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Author Topic: Why is the Chixculub crater a strange shape?  (Read 351 times)

Offline jbel

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Why is the Chixculub crater a strange shape?
« on: 22/09/2016 23:21:59 »
Hey everyone, so I have some persistent questions about the K-PG extinction that just keep nagging at me, and I'd like some fresh perspectives.  So hopefully there are some K-PG extinction people in here. So first off, the Chixculub crater itself, I've looked at the gravity maps of the crater, and it has a strange egg shape, oblong, and is pointed northwest, so clearly the object was travelling southeast to northwest. Why the strange shape? A shallow impact? From what I've been reading lately, the impact wasn't a head-on direct hit, but more of a glancing blow, in other words, the object was travelling at about 30 degrees to the earth at a very shallow angle and then hit, hence the strange shape of the crater. This in turn directed much of the blast at a lateral angle spreading it across a much wider surface area. I must say this makes sense, and accounts for the large losses seen in North America at the K-PG boundary. Next, did the Chixculub impact trigger massive earthquakes which in turn caused a major spike in the Deccan Traps output, which had already been erupting before the impact, and thus, the impact plus the resulting environmental fallout from both the impact and the increased Deccan Traps output led to the poisoning of the atmosphere. It seems obvious that the impact alone would have been more than enough to kill off many fragile ocean dwellers which totally depended on tropical, sun-lit conditions such as the large foraminifera and ammonites. And probably most of the dinosaurs too, but the few that survived the impact and the immediate fallout, would no doubt have suffered greatly from the Deccan Traps and the wasted landscape.

The areas around the Gulf of Mexico are known to have large tsunami deposits from the impact. I believe they've found wood fragments which were washed ashore when the giant waves crested, but how about dinosaur fossils? Do any dinosaur fossils exist in the actual boundary layer? This would be an amazing find.

Lastly, I keep wondering, was the impact from an asteroid or comet? Growing up it was always said that it was an asteroid, but the more I read and look at the crater, I think it may have been a comet. Anyone have any ideas on that? This was clearly a very large object, and the fireball layer exists everywhere all over the earth, and in areas closer to the crater, the spherules are very widely distributed in the boundary. I hope the recent drillings to the crater might help solve this question, is there any way we can determine this?
« Last Edit: 16/11/2016 18:32:29 by chris »


 

Offline jbel

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Re: K-PG Extinction Questions
« Reply #1 on: 13/11/2016 23:25:11 »
Going to bump this since I got no replies, to see if there is any interest in the topic..This past summer drilling was done into the Chixculub Crater for samples to determine how life evolved right afterwards. I still think it was a comet impact rather than an asteroid, maybe one day we will be able to tell one way or the other. Obviously it was a very high energy impact, travelling at a very shallow energy which combined with the angle and the location hit, sent vast blast waves laterally impacting life to the extreme, especially in the Northern Hemisphere. Of course, we can't know how long before the last dinosaur died out after impact, 10 years, 50 years, or 100 years, or maybe a few thousand years later. Hopefully we will someday find more dinosaur remains right at the boundary or maybe even in the impact boundary deposits themselves. I heard of an Ornothimimid bone being found in a tsunami deposit somewhere in Texas, but not sure if that's confirmed or not..

I wonder if the impactor was a comet that broke up such as Shoemaker-Levy 9, looks like there would be a way to discern if it was a comet or asteroid. I'm still thinking it was a comet. It's such a happenstance event, but yet it led the way for our evolution so is highly significant.
 

Offline evan_au

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Re: K-PG Extinction Questions
« Reply #2 on: 14/11/2016 20:54:25 »
Quote from: jbel
I keep wondering, was the impact from an asteroid or comet?
Astronomers are now thinking that the boundary between asteroids and comets is fuzzier than originally thought.

Comets have long been known to contain dust and sand-sized solids - this is what produces meteorite showers.

It has recently been found that some asteroids produce outgassing (like comets do).
On close inspection, the Dawn spacecraft found that the asteroid cum dwarf planet Ceres contains a mixture of both water and rock:
http://www.space.com/33934-dwarf-planet-ceres-ice-volcano-discoveries.html
 

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Re: K-PG Extinction Questions
« Reply #2 on: 14/11/2016 20:54:25 »

 

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