Posted on 03/09/2006 11:57:34 AM PST by blam
Mass Extinctions - A Threat from Outer Space or Our Own Planet's Detox?
University scientists suggest extraterrestrial theories are flawed and that more down to earth factors could have accounted for past mass extinctions
Earth history has been punctuated by several mass extinctions rapidly wiping out nearly all life forms on our planet. What causes these catastrophic events? Are they really due to meteorite impacts? Current research suggests that the cause may come from within our own planet – the eruption of vast amounts of lava that brings a cocktail of gases from deep inside the Earth and vents them into the atmosphere.
University of Leicester geologists, Professor Andy Saunders and Dr Marc Reichow, are taking a fresh look at what may actually have wiped out the dinosaurs 65 million years ago and caused other similarly cataclysmic events, aware they may end up exploding a few popular myths.
The idea that meteorite impacts caused mass extinctions has been in vogue over the last 25 years, since Louis Alverez’s research team in Berkeley, California published their work about an extraterrestrial iridium anomaly found in 65-million-year-old layers at the Cretaceous-Tertiary boundary. This anomaly only could be explained by an extraterrestrial source, a large meteorite, hitting the Earth and ultimately wiping the dinosaurs – and many other organisms - off the Earth’s surface.
Professor Saunders commented:
“Impacts are suitably apocalyptic. They are the stuff of Hollywood. It seems that every kid’s dinosaur book ends with a bang. But are they the real killers and are they solely responsible for every mass extinction on earth? There is scant evidence of impacts at the time of other major extinctions e.g., at the end of the Permian, 250 million years ago, and at the end of the Triassic, 200 million years ago. The evidence that has been found does not seem large enough to have triggered an extinction at these times.” Flood basalt eruptions are – he says - an alternative kill mechanism. These do correspond with all main mass extinctions, within error of the techniques used to determine the age of the volcanism. Furthermore, they may have released enough greenhouse gases (SO2 and CO2) to dramatically change the climate. The largest flood basalts on Earth (Siberian Traps and Deccan Traps) coincide with the largest extinctions (end-Permian, and end-Cretaceous). “Pure coincidence?”, ask Saunders and Reichow.
While this is unlikely to be pure chance, the Leicester researchers are interested in precisely what the kill mechanism may be. One possibility is that the gases released by volcanic activity lead to a prolonged volcanic winter induced by sulphur-rich aerosols, followed by a period of CO2-induced warming.
Professor Andy Saunders and Dr. Marc Reichow at Leicester, in collaboration with Anthony Cohen, Steve Self, and Mike Widdowson at the Open University, have recently been awarded a NERC (Natural Environment Research Council) grant to study the Siberian Traps and their environmental impact.
The Siberian Traps are the largest known continental flood basalt province. Erupted about 250 million years ago at high latitude in the northern hemisphere, they are one of many known flood basalts provinces - vast outpourings of lava that covered large areas of the Earth's surface. A major debate is underway concerning the origin of these provinces –including the Siberian Traps - and their environmental impact.
Using radiometric dating techniques, they hope to constrain the age and, combined with geochemical analysis, the extent, of the Siberian Traps. Measuring how much gas was released during these eruptions 250 million years ago is a considerable challenge. The researchers will study microscopic inclusions trapped in minerals of the Siberian Traps rocks to estimate the original gas contents. Using these data they hope to be able to assess the amount of SO2 and CO2 released into the atmosphere 250 million years ago, and whether or not this caused climatic havoc, wiping out nearly all life on earth. By studying the composition of sedimentary rocks laid down at the time of the mass extinction, they also hope to detect changes to seawater chemistry that resulted from major changes in climate.
From these data Professor Saunders and his team hope to link the volcanism to the extinction event. He explained:
“If we can show, for example, that the full extent of the Siberian Traps was erupted at the same time, we can be confident that their environmental effects were powerful. Understanding the actual kill mechanism is the next stage….watch this space.” More information is available from the website: http://www.le.ac.uk/gl/ads/SiberianTraps/Index.html
Note to editors:
Further information is available from Professor Andy Saunders, Department of Geology, University of Leicester, tel 0116 252 3923, email ads@le.ac.uk; or from Dr Marc Reichow, email mkr6@le.ac.uk
I'm sticking with the meteorite impact theory.
It's those geosynchronous comets dropping alien rain in India I tell ya.
I keep trying to tell you people that the Earth is trying to kill us. It started this fight for survival and it's about time we started fighting back.
It all started when T-Rex's starting dumping their volkswagons and stuck with Hummers and SUVs and poluted the earth so badly that greenhouse gases increased and the ice caps melted and...
The 65M years ago event looks certainly to have been caused by a meteorite impact.
Possibly one or more of the older events might have been volcanic.
What would be the effect if a large meteor hit the Yellow Stone super Volcano area?
It is just a coincidence that a very large rock hit the Earth at just the time that huge volcanic events took place?
I don't think so. There probably is a causal relationship between the two events. There is still the question as to why the geologic record shows such a dramatic decrease of life right after the KT boundary layer.
Probably pretty bad. But it is believed that an impact 17 mya caused the Yellowstone hot spot in the first place.
To the degree the article actually quotes the scientists, it doesn't seem to be a 'one size fits all' proposition in their minds.
And I don't think Alvarez ever hypothesized that meteor impacts explain every extinction, did he?
Journalists just can't get interested unless there's 'conflict', even if they have to fabricate it.
No kidding? I've never heard this before.
Now, I have heard that a comet fragment may have caused the Thera eruption in 1628BC.
How about an impact, which not only clouds over the planet, but also triggers a lot of extra eruptions that put the noxious gases under an insulating blanket which allows both phenomena to multiply the overall effects?
Actually the theory is you get a hotspot and flood basalt on the OPPOSITE side of the planet from the asteroid impact, through focusing of seismic energy.
It's been out there for a while, and the people behind it aren't kooks, but it's not widely accepted. There are some interesting "line ups" of large impacts with hotspots on the other side of the world.
One fly in the ointment is that it's now pretty clear that hotspots aren't perfectly stationary in the mantle with the plates moving over them; the hotspots themselves move some.
Actually the idea of impacts causing a hotspot on the opposite side of the earth has been around a long time...
This is a PDF paper from Sandia National Labs about it in 1994..
http://www.osti.gov/energycitations/servlets/purl/10197028-5vKwmj/webviewable/10197028.pdf
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"The largest flood basalts on Earth (Siberian Traps and Deccan Traps) coincide with the largest extinctions (end-Permian, and end-Cretaceous). 'Pure coincidence?', ask Saunders and Reichow."
The iridium anomalies at various paleontological boundaries exceed the amount of iridium available in the nether regions of the Earth, and yet iridium is common in extraterrestrial trash. 'Pure coincidence?' asks Blam, Civ, and anyone else with functioning brain cells.
Hummmmm, another theory, wonder which one is right.
So9
One thing seldom mentioned, is that the Chixulub impact was right on the edge of the coast.
Imaging how much steam would be generated as a ocean tried to pour into a 120 mile wide white hot crater.
It's the recipe for a pastureized plannet...
No, but in T-Rex and the Crater of Doom, he did suggest that geologists should look for more evidence of giant impacts at extinction boundaries.
Very good book BTW...
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