the picture of what was happening to our planet following the impact at Chicxulub.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/3750765.stm

Published: 2004/05/31 08:35:46 GMT

© BBC MMIV
 
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