Posted on 11/28/2006 7:50:28 PM PST by Al Simmons
Data supports the single-impact theory in a controversial discussion
COLUMBIA, Mo. – The dinosaurs, along with the majority of all other animal species on Earth, went extinct approximately 65 million years ago. Some scientists have said that the impact of a large meteorite in the Yucatan Peninsula, in what is today Mexico, caused the mass extinction, while others argue that there must have been additional meteorite impacts or other stresses around the same time.
A new study provides compelling evidence that "one and only one impact" caused the mass extinction, according to a University of Missouri-Columbia researcher.
"The samples we found strongly support the single impact hypothesis," said Ken MacLeod, associate professor of geological sciences at MU and lead investigator of the study. "Our samples come from very complete, expanded sections without deposits related to large, direct effects of the impact – for example, landslides – that can shuffle the record, so we can resolve the sequence of events well. What we see is a unique layer composed of impact-related material precisely at the level of the disappearance of many species of marine plankton that were contemporaries of the youngest dinosaurs. We do not find any sedimentological or geochemical evidence for additional impacts above or below this level, as proposed in multiple impact scenarios."
MacLeod and his co-investigators studied sediment recovered from the Demerara Rise in the Atlantic Ocean northeast of South America, about 4,500 km (approximately 2,800 miles) from the impact site on the Yucatan Peninsula. Sites closer to and farther from the impact site have been studied, but few intermediary sites such as this have been explored.
Interpretation of samples from locations close to the crater are complicated by factors such as waves, earthquakes and landslides that likely followed the impact and would have reworked the sediment. Samples from farther away received little impact debris and often don’t demonstrably contain a complete record of the mass extinction interval. The Demerara Rise samples, thus, provide an unusually clear picture of the events at the time of the mass extinction.
"With our samples, there just aren’t many complications to confuse interpretation. You could say that you’re looking at textbook quality samples, and the textbook could be used for an introductory class," MacLeod said. "It’s remarkable the degree to which our samples follow predictions given a mass extinction caused by a single impact. Sedimentological and paleontological complexities are minor, the right aged-material is present, and there is no support for multiple impacts or other stresses leading up to or following the deposition of material from the impact."
The impact of a meteorite on the Yucatan Peninsula likely caused massive earthquakes and tsunamis. Dust from the impact entered the atmosphere and blocked sunlight, causing plants to die and animals to lose important sources of food. Temperatures probably cooled significantly around the globe before warming in the following centuries, wildfires on an unprecedented scale may have burned and acid rain might have poured down.
MacLeod and many other scientists believe that these effects led to the relatively rapid extinction of most species on the planet. Some other scientists have argued that a single impact could not have caused the changes observed and say that the impact in the Yucatan predates the mass extinction by 300,000 years.
MacLeod’s co-investigators were Donna L. Whitney from the University of Minnesota, Brian T. Huber from the Smithsonian National Museum of Natural History and Christian Koeberl of the University of Vienna. The study was recently published in the ‘in press’ section of the online version of the Geological Society of America Bulletin. Funding was provided by the U.S. Science Support Program, the U.S. National Science Foundation and the Austrian Science Foundation. Samples were recovered on Leg 207 of the Ocean Drilling Program.
The ozone hole grew to an enormous size, and greenhouse gases such as carbon dioxide and water vapor were introduced into the atmosphere without any regulatory oversight. HIV/AIDS and other diseases of the immune system may have been rampant as well. Homelessness was widespread, as was a lack of affordable health insurance.
But, but, who was driving the SUV's back then that warmed the planet?
Phone call for Mr. Gore, please pick up the white phone -
The one impact theory makes sense. Life had already evolved, long after the bombardment. The possibility of two earth-shaking meteors that close are pretty remote, and if it did happen it was probably a split rock.
Yep...its was God's fault...no Bush's...no I mean it was Dino's for not buying insurance....yeah that's it...where was Fred Flintstone when you needed him
Still very fascinating. When I was in college there were still articles suggesting volcanic activity caused the dinosaur extinction.
Makes one wonder if these impacts are on a regular period or if a random one could be coming in the near future.
You forgot: Women and Minorities Hit Hardest!
The single-bullet theory?
LOL!
You know, I think that giant meteorite impact was orchestrated by the CIA and Israel, to help Halliburton!
I don't support your fascist war on giant meteorites! Besides, the dinosaurs were asking for it ever since they occupied the Arabian peninsula.
You are pinged!
Turf battle?
Any guesses how long the sun was blocked by the debris in the air?
I understand that there was a large flood back in the day. A flood that encompassed the entire earth … could be the reason for the extinction of so may species.
"When I was in college there were still articles suggesting volcanic activity caused the dinosaur extinction."
No reason an impact of this magnitude couldn't have precipitated a few volcanic events. The story doesn't seem to rule it out, only other impact events.
"Makes one wonder if these impacts are on a regular period or if a random one could be coming in the near future."
One man's random is another man's cycle.
Yup. I never paid much attention to the other arguments.
I think the dinosaurs all died because they got tired of constantly being killed off by the scientists.
Translation: Keep pouring in the grant money...Baby needs new shoes!
There was another article posted here last month that pushed that same theory. It sounds more believable than the single impact theory.
http://www.freerepublic.com/focus/f-news/1727198/posts
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