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mutleyeng
2012-Apr-21, 11:52 AM
i seem to recall, many moons ago, there was quite some debate as to whether it was justified to say an asteroid hit wiped out the Dinosaurs.
There was quite a decent argument, it seemed to me at the time, that the asteroid was just he straw that broke the camels back.
Dino was in trouble way before that, with climate change, oxygen levels - there were i think 5 other factors that converged with the asteroid event that finally did for them.
So im wondering, where are we with this now...i hardly ever hear it mentioned any more that the asteroid wasnt wholey culpable.

grapes
2012-Apr-21, 03:48 PM
The K-T extinction (oops, K-Pg) is still controversial, just not as much since Luis died. And we have more data, so less speculation.

http://en.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event

publiusr
2012-Apr-21, 08:05 PM
I think there were even old school geologists who were trying to say that volcanoes could produce shocked quartz and shatter cones. Something about new magma pressing against different types of rock. Don'r really buy into that. Asteroids cause compression--outside in. Magma has gas pressure--more inside out--explaining pumice, vesicles, what-have-you.

Maar craters look like impact craters, so with Gene Shoemaker gone, I expect the words "crypto-volcanic" and "crypto-explosive" to creep back into the uniformitarianist's/gradualist's lexicon.

I wonder if Channeled Scablands left a bad taste in their mouths--seeming to be something from young-earthers looking for THE deluge--as opposed to a still large flood from the failure of an ice dam--just not planet covering (Black Sea actually)

So the gradualists over-compensated by going in the other direction. Catastrophists were seen as nut jobs early on after all.

I think this might even describe why people believe the way they do. Before smokers, extremeophiles, chemosynthesis, impact theory, the calving off of the moon and huge tides to stir chemicals up--all people had was a warm pond where something just kind of happened. Simple folk scoffed at this--it seeming to substitute one miracle for another--thus the resistance to science from the usual suspects who have no use for 'something called volcano monitoring.'

On the other hand, you had folks who embraced the idea of a gradual 'becoming" (to quote Manhunters Tom Noonan)--and that nature was this gradual paradise where nothing quick or violent ever happened before us evil humans came on the scene all uppity with our upright stance and our thumbs.

Both were wrong. You need incredible dynamism and quiescence in combination.

Cougar
2012-Apr-22, 01:50 AM
The K-T extinction (oops, K-Pg) is still controversial, just not as much since Luis died.
http://en.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event (http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event)

That seems to be a pretty good article. I'm not sure what your Luis Alvarez reference means. Of course, he's the one who provided the first scientific evidence of a large impact event (http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event#Impa ct_event) in the form of a concentration of iridium many times greater than normal found in sedimentary layers found all over the world at the Cretaceous–Tertiary boundary.

I guess there is still some controversy whether the impact was the sole cause. But, as wiki reports:


In March 2010 an international panel of scientists endorsed the asteroid hypothesis, specifically the Chicxulub impact, as being the cause of the extinction. A team of 41 scientists reviewed 20 years of scientific literature and in so doing also ruled out other theories such as massive volcanism. They had determined that a 10–15 km (6–9 mi) space rock hurtled into earth at Chicxulub on Mexico's Yucatan Peninsula. The collision would have released the same energy as 100 teratonnes of TNT (420 ZJ).


The megatsunamis would have killed off quite a few lifeforms. And all that dust and sulfuric acid aerosols thrown up in the atmosphere... Many immediate effects and then lasting effects would have wreaked havoc on our dear little Earth for at least a decade. [ETA: As I said, that wiki article spells it all out.] It's a good thing our mammalian forebears at the time were not picky about a fresh meat and vegetable diet. :sick:

grapes
2012-Apr-22, 02:04 AM
It was his son Walter, a geologist, who did the digging. Luis provided the speculation, and was pretty intolerant of dissent--I think that's where his famous insult of "stamp collecting" came from. Some of the older geologists were heavily vested in the volcanic hypothesis too--they fanned the flames too, it wasn't just Luis. Someone told me a story of a screaming match in the street outside AGU one year, with one of the participants holding onto a car door and being dragged away, still shouting at the occupant of the car.

Back when the conferences were fun.

BigDon
2012-Apr-22, 10:25 PM
Coug, mega-tsunamis and the atmosphere of the entire Western Hemisphere heating to 350 F for over three hours.

I'm sure that cause one hell of an El Nino for years to come.

publiusr
2012-Apr-23, 09:16 PM
Not to mention Kerry Emanuels hypercanes-- and the ballistic cloud that would have gone over the heads of smaller mammals

filrabat
2012-Apr-23, 09:32 PM
Then there's the Deccan Traps in India. Millions of sq km of lava bubbling up? That HAD to have some effect! Something on a bigger scale earlier in Siberia was mostly, if not exclusively, responsible for the Permian Extinction. Where do the Deccan Traps enter into the picture?

jlhredshift
2012-Apr-24, 03:31 AM
Dr. Keller still works to oppose the impact theory.

Main Deccan volcanism phase ends near the K–T boundary: Evidence
from the Krishna–Godavari Basin, SE India; G. Keller, et. al. (http://repository.ias.ac.in/4636/1/314.pdf)

John Mendenhall
2012-Apr-24, 05:11 AM
Dr. Keller still works to oppose the impact theory.

Main Deccan volcanism phase ends near the K–T boundary: Evidence
from the Krishna–Godavari Basin, SE India; G. Keller, et. al. (http://repository.ias.ac.in/4636/1/314.pdf)

And there are some that feel that the traps are on the antipodal point from the impacts.

And I suspect that the only land animals that survived were burrowers. The quoted size is 10 kg or less for survivors. About the size of a groundhog . . . .

jlhredshift
2012-Apr-24, 12:37 PM
And there are some that feel that the traps are on the antipodal point from the impacts.

And I suspect that the only land animals that survived were burrowers. The quoted size is 10 kg or less for survivors. About the size of a groundhog . . . .

The Deccan flows were happening before the impact in a major way, and they continued after. There are sections of strata demonstrating that. Peter Ward showed that the ammonoids survived right up to the K/T in Spain. Yet, Bob Bakker thinks it was pathological, and asks "where are the piles of bones right at the boundary?". Jack Horner says when asked "I do not know why, I'm just glad they're gone."

BigDon
2012-Apr-24, 07:19 PM
and Earth was STILL more habital than Mars...

jlhredshift
2012-Apr-24, 08:02 PM
and Earth was STILL more habital than Mars...

You know, that's a good point, for those that could adapt!

distraction tactics
2012-Apr-27, 03:11 AM
I stumbled upon the debate a few years ago during my undergrad and found it fascinating.

Schulte et al (2010) was almost certainly an attempt to silence Keller in the public eye, but while she hasn't done much on the double-impact hypothesis, it looks like she has redoubled her efforts on Deccan volcanism.

mutleyeng
2012-Apr-27, 05:23 PM
thanks all,
I feel that bit better learn'd now