Talk:Impact event
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Great work on the merge Bryan! --mav
- Thanks. :) Bryan
Note the recently raised possibility that the Permian and Cretaceous impact objects causing extinction events may have been massive molten rocks ejected from the flood basalt events which occurred at the same times rather than asteroid impacts -- Derek Ross
- I'd need some pretty good external references before I'd consider that a plausible theory, personally. Basalt flood eruptions are relatively sedate for their size, not like explosive volcanos. And the impacts proposed for these events are huge; Chicxulub Crater is either 180 or 300 kilometers in diameter (jury's not entirely decided yet) and the Bedout is about 200 kilometers in diameter, both of which suggest impactors about 10 kilometers across. An explosion that would hurl a mass that big out of Earth's atmosphere would be about as energetic as the explosion that would result when it falls back in, and I don't think anyone's ever proposed a volcanic eruption anywhere near that violent. The basaltic flood eruptions were dramatic enough as it is without proposing continent-sized explosions accompanying them. Bryan 07:37, 23 May 2004 (UTC)
There's no doubt that it's speculation at the moment based on computer modelling of the mantle. However the modelling has shown that the titanic explosions required to launch these huge masses are possible under the right circumstances (in the model at least). And there is some physical evidence to follow up. See New Scientist (8-May-2004). I just thought that I should make everyone aware of a possible alternative to the asteroid theory, so that we don't start saying is when we should be saying is thought to be. I'm certainly not saying "Drop the asteroid theory. Here's something better". It's early days yet for the "verneshot" theory and, as you say, it involves a major rethink on flood basalt eruptions. -- Derek Ross 19:17, 23 May 2004 (UTC)
I think this is a great article, and I'd like to see it nominated for feature status. There are however a few things that appear to be in need of elaboration; in particular, there ought to be some more info on the direct consequences of a major collision (some of which is mentioned in e.g. crater but should also be covered here).
Thoughts? Fredrik 12:50, 23 May 2004 (UTC)
This is Correct
I would have to say that, scientifically this assumption is correct. And can also be proven.
Ha! You senile liberals on the Wiki are a funny lot.
Partner, this absurd theory was debunked over the past two years. Despite all the lurid magazine covers, it was a rubbish idea and has been abandoned. The dinosaurs were not killed by an asteroid impact. Very theatrical stuff, though - unfortunately not science.
It is also unfortunate that Alvarez and Gould attacked half the scientists in the country who criticized the notion, destroyed their careers and got them dropped from tenure for daring to oppose the screamin' Alvarez brothers. What a shame. (Anonymously contributed by Anonymous User:211.27.137.236 whose contribution can also be enjoyed at Talk:Stephen Jay Gould.)
There is no solid evidence of impacts leading to the four other major mass extinctions, though many scientists assume that they are at least related to impacts. No, this is not a scientific assumption. Even a quick read through Wikipedia entries on Extinction events will correct this impression. I haven't removed this text, however. --Wetman 18:53, 27 Dec 2004 (UTC)
rate of earth impacts
This information is a bit out of date:
The late Eugene Shoemaker of the US Geological Survey came up with an estimate of the rate of Earth impacts, and suggested that an event about the size of the nuclear weapon that destroyed Hiroshima occurs about once a year.
[re: Tunguska] Shoemaker estimated that one of such magnitude occurs about once every 300 years.
See, for instance, Tunguska-type impacts less common than thought (http://www.abc.net.au/science/news/space/SpaceRepublish_731109.htm)
The quotes below are from _The flux of small near-Earth objects colliding with the Earth_ Brown et al. Nature, Volume 420, Issue 6913, pp. 294-296. (2002)
"The Earth is struck by an object with the energy of Tunguska (assumed to be 10 MT) every 1,000 years."
"We estimate that the Earth is on average struck annually by an object of energy ~5 kton (with a possible range of 2-10 kton), and struck each month by an object with 0.3 kt of energy. Every ten years, an object of energy ~50 kton impacts Earth."
--Mu301 14:43, 2 Jan 2005 (UTC)