Posted on 10/30/2007 1:31:46 PM PDT by crazyshrink
Hmm. This article refers to that as a myth, however, it sez that increased CO2 levels could make a small difference (ordinarily, plant cells get overloaded with sugars during peak hours, shut their pores, and run on respiration):
http://environment.newscientist.com/channel/earth/climate-change/dn11655
[snip] However, it is extremely difficult to generalise about the overall impact of the fertilisation effect on plant growth. Numerous groups around the world have been conducting experiments in which plots of land are supplied with enhanced CO2, while comparable nearby plots remain at normal levels... These experiments suggest that higher O2 levels could boost the yields of non-C4 crops by around 13 per cent... However, while experiments on natural ecosystems have also found initial elevations in the rate of plant growth, these have tended to level off within a few years. In most cases this has been found to be the result of some other limiting factor, such as the availability of nitrogen or water. [end snip]
I personally think that the Iridium is ET in origin but, Sunk, we don’t know that as a fact. We merely postulate it as we cannot prove it.
No one was around to see the event and take samples immediately thereafter; however, the ET origin is no longer in dispute (other than by some diehards).
http://palaeo.gly.bris.ac.uk/Communication/Lee/page1.html
[snip]Ir found in sediments is from cosmogenic fallout and constitutes around 0.03 ppb. The levels found at Gubbio are in the order of 500ppb. Higher concentrations can be attributed to longer periods of deposition, in this case the death of many calcium carbonate producers stopping the production of limestone which surrounds the clay layer, thus slow clay deposition could result in higher Ir. But this amount of Ir would require a depositional time of around 500,000 years. The high resolution records at the K-T in Caravaca, Spain ( Smit, 1981 ) however indicate a period of no more than 50 years ( other sites resolve the length of time to roughly 1,000 years ). Combined with this is that the ratio of Ir to platinum, osmium, ruthenium, rhodium and gold are the same ( within 5% ) in the boundary layer as they are in type one carbonaceous chondrite meteorites ( Asaro,1990 ). From this evidence it was clear that at least some form of extraterrestrial influence had taken part in the extinction. [unsnip]
http://www.scn.org/~bh162/iridium.html
[snip] To give you an idea of how rare the element is in sedimentary rocks, in a randomly-selected rock weighing one gram, the amount of iridium contained within it would be less than 1 to 2 BILLIONTHS of a gram (1-2 nanograms). In fact, the amount of iridium is often so small that it sometimes cannot be measured at all using today’s scientific equipment (it is estimated to be as low as 0.05 nanograms/gram of sediment). In the clay layer at the Cretaceous-Paleogene boundary, the concentration of iridium is still unbelievably diluted, but it is abundant enough to be easily measured by instruments... In meteorites (iron meteorites + the stoney meteorites), platinum-group metals are significantly more abundant than they are in rocks in the Earth’s crust, often hundreds to thousands of times more concentrated (averaging about 500 nanograms/gram of meteorite in a type of stoney meteorite called a chondrite) (Alvarez et al., 1980). Iron meteorites contain much higher concentrations of these elements. Platinum-group metals are also found in cometary nuclei, but in a somewhat lesser concentration than in chondrites. [unsnip]
Impacts do not cause volcanic eruptions
Dr. H. Jay Melosh
http://www.lpl.arizona.edu/~jmelosh/ImpactVolcanism.pdf
Not to be argumentative but inquisitive. It is my understanding that the high CO2 levels were accompanied by higher (than current) temperatures. As far as asphyxia, would the location of a dinosaurs brain (deep in a very large head), and being about the size of a walnut, counter this in any way?
Pretty much yes, The impact hypothesis is falsified by the fact that it can't explain how Alligators & Crocodiles, Turtles, 100% of the Amphibians, diatoms, Dinoflagellates, birds, honeybees, 97% of freshwater fish and many others who would have been the 1st to go under an impact scenario with it's resulting nuclear winter all survived unscathed.
I'll go with Geologist Norman Macleod who said it best
"The impact theory says in effect that a rock fell out of the sky and killed everything, except for the things that it didn't kill. I don't think that's much of an explanation."
Not to mention That "Thin" layer of iridium as it is described represents 10,000-100,000 years of sediment. How on Earth could iridium (a heavy metal no less) stay up in the atmosphere that long? It would at most wash out within months if not weeks or days.
are we always teaching our kids false info?
Yep, this is actually similar to global warming, if you remember during the Reagan years the Dinosaurs were killed by an Asteroid hypothesis because of it's "nuclear winter" aspect was embraced by Liberals as an anti-nuclear weapons argument.
For an example see Carl Sagan's The Atmospheric and Climatic Consequences of Nuclear War written in 1983
The higher CO2-higher temperature argument is just part of the global warming politics, as well as the gradualist response to dinosaurs in the Arctic and Antarctic (note that drifting continents doesn’t account for dinos in those places; the fossils are however, there).
No, it’s not wrong. The asteroid impact happened and killed the dinosaurs 65 million years ago.
I never got the nuclear winter argument. Were they libs around when it happened? because they seemed hell bent on making that theory so.
you’re wrong. it was global warming that killed the dinosaurs.
Is there some proof that the Iridium is ET in origin? Volcanoes also emit Iridium. The earth isn’t devoid of Iridium, it is just relatively rare in the crust (like most denser metals).
See Toutain, J., and Meyer, G., 1989, Iridium-bearing sublimates at the hot-spot volcano
What ever happened the the talk about a Shiva Crater [caused by impact off Bombay] as being the cause of the Deccan phenomenon. Also, I tried to respond to another post regarding the antipodal possibility of the Yucatan meteor causing the Deccan events. It did not come up on my computer, but said there should have been two antipodal events. My question: wouldn’t the location of the antipodal reaction depend on the angle of entry of the original boloid?
See the link to the H. Jay Melosh response regarding whether impacts cause volcano outbreaks. :’)
Sea floor records ancient Earth
BBC | Friday, 23 March 2007, 09:09 GMT
Jonathan Fildes Science and technology reporter, BBC News
Posted on 03/24/2007 2:06:03 AM EDT by Ernest_at_the_Beach
http://www.freerepublic.com/focus/f-news/1805973/posts
The quantity of iridium found in the tiny layer at the K-T boundary precludes terrestrial sources.
Fred Flintstone was involved.
Or Sankar Chatterjee's Shiva impact?
Are any other FReepers here at the GSA meeting? Please FReepmail me before you head out of town...maybe we can get together for adult beverages?!
Just had a similar discussion over lunch yesterday (Shoemaker-Levy style impact chain, and impact-triggered volcanism). That didn’t happen to be you at the table, did it? The discussion that followed had to do with basins and mare.
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