When a 6-mile diameter asteroid hit the earth 66 million years ago, there was a HUGE heat of impact.
Some of that heat ended up in the atmosphere, when rock was vaporized, went up into the air, and then condensed again.
So the entire atmosphere of the earth gave off a pulse of infrared heat radiation at about 2700 F, which turned the surface of the earth into an oven for several hours ...
and the dinosaurs roasted.
The consensus seems to be that there were a lot of causes for the extinction of the dinosaurs, but the asteroid strike was the coup de grace.
People dated the asteroid's strike and the extinction of the dinosaurs more accurately, and the dates coincided well enough that they can say the asteroid was what finished the dinosaurs off.
"Dramatic climate variation over the previous million years, including long cold snaps amidst a general Cretaceous hothouse environment, probably brought many creatures to the brink of extinction, and the impact kicked them over the edge.
One cause of the climate variability could have been a sustained series of volcanic eruptions in India that produced the extensive Deccan Traps."
For now, I'm on board with the popular consensus that it was a combination of asteroidal and tectonic events that did in the last world-dominate species. Their demise would have been somewhat gradual based upon the unique global location, environment, size, and adaptability of each species. Of course, numerous species survived and their origins date back 500+ million years. Likely lack of water, food, and breathable air. I give the latter the most credit as the air was likely, loaded with particulates, over-heated, acidic, and oxygen depleted.
Its just that volcanos had been doing their thing for billions of years. Enough evolutionary time passed to allow dinosaurs to evolve, diversify, and thrive. So, why was there the coincidence of a asteroid striking more or less at the time the end came? If volcanos were blowing all the time, would Mother Nature really have allowed giant species to successfully evolve? Its hard to imagine a bunch of T-rex stumbling around gasping for air while searching for food and water, when, bam, an asteroid delivers the coup-de-gras.
Something's fishy. The coincidence is just too divine.
I haven't heard that there was terrible air before the asteroid struck. Afterwards maybe - numerous fires would have polluted the air.
But rather, that there were cold periods from volcanic activity and other causes, and that was what stressed the dino's.
One thing I see over and over again, is how incredibly lucky we are. All the things that could have happened to exterminate us - asteroid strikes etc. etc. etc. - and didn't.
Many thanks for the graph and link. The writing was a bit small for me so I did an image search on it and found a clearer version on a page of the Federation of American Scientists, which also contained a lot of information about impact structures. Very interesting! http://www.fas.org/irp/imint/docs/rst/Sect18/Sect18_4.html#18-11
Neil, this site provides so many different examples of impact craters and descriptions of how they formed, I will be spending a good many hours reading it and having a great time. Thanks for the site.
I'm glad you found a clearer image than the one I provided. There is some interesting information on that chart.
More grist to the mill. One of many sites reporting the recently announced theory that it was in fact a comet not an asteroid that hit Chicxulub 65 million years ago. http://www.bbc.co.uk/news/science-environment-21709229