Skip to comments.Earth's Volcanism Linked To Meteorite Impacts
Posted on 12/13/2002 8:36:39 AM PST by blam
Earth's volcanism linked to meteorite impacts
14:31 13 December 02
Exclusive from New Scientist Print Edition
Space rocks are blamed for violent eruptions (Image: GETTY)
Large meteorite impacts may not just throw up huge dust clouds but also punch right through the Earth's crust, triggering gigantic volcanic eruptions.
The idea is controversial, but evidence is mounting that the Earth's geology has largely been driven by such events. This would also explain why our planet has so few impact crater remnants.
Counting the number of asteroids we see in the sky suggests that over the past 250 million years, Earth should have been hit around 440 times by asteroids larger than one kilometre across. But scientists have found only 38 large impact craters from this period.
Dallas Abbott from Columbia University and her colleague Ann Isley from the State University of New York studied the timing of these 38 impacts and found that they correlate strongly with eruptions of "mantle-plume" volcanoes during the same period.
Most volcanoes come from small amounts of the Earth's upper mantle boiling over, but mantle-plume volcanoes happen when hot rock from deep within the Earth's mantle shoots straight up through the Earth's crust. The timing suggests that these volcanoes are related to asteroid impacts, Abbott and Isley report in Earth and Planetary Science Letters (vol 205, p 53).
Not everyone agrees. "I am not enthusiastic about the idea that impacts systematically control Earth's activity," says Boris Ivanov from the Institute of Geospheres Dynamics in Moscow. He has used computer models to investigate the effect of meteorites on the Earth's crust, and says he does not believe impacts are capable of having a significant effect on the planet's geological processes.
And geochemist Christian Koeberl from Vienna University argues that the dates Abbott used are not reliable. "The impacts and volcanoes can only be correlated to within tens of millions of years," he says. "This doesn't really prove anything."
But elsewhere, there is growing support for the idea that Earth's volcanism may be closely entwined with meteorite impacts.
Adrian Jones and David Price from University College London say Abbott's work backs up their recent computer simulations. These models suggest meteorites bigger than about 10 kilometres across could sometimes punch right through the Earth's crust, causing huge volcanic eruptions (Earth and Planetary Science Letters, vol 202, p 551).
"A large impact has the ability to cause instant melting where it hits, creating its own impact plume in the mantle and resulting in a massive surge of lava spilling out," Jones explains.
Until now Abbott and Isley were not sure how impacts might trigger volcanic eruptions, but the UCL model suggests a mechanism. It would also explain why we do not see as many meteorite craters as we might expect, as the surges of molten rock would obliterate them.
Jones speculates that many of the impact craters Abbott analysed could have been created by mere fragments of bigger asteroids that hit elsewhere at the same time and broke through the crust, ultimately leaving no trace.
For example, the 10 kilometre-wide asteroid that hit Chicxulub in Mexico 65 million years ago is widely blamed for wiping out the dinosaurs. But it could have been a piece from a much bigger rock that hit India, triggering the surge of volcanic activity known as the Deccan Traps.
"Many areas that exhibit extensive volcanism from the past, such as the Deccan Traps and the Siberian Traps, may in fact be sites of gigantic meteorite impacts," says Jones. Perhaps the dinosaurs would have survived a meteorite impact alone, but the double whammy of a meteorite and volcanoes pushed them to extinction.
Considering, for example, that Hawaii and Iceland are hot-spot (or mantle-plume) volcanic zones, they erupt almost continually, so of course you'll be able to get a correlation with such features. And the impact at the end of the Cretateous down in Yucatan did not create a plume, and that was a biggie. Dittoes for the impact at the southern end of the Chesapeake - I don't see a Mt. Norfolk erupting down there.
It would be more impressive if the researchers were able to correlate major impacts with outbreaks of flood basalts. Now THOSE are truly nasty...
The Yellowstone hot spot created the Columbia flood basalts. There does not have to be correlation with an impact to get these events. Plus, 65 million years ago, India was very close to the Reunion hot spot, an extremely active one. They need more evidence and less inference.
This new theory perplexes me; why would Al Gore invent meteorites which could possibly do so much damage to one of his other creations, Earth?
Backtrack the Hawaiian hotspot on the earth's crust to where the impact might have been. Remember hotspots remain stationary in reference to the earth's crust while the plates move over them.
crust s/b core my bad!!!
EXTRATERRESTRIAL INFLUENCES ON MANTLE PLUME ACTIVITY
Earth and Planetary Science Letters
Volume 205, Issues 1-2, 30 December 2002, Pages 53-62
by Dallas H. Abbott and Ann E. Isley
We use time series analysis to compare the impact histories of the Earth and Moon with the record of mantle plume activity. We use events with errors in their ages of 150 Ma. The terrestrial and lunar impact records, when smoothed at a 45-Ma interval, correlate at a 97% confidence level. This high confidence level suggests that we have an adequate sampling of most of the major impact events on the Earth. We then test the idea that existing mantle plumes may be strengthened by impacts. When smoothed at a 45-Ma interval, strong plumes correlate with the terrestrial impact record at better than a 99% confidence level. No time lag is discernible between the data sets, which is expected given their present error level. When the time series are smoothed at a 30-Ma interval, there are 10 major peaks in impact activity. Nine out of ten of these peaks have a counterpart in either or both of the strong mantle plume or the mantle plume time series. As a result, the strong mantle plume and the impact time series correlate at the 97% confidence level. The mantle plume and the impact time series correlate at the 90% confidence level. Finally, the Deccan plume showed greatly increased activity immediately after the Chixculub impact. The results of our analysis suggest that large meteorite and cometary impacts may well increase the amount of volcanism from already active mantle plumes.
Also, I thought that Iceland was an area where the sea floor was spreading.
I read that the Chicxulub meteorite came in at a 35 degree angle, may be that's why it didn't 'punch' through.
Exactly so, even a smaller object hitting at higher angle would be more likely to punch through. Also an object hitting mid-ocean (where the crust is thin) would be more apt to create a plume.
What a world, eh?
Doesn't fit the profile. From Pellegrino's Unearthing Atlantis, it had a long history as a volcanic hotspot before and since the Iron Age biggie that devastated Minoan Crete 70 miles over the water. The Thera (where did you get Exodus?) excavations seem to show pipes for geothermal hot and cold running water.
You're crazy, but I don't see what that has to do with this ;^)
The Deccan traps were not at the antipodes from the Chicxulub impact site. The shock waves from Chicxulub would not meet at that point. A paired asteroid impact could explain both features.
A more interesting question (and possible proof of the theory) is where is the contra coup scars from the Deccan and or Siberian traps? If either one was a scar from a BIG impact, there should be "disturbed" features 180° from it. Anyone know what was opposite India 65 mya? Or Siberia 230 mya? Does either exhibit shattered rock, or have they been subducted in the meanwhile?
The other obvious question is where are the other impact debris, surely all the splatter couldn't have reached escape velocity, could it?
Also, I highly recommended this book: T.rex and the crater of doom by Walter Alvarez, Princton University Press, ISBN 0-691-01630-5. Not only is it a very well told tale of the discovery of the Chicxulub impact site, it is a superb geology text. It packs a tremendous geology education in an accessible, easy to digest and understand form.
The other thing is the Martian volcanos, which correlate with a basin on the other side of the planet and look like a large asteroid plowed right through the planet and punched almost through in the earea of the volcanos, which are grouped in a relatively small area.
Yup, that's my argument against an impact also. It's in an already previously active area.